利用分子標誌輔助選拔低白堊質稻米之優良品系

Abstract

白堊質為影響碾米品質及稻米外觀之重要性狀，本研究目的為藉由分子標誌測定影響白堊質之數量性狀基因位置，進而利用與這些基因緊密連鎖之分子標誌選拔出有較低白堊質表現之優良品系。本研究利用水稻品種越光與臺農67號雜交所產生之840個個體為材料，先以107個F2衍生品系分析112個SSR和InDel分子標誌以建立連鎖圖譜，並配合外表型資料以區間定位法定位F2和F2:3族群之數量性狀基因座，分析性狀包括白堊質米粒比例、白堊質面積及白堊質程度等三種白堊質相關性狀，以及株高、抽穗期、穗數等重要農藝性狀。並根據數量性狀基因座定位之結果，利用三組與白堊質米粒比例性狀緊密連鎖之RM1248、CH0701和RM6306分子標誌和一組與越光食味品質性狀連鎖之分子標誌RM4108輔助選拔出低白堊質稻米之優良品系，結果共篩選出23個優良基因型之品系，發現其中22個品系之白堊質米粒比例皆小於親本臺農67號，符合預期之結果，並證實選拔之效果。最後再針對這些獲選F2:5優良品系中白堊質相關性狀之分離基因座進行純化和單株選拔，將依據其在不同環境下白堊質性狀及其他重要農藝性狀，選拔出低白堊質、食味佳且產量高之優良品系。本研究於早世代（F2世代）即開始利用分子標誌輔助選拔，可大幅減少傳統育種改良過程中所需之人力和時間，且避免氣候或環境之變動影響選拔之效果，本研究結果可作為未來提高水稻育種效率之參考。

Chalkiness is one of the important traits affecting milling quality and appearance of rice grains. The purpose of this study was to identify quantitative trait loci (QTL) associated with grain chalkiness, and select rice superior lines with less grain chalkiness by marker assisted selection (MAS). A total of 840 lines derived from a cross between rice varieties Koshihikari and TNG67 were used as materials. Among these, 107 F2 derived lines were used to build a linkage map composing a total of 112 SSR and InDel polymorphic DNA markers. Phenotypic data of these 107 lines were used to identify QTL for three grain chalkiness related traits, percentage of grains with chalkiness (PGWC), area of chalky endosperm (ACE) and degree of endosperm chalkiness (DEC). QTL of plant height (PH), days to heading (HD) and panicle number (PN) were also identified by interval mapping analysis. According to the QTL mapping result, three markers, RM1248, CH0701 and RM6306, associated with grain chalkiness and one marker, RM4108, associated with eating quality trait were used to assist selecting 23 lines with less grain chalkiness. Twenty-two of the selected lines had better grain chalkiness trait than the referenced parent TNG67, confirming the expectation of MAS effects. The selected F2:5 lines were genetically purified with single plant selection based on marker genotypes of segregating loci correlated with chalkiness grain. According to the grain chalkiness and agronomic traits investigated under different environments, the most promising lines will be recommended. In this study, because MAS for the improvement of grain chalkiness traits was applied at the early generation (F2 generation), the labor and time resources were saved from the traditional breeding procedures, and the environmental disturbance for selection could be avoided. The results of this study can provide information for enhancing rice breeding efficiency.