Analysis Of QTL For Rice Yield And Silicon Content On The Short Arm Of Chromosome 6

Quantitative trait loci (QTL) of rice yield and hull silicon content (HUS) in RM587-RM19784 on the short arm of rice chromosome 6 were dissected by using RHL-derived populations in previous studies. In a region apart from centromere, a HUS QTL qHUS6.1 and a yield-controlling QTL was mapped in a 62.4 kb and 125 kb interval, respectively. In the pericentromere rejoin, QTLs of HUS and rice yield were primarily validated. This study was conducted to fine map qHUS6.1 and to further analyze QTLs of rice yield in RM111-RM19784. Meanwhile, NILs with Zhenshan 97B genetic background were developed to analyze the comprehensive effect and epistasis of two intervals on the short arm of chromosome 6. The main results are summarized as follows:1. Toward qHUS6.1, a quantitative trait locus (QTL) for rice HUS on the short arm of chromosome 6, three sets of near isogenic lines (NIL) with heterogeneous interval RM4923-RM19410, RM19410-Si2944, Si2944-RM204 were developed, respectively. They were grown in the paddy field and measured at maturity for HUS, silicon content in flag leaf (FLS), and stem (STS), respectively. Based on analyses of the phenotypic distribution and variance among different genotypic groups in the same NIL set, qHUS6.1 was delimited to a 29.9 kb region flanked by RM19410 and Si2944. This QTL showed strong additive effects on HUS, FLS and STS, and the enhancing alleles were always derived from the paternal line Milyang 46. The present study will facilitate the cloning of qHUS6.1 and the exploration of new genetic resources for QTL fine mapping.2. Two F2 populations segregating in RM111-RM19715 and Si9337-RM19784 were developed for QTL detection of rice yield in RM111-RM19784 on the short arm of chromosome 6. Two QTLs with same additive effect direction for the number of spikelets per panicle (NSP) were detected, of which qNSP6.2 co-segregating with heading date gene Hd1 had major effect and showed significant effects on the number of grains per panicle (NGP) and grain yield per plant (GY). The other QTL qNSP6.1 locating in an upper region of Hd1 had smaller effect and showed significant effects on GY. The two QTLs for NSP were validated by two NIL sets segregating in two sub-regions of interval RM111-RM19784, and the two QTLs both showed significant effects on NGP and GY in the same additive effect direction as NSP.3. Two individuals with a main heterozygote on the short arm of chromosome 6 and homozygote in the background were selected from the RHL-derived populations. By 2 generations of back-crossing with Zhenshan 97B and 3 generations of selfing, separating populations with Zhenshan 97B genetic background and only differed in a small part on the short arm of chromosome 6 were developed.4. By using the NILs developed above, two intervals RM469-RM6917 and RM3438-Si9337 on the short arm of chromosome 6 were selected for comprehensive effect study and epistasis analysis on rice heading date, yield and silicon content. Based on analyses of the phenotypic distribution and variance among different genotypic groups in the same NIL set, the two intervals both showed significant effects on rice heading date, yield and silicon content, and significant epistasis was detected on HUS: when RM3438-Si9337 was Zhenshan 97B homozygote, the enhancing allele for HUS in RM469-RM6917 was derived from Zhenshan 97B; when RM3438-Si9337 was Milyang 46 homozygote, the enhancing allele for HUS in RM469-RM6917 was derived from Milyang 46.