QTL Analysis of Cold-tolerance at Seedling Stage in Rice

To provided the experimental materials for identifying and cloning the quantitative trait loci （QTLs） of cold tolerance at the seedling stage, the authors analyzed QTLs and evaluated the genetic effects of two parents and a mapping population of 213 lines （recombination inbred lines, RILs） derived from a cross between IR24 and Asominori for cold tolerance at the seedling stage with dead seedling rate by using software QTL IciMapping 4.0, based on a genetic linkage map constructed with 141 SSR molecular markers. The QTLs qCTS -6, qCTS -1 1 and qCTS -1 2 related to cold tolerance at the seedling stage were detected on chromosome 6, 11 and 12, respectively. Individual QTLs （LOD-3.194 3, LOD： 4.688 2, LOD-3.797 0） explained 5.662 7%, 8.549 6% and 12.787 7% of the observed phenotypic variance, respectively. All of the three detected QTLs alleles came from cold-tolerant parent Asominori.

Mapping of QTLs Controlling Panicle Length and Effective Panicle Number of Rice

Panicle length and effective panicle number of rice are closely related to yield. In this experiment, indica V20B as female parent was crossed with javanica CPSLO17 as male parent, recombinant inbred line （RIL） populations were obtained by single seed descent method, and with the RIL populations as mapping populations, QTL mapping and analysis were performed to the two panicle traits, panicle length and effective panicle. A high-density genetic map was constructed with SLAF labels, interval mapping was performed by software Map QTL5 under the threshold of 3.9, and 7 QTLs were detected on 3 chromosomes in total. Among the 7 QTLs, 5 QTLs controlling panicle length （qPLI-1, qPL1-2, qPL6-1, qPI_6-2 and qPL6-3） were located on chromosomes 1 and 6, respectively, and showed the contribution rates of 6.41%, 22.22%, 6.15%, 12.24% and 13.01%, respectively, their effect-increasing loci were mainly from CPSLO17, and qPL1-1 is a new QTL; and 2 QTLs controlling effective panicle number （qPN1 and qPN4） were located on chromosomes 1 and 4, respectively, and exhibited the contribution rates of 13.15% and 8.18%, respectively, and the effect-increasing loci were from parent V2OB. The marking of these loci lays a foundation for further cloning of genes controlling panicle length and effective panicle number and molecular marker-assisted selection.

QTL Mapping of Grain Weight Trait in Rice

To provide new experimental materials for QTL analysis of rice yield trait, we constructed a mapping population of 150 1ines （recombination inbred lines, R1L） derived from a cross between rice varieties V20B and CPSLO17, and localized QTLs and evaluated the genetic effects in the two parents and 150 RILs for thousand-grain weight trait by using internal mapping method of software MapQTL5 combining thousand-grain weight phenotypic data of the RILs. The results showed that a new QTL （qTGW-3） related to thousand-grain weight trait was detected. Individual QTL （LOD=4.14） explained 11.9% of the observed phenotypic variance. And the QTL alleles came from the parent V20B.