Inheritance and allelic relationship between genes conferring resistance to Pyricularia oryzae in rice

Identification and characterization of leaf and neck blast resistant varieties in terms of number of resistance genes and their allelic relationship is a pre-requisite for any breeding program to breed resistant cultivars. Genetics of pathotype specific field resistance was studied in six resistant genotypes against leaf and neck blast pathogen (Pyricularia oryzae). Crosses were attempted in half diallel fashion among themselves and with susceptible parents during Kharif 2017 and 2018. Parents, F1 and F2 generations were evaluated for leaf and neck blast reaction under artificial epiphytotic conditions. Based on the disease reaction of F1 and segregation pattern in F2 populations in Resistant (R) × Susceptible (S) and Resistant (R) × Resistant (R) crosses, it was observed that resistance in genotypes HPR 2880, HPR 3001, HPR 3007 and Kasturi were governed by two independently inherited dominant resistance genes whereas, three resistance genes conferred resistance in genotypes HPR 1156 and HPR 3010 for both leaf and neck blast. Segregation pattern in F2 populations in R × R crosses suggested that resistance genes for leaf and neck blast have at least one common allele in genotypes, HPR 2880, HPR 3001, HPR 3007 and Kasturi which are different from the genes identified in genotypes, HPR 1156 and HPR 3010.