OAR@ICRISATStudies on diversity of Scilerotium rolfsii Sacc. and induced systemic resistance in Groundnut (Arachis hypogaea L.) against stem rot pathogenNHaveriauthorGroundnut (Arachis hypogaea L.) is an important oilseed crop grown in India. Of the various diseases inciting groundnut, the stem rot caused by S. rolfsii is a potential threat to groundnut production. The present investigations were carried out to assess the diversity of S. rolfsii causing stem rot of groundnut and to identify the potent fungal and bacterial biocontrol agents for effective management of disease. The roving survey conducted during kharif, 2013 and kharif, 2014 in major groundnut growing areas of India recorded 11.23 to 55.40% and 10.11 to 59.33% incidence of stem rot respectively. Among various states surveyed, Gujarat recorded highest incidence whereas Telangana documented least incidence. Gujrat, parts in Maharashtra and Tamil Nadu recorded comparatively higher incidence where the crop was grown in black soils with susceptible cultivars continuously as sole crop. Totally 60 isolates of S. rolfsii were collected from varied geographical areas during survey. The medium Richards’s broth was found to be best supporting medium for in vitro oxalic acid production by S. rolfsii. Further, the 60 of isolates exhibited wide variation in in vitro oxalic acid production. The 15g inoculum level of S. rolfsii per 7” pot was found most effective and suitable for glasshouse studies. All the 60 isolates of S. rolfsii in the study were found pathogenic. Further, there was great variation among the isolates for virulence levels on three groundnut cultivars, hence the isolates were grouped into two categories viz., highly virulent (n=56) and less virulent (n=4). Further, there was a positive correlation found between the amount of oxalic acid produced in vitro and virulence of the isolates. Thus, the highly virulent isolates produced significantly highest amount of oxalic acid (0.99-2.85 mg/ml) whereas less virulent isolates produced least amount (0.64-0.78 mg/ml). Culturally the 60 isolates of S. rolfsii were found diverse. The growth rate, biomass production of isolates tested was ranged from 0.66 to 1.29 mm/hr and 6.82 to 14.62 mg/day respectively. All the isolates produced sclerotia on PDA medium. Most of the isolates produced the colonies which were raised at ends (n=27) followed by flat type (n=20) and raised type (n=13). As per mycelial growth type, most of the isolates were found highly profuse in growth (n=36) and few were profuse (n=24).Groundnut2017Professor Jayashankar Telangana State Agricultural University;Department of Plant PathologyThesis

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