增加穗粒数的水稻染色体代换系Z747鉴定及相关性状QTL定位

Identification of rice chromosome segment substitution Line Z747 with increased grain number and QTL mapping for related traits

增加穗粒数对水稻高产品种培育至关重要。其遗传基础复杂,由多基因控制。水稻染色体片段代换系可以将多基因控制的复杂性状分解,因而是理想的遗传研究材料。本研究通过高代回交和自交结合分子标记辅助选择方法,鉴定了一个以日本晴为受体、西恢18为供体亲本的、含有15个代换片段的增加穗粒数的水稻染色体片段代换系Z747,平均代换长度为4.49 Mb。与受体日本晴相比, Z747的每穗总粒数、一次枝梗数、二次枝梗数、穗长和粒长显著增加,粒宽显著变窄、结实率显著降低,但结实率仍为81%。进一步以日本晴和Z747杂交构建的次级F2群体鉴定出46个相关性状的QTL,分布于水稻1号、2号、3号、5号、6号、9号、11号和12号染色体上。其中qGPP12、qPH-3-1、qPH-3-2等12个QTL可能与已克隆的基因等位, qSPP9等34个可能是新鉴定的QTL。Z747的每穗总粒数由2个具有增加粒数效应的QTL (qSPP3和qSPP5)和1个具有减少粒数效应的QTL (qSPP9)控制。研究结果对主效QTL的精细定位和克隆、以及有利基因的单片段代换系培育有重要意义。

Increasing grain number per panicle is important for rice breeding for high yield. Its inheritance is very complex and controlled by many genes. Chromosome segment substitution lines can dissect complex traits controlled by many genes, and thus are ideal genetic research materials. Here, an excellent rice chromosome segment substitution line Z747 with increased grain number was identified from recipient Nipponbare and donor Xihui 18 through advanced backcrossing and inbreeding combined SSR marker-assisted selection. Z747 carried fifteen substitution segments with 4.49 Mb of average length. Compared with Nipponbare, Z747 had significantly increased spikelet number per panicle, number of primary branches, number of secondary branches, panicle length and grain length, and decreased grain width and seed setting rate. However, the seed setting rate in Z747 was still up to 81%. Furthermore, secondary F2 population from crosses between Nipponbare and Z747 was used to map QTL for related traits. A total of 46 QTLs distributed on chromosomes 1, 2, 3, 5, 6, 9, 11, and 12 were detected. Among them, 12 QTLs such as qGPP12, q PH-3-1, and qPH-3-2 etc. might be alleles of cloned genes, and the remaining 34 QTLs such as qSPP9 etc. might not be identified in the past. The spikelet number per panicle of Z747 was mainly controlled by two QTLs(qSPP3 and qSPP5) with effects of increasing spikelet number and one(qSPP9) with decreasing effects. These results are important for fine mapping and cloning of major QTL, and developing single-segment substitution lines carrying favorable QTLs.