中文摘要：

以分子标记辅助选择的手段有目的地进行基因聚合育种,对于加快育种进程具有重要的意义。而基因的加性和上位性效应是决定基因聚合能否成功的关键。本文以16个单片段代换系（SSSL）及15个双片段代换系分析了水稻粒型性状QTL的加性及上位性效应。共检测到9个水稻粒型性状QTL,包括4个粒长QTL、1个粒宽QTL和4个籽粒长宽比QTL,分别位于第2、第3、第4、第7和第10染色体上。此外,还检测出7对双基因互作,其中3对为有显著效应的两座位间互作,1对为两座位均没有显著效应的座位间互作,3对为1个有显著效应的座位与1个没有显著效应的座位间互作。本文结果进一步揭示了同一粒长QTL与不同单片段代换系聚合时会产生不同的互作效应,只有当上位性效应与目标基因的加性效应同向时,才可以达到明显改良粒长的效果。而且,2个长粒或2个短粒QTL聚合很难再产生更长或更短的籽粒。以上结果对于通过分子标记辅助育种手段改良水稻粒型具有重要意义。

英文摘要：

It is important to accelerate breeding process by pyramiding genes purposefully with molecular marker-assisted selection methods.Additive and epistatic effects of genes are the key to the success in genes pyramiding breeding.In this paper,additive and epistatic effects of QTLs for rice grain shape were analyzed using 16 single segment substitution lines（SSSL）and 15 double segment substitution lines（DSSL）.A total of nine QTLs were identified on the chromosomes 2,3,4,7,and 10 respectively,containing four for grain length,one for grain width and four for ratio of grain length to width.Furthermore,seven pairs of digenic interactions were detected for the grain shape.Among them,three interactions occurred between two loci with obvious effects on the traits,one interaction did not have obvious effects at both two loci,and three interactions occurred between one locus with and another without main effect at the single-locus level.Again,the results also indicated that the epistatic effects were different when the same QTL controlling grain length was pyramided with various SSSLs.Only when the epistatic effects were syntropic with the additive effects of the target genes,the pyramiding effect could be obvious.Moreover,longer or shorter grain was difficult to be obtained by pyramiding two QTLs controlling long grain or two QTLs for short grain.The results are important for improving grain shape by molecular marker assisted selection.