M. K. SHIVAPRAKASHBINDUSHREE, C.2023-01-142023-01-142021-12-29Th-13069https://krishikosh.egranth.ac.in/handle/1/5810192331Actinobacteria, a Gram positive bacteria and a major source of most of the antibiotics being used, are also being explored as plant growth promoting and biocontrol agent for various crop plants. When compared with other groups of microorganism, actinobacteria are relatively less explored with agricultural perspective. The present study was conducted with a view to isolate and screen actinobacteria from natural ecosystems and evaluate their potential for plant growth promoting and biocontrol activity. A total of 120 actinobacterial isolates were isolated from rhizospheric soil (n=4), forest soil (n=39) and compost (n=40). The functional potentialities of the isolates recorded were phosphate solubilization, siderophore, IAA, gibberellic acid, cytokinin and ammonia production. The SA12 isolate of rhizospheric soil, was found to be highest producer of IAA (63.33 μg/mL) and gibberallic acid (40.53μg/mL). The FA13 isolate showed highest cytokinin production (30.16 μg/mL). The SA12 exhibited maximum phosphate solubilization activity (32.87 mg/mL), while the isolate SA12 and CA18 showed maximum ammonia production (32.87 mg/mL 30.05 and mg/mL). Forty two isolates out of 120 displayed antagonistic activity against different plant pathogenic fungi (Fusarium oxysporum, Pythium sp., Sclerotium rolfsii and Alternaria sp) and thirty actinobacterial isolates displayed antagonistic activity against plant pathogenic bacteria Xanthomonas campestris and Ralstonia solanacearum. The results indicated that the isolates, FA15, FA13, SA12, CA18 and CA4 were prominent in inhibiting the growth of all the pathogens and were selected further screening for biocontrol efficiency and seedling vigour in solanaceous vegetable crops under greenhouse conditions. The treatment received inoculum of consortium of selected actinobacterial isolates had shown significant biocontrol efficiency against the damping off, wilt pathogens and seedling vigour index in seeding tray and pot culture experiments.EnglishThesis