Inheritance of Blast Resistance and Associated Microsatellite Markers in Rice Cultivar ‘Laxmi’

Leaf blast, caused by Magnaporthe oryzae is a major disease of rice (Oryza sativa L.) in many rice-growing environments. Rice breeders continuously seek new sources of resistance for improving resistance of commercial cultivars. This study was undertaken to determine the inheritance of blast resistance in the rice cultivar Laxmi . Both parents, and their F1, F2, backcross, F3 and F4 progeny were studied to determine the inheritance of blast resistance in a cross between resistant (R) Laxmi and susceptible (S) Mahsuri cultivars. Ten homozygous resistant and 10 homozygous susceptible F5 progeny based on their blast reaction in F3 from the above cross were subjected to microsatellite marker analysis to determine the linkage between resistance and marker. The F1 plants were blast-resistant. The test cross progeny segregated in a ratio of 1R:1S. The F2 population segregated into 3R:1S ratio. The F3 and F4 progeny showed a segregation ratio of 1R:2Sg (segregating):1S. RM25 and RM310 markers showed association with resistant and susceptible progeny. We conclude that blast resistance in Laxmi is governed by a single dominant gene located on chromosome 8 of rice, which is linked to RM25 and RM310 microsatellite markers. This source of blast resistance could be useful in the Himalayan and other rice-growing environments. This information could be used in marker-assisted selection for blast resistance in rice crosses involving Laxmi