Studies on agronomic genes in rice.

本研究的目的是探讨为什么遗传多样性，特别是在农艺性状，保持在作物物种。为了了解正在进行的微观进化过程，在野生稻和栽培稻中研究了响应温度（抗寒性）、光周期（开花时间）和生物环境（与杂草的竞争）的遗传改变。这些性状的适应机制不能很好地用少数主效基因解释，表明上位性，基因型×环境（GE）的互作和连锁基因参与除了基因与小的加性效应。结果表明，上位性效应和GE互作效应的存在对水稻遗传多样性的维持起着重要作用。遗传多样性也受到当前微观进化力量模式（如基因流动和选择）和系统发育历史的影响。农艺基因的系谱学提供了对它们历史的深入了解。出乎意料的是，“绿色革命”基因（sd 1）在野生祖先中预先存在，表明农民选择它来获得高产，以应对农业实践的改变。相反，在C、A和wx基因的情况下，表明变体通过自然或人工选择从地方品种产生。这些结果使我们认为每个基因都有一个独特的历史，这可能反映了自然选择和/或人工选择的不同模式。农民似乎从野生种群中挖掘了sd 1等位基因，并将其保留在不同的地方品种中，而农民则有意识或无意识地从地方品种中选择了C、wx和A基因的新突变。因此，地方品种也有望保留农艺学上有价值的基因，即使核苷酸多样性的减少是由于驯化造成的种群瓶颈。

The objective of this study is to examine why genetic diversity, especially in agronomic traits, is maintained in crop species. To understand ongoing micro-evolutionary processes, genetic alterations in response to temperature (cold resistance), photoperiod (flowering time) and biotic environments (competition with weeds) were investigated in wild and cultivated rice. The adaptive mechanism in these traits was not well explained by a few major genes, suggesting that epistasis, genotype x environment (GE) interaction and linked genes were involved in addition to genes with a small additive effect. The results showed that the presence of epistasis and GE interaction play a significant role for the maintenance of genetic diversity in rice. Genetic diversity is also affected both by current patterns of micro-evolutionary forces, such as gene flow and selection, and by the phylogenetic history. Genealogies of agronomic genes provided insight into their history. Unexpectedly, "Green Revolution" gene (sd1) preexisted in the wild ancestor, showing that farmers have selected it to obtain a high yield in response to altered practices in agriculture. In contrast, in the case of C, A and wx genes, it was indicated that variants have generated from landraces through natural or artificial selection. These results lead us to consider that each of the genes has a unique history, which might reflect on different patterns of natural and/or artificial selection. It seems that farmers have mined the sd1 allele from the wild population and have maintained it in different landraces, while farmers have selected newly arisen mutations from landraces in the case of C, wx and A genes consciously or unconsciously. Therefore, landraces are also expected to preserve agronomically valuable genes, even if a reduction in nucleotide diversity was caused by the population bottleneck due to domestication.