Nematology Plant Pathology

Background: Plant parasitic nematodes are dangerous pests that damage various agricultural crops and decrease their productivity. Objective: The resistance of new lines of wheat (Triticum aestivum L.) plants obtained under in vitro conditions on the MS media containing microbial bioregulators to plant parasitic nematodes was studied under in vitro and greenhouse conditions. Method: Here we conducted physiological and molecular-genetic studies of resistance of wheat plants to nematodes. Results. In vitro experiments showed that wheat plants grown on MS media with microbial bioregulators had 20-37 % of infestation with cereal cyst nematode Heterodera avenae, significantly lower when compared with 73 % of infestation of the control plants grown without bioregulators. Bio-regulators increased morphometric parameters of the wheat plants obtained under in vitro conditions on MS media and further grown under greenhouse conditions on the natural invasive background: stem height increased 13.6-37.5 %, flag leaf length 18.0-19.3 %, ear length 6.8-24.6 %, and ear weight 27.0-54.5 %, when compared with control wheat plants. The difference in the degree of hybridizated molecules mRNA and si/miRNA from control and experimental wheat plants increased: 15-39 % in plants grown under in vitro conditions on the invasive background created by H. avenae and 33-56 % in seeds of plants grown under greenhouse conditions on the natural invasive background. The silencing activity of si/miRNA from wheat plants grown on MS media with bioregulators increased: 20-51 % in plants grown under in vitro conditions on the invasive background created by H. avenae or 38-64 % in plants grown under greenhouse conditions on the natural invasive background. Conclusion: Our studies confirm the RNAi-mediated resistance to plant nematodes of wheat plants obtained on media with microbial bioregulators and grown under in vitro and greenhouse conditions.

Root-knot nematodes are mainly controlled by using synthetic nematicides, but their excessive use is prohibited due to associated health hazards which demand for suitable alternatives. The overreliance on nematicides can be curtailed by using biological control agents possessing nematicidal or nematostatic properties. Therefore, in the present study, effectiveness of seven indigenous species of Trichoderma were tested for their ability to suppress the population of Javanese root-knot nematode, Meloidogyne javanica, and improve growth variables of green gram. All the Trichoderma species resulted in an increase in shoot and root lengths and shoot weight while a decrease was observed in root weight. Maximum increase in shoot length (45.5%) was found in case of T. harzianum followed by T. hamatum and T. viride whereas the increase was the minimum where T. pseudokoningii and T. koningii were applied. Similarly, maximum increase in shoot weight was recorded with T. viride (56.1%) followed by T. harzianum (55%) and the minimum with T. pseudokoningii. As regards root length, it was the maximum in treatments with T. hamatum (46.2%) and T. harzianum (45.1%) and minimum with those where T. koningii and T. pseudokoningii were applied. Contrarily, maximum reduction in root weight was observed in treatments where T. harzianum (37.8%) and T. viride (35.8%) were applied while T. koningii and T. pseudokoningii resulted in minimum decrease. All the Trichoderma species significantly caused reductions in the number of galls and eggs and reproductive factor of the nematode over control. Maximum reduction in numbers of galls and eggs were observed with T. viride (49 and 53%) followed by T. harzianum (46 and 53%) while the minimum reduction was recorded with T. pseudokoningii followed by T. atroviride. Likewise, T. viride caused the maximum reduction in reproductive factor of M. javanica (81%) followed by T. harzianum (78%) and T. asperellum (75%). On the other hand, the minimum reductions in reproductive factor were observed with T. pseudokoningii and T. koningii. K Content courtesy of Springer Nature, terms of use apply. Rights reserved.

Abstract
Purpose – The purpose of this paper is to investigate the ability of four microorganisms to reduce
disease infection of root lesion nematode (Pratylenchus spp.) and Fusarium spp. the causal agent of
wilt/root-rot disease complex in chickpea.
Design/methodology/approach – A pot experiment was conducted for three consecutive winter
seasons. A completely randomized design with five replicates was adopted. Two Bacillus isolates and
Trichoderma harzianum and T. viride and their combinations were applied in infected soil. The effect
on plant growth parameters, disease incidence and severity, root necrosis, weight of shoot and root,
nematode population density and reproductive index were assessed.
Findings – The applications significantly ( p¼0.05) reduced the wilt/root-rot diseases complex.
The reduction was attributed to the decline of the population density of nematodes in soil and root, and
the suppression of the disease complex compared to controls, represented by reproductive index
and the disease intensity index. Combinations were better than individual inoculation. The use of Bacillus
isolate B3 and T. harzianum increased the number of flowers by 88.34 per cent. Reduction in the severity
of root necrosis was in the range of 2.22-5.55 within a scale of 1-10. These findings indicate the
significance of utilizing local bioagents for control of wilt/root-rot disease complex in chickpea plants.
Originality/value – The microorganisms used in this study are indigenous.

A green house study was conducted to evaluate the comparative efficacy of Pasteuria
penetrans under the influence of organic amendments of four oil seed cakes namely
Azadirachta indica (Locally known as Neem), castor (Ricinus communis), mustard
(Brassica campestris) and Citrullus (Citrullus colocynthis) on suppression of populations of
Meloidogyne incognita in Chilli. Oil seed cakes were applied at the rate of 20 mg/Pot (500
kg/ha), either individually or in combination with one dose of P. penetrans (100 g/kg soil).
Application of oil seed cakes and P. penetrans, singly or in combination, proved effective
in reduction of gall and final root-knot nematode population. Combination of castor and
P. penetrans showed greater reduction in galling index (84.75%) and final population
(85.74%) over the M. incognita control than other treatments. In addition, oil seed cake
significantly improved the shoot and root dry matter of chilli. Among the four oil cakes tested, the combined application of P. penetrans with castor oil cake seemed to be more promising in the management of M. incognita in chilli as it resulted in greater nematode suppression and improved plant health.

A study was conducted in both greenhouse and field to determine the use of agro-industrial waste and organic amendments in the management of root-knot nematodes (RKN) in Solanum nigrum. Treatments included cattle manure (CM), goat manure (GM),
Tithonia diversifolia (Td) and agro-industrial wastes of tea [Camellia sinensis residue (Tres)] and pyrethrum [Chrysanthemum
cinerariafolium Vis.] pymarc (Pm) and vegetable waxy resins (VWR). They were incorporated in sterilized soil at their respective
rates into 1 kg plastic pots and S. nigrum seedlings planted, across the treatments, two weeks later. Ten egg-masses were inoculated
into three pots for each amendment with uninoculated and unamended pots serving as controls. Field experiment was also conducted on plots measuring 1.2x3.2 m in Kisii County, with unamended plots serving as control. The experiments were arranged in randomized complete block design with four replications. All experiments were terminated 60 days after inoculation and data on plant growth and disease parameters collected. The results revealed suppression of RKN population and reproduction by the various amendments compared to their controls in both field and greenhouse. Improved plant growth was also recorded in all the amendments in both tests except for Tres. However, higher levels of Tres and VWR application caused stunted growth despite significant reductions in GI, Rf and J2 populations. These organic amendments can be used as alternatives in eco-friendly management of Meloidogyne species and
other plant parasitic nematodes.

nematode Meloidogyne incognita and every year this nematode causes great
loss to the crop. The present study investigated the cumulative effect of two
biocontrol agents viz. Pasteuria penetrans and Paecilomyces lilacinus against
M. incognita. Two doses of P. penetrans i.e. 50g/Kg and 100g/Kg infested soil
were applied either alone or in combination with two doses of P. lilacinus i.e.
4g spore culture/Kg and 6g spore culture/Kg of soil. Application of P. penetrans
with P. lilacinus resulted into relatively better improvement in various
growth attributes of chilli when compared with the individual application.
Amongst the various treatments tested combined application with the
higher dose of both bioagents (i.e. 100g P. penetrans infested soil with 6g of
P. lilacinus/Kg) showed maximum improvement in fresh and dry weight of
shoot and root over the nematode check and it was almost at par with that
of the absolute check. The combined application of both the bioagents at
higher dose resulted in 139 and 84% increase in dry weight of shoot and root over the nematode check respectively. The combined application of both the bioagents was also observed to cause higher reduction in gall number and nematode population than their individual application except for the treatment having lower dose of the P. penetrans with P. lilacinus where reduction in both the parameters was observed to be at par with that of the either dose of P. penetrans or higher dose of P. lilacinus. Combined application with higher dose of P. penetrans and P. lilacinus showed maximum reduction of 62.6 and 82.2% in gall numbers and nematode population over the nematode
check.

The present work was conducted to study the efficacy of compost powder and compost extract (tea) in the management of root rot and root-knot nematode disease complex infecting pepper plants under in vitro and in vivo. The inhibitory effect of compost extract concentrations (25%, 50%, 75 and 100%) on Fusarium solani (Mart.) Sacc and Rhizoctonia solani Kühn were evaluated, the latter was higher sensitive than F. solani by 88.33% and 82.83%, respectively at 100% concentration. The results also, showed that nematicidal effect of unsterilized compost tea (65.98% and 52.3%) was significantly more than sterilized compost tea (54.02% and 45.9%) on the rate of Meloidogyne incognita egg hatching and juvenile mortality, respectively in all tested concentrations. In vivo, the obtained results cleared a decrease in the root rot incidence percentage in disease complex of both compost powder and compost tea extract to 22.1% and 20.1% compared with control treatment. Application of compost powder with the recommended dose, as well as the compost tea extract, led to a significant decrease in gall number (64 and 59 galls/root) compared to the comparative treatment (108 galls/root). This result has led to a significant reduction in egg-masses formation. Furthermore, the obtained results indicated that plant growth parameters significantly increased (plant length, fresh and dry weights) by the application of compost and compost tea extract. In general, application of compost and compost tea extract might be a safe and eco-friendly tool in the sustainable management of disease complex.

Evaluation of prevalence and incidence of citrus slow decline disease in citrus orchards in district Layyah. Abstract An assessment was accomplished, to evaluate the prevalence and incidence of Tylenchus semipenetrans (Cobb.) in district Layyah, in the year 2016. A total of 180 soil and root samples were collected from 60 localities of district Layyah in Pakistan. The analysis revealed that 46.67% of the samples were infested with the nematode. Maximum infestation (61.67%) was recorded in tehsil Chobara followed by Layyah (43.34%) and Karor lal-eesan (31.67%), respectively. In tehsil Chobara nematode in soil ranged from 1,102 to 11,070 per kg of soil and number of females ranged from 274 to 1,202 per gram of root followed by tehsil Layyah and Karor lal-eesan ranged from 918 to 10,430 and 1,018 to 9,854 and females per gram of root ranged from 168 to 857 and 120 to 990 respectively. This information is useful to create awareness about the citrus slow decline disease and for its rapid precautionary measures.

The present study was conducted during the period of 2015-16 (June-September) to characterize morphological profiles of Meloidogyne javanica from Papaya and Pumpkin in Himachal Pradesh, India. Affected plants displayed poor growth and significant galling on roots. Serious infections resulted in formation of large numbers of galls, wilted leaves, root rot, and then plant death. Morphological as well as morphological studies were carried out for confirmation of referred species. The present specimens have greater body length (550-789 vs. 541-804 µm), body width (320-550 µm vs. 311-581 µm) and longer spear length (16-22 vs. 14-20 µm) as compared to the earlier described populations by several authors. Morphometrics and female perineal pattern of the isolates fit within the ranges for M. javanica. Perineal patterns were oval to squarish in shape, usually with coarse, broken striae and with conspicuous lateral lines. Females had robust stylet with a dorsally curved cone and large transversely ovoid knobs that are offset from the shaft. This species of root-knot nematode was reported for first time from the state.