酒米品種美山錦之苗期高度耐寒性基因的定位

Abstract

低溫寒害長期以來都是造成臺灣水稻產量損失的主要天然災害之一，其中又以第一期稻作秧苗期最常發生，會導致生長緩慢及秧苗矮小，甚至黃化枯萎。為避免寒害造成水稻產量的重大損失，選育耐寒品種才是根本且有效的策略。因此本研究以日本高耐寒酒米品種「美山錦」及臺灣的良質栽培品種「臺南16號」兩稉稻品種作為雜交親本，利用其F_(2:3)族群進行苗期耐寒性的基因座定位，並探討其遺傳機制。結果顯示，本研究共定位到四個苗期耐寒性相關的QTL，其耐寒等位基因皆來自美山錦品種，可提高苗期之耐寒性。其中qLTT-2及qLTT-7效應較小且耐寒外表型為隱性遺傳模式；qLTT-5及qLTT-6效應較大且耐寒外表型為加性遺傳模式。由前人選殖之耐寒基因所對應本研究QTL所在範圍進行DNA定序，結果並未發現兩雜交親本間DNA序列之差異，表示本研究所涉及之基因可能在此些選殖基因之外。此外，本研究同時使用與qLTT-5及qLTT-6緊密連鎖之分子標誌RM17764及CH0629篩選耐寒個體，發現其正確率可達100 %，將可有效利用於苗期耐寒品系之選拔。本研究成功以兩稉稻雜交族群進行高耐寒酒米品種美山錦苗期耐寒性的QTL定位及遺傳分析，其結果可作為未來水稻耐寒遺傳研究抑或耐寒品種選育之參考。

Cold surges is one of the main natural disasters causing rice production loss in Taiwan. This low temperature stress usually happens at the seedling stage of the first cropping season, which severely decreases seedling vigor by causing slow growth, leaf yellowing, or even wilting. To avoid the yield loss caused by cold surges, breeding for a cold tolerant rice variety is an efficient way to tackle the problem. In this study, we carried out a quantitative trait loci (QTL) mapping of low temperature tolerance at seedling stage (LTT-S) and analyzed the genetic mechanisms in an F_(2:3) population derived from the cross between Miyamanishiki (Mi), a highly low temperature tolerant Japanese sake-brewing cultivar, and Tainan 16 (TN16), a Taiwanese japonica rice variety. The result shows that there are four QTL associated with LTT-S, and the tolerant alleles are all from Mi. qLTT-2 and qLTT-7 are minor QTL and their phenotypes of LTT-S are persumed as the recessive genetic mechanism; qLTT-5 and qLTT-6 are the major QTL and their phenotypes of LTT-S are persumed as the additive genetic mechanism. We also carried out DNA sequencing on annotated cold tolerance relating genes within QTL intervals of our study, but we did not detect any difference between DNA sequences of Mi and TN16, indicating that those genes are not related to QTL associated with LTT-S in this study. Furthermore, we used two SSR markers (RM17764 and CH0629) which are closely linked with qLTT-5 and qLTT-6 to select low temperature tolerant lines. By using these two markers, we obtained 100 % accuracy, suggesting that these markers can be applied to the selection of LTT-S. The results of QTL mapping and genetic analysis could provide useful information for future genetic studies and breeding programs on LTT-S of rice.