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CROP BREEDING & GENETICS

Mapping of Quantitative Trait Loci Using a Doubled-Haploid Population from the Cross of Indica and Japonica Cultivars of Rice

^a Plant Breeding and Biotechnology Division, Philippine Rice Research Institute (PhilRice)-Los Baños, Pili Drive, College, Los Baños 4031
^b Plant Breeding, Genetics, and Biotechnology Division, International Rice Research Institute (IRRI), Los Baños 4030, Laguna, Philippines
^c Bioprocess Engineering Division, Faculty of Agriculture, Yamagata University, 1-23 Wakaba-machi, Tsuruoka, Yamagata 997-8555, Japan. The study is part of the Ph.D. dissertation of the senior author, V.C. Lapitan, under the Japan Society for the Promotion of Science (JSPS) RONPAKU Program

^* Corresponding author (tabe{at}tds1.tr.yamagata-u.ac.jp).

Improving the cooking and eating quality of grain has always been an important consideration in most rice (Oryza sativa L.) breeding programs. In this study, an established rice doubled-haploid (DH) population consisting of 219 lines from anther culture of the F1 of indica variety PSB Rc10 and japonica variety Nipponbare was used to identify the quantitative trait loci (QTL) for amylose content (AC), gel consistency (GC), and gelatinization temperature (GT). Two hundred five simple sequence repeat (SSR) markers were used to construct a genetic linkage map covering the 12 chromosomes. A total of 13 QTLs were identified—three for AC and five each for GC and GT. Eight QTLs had major effects from which seven coincided with the most important loci identified in previous reports. All QTLs for AC were shown to have major effects on GC and GT. The QTL with the largest effect, which accounted for 74% of the AC variation corresponded to the waxy (Wx) locus while the other two QTLs were located above and below this region. The significant phenotypic correlations of these traits may underlie the colocalization of their QTLs. A major QTL specifying GT was detected within the alkali degeneration (Alk) locus. Other minor QTLs were identified for GC in chromosomes 2 and 8 and for GT in chromosome 2. Utilization of a homozygous DH population with relatively large sample size might have increased the accuracy of mapping these QTLs. The results thus obtained are valuable in breeding rice varieties with better grain quality.

Abbreviations: AC, amylose content • alk, alkali degeneration gene • ASV, alkali spreading value • DH, doubled haploid • GC, gel consistency • GT, gelatinization temperature • IRRI, International Rice Research Institute • MAS, marker-assisted selection • PhilRice, Philippine Rice Research Institute • SSR, simple sequence repeat • Wx, waxy gene