Eco-physiological analysis on hybrid rice productivity using genome information

水稻（Oryza sativa L.）包括两个亚种，即ssp。japonica和ssp. indica。尽管在以往的水稻育种中很少采用籼粳亚种间杂交，但人们已经意识到，籼粳杂种在许多农艺性状上表现出显著的杂种优势，如生物产量、抗逆性、本项目旨在阐明这些性状在表现出高的粳稻×籼稻杂交分离群体中是如何受到遗传控制的。杂种优势为此，我们利用本实验室最初培育的Nekken 2（低地粳稻）× Gaya（低地籼稻）重组自交系、Kamenoo（低地粳稻）× Dular（雨养-低地籼稻）重组自交系和IR 36（低地籼稻）× Genjah Wangkal（高地粳稻）重组自交系进行了数量性状位点（QTL）分析。我们发现基因间互作（上位性）是许多性状超亲分离的主要原因。我们还发现了一些性状的连锁小QTL（如：分蘖芽休眠和叶时期）对它们的产量（例如分蘖数）具有倍增的大的影响，这表明上位性至少部分地在形态水平上被整合。

Rice (Oryza sativa L.) includes two subspecies, namely ssp. japonica and ssp.indica. Although japonica-indica intersubspecific cross has been very rarely used in the past rice breeding programs, rice breeders have been aware that hybrid plants between japonica x indica cross frequently exhibit notable heterosis in many agronomic traits such as biomass production, stress tolerances, etc. This project was aimed to clarify how these characters are controlled genetically in segregating populations from japonica x indica crosses that show high heterosis. For this purpose, we carried out quantitative trait locus (QTL) analyses using Nekken 2 (lowland japonica) x Gaya (lowland indica) recombinant inbred lines, Kamenoo (lowland japonica) x Dular (rainfed-lowland indica) recombinant inbred lines, and IR36 (lowland indica) x Genjah Wangkal (upland japonica) recombinant inbred lines which were originally developed in our laboratory. We found that gene to gene interactions (epistasis) are the major cause of transgressive segregation in many traits. We also found that linked small QTLs for some traits (eg. tiller bud dormancy and phyllochron) have a multiplicative large effect on their product (e.g. tiller number), suggesting that epistasis is, at least in part, integrated at morphological level.