利用分子標誌輔助回交育種以改良秈稻與稉稻品種之苗期耐寒性

Abstract

水稻的苗期生長容易受到低溫的不良影響，臺灣第一期作所栽培的水稻就經常遭受冬末春初的低溫危害。為了減少低溫對農業的損失，選育具有較佳耐寒性的品種是一種有效的方法。由於在臺灣，秈稻栽培品種台中秈10號和稉稻栽培品種台農71號具有苗期對低溫敏感的特性。而美國加州主要種植的稉稻品種 M202 具有優良的低溫耐性，其耐寒性相關的 qCTS12 基因已被發現。因此，本研究的主要目標是分別產生秈稻和稉稻的回交族群，並利用SSR分子標誌為輔助選育工具，將 qCTS12 基因導入兩個不耐寒的水稻品種中，希望藉此提升水稻的耐寒性。在秈稻品種改良方面，連續進行了 BC1F1、BC2F1 和 BC3F1 三個世代的選拔工作，使用兩個緊密連鎖的分子標誌 RM24424 和 RM24449 進行前景選拔。並且利用 22 個分佈在其他11對染色體上的分子標誌分析 BC1F1和 BC2F1 世代選獲個體的輪迴親背景。最終，根據前景選拔和 BC2F1 背景分析的結果，選出了 BC3F1 編號 #3-55-4 單株，並將進行自交產生 BC3F2，以選育出具有高耐寒性的台中秈10號近似同源系。同時，本研究也在M202和台中秈10號之間的 OsGSTZ1 基因DNA序列中發現了兩個錯譯突變，這可能導致兩個品種之間耐寒性的差異。在稉稻品種改良方面，則使用了 RM24427 和 RM24449 兩個分子標誌進行前景選拔。並且亦以 22 個分子標誌分析 BC1F1和BC2F1 世代選獲個體輪迴親背景。然而，根據 BC1F2 的耐寒性外表型調查和OsGSTZ 基因DNA序列分析的結果，推測導入 qCTS12 對於台農 71 號之耐寒性的改良效果可能不明顯。未來以分子輔助選種所選拔出來的個體，尚需進行實際田間耐寒性檢定，與回交親本之表現相互比較，以驗證選拔品系之耐寒性，期望最終可成功獲得具有高苗期耐寒性之優良品種。

The rice seedling is easily damaged by low temperature, especially when it is grown during late winter and early spring of the first crop season in Taiwan. To reduce the production losses caused by low temperature, breeding new varieties with better cold tolerance is a feasible approach. Due to the less cold tolerance for leading indica- type variety Taichung Sen No.10 (TCS10) and japonica- type variety Tainung 71 (TNG71), one cold tolerance gene qCTS12 of the cultivar M202 was introduced from California (USA) to improve their cold tolerance by marker-assisted backcross (MAB) method in this study. In the improvement of indica rice variety TCS10, three generations of backcrossing BC1F1, BC2F1, and BC3F1 were successfully conducted with two SSR markers (RM24424 and RM24449) closely linked with QTL-qCTS12 for foreground selection, and additional 22 markers distributed in chromosomes 1 to 11 for background selection. Based on the results of foreground and background selections, one plant (#3-55-4) of BC3F1 was selected for selfing to generate cold tolerant BC3F2 progenies. Furthermore, two missense mutations were found in the DNA sequences of OsGSTZ1 gene between M202 and TCS10 indicating the potential cause in the cold tolerance difference between the two varieties. Similar MAB method was conducted in the improvement of japonica rice variety TNG71. Two SSR markers (RM24427 and RM24449) for foreground selection and 22 extra markers for background selection were also applied. However, according to the phenotypes of individuals in the BC1F2 population and no DNA sequence variation between M202 and TNG71 was found on OsGSTZ1and OsGSTZ2 genes, it indicated that the cold tolerance attributed from the qCTS12 gene was not significantly. It is suggested that the field cold tolerance tests including two parents as checks are necessary for the lines selected in this study. The ultimate goal is obtaining excellent varieties with high seedling cold tolerance.