Genetic dissection of a thousand-grain weight quantitative trait locus on rice chromosome 1

Thousand-grain weight (TGWT) is an important factor affecting grain yield as well as grain quality in rice. A quantitative trait locus (QTL) qTGWT1-1 for TGWT was detected previously near DNA marker RG532 on the short arm of chromosome 1 in a recombinant inbred line (RIL) population derived from the indica-indica rice cross Zhengshan97B (ZS97B)/Milyang46 (MY46). In this study, two residual heterozygous lines (RHLs), Ch1 and Ch2, derived from the ZS97B/MY46 RIL F₇ population, were used to develop two F₆ populations, RIL-1 and RIL-2. The genome of Ch1 and Ch2 contains a heterozygous region flanked by RM1–RM3746 and RM151–RM243 on the short arm of chromosome 1, respectively, but is homozygous in other regions. Two tightly linked QTLs, Gw1-1 and Gw1-2, with the same additive direction and similar effect on TGWT, were detected in the region of QTL qTGWT1-1 in population RIL-2. No QTL was detected in the population RIL-1. Four individual RHLs from the population RIL-2 carrying heterozygous segments flanked by RM151–RM10404, RM10381–RM243, RM10435–RM259 and RM10398–RM5359, respectively, were chosen to develop four F₂ populations. Ten maternal homozygotes and 10 paternal homozygotes were selected from each of the four F₂ populations derived from the four RHLs. The four sets of near isogenic lines (NILs) were grown for phenotyping of TGWT and delimitation of Gw1-1 and Gw1-2. Results showed that Gw1-1 and Gw1-2 were located in the intervals RM10376–RM10398 and RM10404–RM1344 which cover 392.9 and 308.5 kb regions, respectively. The enhancing alleles were from ZS97B at both loci, and no significant interactions were detected. Genetic dissection of Gw1-1 and Gw1-2 has laid a foundation for their cloning and molecular breeding of grain yield and quality in rice. Supported by the Natural Science Foundation of Zhejiang Province (Grant No. R306285), Rice Breeding Project of Zhejiang Province (Gant No. 2007C12904) and National Natural Science Foundation of China (Grant No. 30623006)