The fungus Magnaporthiopsis maydis causes severe damage to sensitive maize hybrids throughout Egy... more The fungus Magnaporthiopsis maydis causes severe damage to sensitive maize hybrids throughout Egypt, Israel, India, Spain, and other countries. Maize, Lupine, and cotton are the only known hosts of M. maydis. Identification of new plant hosts that can assist in the survival of the pathogen is an essential step in restricting disease outbreak and spread. Here, by field survey and growth chamber pathogenicity test, accompanied by real-time PCR analysis, the presence of the fungal DNA inside the roots of cotton plants was confirmed in infested soil. Moreover, we identified M. maydis in green foxtail and watermelon. Infected watermelon sprouts had delayed emergence and development, were shorter, and had reduced root and shoot biomass. M. maydis infection also affected root biomass and phenological development of cotton plants but caused only mild symptoms in green foxtail. No M. maydis DNA was detected in barley, and the plants showed no disease symptoms except for reduced shoot weight.
Magnaporthiopsis maydis is a maize pathogen that causes severe damage to commercial corn fields i... more Magnaporthiopsis maydis is a maize pathogen that causes severe damage to commercial corn fields in the late growth stages. Late wilt disease (LWD) has spread since its discovery in the 1960s in Egypt and is now reported in about 10 countries. The pathogen has a hidden endophytic lifecycle in resistant corn plants and secondary hosts such as green foxtail, watermelon lupin and cotton. At the same time, it could be an opportunist and hinder the host development under the right conditions. This study uncovered M. maydis interactions with newly identified maize endophytes. To this end, six fungi were isolated from the seeds of three sweet corn cultivars having varying susceptibility to LWD. These isolates were identified using colony morphology and microscopic characterization, universal internal transcribed spacer (ITS) molecular targeting and phylogenetic analysis. Most of them belonged to pathogenic species. Compared to three previously identified bioprotective microorganisms, the new species were tested for their ability to secrete metabolites that repress M. maydis in vitro and to antagonize it in a solid media confront test and a seedlings pathogenicity assay. The opportunistic fungal species Aspergillus flavus (ME1), Aspergillus terreus (PE3) and the reference biocontrol bacteria Bacillus subtilis (R2) achieved the highest M. maydis inhibition degree in the plates tests (74-100% inhibition). The seedlings’ pathogenicity assay that predicts the seeds’ microflora resistance to M. maydis highlighted the bio-shielding potential of most species (23% or more epicotyl elongation over the infected control). Fusarium sp. (ME2) was the leading species in this measure (43% enhancement), and B. subtilis gave the best protection in terms of seeds’ germination (50%) and sprouts’ biomass (34%). The results of this study could enhance our understanding of the pathobiome’s role in the context of LWD and represent a first step in using the seeds’ natural protective microflora to develop novel management strategies.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Charcoal rot disease (CRD), caused by the phytopathogenic fungus Macrophomina phaseolina, is a si... more Charcoal rot disease (CRD), caused by the phytopathogenic fungus Macrophomina phaseolina, is a significant threat to cotton production in Israel and worldwide. The pathogen secretes toxins and degrading enzymes that disrupt the water and nutrient uptake, leading to death at the late stages of growth. While many control strategies were tested over the years to reduce CRD impact, reaching that goal remains a significant challenge. The current study aimed to establish, improve, and deepen our understanding of a new approach combining biological agents and chemical pesticides. Such intervention relies on reducing fungicides while providing stability and a head start to eco-friendly bio-protective Trichoderma species. The research design included sprouts in a growth room and commercial field plants receiving the same treatments. Under a controlled environment, comparing the bio-based coating treatments with their corresponding chemical coating partners resulted in similar outcomes in most measures. At 52 days, these practices gained up to 38% and 45% higher root and shoot weight and up to 78% decreased pathogen root infection (tracked by Real-Time PCR), compared to non-infected control plants. Yet, in the shoot weight assessment (day 29 post-sowing), the treatment with only biological seed coating outperformed (p < 0.05) all other biological-based treatments and all Azoxystrobin-based irrigation treatments. In contrast, adverse effects are observed in the chemical seed coating group, particularly in above ground plant parts, which are attributable to the addition of Azoxystrobin irrigation. In the field, the biological treatments had the same impact as the chemical intervention, increasing the cotton plants’ yield (up to 17%), improving the health (up to 27%) and reducing M. phaseolina DNA in the roots (up to 37%). When considering all treatments within each approach, a significant benefit to plant health was observed with the bio-chemo integrated management compared to using only chemical interventions. Specific integrated treatments have shown potential in reducing CRD symptoms, such as applying bio-coating and sprinkling Azoxystrobin during sowing. Aerial remote sensing based on high-resolution visible-channel (RGB), green–red vegetation index (GRVI), and thermal imaging supported the above findings and proved its value for studying CRD control management. This research validates the combined biological and chemical intervention potential to shield cotton crops from CRD.
Fusarium basal rot disease (FBR) is a destructive threat to onion crops around the globe. It caus... more Fusarium basal rot disease (FBR) is a destructive threat to onion crops around the globe. It causes seedlings’ death, development disruption, and pre- and post-harvest bulb infection and rotting, with a concern for toxin infestation. It is an emerging disease in Israel, with new reports from farms nationwide. Recently, we reported on a full-season pot experiment to protect two leading commercial cultivars against FBR chemically. Here, we present new real-time qPCR molecular tracking of the pathogens inside the host plant and compare the infection levels to a deep analysis of the impacts of this experiment’s treatments on plant growth and health indexes. The new findings reveal variations within each treatment’s effectiveness regarding sprout development and bulb ripening stages. For instance, in the yellow Orlando cv., high protection was obtained with Azoxystrobin + Tebuconazole (Az-Te) in sprouts against F. oxysporum f. sp. cepae and with Fludioxonil + Sedaxen in mature plants against Fusarium acutatum. Thus, combining these fungicides may protect plants throughout their lifecycle. Also, Prochloraz at low dose was highly efficient in the Orlando cv. Still, to shield red Noam cv. plants from both pathogens, increasing this fungicide concentration towards the season-ending should be preferred. The qPCR tracking showed that all chemical treatments tested could reduce infection from pathogens by 80–90%, even with compounds such as Az-Te that were less effective. This implies that the pesticide was effective but probably phytotoxic to the plants, and thus, lower dosages must be considered. The molecular-based analysis discloses the high infection ability of F. oxysporum f. sp. cepae compared to F. acutatum in both cultivars. It also indicates an antagonism between those species in the Orlando cv. and synergism in the Noam cv. The current work reveals weak and strong points in chemical FBR protection and offers new ways to improve its application. The qPCR-based method enables us to closely monitor the pathogenesis and efficacy of chemical-preventing treatments and optimize crop-protection protocols.
Fusarium basal rot disease (FBR) is considered a serious threat to commercial onion production in... more Fusarium basal rot disease (FBR) is considered a serious threat to commercial onion production in Israel and worldwide. Today, coping means applied in Israel against the disease have limited efficiency and include a four-year crop cycle and disinfecting the soil with metam sodium. At the same time, agricultural tools (harrows, plows, etc.), contaminated equipment and workers facilitate spread of the disease to new growth areas, and the field disease incidence in Israel now reaches 8% of yields in heavily infected areas. Infected onions do not always show disease symptoms and the problem worsens if they arrive at storage facilities, especially since this pathogen genus produces known toxins. The current study aims at examining the potential of chemical control to reduce the damage caused by this disease. To this end, nine commercial fungicides were scanned in plate sensitivity assay against the main pathogens involved, Fusarium oxysporum f. sp. cepae and Fusarium acutatum. Several fungicides were found to be highly effective against the two pathogens, especially the mixtures Azoxystrobin + Difenoconazole, Fluopyram + Trifloxystrobin, or the Fluazinam compounds. Three selected preparations previously tested in seedlings were evaluated here in a full growing season. Prochloraz successfully protected the Orlando variety (white onion, Riverside cv.) and the Noam variety (red onion) at all growth stages against F. oxysporum f. sp. cepae. At the same time, this treatment was ineffective against F. acutatum in Noam cv. Another anti-fungal preparation, Fludioxonil + Sedaxen mixture, showed a wider range of effectiveness at the season’s end against the two Fusarium species tested in both onion cultivars. These results are an important step towards developing FBR control in commercial onion fields. Follow-up work is needed to optimize the pesticides’ concentrations and their application methods and to test them on a field scale. Interestingly, these pathogens were more aggressive towards the cultivar from which they were isolated: F. oxysporum f. sp. cepae to the red onion Noam cv. and F. acutatum to the white Orlando cv. Infecting the plants with both pathogens reduced disease symptoms in the white Orlando cv, suggesting antagonistic interactions in this onion genotype.
The fungus Macrophomina phaseolina causes charcoal rot disease (CRD) in cotton, whose symptoms de... more The fungus Macrophomina phaseolina causes charcoal rot disease (CRD) in cotton, whose symptoms develop in the late stages of growth and result in wilting and death. Despite significant research efforts to reduce disease incidences, effective control strategies against M. phaseolina are an ongoing scientific effort. Today’s CRD control tends toward green options to reduce the chemicals’ environmental footprint and health risks. Here, different Trichoderma species were examined separately and in combination with Azoxystrobin (AS) in semi-field open-enclosure pots and a commercial field throughout a full season. In the pot experiment, the T. asperellum (P1) excelled and led to improvement in growth (13%–14%, day 69) and crops (the number of capsules by 36% and their weight by 78%, day 173). The chemical treatment alone at a low dose had no significant impact. Still, adding AS improved the effect of T. longibrachiatum (T7507) and impaired P1 efficiency. Real-time PCR monitoring of the pathogen DNA in the plants’ roots at the harvest (day 176), revealed the efficiency of the combined treatments: T. longibrachiatum (T7407 and T7507) + AS. In a commercial field, seed dressing with a mixture of Trichoderma species (mix of P1, T7407, and Trichoderma sp. O.Y. 7107 isolate) and irrigation of their secreted metabolites during seeding resulted in the highest yields compared with the control. Applying only AS irrigation at a low dose (2,000 cc/ha), with the sowing, was the second best in promoting crops. The molecular M. phaseolina detection showed that the AS at a high dose (4,000 cc/ha) and the biological mix treatments were the most effective. Reducing the AS chemical treatment dosages by half impaired its effectiveness. Irrigation timing, also studied here, is proven vital. Early water opening during the late spring suppresses the disease outburst and damages. The results demonstrated the benefits of CRD bio-shielding and encouraged to explore the potential of a combined bio-chemo pest control approach. Such interphase can be environmentally friendly (reducing chemical substances), stabilize the biological treatment in changing environmental conditions, achieve high efficiency even in severe CRD cases, and reduce the development of fungicide resistance.
Today’s fungal plant disease control efforts tend towards environmentally friendly and reduced ch... more Today’s fungal plant disease control efforts tend towards environmentally friendly and reduced chemical applications. While traditional broad-spectrum fungicides provide efficient protection to many field crops, they pose a risk to the soil’s beneficial microflora and a potential health hazard. Moreover, their intensive use often evokes the appearance of resistant pathogens. On the other hand, biocontrol agents such as Trichoderma spp. provide a green solution but often cannot shield the plants from aggressive disease outbreaks. Integrated biological and chemical disease control can combine the benefits of both methods while reducing their drawbacks. In the current study, such a bio-chemo approach was developed and evaluated for the first time against the maize late wilt pathogen, Magnaporthiopsis maydis. Combinations of four Trichoderma species and Azoxystrobin were tested, starting with an in vitro seed assay, then a growth room sprouts trial, and finally a semi-field, full-season pot experiment. In the plates assay, all four Trichoderma species, Trichoderma sp. O.Y. (T14707), T. longibrachiatum (T7407), T. asperellum (P1) and T. asperelloides (T203), grew (but with some delay) in the presence of Azoxystrobin minimal inhibition concentration (0.005 mg/L). The latter two species provided high protection to sprouts in the growth room and to potted plants throughout a full season in a semi-field open-enclosure trial. At harvest, the P1 and T203 bio-shielding exhibited the best parameters (statistically significant) in plant growth promotion, yield increase and late wilt protection (up to 29% health recovery and 94% pathogen suppression tracked by real-time PCR). When applied alone, the Azoxystrobin treatment provided minor (insignificant) protection. Adding this fungicide to Trichoderma spp. resulted in similar (statistically equal) results to their sole application. Still, the fact that Azoxystrobin is harmless to the beneficial Trichoderma species over a complete semi-field condition is a great opening stage for carrying out follow-up studies validating the integrated control in a commercial field situation challenged with acute disease stress.
The charcoal rot (CRD) disease agent, the soil fungus Macrophomina phaseolina, survives by develo... more The charcoal rot (CRD) disease agent, the soil fungus Macrophomina phaseolina, survives by developing reproductive units (spores and pycnidia) and infects various host plants. In cotton plants, the disease can lead to dehydration and death of the host plant at late-season stages. Pima cv. cotton plants, the leading cotton crop in Israel, are particularly susceptible to this disease. Developing biological pesticides against soil diseases is at the forefront of scientific research globally and their importance is increasing due to the world's trend towards a reduction in the use of chemical fungicides. In this work, eight Trichoderma isolates were tested under laboratory conditions against M. phaseolina. Two T. longibrachiatum isolates (T7507 and T7407) and a T. asperellum isolate (P1) achieved promising results. The bioprotective properties of these isolates' secreted metabolites were evaluated in solid and liquid cultures. The T7407 strain was the most influential in the solid medium with 55% inhibition capacity; the P1 strain excelled in the liquid medium with 62% inhibition capacity. The three M. phaseolina isolates were then tested in seedlings (up to 42 days) against controls: non-infected plants, infected unshielded plants, and plants treated with non-influencing Trichoderma isolate (O.Y. 14707). The bio-shielding agents were added directly to the seeds with the sowing in this growth room pathogenicity assay. At the experiment's end, the T. longibrachiatum (T7407) treatment markedly improved the plants' wet weight (45%), height (32%) and phenological development (56%) compared to the non-influencing Trichoderma species control. Since the disease is commonly latent in sprouts, statistical differences in the plants' growth parameters are challenging to reach, as occurred here. Still, the real-time PCR tracking of the pathogen DNA inside the plants' roots revealed dramatic changes. The pathogen DNA dropped to nearzero levels in the T. longibrachiatum-and T. asperellum-treated plants. Interestingly, the O.Y. 14707 isolate, which showed no bioprotective properties in the lab tests or plants' growth indices, had a similar significant repression impact on the pathogen roots infection. The results of this work demonstrate the importance of the early molecular assessment of preventive treatment effectiveness against M. phaseolina before a full growing season evaluation.
Magnaporthiopsis maydis late wilt disease (LWD) in corn is considered to be the most severe in Is... more Magnaporthiopsis maydis late wilt disease (LWD) in corn is considered to be the most severe in Israel and Egypt and poses a significant threat in other countries. Research efforts extending over a period of five decades led to the development of chemical, biological, agrotechnical, physical (solar disinfection) and other means for controlling late wilt disease. Today, some applications can reduce damage even in severe cases. However, cultivating disease-resistant maize varieties is the primary means for reducing the disease’s impact. The current work uses a rapid (six days) laboratory seedling pathogenicity test and a full-season open encloser semi-field conditioned pots assay (101 days) to classify maize varieties according to their LWD resistance. To better evaluate differences between the cultivars, a real-time based molecular assay was applied to track the pathogen’s presence in the plants’ tissues, and visible light aerial imaging was used in parallel. The findings show that in cases of extreme sensitivity or tolerance (for example, in the highly susceptible Megaton cultivar (cv.) or the resistant Hatai cv.), a similarity in the results exists between the different methods. Thus, a reliable estimate of the varieties’ sensitivity can be obtained in a seed assay without the need for a test carried out throughout an entire growing season. At the same time, in most situations of partial or reduced LWD sensitivity/resistance, there is no match between the various tests, and only the entire growing season can provide the most reliable results. Tracking the amount of M. maydis DNA in the plants’ bodies is a precise, sensitive scientific tool of great importance for studying the development of the disease and the factors affecting it. Yet, no complete overlap exists between the fungal DNA amount and symptom severity. Such a correlation exists in high sensitivity or resistance cases but not in intermediate situations. Still, the valuation of the pathogen’s establishment in asymptomatic corn hybrids can indicate the degree of LWD immunity and the chance of susceptibility development.
CONTEXT: Maize late wilt disease caused by the fungus Magnaporthiopsis maydis significantly damag... more CONTEXT: Maize late wilt disease caused by the fungus Magnaporthiopsis maydis significantly damages crops in Israel and in other countries. Resistant maize cultivars are the preferred method for restraining the disease. However, the pathogen populations of Spain and Egypt have varying aggressiveness, and virulent strains can overcome host resistance. In 2001 and from 2016-2019, 17 M. maydis strains were isolated from infected maize fields in Israel. OBJECTIVE: The current study characterized the difference in virulence among those isolates. METHODS: The isolates' effects on seed germination, plant development, and severity of disease symptoms were evaluated. RESULTS AND CONCLUSIONS: The isolates from Israel display a diverse degree of aggressiveness that is not linked to their geographic distribution. The virulent strains are found in mixed populations, whereas less virulent M. maydis isolates exist. Aggressive strains harmed the development of plants and ears and caused severe wilting and death. In contrast, plants inoculated with less virulent strains exhibited only mild dehydration signs, and crop yield was similar to that of the non-infected control. Interestingly, different host cultivars can evoke specific virulence of M. maydis strains. Moreover, some pathogen strains significantly repress plant development, while the impact of other strains was evidenced by wilting symptoms. SIGNIFICANCE: The current research further increases our understanding of the pathogen and our ability to control it.
6-pentyl-α-pyrone (6-PP) is a powerful Magnaporthiopsis maydis antifungal compound, recently disc... more 6-pentyl-α-pyrone (6-PP) is a powerful Magnaporthiopsis maydis antifungal compound, recently discovered when the potent growth medium of Trichoderma asperellum was analyzed. Despite its high potential in plate assay, it was not inspected for plant treatment prevention. Late wilt disease, caused by the fungus M. maydis, threatens commercial maize production in high-risk areas. Thus, the search for control options against the pathogen is one of the top priorities in Israel, Egypt, and other countries. Disease-resistant maize genotypes can reduce the damages. Yet, aggressive variants of the fungus can overcome host resistance. The current study aimed at inspecting T. asperellum and its secreted metabolite, pure 6-PP, against the pathogen in plants over a full growth period. First, adding T. asperellum directly to seeds with sowing provides significant protection to sprouts (up to 42 days) in a growth room, with more than two-fold growth promotion and reduced pathogen root infection (detected by real-time PCR). The same procedure applied in a commercial field was less beneficial in rescuing the plants’ growth and yield. Still, it reduced the cobs’ symptoms by 11% and resulted in nine-fold lower levels of the pathogen’s DNA in the stem tissue. Second, the T. asperellum purified 6-PP compound (30 µg/seed) was used in seed coating and tested against the T. asperellum secretory metabolites’ crude (diluted to 50%). At the season’s end, these treatments improved plant biomass by 90–120% and cob weight by 60%. Moreover, the treatments significantly (p < 0.05) reduced the symptoms (up to 20%) and pathogen infection (94–98%). The current study’s results reveal the potential of 6-PP as a new fungicide against M. maydis. Such a treatment may protect maize plants from other soil diseases.
In recent years, worldwide scientific efforts towards controlling maize late wilt disease (LWD) h... more In recent years, worldwide scientific efforts towards controlling maize late wilt disease (LWD) have focused on eco-friendly approaches that minimize the environmental impact and health risks. This disease is considered to be the most severe threat to maize fields in Israel and Egypt, and a major growth restraint in India, Spain, and Portugal. Today’s most commonly used method for LWD control involving resistant maize genotypes is under constant risk from aggressive pathogen lines. Thus, this study’s objectives were to evaluate the effect of crop rotation and avoiding tillage on restraining the disease. Such an agrotechnical approach will support the continuity of soil mycorrhiza networks, which antagonize the disease’s causal agent, Magnaporthiopsis maydis. The method gained positive results in previous studies, but many knowledge gaps still need to be addressed. To this end, a dual-season study was conducted using the LWD hyper-susceptible maize hybrid, Megaton cv. The trials were performed in a greenhouse and in the field over full dual-growth seasons (wheat or clover as the winter crop followed by maize as the summer crop). In the greenhouse under LWD stress, the results clearly demonstrate the beneficial effect of maize crop rotation with clover and wheat on plant weight (1.4-fold), height (1.1–1.2-fold) and cob yield (1.8–2.4-fold), especially in the no-till soil. The clover-maize growth sequence excels in reducing disease impact (1.7-fold) and pathogen spread in the host tissues (3-fold). Even though the wheat-maize crop cycle was less effective, it still had better results than the commercial mycorrhizal preparation treatment and the uncultivated non-infected soil. The results were slightly different in the field. The clover-maize rotation also achieved the best growth promotion and disease restraint results (2.6-fold increase in healthy plants), but the maize rotation with wheat showed only minor efficiency. Interestingly, pre-cultivating the soil with clover had better results in no-till soil in both experiments. In contrast, the same procedure with wheat had a better impact when tillage was applied. It may be concluded that crop rotation and soil cultivation can be essential in reducing LWD, but other factors may affect this approach’s benefits in commercial field growth.
Late wilt is a destructive disease of corn: outbreaks occur at the advanced growth stage and lead... more Late wilt is a destructive disease of corn: outbreaks occur at the advanced growth stage and lead to severe dehydration of susceptible hybrids. The disease’s causal agent is the fungus Magnaporthiopsis maydis, whose spread relies on infested soils, seeds, and several alternative hosts. The current study aimed at advancing our understanding of the nature of this plant disease and revealing new ways to monitor and control it. Two field experiments were conducted in a heavily infested area in northern Israel seeded with highly sensitive corn hybrid. The first experiment aimed at inspecting the Azoxystrobin (AS) fungicide applied by spraying during and after the land tillage. Unexpectedly, the disease symptoms in this field were minor and yields were high. Nevertheless, up to 100% presence of the pathogen within the plant’s tissues was measured using the quantitative real-time PCR method. The highest AS concentration tested was the most effective treatment, and resulted in a 6% increase...
The soil fungus Macrophomina phaseolina, the charcoal rot disease agent, poses a major threat to ... more The soil fungus Macrophomina phaseolina, the charcoal rot disease agent, poses a major threat to cotton fields. In Israel, highly infected areas are also inhabited by the maize pathogen Magnaporthiopsis maydis. This study reveals the relationships between the two pathogens and their impact on cotton sprouts. Infecting the soil 14 days before sowing (DBS) with each pathogen or with M. phaseolina before M. maydis caused a strong inhibition (up to 50-65%) of the sprouts' development and survival, accompanied by each pathogen's high DNA levels in the plants. However, combined or sequence infection with M. maydis first led to two distinct scenarios. This pathogen acted as a beneficial protective endophyte in one experiment, leading to significantly high emergence and growth indices of the plants and a ca. 10-fold reduction in M. phaseolina DNA in the sprouts' roots. In contrast, M. maydis showed strong virulence potential (with 43-69% growth and survival suppression) in the other experiment, proving its true nature as an opportunist. Interestingly, soil inoculation with M. phaseolina first, 14 DBS (but not at sowing), shielded the plants from M. maydis' devastating impact. The results suggest that the two pathogens restrict each other, and this equilibrium may lead to a moderate disease burst.
ABSTRACT Cutinases and pectinases, that enable the penetration of pathogenic fungi into the inner... more ABSTRACT Cutinases and pectinases, that enable the penetration of pathogenic fungi into the inner layers of the host plants, may act as a bio-agents to scour the outer layer of the cotton fabric cuticle. This research examined the production and purification of the extracellular cutinase from the phytopathogenic fungus Fusarium oxysporum and its potential use for this purpose. Addition of apple cutin, its constituents or 1-hexadecanol to the fungus growth medium resulted in an enhanced secretion of cutinase into the extracellular fluid. The crude enzyme was purified and assayed using a new synthesized substrate, 4-nitrophenyl (16-methyl sulfide ester) hexadecanoate that proved to be highly specific and could substitute traditional methods employing radioactive labeled cutin. A novel technique based on the use of the protein cellulose-binding domain fused to glucoronidase (CBD-GUS) enabled an accurate determination of the extent of wax removal by cutinase. An increase in the levels of the CBD-GUS bound to the exposed cellulose correlated with an increase in the fabric’s hydrophilicity and weight loss. The major constituents released from the fabric were analyzed using ELSD-HPLC and GC-MS and found to contain 16:0 and 18:0 fatty acid chains.
Late wilt, a severe vascular disease of maize caused by the fungus Harpophora maydis, is characte... more Late wilt, a severe vascular disease of maize caused by the fungus Harpophora maydis, is characte-rized by relatively rapid wilting of maize plants before tasseling and until shortly before maturity. In Egypt and Israel, the disease is considered to be a major problem. The pathogen is currently controlled using cultivars of maize having reduced sensitivity, but the fungi can undergo patho-genic variations and become a threat to resistance cultivars as well. The abiotic and biotic factors influencing the infection and disease development are not fully determined. To impose stress in a uniform and chronic manner, we expose the Israeli H. maydis isolates colonies or spores to light, different pH, ionic and hyperosmotic pressures (induced with KCl or sorbitol) or oxygen-related stresses (induced with oxygen enrichment, menadione or peroxide). The optimum pH for both hyphal development and spore germination was pH = 5- 6, similar to reports for the Egyptian, In-dian and Hungarian isolate...
Control of maize late wilt disease (LWD) has been at the forefront of research efforts since the ... more Control of maize late wilt disease (LWD) has been at the forefront of research efforts since the discovery of the disease in the 1960s. The disease has become a major economic restraint in highly affected areas such as Egypt and Israel, and is of constant concern in other counties. LWD causes dehydration and collapsing at a late stage of maize cultivation, starting from the male flowering phase. The disease causal agent, Magnaporthiopsis maydis, is a seed- and soil-borne phytoparasitic fungus, penetrating the roots at sprouting, colonizing the vascular system without external symptoms, and spreading upwards in the xylem, eventually blocking the water supply to the plant’s upperparts. Nowadays, the disease’s control relies mostly on identifying and developing resistant maize cultivars. Still, host resistance can be limited because M. maydis undergoes pathogenic variations, and virulent strains can eventually overcome the host immunity. This alarming status is driving researchers to continue to seek other control methods. The current review will summarize the various strategies tested over the years to minimize the disease damage. These options include agricultural (crop rotation, cover crop, no-till, flooding the land before sowing, and balanced soil fertility), physical (solar heating), allelochemical, biological, and chemical interventions. Some of these methods have shown promising success, while others have contributed to our understanding of the disease development and the environmental and host-related factors that have shaped its outcome. The most updated global knowledge about LWD control will be presented, and knowledge gaps and future aims will be discussed.
Late wilt (LWD) is a vascular wilt disease that outbursts late in maize development, usually duri... more Late wilt (LWD) is a vascular wilt disease that outbursts late in maize development, usually during or after flowering. The disease causal agent, the soil and seed-borne fungi, Magnaporthiopsis maydis, causes significant economic losses in Egypt, Israel, Spain, Portugal, and India. Since its discovery in the early 1960s in Egypt, the knowledge base of the disease was significantly expanded. This includes basic information on the pathogen and its mode of action, disease symptoms and damages, methods to study and monitor the pathogen, and above all, control strategies to restrain M. maydis and reduce its impact on commercial maize production. Three approaches stand out from the various control methods inspected. First, the traditional use of chemical pesticides was investigated extensively. This approach gained attention when, in 2018-2020, a feasible and economical treatment based on Azoxystrobin (alone or in combination with other fungicides) was proven to be effective even in severe cases of LWD. Second, the growing trend of replacing chemical treatments with eco-friendly biological and other green protocols has become increasingly important in recent years and has already made significant achievements. Last but not least, today's leading strategy to cope with LWD is to rely on resistant maize genotypes. The past two decades' introduction of molecular-based diagnostic methods to track and identify the pathogen marked significant progress in this global effort. Still, worldwide research efforts are progressing relatively slowly since the disease is considered exotic and unfamiliar in most parts of the world. The current review summarizes the accumulated knowledge on LWD, its causal agent, and the disease implications. An additional important aspect that will be addressed is a future perspective on risks and knowledge gaps.
Soil-borne diseases in field crops pose a significant threat to crop yield. Early detection is es... more Soil-borne diseases in field crops pose a significant threat to crop yield. Early detection is essential for applying agro-technical solutions and deterrence material, and reducing the number of treatments in disease-free areas. Remote sensing tools were developed for the early detection of late wilt disease (LWD) and white mould (WM) caused by the pathogen Magnaporthiopsis maydis and Sclerotium Rolfsii, respectively. Agricultural fields with a history of infection with LWD and WM were selected. Thermal and visible light aerial imagery were obtained using unmanned aerial vehicles. Remotely sensed findings were validated with ground monitoring. The thermal sensor detected the onset of disease even before it could be traced by visible light. Both visible and thermal imaging were effective in detecting LWD and WM and matched the dehydration symptoms and sclerotia detected in-situ. Early detection of diseases may reduce pesticide application, and increase crop yield, thus achieving environmental and commercial advantages.
The fungus Magnaporthiopsis maydis causes severe damage to sensitive maize hybrids throughout Egy... more The fungus Magnaporthiopsis maydis causes severe damage to sensitive maize hybrids throughout Egypt, Israel, India, Spain, and other countries. Maize, Lupine, and cotton are the only known hosts of M. maydis. Identification of new plant hosts that can assist in the survival of the pathogen is an essential step in restricting disease outbreak and spread. Here, by field survey and growth chamber pathogenicity test, accompanied by real-time PCR analysis, the presence of the fungal DNA inside the roots of cotton plants was confirmed in infested soil. Moreover, we identified M. maydis in green foxtail and watermelon. Infected watermelon sprouts had delayed emergence and development, were shorter, and had reduced root and shoot biomass. M. maydis infection also affected root biomass and phenological development of cotton plants but caused only mild symptoms in green foxtail. No M. maydis DNA was detected in barley, and the plants showed no disease symptoms except for reduced shoot weight.
Magnaporthiopsis maydis is a maize pathogen that causes severe damage to commercial corn fields i... more Magnaporthiopsis maydis is a maize pathogen that causes severe damage to commercial corn fields in the late growth stages. Late wilt disease (LWD) has spread since its discovery in the 1960s in Egypt and is now reported in about 10 countries. The pathogen has a hidden endophytic lifecycle in resistant corn plants and secondary hosts such as green foxtail, watermelon lupin and cotton. At the same time, it could be an opportunist and hinder the host development under the right conditions. This study uncovered M. maydis interactions with newly identified maize endophytes. To this end, six fungi were isolated from the seeds of three sweet corn cultivars having varying susceptibility to LWD. These isolates were identified using colony morphology and microscopic characterization, universal internal transcribed spacer (ITS) molecular targeting and phylogenetic analysis. Most of them belonged to pathogenic species. Compared to three previously identified bioprotective microorganisms, the new species were tested for their ability to secrete metabolites that repress M. maydis in vitro and to antagonize it in a solid media confront test and a seedlings pathogenicity assay. The opportunistic fungal species Aspergillus flavus (ME1), Aspergillus terreus (PE3) and the reference biocontrol bacteria Bacillus subtilis (R2) achieved the highest M. maydis inhibition degree in the plates tests (74-100% inhibition). The seedlings’ pathogenicity assay that predicts the seeds’ microflora resistance to M. maydis highlighted the bio-shielding potential of most species (23% or more epicotyl elongation over the infected control). Fusarium sp. (ME2) was the leading species in this measure (43% enhancement), and B. subtilis gave the best protection in terms of seeds’ germination (50%) and sprouts’ biomass (34%). The results of this study could enhance our understanding of the pathobiome’s role in the context of LWD and represent a first step in using the seeds’ natural protective microflora to develop novel management strategies.
This article is an open access article distributed under the terms and conditions of the Creative... more This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY
Charcoal rot disease (CRD), caused by the phytopathogenic fungus Macrophomina phaseolina, is a si... more Charcoal rot disease (CRD), caused by the phytopathogenic fungus Macrophomina phaseolina, is a significant threat to cotton production in Israel and worldwide. The pathogen secretes toxins and degrading enzymes that disrupt the water and nutrient uptake, leading to death at the late stages of growth. While many control strategies were tested over the years to reduce CRD impact, reaching that goal remains a significant challenge. The current study aimed to establish, improve, and deepen our understanding of a new approach combining biological agents and chemical pesticides. Such intervention relies on reducing fungicides while providing stability and a head start to eco-friendly bio-protective Trichoderma species. The research design included sprouts in a growth room and commercial field plants receiving the same treatments. Under a controlled environment, comparing the bio-based coating treatments with their corresponding chemical coating partners resulted in similar outcomes in most measures. At 52 days, these practices gained up to 38% and 45% higher root and shoot weight and up to 78% decreased pathogen root infection (tracked by Real-Time PCR), compared to non-infected control plants. Yet, in the shoot weight assessment (day 29 post-sowing), the treatment with only biological seed coating outperformed (p < 0.05) all other biological-based treatments and all Azoxystrobin-based irrigation treatments. In contrast, adverse effects are observed in the chemical seed coating group, particularly in above ground plant parts, which are attributable to the addition of Azoxystrobin irrigation. In the field, the biological treatments had the same impact as the chemical intervention, increasing the cotton plants’ yield (up to 17%), improving the health (up to 27%) and reducing M. phaseolina DNA in the roots (up to 37%). When considering all treatments within each approach, a significant benefit to plant health was observed with the bio-chemo integrated management compared to using only chemical interventions. Specific integrated treatments have shown potential in reducing CRD symptoms, such as applying bio-coating and sprinkling Azoxystrobin during sowing. Aerial remote sensing based on high-resolution visible-channel (RGB), green–red vegetation index (GRVI), and thermal imaging supported the above findings and proved its value for studying CRD control management. This research validates the combined biological and chemical intervention potential to shield cotton crops from CRD.
Fusarium basal rot disease (FBR) is a destructive threat to onion crops around the globe. It caus... more Fusarium basal rot disease (FBR) is a destructive threat to onion crops around the globe. It causes seedlings’ death, development disruption, and pre- and post-harvest bulb infection and rotting, with a concern for toxin infestation. It is an emerging disease in Israel, with new reports from farms nationwide. Recently, we reported on a full-season pot experiment to protect two leading commercial cultivars against FBR chemically. Here, we present new real-time qPCR molecular tracking of the pathogens inside the host plant and compare the infection levels to a deep analysis of the impacts of this experiment’s treatments on plant growth and health indexes. The new findings reveal variations within each treatment’s effectiveness regarding sprout development and bulb ripening stages. For instance, in the yellow Orlando cv., high protection was obtained with Azoxystrobin + Tebuconazole (Az-Te) in sprouts against F. oxysporum f. sp. cepae and with Fludioxonil + Sedaxen in mature plants against Fusarium acutatum. Thus, combining these fungicides may protect plants throughout their lifecycle. Also, Prochloraz at low dose was highly efficient in the Orlando cv. Still, to shield red Noam cv. plants from both pathogens, increasing this fungicide concentration towards the season-ending should be preferred. The qPCR tracking showed that all chemical treatments tested could reduce infection from pathogens by 80–90%, even with compounds such as Az-Te that were less effective. This implies that the pesticide was effective but probably phytotoxic to the plants, and thus, lower dosages must be considered. The molecular-based analysis discloses the high infection ability of F. oxysporum f. sp. cepae compared to F. acutatum in both cultivars. It also indicates an antagonism between those species in the Orlando cv. and synergism in the Noam cv. The current work reveals weak and strong points in chemical FBR protection and offers new ways to improve its application. The qPCR-based method enables us to closely monitor the pathogenesis and efficacy of chemical-preventing treatments and optimize crop-protection protocols.
Fusarium basal rot disease (FBR) is considered a serious threat to commercial onion production in... more Fusarium basal rot disease (FBR) is considered a serious threat to commercial onion production in Israel and worldwide. Today, coping means applied in Israel against the disease have limited efficiency and include a four-year crop cycle and disinfecting the soil with metam sodium. At the same time, agricultural tools (harrows, plows, etc.), contaminated equipment and workers facilitate spread of the disease to new growth areas, and the field disease incidence in Israel now reaches 8% of yields in heavily infected areas. Infected onions do not always show disease symptoms and the problem worsens if they arrive at storage facilities, especially since this pathogen genus produces known toxins. The current study aims at examining the potential of chemical control to reduce the damage caused by this disease. To this end, nine commercial fungicides were scanned in plate sensitivity assay against the main pathogens involved, Fusarium oxysporum f. sp. cepae and Fusarium acutatum. Several fungicides were found to be highly effective against the two pathogens, especially the mixtures Azoxystrobin + Difenoconazole, Fluopyram + Trifloxystrobin, or the Fluazinam compounds. Three selected preparations previously tested in seedlings were evaluated here in a full growing season. Prochloraz successfully protected the Orlando variety (white onion, Riverside cv.) and the Noam variety (red onion) at all growth stages against F. oxysporum f. sp. cepae. At the same time, this treatment was ineffective against F. acutatum in Noam cv. Another anti-fungal preparation, Fludioxonil + Sedaxen mixture, showed a wider range of effectiveness at the season’s end against the two Fusarium species tested in both onion cultivars. These results are an important step towards developing FBR control in commercial onion fields. Follow-up work is needed to optimize the pesticides’ concentrations and their application methods and to test them on a field scale. Interestingly, these pathogens were more aggressive towards the cultivar from which they were isolated: F. oxysporum f. sp. cepae to the red onion Noam cv. and F. acutatum to the white Orlando cv. Infecting the plants with both pathogens reduced disease symptoms in the white Orlando cv, suggesting antagonistic interactions in this onion genotype.
The fungus Macrophomina phaseolina causes charcoal rot disease (CRD) in cotton, whose symptoms de... more The fungus Macrophomina phaseolina causes charcoal rot disease (CRD) in cotton, whose symptoms develop in the late stages of growth and result in wilting and death. Despite significant research efforts to reduce disease incidences, effective control strategies against M. phaseolina are an ongoing scientific effort. Today’s CRD control tends toward green options to reduce the chemicals’ environmental footprint and health risks. Here, different Trichoderma species were examined separately and in combination with Azoxystrobin (AS) in semi-field open-enclosure pots and a commercial field throughout a full season. In the pot experiment, the T. asperellum (P1) excelled and led to improvement in growth (13%–14%, day 69) and crops (the number of capsules by 36% and their weight by 78%, day 173). The chemical treatment alone at a low dose had no significant impact. Still, adding AS improved the effect of T. longibrachiatum (T7507) and impaired P1 efficiency. Real-time PCR monitoring of the pathogen DNA in the plants’ roots at the harvest (day 176), revealed the efficiency of the combined treatments: T. longibrachiatum (T7407 and T7507) + AS. In a commercial field, seed dressing with a mixture of Trichoderma species (mix of P1, T7407, and Trichoderma sp. O.Y. 7107 isolate) and irrigation of their secreted metabolites during seeding resulted in the highest yields compared with the control. Applying only AS irrigation at a low dose (2,000 cc/ha), with the sowing, was the second best in promoting crops. The molecular M. phaseolina detection showed that the AS at a high dose (4,000 cc/ha) and the biological mix treatments were the most effective. Reducing the AS chemical treatment dosages by half impaired its effectiveness. Irrigation timing, also studied here, is proven vital. Early water opening during the late spring suppresses the disease outburst and damages. The results demonstrated the benefits of CRD bio-shielding and encouraged to explore the potential of a combined bio-chemo pest control approach. Such interphase can be environmentally friendly (reducing chemical substances), stabilize the biological treatment in changing environmental conditions, achieve high efficiency even in severe CRD cases, and reduce the development of fungicide resistance.
Today’s fungal plant disease control efforts tend towards environmentally friendly and reduced ch... more Today’s fungal plant disease control efforts tend towards environmentally friendly and reduced chemical applications. While traditional broad-spectrum fungicides provide efficient protection to many field crops, they pose a risk to the soil’s beneficial microflora and a potential health hazard. Moreover, their intensive use often evokes the appearance of resistant pathogens. On the other hand, biocontrol agents such as Trichoderma spp. provide a green solution but often cannot shield the plants from aggressive disease outbreaks. Integrated biological and chemical disease control can combine the benefits of both methods while reducing their drawbacks. In the current study, such a bio-chemo approach was developed and evaluated for the first time against the maize late wilt pathogen, Magnaporthiopsis maydis. Combinations of four Trichoderma species and Azoxystrobin were tested, starting with an in vitro seed assay, then a growth room sprouts trial, and finally a semi-field, full-season pot experiment. In the plates assay, all four Trichoderma species, Trichoderma sp. O.Y. (T14707), T. longibrachiatum (T7407), T. asperellum (P1) and T. asperelloides (T203), grew (but with some delay) in the presence of Azoxystrobin minimal inhibition concentration (0.005 mg/L). The latter two species provided high protection to sprouts in the growth room and to potted plants throughout a full season in a semi-field open-enclosure trial. At harvest, the P1 and T203 bio-shielding exhibited the best parameters (statistically significant) in plant growth promotion, yield increase and late wilt protection (up to 29% health recovery and 94% pathogen suppression tracked by real-time PCR). When applied alone, the Azoxystrobin treatment provided minor (insignificant) protection. Adding this fungicide to Trichoderma spp. resulted in similar (statistically equal) results to their sole application. Still, the fact that Azoxystrobin is harmless to the beneficial Trichoderma species over a complete semi-field condition is a great opening stage for carrying out follow-up studies validating the integrated control in a commercial field situation challenged with acute disease stress.
The charcoal rot (CRD) disease agent, the soil fungus Macrophomina phaseolina, survives by develo... more The charcoal rot (CRD) disease agent, the soil fungus Macrophomina phaseolina, survives by developing reproductive units (spores and pycnidia) and infects various host plants. In cotton plants, the disease can lead to dehydration and death of the host plant at late-season stages. Pima cv. cotton plants, the leading cotton crop in Israel, are particularly susceptible to this disease. Developing biological pesticides against soil diseases is at the forefront of scientific research globally and their importance is increasing due to the world's trend towards a reduction in the use of chemical fungicides. In this work, eight Trichoderma isolates were tested under laboratory conditions against M. phaseolina. Two T. longibrachiatum isolates (T7507 and T7407) and a T. asperellum isolate (P1) achieved promising results. The bioprotective properties of these isolates' secreted metabolites were evaluated in solid and liquid cultures. The T7407 strain was the most influential in the solid medium with 55% inhibition capacity; the P1 strain excelled in the liquid medium with 62% inhibition capacity. The three M. phaseolina isolates were then tested in seedlings (up to 42 days) against controls: non-infected plants, infected unshielded plants, and plants treated with non-influencing Trichoderma isolate (O.Y. 14707). The bio-shielding agents were added directly to the seeds with the sowing in this growth room pathogenicity assay. At the experiment's end, the T. longibrachiatum (T7407) treatment markedly improved the plants' wet weight (45%), height (32%) and phenological development (56%) compared to the non-influencing Trichoderma species control. Since the disease is commonly latent in sprouts, statistical differences in the plants' growth parameters are challenging to reach, as occurred here. Still, the real-time PCR tracking of the pathogen DNA inside the plants' roots revealed dramatic changes. The pathogen DNA dropped to nearzero levels in the T. longibrachiatum-and T. asperellum-treated plants. Interestingly, the O.Y. 14707 isolate, which showed no bioprotective properties in the lab tests or plants' growth indices, had a similar significant repression impact on the pathogen roots infection. The results of this work demonstrate the importance of the early molecular assessment of preventive treatment effectiveness against M. phaseolina before a full growing season evaluation.
Magnaporthiopsis maydis late wilt disease (LWD) in corn is considered to be the most severe in Is... more Magnaporthiopsis maydis late wilt disease (LWD) in corn is considered to be the most severe in Israel and Egypt and poses a significant threat in other countries. Research efforts extending over a period of five decades led to the development of chemical, biological, agrotechnical, physical (solar disinfection) and other means for controlling late wilt disease. Today, some applications can reduce damage even in severe cases. However, cultivating disease-resistant maize varieties is the primary means for reducing the disease’s impact. The current work uses a rapid (six days) laboratory seedling pathogenicity test and a full-season open encloser semi-field conditioned pots assay (101 days) to classify maize varieties according to their LWD resistance. To better evaluate differences between the cultivars, a real-time based molecular assay was applied to track the pathogen’s presence in the plants’ tissues, and visible light aerial imaging was used in parallel. The findings show that in cases of extreme sensitivity or tolerance (for example, in the highly susceptible Megaton cultivar (cv.) or the resistant Hatai cv.), a similarity in the results exists between the different methods. Thus, a reliable estimate of the varieties’ sensitivity can be obtained in a seed assay without the need for a test carried out throughout an entire growing season. At the same time, in most situations of partial or reduced LWD sensitivity/resistance, there is no match between the various tests, and only the entire growing season can provide the most reliable results. Tracking the amount of M. maydis DNA in the plants’ bodies is a precise, sensitive scientific tool of great importance for studying the development of the disease and the factors affecting it. Yet, no complete overlap exists between the fungal DNA amount and symptom severity. Such a correlation exists in high sensitivity or resistance cases but not in intermediate situations. Still, the valuation of the pathogen’s establishment in asymptomatic corn hybrids can indicate the degree of LWD immunity and the chance of susceptibility development.
CONTEXT: Maize late wilt disease caused by the fungus Magnaporthiopsis maydis significantly damag... more CONTEXT: Maize late wilt disease caused by the fungus Magnaporthiopsis maydis significantly damages crops in Israel and in other countries. Resistant maize cultivars are the preferred method for restraining the disease. However, the pathogen populations of Spain and Egypt have varying aggressiveness, and virulent strains can overcome host resistance. In 2001 and from 2016-2019, 17 M. maydis strains were isolated from infected maize fields in Israel. OBJECTIVE: The current study characterized the difference in virulence among those isolates. METHODS: The isolates' effects on seed germination, plant development, and severity of disease symptoms were evaluated. RESULTS AND CONCLUSIONS: The isolates from Israel display a diverse degree of aggressiveness that is not linked to their geographic distribution. The virulent strains are found in mixed populations, whereas less virulent M. maydis isolates exist. Aggressive strains harmed the development of plants and ears and caused severe wilting and death. In contrast, plants inoculated with less virulent strains exhibited only mild dehydration signs, and crop yield was similar to that of the non-infected control. Interestingly, different host cultivars can evoke specific virulence of M. maydis strains. Moreover, some pathogen strains significantly repress plant development, while the impact of other strains was evidenced by wilting symptoms. SIGNIFICANCE: The current research further increases our understanding of the pathogen and our ability to control it.
6-pentyl-α-pyrone (6-PP) is a powerful Magnaporthiopsis maydis antifungal compound, recently disc... more 6-pentyl-α-pyrone (6-PP) is a powerful Magnaporthiopsis maydis antifungal compound, recently discovered when the potent growth medium of Trichoderma asperellum was analyzed. Despite its high potential in plate assay, it was not inspected for plant treatment prevention. Late wilt disease, caused by the fungus M. maydis, threatens commercial maize production in high-risk areas. Thus, the search for control options against the pathogen is one of the top priorities in Israel, Egypt, and other countries. Disease-resistant maize genotypes can reduce the damages. Yet, aggressive variants of the fungus can overcome host resistance. The current study aimed at inspecting T. asperellum and its secreted metabolite, pure 6-PP, against the pathogen in plants over a full growth period. First, adding T. asperellum directly to seeds with sowing provides significant protection to sprouts (up to 42 days) in a growth room, with more than two-fold growth promotion and reduced pathogen root infection (detected by real-time PCR). The same procedure applied in a commercial field was less beneficial in rescuing the plants’ growth and yield. Still, it reduced the cobs’ symptoms by 11% and resulted in nine-fold lower levels of the pathogen’s DNA in the stem tissue. Second, the T. asperellum purified 6-PP compound (30 µg/seed) was used in seed coating and tested against the T. asperellum secretory metabolites’ crude (diluted to 50%). At the season’s end, these treatments improved plant biomass by 90–120% and cob weight by 60%. Moreover, the treatments significantly (p < 0.05) reduced the symptoms (up to 20%) and pathogen infection (94–98%). The current study’s results reveal the potential of 6-PP as a new fungicide against M. maydis. Such a treatment may protect maize plants from other soil diseases.
In recent years, worldwide scientific efforts towards controlling maize late wilt disease (LWD) h... more In recent years, worldwide scientific efforts towards controlling maize late wilt disease (LWD) have focused on eco-friendly approaches that minimize the environmental impact and health risks. This disease is considered to be the most severe threat to maize fields in Israel and Egypt, and a major growth restraint in India, Spain, and Portugal. Today’s most commonly used method for LWD control involving resistant maize genotypes is under constant risk from aggressive pathogen lines. Thus, this study’s objectives were to evaluate the effect of crop rotation and avoiding tillage on restraining the disease. Such an agrotechnical approach will support the continuity of soil mycorrhiza networks, which antagonize the disease’s causal agent, Magnaporthiopsis maydis. The method gained positive results in previous studies, but many knowledge gaps still need to be addressed. To this end, a dual-season study was conducted using the LWD hyper-susceptible maize hybrid, Megaton cv. The trials were performed in a greenhouse and in the field over full dual-growth seasons (wheat or clover as the winter crop followed by maize as the summer crop). In the greenhouse under LWD stress, the results clearly demonstrate the beneficial effect of maize crop rotation with clover and wheat on plant weight (1.4-fold), height (1.1–1.2-fold) and cob yield (1.8–2.4-fold), especially in the no-till soil. The clover-maize growth sequence excels in reducing disease impact (1.7-fold) and pathogen spread in the host tissues (3-fold). Even though the wheat-maize crop cycle was less effective, it still had better results than the commercial mycorrhizal preparation treatment and the uncultivated non-infected soil. The results were slightly different in the field. The clover-maize rotation also achieved the best growth promotion and disease restraint results (2.6-fold increase in healthy plants), but the maize rotation with wheat showed only minor efficiency. Interestingly, pre-cultivating the soil with clover had better results in no-till soil in both experiments. In contrast, the same procedure with wheat had a better impact when tillage was applied. It may be concluded that crop rotation and soil cultivation can be essential in reducing LWD, but other factors may affect this approach’s benefits in commercial field growth.
Late wilt is a destructive disease of corn: outbreaks occur at the advanced growth stage and lead... more Late wilt is a destructive disease of corn: outbreaks occur at the advanced growth stage and lead to severe dehydration of susceptible hybrids. The disease’s causal agent is the fungus Magnaporthiopsis maydis, whose spread relies on infested soils, seeds, and several alternative hosts. The current study aimed at advancing our understanding of the nature of this plant disease and revealing new ways to monitor and control it. Two field experiments were conducted in a heavily infested area in northern Israel seeded with highly sensitive corn hybrid. The first experiment aimed at inspecting the Azoxystrobin (AS) fungicide applied by spraying during and after the land tillage. Unexpectedly, the disease symptoms in this field were minor and yields were high. Nevertheless, up to 100% presence of the pathogen within the plant’s tissues was measured using the quantitative real-time PCR method. The highest AS concentration tested was the most effective treatment, and resulted in a 6% increase...
The soil fungus Macrophomina phaseolina, the charcoal rot disease agent, poses a major threat to ... more The soil fungus Macrophomina phaseolina, the charcoal rot disease agent, poses a major threat to cotton fields. In Israel, highly infected areas are also inhabited by the maize pathogen Magnaporthiopsis maydis. This study reveals the relationships between the two pathogens and their impact on cotton sprouts. Infecting the soil 14 days before sowing (DBS) with each pathogen or with M. phaseolina before M. maydis caused a strong inhibition (up to 50-65%) of the sprouts' development and survival, accompanied by each pathogen's high DNA levels in the plants. However, combined or sequence infection with M. maydis first led to two distinct scenarios. This pathogen acted as a beneficial protective endophyte in one experiment, leading to significantly high emergence and growth indices of the plants and a ca. 10-fold reduction in M. phaseolina DNA in the sprouts' roots. In contrast, M. maydis showed strong virulence potential (with 43-69% growth and survival suppression) in the other experiment, proving its true nature as an opportunist. Interestingly, soil inoculation with M. phaseolina first, 14 DBS (but not at sowing), shielded the plants from M. maydis' devastating impact. The results suggest that the two pathogens restrict each other, and this equilibrium may lead to a moderate disease burst.
ABSTRACT Cutinases and pectinases, that enable the penetration of pathogenic fungi into the inner... more ABSTRACT Cutinases and pectinases, that enable the penetration of pathogenic fungi into the inner layers of the host plants, may act as a bio-agents to scour the outer layer of the cotton fabric cuticle. This research examined the production and purification of the extracellular cutinase from the phytopathogenic fungus Fusarium oxysporum and its potential use for this purpose. Addition of apple cutin, its constituents or 1-hexadecanol to the fungus growth medium resulted in an enhanced secretion of cutinase into the extracellular fluid. The crude enzyme was purified and assayed using a new synthesized substrate, 4-nitrophenyl (16-methyl sulfide ester) hexadecanoate that proved to be highly specific and could substitute traditional methods employing radioactive labeled cutin. A novel technique based on the use of the protein cellulose-binding domain fused to glucoronidase (CBD-GUS) enabled an accurate determination of the extent of wax removal by cutinase. An increase in the levels of the CBD-GUS bound to the exposed cellulose correlated with an increase in the fabric’s hydrophilicity and weight loss. The major constituents released from the fabric were analyzed using ELSD-HPLC and GC-MS and found to contain 16:0 and 18:0 fatty acid chains.
Late wilt, a severe vascular disease of maize caused by the fungus Harpophora maydis, is characte... more Late wilt, a severe vascular disease of maize caused by the fungus Harpophora maydis, is characte-rized by relatively rapid wilting of maize plants before tasseling and until shortly before maturity. In Egypt and Israel, the disease is considered to be a major problem. The pathogen is currently controlled using cultivars of maize having reduced sensitivity, but the fungi can undergo patho-genic variations and become a threat to resistance cultivars as well. The abiotic and biotic factors influencing the infection and disease development are not fully determined. To impose stress in a uniform and chronic manner, we expose the Israeli H. maydis isolates colonies or spores to light, different pH, ionic and hyperosmotic pressures (induced with KCl or sorbitol) or oxygen-related stresses (induced with oxygen enrichment, menadione or peroxide). The optimum pH for both hyphal development and spore germination was pH = 5- 6, similar to reports for the Egyptian, In-dian and Hungarian isolate...
Control of maize late wilt disease (LWD) has been at the forefront of research efforts since the ... more Control of maize late wilt disease (LWD) has been at the forefront of research efforts since the discovery of the disease in the 1960s. The disease has become a major economic restraint in highly affected areas such as Egypt and Israel, and is of constant concern in other counties. LWD causes dehydration and collapsing at a late stage of maize cultivation, starting from the male flowering phase. The disease causal agent, Magnaporthiopsis maydis, is a seed- and soil-borne phytoparasitic fungus, penetrating the roots at sprouting, colonizing the vascular system without external symptoms, and spreading upwards in the xylem, eventually blocking the water supply to the plant’s upperparts. Nowadays, the disease’s control relies mostly on identifying and developing resistant maize cultivars. Still, host resistance can be limited because M. maydis undergoes pathogenic variations, and virulent strains can eventually overcome the host immunity. This alarming status is driving researchers to continue to seek other control methods. The current review will summarize the various strategies tested over the years to minimize the disease damage. These options include agricultural (crop rotation, cover crop, no-till, flooding the land before sowing, and balanced soil fertility), physical (solar heating), allelochemical, biological, and chemical interventions. Some of these methods have shown promising success, while others have contributed to our understanding of the disease development and the environmental and host-related factors that have shaped its outcome. The most updated global knowledge about LWD control will be presented, and knowledge gaps and future aims will be discussed.
Late wilt (LWD) is a vascular wilt disease that outbursts late in maize development, usually duri... more Late wilt (LWD) is a vascular wilt disease that outbursts late in maize development, usually during or after flowering. The disease causal agent, the soil and seed-borne fungi, Magnaporthiopsis maydis, causes significant economic losses in Egypt, Israel, Spain, Portugal, and India. Since its discovery in the early 1960s in Egypt, the knowledge base of the disease was significantly expanded. This includes basic information on the pathogen and its mode of action, disease symptoms and damages, methods to study and monitor the pathogen, and above all, control strategies to restrain M. maydis and reduce its impact on commercial maize production. Three approaches stand out from the various control methods inspected. First, the traditional use of chemical pesticides was investigated extensively. This approach gained attention when, in 2018-2020, a feasible and economical treatment based on Azoxystrobin (alone or in combination with other fungicides) was proven to be effective even in severe cases of LWD. Second, the growing trend of replacing chemical treatments with eco-friendly biological and other green protocols has become increasingly important in recent years and has already made significant achievements. Last but not least, today's leading strategy to cope with LWD is to rely on resistant maize genotypes. The past two decades' introduction of molecular-based diagnostic methods to track and identify the pathogen marked significant progress in this global effort. Still, worldwide research efforts are progressing relatively slowly since the disease is considered exotic and unfamiliar in most parts of the world. The current review summarizes the accumulated knowledge on LWD, its causal agent, and the disease implications. An additional important aspect that will be addressed is a future perspective on risks and knowledge gaps.
Soil-borne diseases in field crops pose a significant threat to crop yield. Early detection is es... more Soil-borne diseases in field crops pose a significant threat to crop yield. Early detection is essential for applying agro-technical solutions and deterrence material, and reducing the number of treatments in disease-free areas. Remote sensing tools were developed for the early detection of late wilt disease (LWD) and white mould (WM) caused by the pathogen Magnaporthiopsis maydis and Sclerotium Rolfsii, respectively. Agricultural fields with a history of infection with LWD and WM were selected. Thermal and visible light aerial imagery were obtained using unmanned aerial vehicles. Remotely sensed findings were validated with ground monitoring. The thermal sensor detected the onset of disease even before it could be traced by visible light. Both visible and thermal imaging were effective in detecting LWD and WM and matched the dehydration symptoms and sclerotia detected in-situ. Early detection of diseases may reduce pesticide application, and increase crop yield, thus achieving environmental and commercial advantages.
The maize (Zea mays L.) late wilt disease, caused by the fungus Magnaporthiopsis maydis, is consi... more The maize (Zea mays L.) late wilt disease, caused by the fungus Magnaporthiopsis maydis, is considered the most severe threat to commercial maize production in Israel and Egypt. Various control strategies have been inspected over the years. The current scientific effort is focusing on eco-friendly approaches against the disease. The genus Trichoderma, a filamentous soil and plant root-associated fungi, is one of the essential biocontrol species, demonstrating over 60% of all the listed biocontrol agents used to reduce plant infectious diseases. They produce different enzymes and elicit defense responses in plants, playing a significant role in biotic and abiotic stress tolerance, hyphal growth, and plant growth promotion. Trichoderma asperellum was found to have biocontrol ability and protect crops against various plant pathogenic fungi, including the maize late wilt disease causal agent. This research aimed at isolating and identifying T. asperellum secondary metabolites with antifungal action against M. maydis. From T. asperellum growth medium, the 6-Pentyl-α-pyrone secondary metabolite was isolated and identified with high potent antifungal activity against M. maydis. This compound previously exhibited antifungal activities towards several plant pathogenic fungi. Achieving clean and identified T. asperellum active ingredient(s) secreted product(s) is the first step in revealing their commercial potential as new fungicides. Follow-up studies should test this component against the LWD pathogen in potted sprouts and the field.
Economical treatment of maize late wilt disease in the field (article in Hebrew), 2019
Sweet corn, silage and grain crops have been facing the threat of severe corn disease for many ye... more Sweet corn, silage and grain crops have been facing the threat of severe corn disease for many years, spreading to various parts of Israel. Over the past few years, we conducted a series of field experiments, with the assistance of Netafim Israel, growers' associations and farmers from the Galilee region. In 2017-2018, this research led to a historic breakthrough: for the first time, 60 years since its discovery, an economically feasible solution was found for late wilt disease of corn in Israel. The successful treatment protocol is based on changing the cultivation method, changing the traditional irrigation method used in most corn growing areas in Israel, and the sophisticated integration of pesticide mixtures in a schedule adapted to key points in the development of the disease. This method can now be widely applied in commercial fields for the protection of sensitive corn varieties.
Late wilt disease in corn is caused by the fungus Harpophora maydis, which is distributed in the soil and seeds, penetrates the plant and blocks the water supply to its upper parts. The disease, considered to be the most severe corn disease in our region, was first discovered in Egypt in 1960, where it still causes serious damage. The disease is now reported in 11 countries. In Israel, it has existed for 40 years in the Upper Galilee, especially in the Hula Valley, and in the past decade, has spread to the south of the country. In heavily contaminated fields and in sensitive maize cultivars, the pathogen can cause 100% infection and total yield loss. The disease is characterized by rapid wilt of corn, which usually occurs two to three weeks before harvesting. In the past, attempts had been made to control the pathogen using different methods, including agricultural (balanced soil fertility and flood fallowing), chemical, biological, physical (solar heating) and plant compounds. Despite the potential of some of these methods, the only means applied in Israel to date to restrict the disease is the use of resistant corn varieties. However, in Egypt and Spain, virulent pathogen strains that threaten resistance maize cultivars have been found.
The research team led by Dr. Ofir Degani from the Migal - Galilee Research Institute and Tel-Hai College, funded and supported by Netafim Israel, the Consultation Service of the Israel Ministry of Agriculture and Rural Development, and growers' associations has recently led to a breakthrough of historical significance. For the first time, 60 years since the discovery of late wilt disease, an efficient and economically feasible solution has been found that can be used on a large scale to protect sensitive corn varieties in commercial fields.
This solution, published in December 2018 in the leading scientific journal PloS ONE, saves about 40% of irrigation costs and combines antifungal mixtures with different action mechanisms to prevent resistance development. The new application was tested in field trials in 2017-2018 and included the injection of irrigation material at intervals of 15, 30 and 45 days from sowing of the substances Difenoconazole + Azoxystrobin (commercial name Ortiva-Top, manufactured by Syngenta, Basel, Switzerland, supplied by Adama Makhteshim, Airport City, Israel) or other fungicide mixtures. Savings in the deployment of irrigation lines was ensured by using a drip line for two adjacent rows (a row spacing of 50 cm instead of 96 cm), a row space that maintains the effective concentration of the fungicide in the soil. Recently developed real-time PCR-based molecular detection showed that following the treatment of Ortiva-Top, the amount of pathogen DNA in the host tissue decreased to near zero levels. The successful treatments using Ortiva-Top resulted in a 100% decrease in dehydration symptoms and a 100% increase in crop yield, together with an approximately 40% increase in crop quality (the yield classified as A class that had a cob weight exceeding 250 g). These results were also obtained in an alternative protocol – the replacement of pesticides based on Ortiva-Top in the first application and the application of pesticides with a different mechanism of action in the second and third applications. A remote sensing evaluation of the efficacy of the treatments using a quadcopter equipped with a thermal camera carried out by Asaf Chen’s research team (Migal - Galilee Research Institute) supported the results and proved its effectiveness as a research tool for diagnosing infected fields.
These results are the fruits of a decade of research (since 2008) in which a fundamental understanding of the pathogen H. maydis and the generation and development of late wilt disease in Israel was established. During this period, new research methods such as sensitive molecular tests (PCR and qPCR) were developed to diagnose fungal violence and detect the pathogen inside the host plant tissue. In addition, a link was found to plant hormones that regulates the development of the pathogen. Complex field trials that were carried out annually over a full growing season (about 80 days) since 2009 led to this important discovery. However, the work on late wilt disease does not end here. In the past two years, Dr. Degani's research team identified the presence of H. maydis in secondary hosts, such as cotton, watermelon and green foxtail (Setaria viridis), which could assist in the survival of the pathogen, developed an environmentally friendly biological control method to control the pathogen, and established a new bio-assay for examining soils suspected of being infected with the pathogen. These new findings, which are currently in the process of being prepared for scientific publication, are encouraging the continuation and enhancement of the research.
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Late wilt disease in corn is caused by the fungus Harpophora maydis, which is distributed in the soil and seeds, penetrates the plant and blocks the water supply to its upper parts. The disease, considered to be the most severe corn disease in our region, was first discovered in Egypt in 1960, where it still causes serious damage. The disease is now reported in 11 countries. In Israel, it has existed for 40 years in the Upper Galilee, especially in the Hula Valley, and in the past decade, has spread to the south of the country. In heavily contaminated fields and in sensitive maize cultivars, the pathogen can cause 100% infection and total yield loss. The disease is characterized by rapid wilt of corn, which usually occurs two to three weeks before harvesting. In the past, attempts had been made to control the pathogen using different methods, including agricultural (balanced soil fertility and flood fallowing), chemical, biological, physical (solar heating) and plant compounds. Despite the potential of some of these methods, the only means applied in Israel to date to restrict the disease is the use of resistant corn varieties. However, in Egypt and Spain, virulent pathogen strains that threaten resistance maize cultivars have been found.
The research team led by Dr. Ofir Degani from the Migal - Galilee Research Institute and Tel-Hai College, funded and supported by Netafim Israel, the Consultation Service of the Israel Ministry of Agriculture and Rural Development, and growers' associations has recently led to a breakthrough of historical significance. For the first time, 60 years since the discovery of late wilt disease, an efficient and economically feasible solution has been found that can be used on a large scale to protect sensitive corn varieties in commercial fields.
This solution, published in December 2018 in the leading scientific journal PloS ONE, saves about 40% of irrigation costs and combines antifungal mixtures with different action mechanisms to prevent resistance development. The new application was tested in field trials in 2017-2018 and included the injection of irrigation material at intervals of 15, 30 and 45 days from sowing of the substances Difenoconazole + Azoxystrobin (commercial name Ortiva-Top, manufactured by Syngenta, Basel, Switzerland, supplied by Adama Makhteshim, Airport City, Israel) or other fungicide mixtures. Savings in the deployment of irrigation lines was ensured by using a drip line for two adjacent rows (a row spacing of 50 cm instead of 96 cm), a row space that maintains the effective concentration of the fungicide in the soil. Recently developed real-time PCR-based molecular detection showed that following the treatment of Ortiva-Top, the amount of pathogen DNA in the host tissue decreased to near zero levels. The successful treatments using Ortiva-Top resulted in a 100% decrease in dehydration symptoms and a 100% increase in crop yield, together with an approximately 40% increase in crop quality (the yield classified as A class that had a cob weight exceeding 250 g). These results were also obtained in an alternative protocol – the replacement of pesticides based on Ortiva-Top in the first application and the application of pesticides with a different mechanism of action in the second and third applications. A remote sensing evaluation of the efficacy of the treatments using a quadcopter equipped with a thermal camera carried out by Asaf Chen’s research team (Migal - Galilee Research Institute) supported the results and proved its effectiveness as a research tool for diagnosing infected fields.
These results are the fruits of a decade of research (since 2008) in which a fundamental understanding of the pathogen H. maydis and the generation and development of late wilt disease in Israel was established. During this period, new research methods such as sensitive molecular tests (PCR and qPCR) were developed to diagnose fungal violence and detect the pathogen inside the host plant tissue. In addition, a link was found to plant hormones that regulates the development of the pathogen. Complex field trials that were carried out annually over a full growing season (about 80 days) since 2009 led to this important discovery. However, the work on late wilt disease does not end here. In the past two years, Dr. Degani's research team identified the presence of H. maydis in secondary hosts, such as cotton, watermelon and green foxtail (Setaria viridis), which could assist in the survival of the pathogen, developed an environmentally friendly biological control method to control the pathogen, and established a new bio-assay for examining soils suspected of being infected with the pathogen. These new findings, which are currently in the process of being prepared for scientific publication, are encouraging the continuation and enhancement of the research.