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ThesisItem Open Access Management of aerial blight of soybean (Rhizoctonia solani Kühn) through resistant sources, fungicides and chitosan nanoparticles(G.B. Pant University of Agriculture and Technology, Pantnagar - 263145 (Uttarakhand), 2020-02) Arya, Chandra; Singh, K.P.Soybean (Glycin max L. Merril) is one of the most important seed legumes, which contributes 25 % of the global edible oil and about two- third of the world’s protein. Among the major diseases infecting soybean crop, aerial blight caused by the fungus Rhizoctonia solani Kuhn is most destructive and leads to huge yield losses every year around the world. The disease produces dark brown irregular spots on leaves and plant parts making the plant unproductive. Use of resistant varieties is an effective strategy for management of the disease. Sixteen soybean varieties were screened against aerial blight for two years viz., Kharif 2017 and 2018. It was observed that disease pressure was high during 2017 as compared to 2018. In 2017, the varieties PS-1572, PS-1583 and PS-1518 were found to be resistant against RAB whereas in 2018, the varieties showing resistant reaction were PS-1518, PS-1556, PS-1572 and PS-1583. Out of the 16 varieties screened against RAB, four varieties viz., PS-1518, PS-1572, PS -1556 and PS-1583 were found to be resistant in the pooled data while six varieties viz, PS1546, PK-262, PK-472, NRC-7, PS-1029 and PS-1092 exhibited a moderately resistant reaction to RAB. The effect of five different growth media against Rhizoctonia solani was also studied. Out of the five media used in the study, Czapek’s dox agar media was found best for mycelial growth and development and Corn meal agar was found best for the sclerotia production. Five new generation fungicides were also tested in vitro against the fungus, out of which, Nativo 75% WG (tebuconazole 50% + trifloxystrobin 25%) was found to be the most effective with 100 percent growth inhibition at 5 ppm and above concentrations. The effect of chitosan nanoparticles (CNPs) on the growth of R. solani was also tested. The most effective concentration of CNPs was 1 ppm which gave 67.77 percent growth inhibition of the fungus. The effect of chitosan nanoparticles on growth parameters of soybean was also studied. It was observed that 100 ppm concentration of CNPs gave 100 percent germination in case of JS-335 and 99.33 per cent in case of PS-1024 as compared to control with 90 an 80 per cent germination, respectively. The germination percentage was 99.33 and 88.67 and 97.33 and 70.00 per cent at 75 and 50 ppm concentration in JS335 and PS1024 respectively. Energy of emergence and germination index found to be highly effective at 100 ppm in PS- 1024 and JS-335. But the mean germination time was found lowest with 5.07 days in JS-335 as compared to control. The 50 ppm concentration of CNPs gave the highest mean germination time with 5.25 and 5.24 days in PS-1024 and JS 335, respectively. Treatment with chitosan nanoparticles was found to increase the root/shoot ratio and vigour index at a concentration of 100 ppm. Effect of chitosan nanoparticles on the fungal mycelium was studied using scanning electron microscopy and it was observed that in control, the mycelia were septate and uniformly branched with prominent constrictions at the branching point while in the treated plate, the mycelium was observed to be distorted with irregular septation or complete absence of septa, change in cell permeability, loss off cell turgidity, with a collapsed cell wall which was intermixed to form a clump of unevenly distributed cytoplasm.