The use of molecular information for plant breeding

本研究的目的是通过分子手段选择和创造水稻的新基因。首先，对影响食味品质的Wx基因顺式作用元件的多样性进行了研究。通过比较DNA序列和重组频率，发现WX GO中的区域具有重组活性，并且有可能重组水稻品种之间存在的不同顺式作用元件。其次，进行了诱导反式作用突变基因的实验。灌浆期的低温促进了Wx基因的表达，导致稻米的食味品质变差。利用Wx突变体在低温下可直观检测到直链淀粉含量增加的特点，筛选EMS处理后对温度不敏感的突变体。Western blotting分析表明，一个突变株系对Wx的表达不敏感。本研究结果表明，该突变体有助于稳定稻米的食用品质。由于该突变体不易转移到水稻品种中，因此建议选育具有渗漏表型的水稻品系进行诱变育种，以便更快地利用它。

The objectives of the present study is to select and create new genes by means of molecular approaches in rice. Firstly, the experiments were carried out regarding the diversification of cis-acting elements of the Wx gene whose expressions have a role for eating quality. By comparing DNA sequences and recombination frequency, it was found that the region in the Wx gone is recombinationally active and it is possible to recombine different cis-acting elements which are present among rice cultivars. Secondly, the experiments were carried out to induce trans-acting mutant genes. The Wx gene expression is enhanced by cool temperatures during the grain-filling period, causing unfavorable eating quality of rice. A leaky wx mutant were used to screen temperature-insensitive mutations after EMS treatments since the increment of amylose was visually detected under low temperatures. A mutant line was proved by western blotting analysis to be temperature-insensitive regarding the Wx expression. The present results revealed that this mutant is useful for stable eating quality of rice. Since the transfer of the mutant into rice cultivars is not easy, it is suggested that mutation breeding of rice lines carrying the leaky phenotype could be more practical for its prompt use.