水稻种子活力QTL定位及上位性分析

利用1个粳／籼交来源(Lemont／Teqing)、包含264个重组自交系的作图群体，采用纸卷法在18℃培养箱中进行2次重复的发芽实验，考察了种子发芽7d、9d和1ld的发芽率，种子发芽15d后的芽长及干重等种子活力的相关性状。结合一张含有198个DNA标记的连锁图谱，用作图软件QTLMapper1．0定位与种子活力相关的QTL。共检测到13个主效应QTL，这些QTL对性状的贡献率为2．9％～12．7％，平均贡献率为6．2％。同时检测到18对贡献率≥5％的互作位点，其贡献率为5．1％～11．8％，平均贡献率为6．9％，比检测到的主效应QTL的平均贡献率稍大。种子活力相关性状的大多数主效应和互作QTL成串分布于少数几个染色体区段(Chromosome Regions，CRs)，并且成串分布在同一染色体区段的QTL效应的方向总是一致，该结果与这些性状在表型上的正相关相一致。若将成串分布有3个及3个以上种子活力相关性状QTL的CRs视为与种子活力高度相关的CRs，则共检测到7个上述与种子活力高度相关的CRs，分别分布在水稻12条染色体中的7条染色体上。根据所含QTL的种类(主效应QTL或／和上位性QTL)可将这些CRs分成以下3种：1)M-CRs：只含有主效应QTL，如CR^sv-7；2)E-CRs：所含位点没有主效应，但与其他位点发生互作，如CR^sv-1、CR^sv-6和CR^sv-12；3)ME-CRs：既含有主效应QTL、也含有与其他位点产生互作的互作位点，如CR^sv-2、CR^sv-5和CR^sv-8。另外还发现，有的CR上的位点同时与多个不同CR上的位点互作，影响种子活力的相关性状。与前入的研究结果相比较，发现有些与种子活力高度相关的CR可在不同研究者所用的不同定位群体中被检测到，而有的CR只在特定的定位群体中被检测到。由此表明，水稻种子活力具有丰富的遗传多样性和复杂的遗传基础，其主效QTL和互作位点可能基于遗传背景的不同而相互转化。

Identification of Chromosome Regions Associated with Seedling Vigor in Rice

Seedling vigor is important for optimum stand establishment in rice cropping. In this paper,a set of 264 F12 re-combinant inbred lines (RILs) derived by single seed descent from a cross between Lemont (japonica) and Teqing ( indi-ca) was phenotyped for three seedling vigor related traits,including seed germination rate (GR) , seedling shoot length and dry weight by the rolled paper towel tests. The phenotype data and a linkage map consisting of 198 DNA markers were com-bined to map quantitative trait loci (QTL) for seedling vigor by using a computer program QTL Mapperl. 0. A total of 13 pu-tative main-effect QTL were detected. All of these QTL had much smaller effects on the traits with a mean R2 of 6. 2% ,ran-ging from 2.9% to 12.7%. As for digenic interaction, 18 pairs of epistatic loci with R2 ≥5% were resolved with a mean R2 of 6.9% ,ranging from 5.1% to 11.8% ,which was slightly larger than that of the main-effect QTL identified for the traits.The majority of the main-effect and epistatic loci detected for seedling vigor related traits were clustered in a few chromo-some regions. Together, seven such chromosome regions (CRs) , each with three or more seedling vigor main-effect and epi-static loci,were found to be highly associated with seedling vigor. These CRs can be classified into three types,i, e. M-CRs,E-CRs and ME-CRs. For some CRs just like CRsv-6,the QTL within one CR were found to interact simultaneously with QTL within more than one other CRs to affect different seedling vigor related traits. The above results revealed that seedling vigor in rice is controlled by many loci, most of which have relatively small effects. Comparatively, epistasis as a genetic factor would be more important than main-effects of QTL for seedling vigor in rice. Nevertheless, the effects of the QTL are still large enough to be detected and in fact several chromosome regions were found to be highly associated with seedling vigor in very different populations as compared with previous studies. Molecular tagging of favorable alleles and marker-aided selec-tion strategy may,therefore,be a promising approach to the improvement of rice seedling vigor.