Canker symptoms were observed on almond trees in the Fez-Meknes region, Morocco. Isolations were ... more Canker symptoms were observed on almond trees in the Fez-Meknes region, Morocco. Isolations were conducted from the infected branch and trunk showing internal and external brown lesions. Four representative fungal isolates were screened, and their identities were confirmed by cultural traits and sequence analysis of DNA using two genes, the ITS region (internal transcribed spacer) and calmodulin (cmdA). The identified fungi were Curvularia hawaiiensis, Fusarium ambrosium, Lasiodiplodia theobromae, and Chondrestereum purpureum. The pathogenicity test on almond twigs revealed that these species were pathogenic to their host with different degrees of virulence, with Lasiodiplodia theobromae as the most virulent causing the longest necrotic lesion (285.17 mm) and the death of twigs. Physiological traits analysis of the above-mentioned fungi showed that the optimum mycelium growth response at different temperatures varies from 10 to 35 °C, while the pH ranges between 3.0 and 8.0. This st...
This study aimed at evaluating the effect of environmental factors temperature and water potentia... more This study aimed at evaluating the effect of environmental factors temperature and water potential (Ψw) on the growth of Neocosmospora (Fusarium) solani and three Fusarium species (F. oxysporum, F. equiseti and F. brachygibbosum) associated with citrus dry root rot and to determine the optimum and marginal rate for their growth. The effects of incubation temperature (5-40 °C), water potentials (Ψw) (- 15.54; - 0.67 MPa) (0.89-0.995 aw) and their interaction (5-30 °C) was evaluated on the in vitro radial growth rates of Fusarium spp. and on their lag phase. Secondary models were used to model the combined effect of these factors on radial growth rate. The results underlined a highly significant effects (P < 0.001) of Ψw and temperature and their interactions on radial growth rates and lag phases (λ). The Four studied species were shown tolerant to a temperature of 35 °C with an optimum mycelial growth at 30 for N. solani and F. oxysporum and at 25 °C for F. equiseti and F. brachygibbosum. However, no growth was observed at both temperatures 5 and 40 °C and at Ψw of - 9.68 MPa (0.93 aw). The optimum water potential for growth was ≥- 2.69 MPA (>0.98 aw). The results from the polynomial model and response surface showing good agreement between observed and predicted values. The external validation on citrus fruit indicated slight differences between predicted and observed values of radial growth. The results of this study will be beneficial for understanding the ecological knowledge of these species and thereby limited preventively their occurrence.
Cucurbits are among the most cultivated crops, and the most economically important species are me... more Cucurbits are among the most cultivated crops, and the most economically important species are melon (Cucumis melo L.), cucumber (Cucumis sativus L.), watermelon (Citrullus lanatus Thumb.), squash (Cucurbita pepo L.), and pumpkin (Cucurbita spp.). These crops have become important income sources providing export and local consumption commodities in many Mediterranean countries. Increased area of cucurbits has led to the emergence of several viral diseases, which can have impacts on crop production and threaten agricultural sustainability. An overview of the most damaging cucurbit viruses in the Mediterranean area is provided to improve understanding of the diseases they cause and to emphasize effective disease management strategies. An updating of the geographical distribution of these viruses, the symptoms they cause and their means of transmission is also provided. Disease management methods and measures by farmers and phytosanitary authorities to address the virus outbreaks are o...
Monilinia fructigena is one of the most important fungal pathogens causing brown rot on apple and... more Monilinia fructigena is one of the most important fungal pathogens causing brown rot on apple and is heavily affecting fruit production. The main objective of this study was to screen for potential bacterial isolates with higher antagonistic activity against M. fructigena. Our study focused on the identification of potential bacterial isolates capable of reducing both the mycelial growth of M. fructigena and the disease severity using in vitro and in planta trials, respectively. To achieve this goal, thirteen bacteria, isolated from natural soil, were evaluated for their abilities to produce lytic enzymes (amylase, cellulase and protease), hydrocyanic acid (HCN) and lipopeptides (bacillomycin, fengycin, iturin and surfactin). Further, results from the dual culture method, volatile and bacterial free-cell filtrate bioassays indicated that tested isolates showed a fungicidal activity against the mycelial growth of M. fructigena. Thus, out of the 13 isolates tested, 12 exhibited signif...
Citrus stubborn was initially observed in California in 1915 and was later proven as a graft-tran... more Citrus stubborn was initially observed in California in 1915 and was later proven as a graft-transmissible disease in 1942. In the field, diseased citrus trees have compressed and stunted appearances, and yield poor-quality fruits with little market value. The disease is caused by Spiroplasma citri, a phloem-restricted pathogenic mollicute, which belongs to the Spiroplasmataceae family (Mollicutes). S. citri has the largest genome of any Mollicutes investigated, with a genome size of roughly 1780 Kbp. It is a helical, motile mollicute that lacks a cell wall and peptidoglycan. Several quick and sensitive molecular-based and immuno-enzymatic pathogen detection technologies are available. Infected weeds are the primary source of transmission to citrus, with only a minor percentage of transmission from infected citrus to citrus. Several phloem-feeding leafhopper species (Cicadellidae, Hemiptera) support the natural spread of S. citri in a persistent, propagative manner. S. citri-free bu...
Revue Marocaine des Sciences Agronomiques et Vétérinaires, 2020
Fire Blight, caused by Erwinia amylovora, is one of major economic threats to pear and apple grow... more Fire Blight, caused by Erwinia amylovora, is one of major economic threats to pear and apple growing areas worldwide. In Morocco, this devastating bacterium was first detected in 2006 on pear plantations in Ain Orma district of the Meknes region. Since then, the pathogen was progressively spreading to different regions of pear, apple and quince production, resulting in important losses. As a result, over 2312 Ha of pear, quince and apple orchards were eradicated in 2013. The situation was described as an economic disaster never seen before in the country. Currently, the middle Atlas region, the stronghold of the Moroccan rosaceous production, was entirely affected by this disease. Following the appearance of the bacterium, several approaches including morphological, physiological, biochemical, serological and molecular traits, were undertaken for the early detection and identification of E. amylovora. In this review, we discuss rigorous actions taken by Moroccan authorities to overc...
After harvest, numerous plant pathogenic fungi can infect fresh fruits during transit and storage... more After harvest, numerous plant pathogenic fungi can infect fresh fruits during transit and storage. Although synthetic fungicides are often used to manage postharvest fruit diseases, their application may lead to problems such as the development of fungicide resistance and residues on fruits. In the present study, the antifungal potential of nine commercial essential oils (EOs) extracted from Eucalyptus radiata ssp. radiata, Mentha pulegium, Rosmarinus officinalis, Origanum compactum, Lavandula angustifolia, Syzygium aromaticum, Thymus vulgaris, Citrus aurantium, and Citrus sinensis were tested against the apple brown rot fungi Monilinia laxa and Monilinia fructigena at different concentrations in vitro (against mycelial growth and spore germination) and in vivo (on detached apple fruit and in semi-commercial postharvest conditions). In addition, fruit quality parameters were evaluated and the composition of the EOs was characterized by Fourier transform infrared (FT-IR) spectroscopy...
Since 1998, Tomato yellow leaf curl virus was detected on tomato in Morocco. The virus was first ... more Since 1998, Tomato yellow leaf curl virus was detected on tomato in Morocco. The virus was first detected near Casablanca and was later discovered in several regions particularly in the south near Agadir and in the north east near Berkane (DPVCTFR, personal communication). Economic losses ranged between 20 and 100%. In 1999, Tomato yellow leaf curl Sardinia virus was detected from Agadir. High populations of Bemisia tabaci, the vector of these viruses, were observed on tomato, other crops and weeds. Only biotype Q was identified in B. tabaci populations from Agadir. No sample were analysed so far from the north of the country. Since biotype B was reported from several Mediterranean countries, it was assumed that this cosmopolitan biotype could be present in Morocco. Therefore a survey of B. tabaci was undertaken in several regions to determine which are the biotypes present in Morocco and particularly in the north. Samples were collected from the north eastern Mediterranean coast (S...
Tomato yellow leaf curl virus and Tomato yellow leaf curl Sardinia virus (genus Begomovirus, fami... more Tomato yellow leaf curl virus and Tomato yellow leaf curl Sardinia virus (genus Begomovirus, family Geminiviridae) are infecting tomato crops in Southern Morocco in the region of Agadir with yield losses ranging between 20 and 100%. The severity of the infections has obliged the tomato growers to protect their crops from infestations of Bemisia tabaci, the vector of begomoviruses, using inseetproof screens. The aim of our study was to monitor the flight activities of B. tabaci over time at different heights and different directions (cylindrical yellow traps at 0.3 m, 1.30 m, 2.30 m, 3.30 m, 4.30 m high), and to assess their infectivity. Flight activities, recorded during 4 months in 2002 and 6 months in 2003 during the tomato growing season, were correlated with some weather factors. The ratio B. tabaci/ Trialeurodes vaporariorum was assessed on batches of tomato plants that were placed around the trapping mast and weekly changed. These plants were also used to monitor the infectivi...
TYLCV-IS76 is an unusual recombinant between Tomato yellow leaf curl virus (TYLCV) and Tomato yel... more TYLCV-IS76 is an unusual recombinant between Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV) (Begomovirus, Geminiviridae). In contrast with the previously reported TYLCV/TYLCSV recombinants, TYLCV-IS76 has a typical recombination breakpoint (RB) in the intergenic region (at position 76), and has replaced its parental viruses in the Souss (Southern Morocco). The population shift coincided with the deployment of Ty-1 resistant tomato cultivars, and according to experimental studies, has been driven by a strong positive selection in tomato plants of the resistant cultivars bearing the Ty-1 gene. Although Ty-1 resistant cultivars are extensively used in the Mediterranean countries in which TYLCV and TYLCSV were reported, TYLCV-IS76 has not been reported outside Morocco. This, in combination with the non-canonical recombination pattern, suggests that its generation may not be straightforward, although TYLCV and TYLCSV are highly recombinogenic. H...
Citrus exocortis viroid (CEVd) and hop stunt viroid (HSVd) are the main viroids circulating in al... more Citrus exocortis viroid (CEVd) and hop stunt viroid (HSVd) are the main viroids circulating in all citrus-growing areas worldwide, and causing two well-known diseases on citrus trees; exocortis and cachexia, respectively. These viroids are small, covalently closed single-stranded RNA, allocated to the Pospiviroidae family. CEVd is the first viroid being described on citrus trees in 1948 in California. It is considered the largest citrus viroid at 371 nucleotides. It causes bark scaling disorder on the rootstock of citrus trees grafted on trifoliate orange and its hybrids and can cause dwarfing of trees grown on these rootstocks. HSVd was first observed in 1945 in Florida. It consists of 299 nucleotides. Stunting, chlorosis, bark gumming, stem pitting, decline, and depressions in the wood are the main symptoms of HSVd in mandarin and its hybrids. The introduction and propagation of infected budwoods are the main causes of viroids spread in citrus orchards. These agents are mechanical...
Canker symptoms were observed on almond trees in the Fez-Meknes region, Morocco. Isolations were ... more Canker symptoms were observed on almond trees in the Fez-Meknes region, Morocco. Isolations were conducted from the infected branch and trunk showing internal and external brown lesions. Four representative fungal isolates were screened, and their identities were confirmed by cultural traits and sequence analysis of DNA using two genes, the ITS region (internal transcribed spacer) and calmodulin (cmdA). The identified fungi were Curvularia hawaiiensis, Fusarium ambrosium, Lasiodiplodia theobromae, and Chondrestereum purpureum. The pathogenicity test on almond twigs revealed that these species were pathogenic to their host with different degrees of virulence, with Lasiodiplodia theobromae as the most virulent causing the longest necrotic lesion (285.17 mm) and the death of twigs. Physiological traits analysis of the above-mentioned fungi showed that the optimum mycelium growth response at different temperatures varies from 10 to 35 °C, while the pH ranges between 3.0 and 8.0. This st...
This study aimed at evaluating the effect of environmental factors temperature and water potentia... more This study aimed at evaluating the effect of environmental factors temperature and water potential (Ψw) on the growth of Neocosmospora (Fusarium) solani and three Fusarium species (F. oxysporum, F. equiseti and F. brachygibbosum) associated with citrus dry root rot and to determine the optimum and marginal rate for their growth. The effects of incubation temperature (5-40 °C), water potentials (Ψw) (- 15.54; - 0.67 MPa) (0.89-0.995 aw) and their interaction (5-30 °C) was evaluated on the in vitro radial growth rates of Fusarium spp. and on their lag phase. Secondary models were used to model the combined effect of these factors on radial growth rate. The results underlined a highly significant effects (P < 0.001) of Ψw and temperature and their interactions on radial growth rates and lag phases (λ). The Four studied species were shown tolerant to a temperature of 35 °C with an optimum mycelial growth at 30 for N. solani and F. oxysporum and at 25 °C for F. equiseti and F. brachygibbosum. However, no growth was observed at both temperatures 5 and 40 °C and at Ψw of - 9.68 MPa (0.93 aw). The optimum water potential for growth was ≥- 2.69 MPA (>0.98 aw). The results from the polynomial model and response surface showing good agreement between observed and predicted values. The external validation on citrus fruit indicated slight differences between predicted and observed values of radial growth. The results of this study will be beneficial for understanding the ecological knowledge of these species and thereby limited preventively their occurrence.
Cucurbits are among the most cultivated crops, and the most economically important species are me... more Cucurbits are among the most cultivated crops, and the most economically important species are melon (Cucumis melo L.), cucumber (Cucumis sativus L.), watermelon (Citrullus lanatus Thumb.), squash (Cucurbita pepo L.), and pumpkin (Cucurbita spp.). These crops have become important income sources providing export and local consumption commodities in many Mediterranean countries. Increased area of cucurbits has led to the emergence of several viral diseases, which can have impacts on crop production and threaten agricultural sustainability. An overview of the most damaging cucurbit viruses in the Mediterranean area is provided to improve understanding of the diseases they cause and to emphasize effective disease management strategies. An updating of the geographical distribution of these viruses, the symptoms they cause and their means of transmission is also provided. Disease management methods and measures by farmers and phytosanitary authorities to address the virus outbreaks are o...
Monilinia fructigena is one of the most important fungal pathogens causing brown rot on apple and... more Monilinia fructigena is one of the most important fungal pathogens causing brown rot on apple and is heavily affecting fruit production. The main objective of this study was to screen for potential bacterial isolates with higher antagonistic activity against M. fructigena. Our study focused on the identification of potential bacterial isolates capable of reducing both the mycelial growth of M. fructigena and the disease severity using in vitro and in planta trials, respectively. To achieve this goal, thirteen bacteria, isolated from natural soil, were evaluated for their abilities to produce lytic enzymes (amylase, cellulase and protease), hydrocyanic acid (HCN) and lipopeptides (bacillomycin, fengycin, iturin and surfactin). Further, results from the dual culture method, volatile and bacterial free-cell filtrate bioassays indicated that tested isolates showed a fungicidal activity against the mycelial growth of M. fructigena. Thus, out of the 13 isolates tested, 12 exhibited signif...
Citrus stubborn was initially observed in California in 1915 and was later proven as a graft-tran... more Citrus stubborn was initially observed in California in 1915 and was later proven as a graft-transmissible disease in 1942. In the field, diseased citrus trees have compressed and stunted appearances, and yield poor-quality fruits with little market value. The disease is caused by Spiroplasma citri, a phloem-restricted pathogenic mollicute, which belongs to the Spiroplasmataceae family (Mollicutes). S. citri has the largest genome of any Mollicutes investigated, with a genome size of roughly 1780 Kbp. It is a helical, motile mollicute that lacks a cell wall and peptidoglycan. Several quick and sensitive molecular-based and immuno-enzymatic pathogen detection technologies are available. Infected weeds are the primary source of transmission to citrus, with only a minor percentage of transmission from infected citrus to citrus. Several phloem-feeding leafhopper species (Cicadellidae, Hemiptera) support the natural spread of S. citri in a persistent, propagative manner. S. citri-free bu...
Revue Marocaine des Sciences Agronomiques et Vétérinaires, 2020
Fire Blight, caused by Erwinia amylovora, is one of major economic threats to pear and apple grow... more Fire Blight, caused by Erwinia amylovora, is one of major economic threats to pear and apple growing areas worldwide. In Morocco, this devastating bacterium was first detected in 2006 on pear plantations in Ain Orma district of the Meknes region. Since then, the pathogen was progressively spreading to different regions of pear, apple and quince production, resulting in important losses. As a result, over 2312 Ha of pear, quince and apple orchards were eradicated in 2013. The situation was described as an economic disaster never seen before in the country. Currently, the middle Atlas region, the stronghold of the Moroccan rosaceous production, was entirely affected by this disease. Following the appearance of the bacterium, several approaches including morphological, physiological, biochemical, serological and molecular traits, were undertaken for the early detection and identification of E. amylovora. In this review, we discuss rigorous actions taken by Moroccan authorities to overc...
After harvest, numerous plant pathogenic fungi can infect fresh fruits during transit and storage... more After harvest, numerous plant pathogenic fungi can infect fresh fruits during transit and storage. Although synthetic fungicides are often used to manage postharvest fruit diseases, their application may lead to problems such as the development of fungicide resistance and residues on fruits. In the present study, the antifungal potential of nine commercial essential oils (EOs) extracted from Eucalyptus radiata ssp. radiata, Mentha pulegium, Rosmarinus officinalis, Origanum compactum, Lavandula angustifolia, Syzygium aromaticum, Thymus vulgaris, Citrus aurantium, and Citrus sinensis were tested against the apple brown rot fungi Monilinia laxa and Monilinia fructigena at different concentrations in vitro (against mycelial growth and spore germination) and in vivo (on detached apple fruit and in semi-commercial postharvest conditions). In addition, fruit quality parameters were evaluated and the composition of the EOs was characterized by Fourier transform infrared (FT-IR) spectroscopy...
Since 1998, Tomato yellow leaf curl virus was detected on tomato in Morocco. The virus was first ... more Since 1998, Tomato yellow leaf curl virus was detected on tomato in Morocco. The virus was first detected near Casablanca and was later discovered in several regions particularly in the south near Agadir and in the north east near Berkane (DPVCTFR, personal communication). Economic losses ranged between 20 and 100%. In 1999, Tomato yellow leaf curl Sardinia virus was detected from Agadir. High populations of Bemisia tabaci, the vector of these viruses, were observed on tomato, other crops and weeds. Only biotype Q was identified in B. tabaci populations from Agadir. No sample were analysed so far from the north of the country. Since biotype B was reported from several Mediterranean countries, it was assumed that this cosmopolitan biotype could be present in Morocco. Therefore a survey of B. tabaci was undertaken in several regions to determine which are the biotypes present in Morocco and particularly in the north. Samples were collected from the north eastern Mediterranean coast (S...
Tomato yellow leaf curl virus and Tomato yellow leaf curl Sardinia virus (genus Begomovirus, fami... more Tomato yellow leaf curl virus and Tomato yellow leaf curl Sardinia virus (genus Begomovirus, family Geminiviridae) are infecting tomato crops in Southern Morocco in the region of Agadir with yield losses ranging between 20 and 100%. The severity of the infections has obliged the tomato growers to protect their crops from infestations of Bemisia tabaci, the vector of begomoviruses, using inseetproof screens. The aim of our study was to monitor the flight activities of B. tabaci over time at different heights and different directions (cylindrical yellow traps at 0.3 m, 1.30 m, 2.30 m, 3.30 m, 4.30 m high), and to assess their infectivity. Flight activities, recorded during 4 months in 2002 and 6 months in 2003 during the tomato growing season, were correlated with some weather factors. The ratio B. tabaci/ Trialeurodes vaporariorum was assessed on batches of tomato plants that were placed around the trapping mast and weekly changed. These plants were also used to monitor the infectivi...
TYLCV-IS76 is an unusual recombinant between Tomato yellow leaf curl virus (TYLCV) and Tomato yel... more TYLCV-IS76 is an unusual recombinant between Tomato yellow leaf curl virus (TYLCV) and Tomato yellow leaf curl Sardinia virus (TYLCSV) (Begomovirus, Geminiviridae). In contrast with the previously reported TYLCV/TYLCSV recombinants, TYLCV-IS76 has a typical recombination breakpoint (RB) in the intergenic region (at position 76), and has replaced its parental viruses in the Souss (Southern Morocco). The population shift coincided with the deployment of Ty-1 resistant tomato cultivars, and according to experimental studies, has been driven by a strong positive selection in tomato plants of the resistant cultivars bearing the Ty-1 gene. Although Ty-1 resistant cultivars are extensively used in the Mediterranean countries in which TYLCV and TYLCSV were reported, TYLCV-IS76 has not been reported outside Morocco. This, in combination with the non-canonical recombination pattern, suggests that its generation may not be straightforward, although TYLCV and TYLCSV are highly recombinogenic. H...
Citrus exocortis viroid (CEVd) and hop stunt viroid (HSVd) are the main viroids circulating in al... more Citrus exocortis viroid (CEVd) and hop stunt viroid (HSVd) are the main viroids circulating in all citrus-growing areas worldwide, and causing two well-known diseases on citrus trees; exocortis and cachexia, respectively. These viroids are small, covalently closed single-stranded RNA, allocated to the Pospiviroidae family. CEVd is the first viroid being described on citrus trees in 1948 in California. It is considered the largest citrus viroid at 371 nucleotides. It causes bark scaling disorder on the rootstock of citrus trees grafted on trifoliate orange and its hybrids and can cause dwarfing of trees grown on these rootstocks. HSVd was first observed in 1945 in Florida. It consists of 299 nucleotides. Stunting, chlorosis, bark gumming, stem pitting, decline, and depressions in the wood are the main symptoms of HSVd in mandarin and its hybrids. The introduction and propagation of infected budwoods are the main causes of viroids spread in citrus orchards. These agents are mechanical...
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