S.K. PrashanthiSowmya H.M.2016-11-112016-11-112011http://krishikosh.egranth.ac.in/handle/1/85192Rice blast caused by Pyricularia grisea (Cooke) Sacc. continues to be a serious constraint to rice production in both tropical and temperate regions. Roving survey carried out during kharif 2010 in Karnataka showed that blast severity ranged from 20.17 to 58.72 per cent disease index. Field screening of 210 genotypes against blast showed that, seven genotypes viz., Casebatta, Jasmine -85, Siddasala, IR-64, Diamond Sona, Vajram, MGD 101 were resistant to both leaf and neck blast. Fifty five genotypes were resistant and eighty five genotypes were moderately resistant to leaf blast. Influence of blast on different biochemical components present in resistant, moderately resistant and susceptible genotypes at different stages of blast infection was investigated. Total phenol, Orthodihydroxy-phenol, total sugar, reducing sugar and non reducing sugar content was more in resistant and moderately resistant varieties compared to susceptible genotypes at all the stages of infection but they decreased slightly during neck blast stage. Accumulation and increase of phenol content in resistant genotypes was quick and more compared to moderately resistant and susceptible genotypes. Total amino acid content was more in resistant genotypes compared to susceptible genotypes. Total amino acid content increased from before disease initiation stage to neck blast stage. Protein content was more in susceptible genotypes compared to resistant and moderately resistant varieties and it decreased from before initiation stage to neck blast stage rapidly. Decrease of protein content from before disease initiation stage to peak stage was maximum in resistant varieties than moderately resistant and susceptible varieties. Isozyme study on peroxidase activity indicated significant variations among resistant, moderately resistant and susceptible genotypes. Phenylalanine ammonia lyase activity was more in resistant genotypes compared to moderately resistant and susceptible genotypes.Thesis