Mapping quantitative trait loci conferring blast resistance in upland indica rice (Oryza sativa L.)

A genetic analysis of blast resistance in upland rice variety is very crucial. In this study, we performed a linkage mapping of quantitative trait loci (QTLs) for blast resistance using an advanced backcross population from a cross between Way Rarem (susceptible indica variety) and Oryzica Llanos 5 (durable resistant indica variety). A transgressive segregation was observed in the advanced backcross population of Way Rarem//Oryzica Llanos 5. A total of 16 QTLs have been identified along chromosomes 1, 3, 5, 6, 7, 8, 9, and 11 against eight blast pathogen isolates. Each QTL accounted from 11.31 to 45.11% of the variation in blast resistance. Most QTLs showed race specificity, demonstrating the small effect of such QTLs. Unexpectedly, several superior blast resistance alleles were contributed by Way Rarem, the susceptible-recurrent parent. Among eight candidate defense response genes detected in several loci, a single gene (oxalate oxidase) present on chromosome 3 was found to be associated with blast resistance in upland indica rice. Ultimately, these advanced backcross lines with resistance to blast tagged by markers might be useful for pyramiding blast resistance alleles in upland rice.