Genetic and Agronomic Analysis of a Recombinant Inbred Line Population to Map Quantitative Trait Loci for Blast Resistance and Select Promising Lines in Rice

Abstract

Koshihikari has been one of the most popular rice cultivars with good eating quality since the 1960s despite its susceptibility to blast disease and lodging. To map the genes controlling blast resistance and to develop promising blast-resistant breeding lines inheriting Koshihikari’s high eating quality, a recombinant inbred line (RIL) population was developed from a cross between Koshihikari and a blast resistance donor with early maturity, Baegilmi. A total of 394 Koshihikari × Baegilmi RILs (KBRIL), and the two parents, were evaluated for blast resistance and major agronomic traits including heading date, culm length, panicle length, and tiller number. A linkage map encompassing 1,272.7 cM was constructed from a subset of the KBRIL (n = 142) using 130 single nucleotide polymorphisms. Two quantitative trait loci (QTL) for blast resistance, qBL1.1 harboring Pish/Pi35 and qBL2.1 harboring Pib, were mapped onto chromosomes 1 and 2, respectively. qBL1.1 was detected in both of the experimental sites, Namwon and Jeonju, while qBL2.1 was only detected in Namwon. qBL1.1 and qBL2.1 did not affect agronomic traits, including heading date, culm length, panicle length, and tiller number. From the 394 KBRILs, lines that were phenotypically similar to Koshihikari were selected according to heading date and culm length and were further divided into the following two groups based on blast resistance: Koshishikari-type blast resistant lines (KR, n = 15) and Koshishikari-type blast susceptible lines (KS, n = 15). Although no significant differences were observed in the major agronomic traits between the two groups, the KR group produced a greater mean head rice ratio than the KS group. The present study provides useful materials for developing blast-resistant cultivars that inherit both Koshihikari’s high eating quality and Baegilmi’s blast resistance.