LAL AHAMED, M.SAILEELA, M2021-09-032021-09-032021-09-03https://krishikosh.egranth.ac.in/handle/1/5810175027PHYLOGENY ANALYSIS OF KURNOOL STRAINS OF Sclerotium rolfsii CAUSING COLLAR ROT IN CHICKPEAThe present study was conducted to study the variability in Sclerotium rolfsii isolates of Kurnool District of Andhra Pradesh using morphological characters and molecular markers like ITS, RAPD and ISSR. A roving survey was conducted to record incidence of collar rot disease in the fields of chickpea in Kurnool district of Andhra Pradesh during rabi 2019 - 2020. The disease incidence range was 7.5% to 19.5% with an average of 12.57% in the Kurnool district. 33 villages diseased samples were collected and 18 S. rolfsii isolates were isolated. They were designated as KCSR 1 to KCSR 18. The isolates varied in their morphological characters viz., mycelia growth rate (15.2mm/day to 25mm/day), colony colour (pure white to dull white), mycelia appearance and dispersion (mat to flower ; compact and fluffy). These were grouped into moderate, fast and very fast based on mycelial growth rate and the isolates, KCSR 11 and KCSR 16, were identified as fast and slow growing isolates, respectively. Further, sclerotial traits like sclerotia initiation (5 to 10 days), 100 sclerotia weight (40 to 320mg), number of sclerotia (25 to 124 ), sclerotia colour (black in KCSR16 golden brown in KCSR 18 and light brown to dark brown in remaining isolates) and site of sclerotial production (KCSR 12 - peripheral, KCSR 16 - top of petriplate, remaining isolates - peripheral, scattered, clustered at centre and to sides of plate) showed sufficient variability indicating their usefulness in characterization. Among the isolates, KCSR 16 is unique from others in having low growth rate, high test weight, black coloured sclerotia and sclerotial arrangement on top of plate. The isolate, KCSR 16, recorded high aggressiveness on susceptible chickpea variety, L550, by recording disease incidence of 95.67% in 8 days.EnglishThesis