Inheritance patterns and identification of microsatellite markers linked to the rice blast resistance in BC2F1 population of rice breeding

The BC2F1 population was derived from a cross between rice variety, MR219 (susceptible to blast) and Pongsu Seribu 1 (resistant to blast). The objectives of this research were to know the inheritance pattern of blast resistance and to identify the linked markers associated with blast resistance in BC2F1 population. Sixteen microsatellite markers were found as polymorphic between the parents related to blast resistant genes (Pi-genes). Among the selected blast resistant linked markers, two markers RM6836 and RM8225 showed expected testcross ratio (1:1) for single-gene model in the BC2F1 population with the association between resistant and susceptible progeny. A total of 333-BC2F1 plants were challenged with the most virulent pathotype P7.2 of Magnaporthe oryzae. Chi-square (chi(2)) analysis for phenotypic segregation in single-gene model showed goodness of fit (P = 0.4463) to the expected segregation ratio (1:1). In marker segregation analysis, two polymorphic markers (RM6836 and RM8225) clearly showed goodness of fit to the expected segregation testcross ratio (1: 1) for the single-gene model. The marker RM8225 and RM6836 showed significant R-2 values higher than 10 for the trait of the blast lesions degree (BLD). The positions of RM6836 and RM8225 markers on rice chromosome 6 and the distance between these two markers is 0.2 cM. We conclude that single dominant gene control the blast resistance in Pongsu Seribu 1 located on chromosome 6, which is linked to RM8225 and RM6836 microsatellite markers. This information could be useful in marker-assisted selection for blast resistance in rice breeding involving Pongsu Seribu 1.