Race specific and non-specific resistance to Magnaporthe oryzae and QTL mapping in wild introgression lines using the standard differential system

Blast disease caused by Magnaporthe oryzae is one of the major challenges to rice crop production worldwide. Wild and related species are potential source of novel alleles or genes for crop improvement especially for biotic stress resistance. This study was designed to characterize blast resistance in a set of wild introgression lines developed in the background of Indian mega rice variety Swarna. The introgression lines (INLs) under this study showed spectra of resistance across the different blast isolates inoculated. Monogenic differential varieties with known specific Pi genes and the susceptible checks were used in phenotyping. This study confirmed the usefulness of the differential system consisting of monogenic varieties and differential blast isolates for the systematic characterization of resistance in novel germplasm and to understand the genetic architecture of blast resistance. Twelve race specific quantitative trait loci (QTL) for partial resistance to disease were detected in these wild introgression lines from O.nivara using composite interval mapping. Of these, 10 were showing resistance to only one isolate each, while QTL detected in chromosome 3 showed resistance against isolates JPF514 and PHL16. While most of the QTLs mapped to previously reported defense related genes whereas two QTLs qBL2.2 and qBL5.1 between RM106—RM5460 and RM5140—RM289 with PVE% of 12.28 and 12.48 respectively are novel with no known blast resistance related genes reported within the locus. This study helps to provide developing the basis for future investigations on race specific or broad-spectrum resistance in rice and related crop species.