Inheritance of blast resistance and identification of SSR marker associated with it in rice cultivar RDN 98-2

Abstract

An F2 population was developed from a cross between rice (Oryza sativa L.) genotypes, EK 70 (highly susceptible to blast) and RDN 98-2-3-5-14 (resistant to blast), to study the inheritance of blast resistance and to identify the marker associated with resistance. The F2 population segregated in 3:1 ratio for resistance: susceptible under hot spot conditions for blast suggesting monogenic control of resistance in this population. Bulk segregant analysis conducted using a total of 25 SSR markers identified two SSRs to be polymorphic between the parents and the corresponding bulks. One of these SSR markers RM204 which has been reported to be mapped on the short arm of chromosome 6 and in close proximity of blast resistance gene/QTLs in other studies showed expected segregation ratio (1:2:1) for single gene model in the F2 population. This marker was found significantly associated with blast resistance on regression analysis. Rice is the world’s largest food crop, providing caloric needs to millions of people daily. Rice suffers attack by a large number of pests and pathogens, which under epidemic conditions, cause serious yield losses. Among these, rice blast caused byMagnaporthe grisea (Hebert) Barr. (Barr 1977), synonym M. oryzae is one of the most devastating and destructive diseases of rice worldwide. Under heavy dew, arial plant parts are affected, leaf surface becomes speckled with oval lesions and plants are liable to lodging if nodes are infected. If the panicles are infected, it also results in severe yield losses (Ou 1985). Resistance to the M. oryzae is a classic gene-for-gene system, where a major resistance gene is effective against