(59(4):275-288)Rice Genetic Variation under the Three-Step Propagation System

本研究的目的為探討水稻良種繁殖三級制度中各級種子之遺傳一致性；以對於2004 至2005 年台灣地區良質米水稻品種具有完全鑑別力之23 個SSR 標誌為分析工具，而各品種遺傳組成之標準資料，係以2004 年第二期作良種繁殖更新計畫中所生產之原原種種子為基礎。標準資料顯示大多品種原始種子與原原種之遺傳組成一致，且為單一基因型，僅台稉11、16 號與台農秈22 號以及高雄139、145號品種內並存多種基因型。以2005 年第一期作所衍生的77 處原種田，探討良種繁殖制度下各原種種子的變異性，各品種與其基礎資料相互比較後，結果顯示大體上品種之原種均與上一期作之原原種遺傳組成一致，但台稉9 號原種與其原原種部份不一致，及台稉16 號品種內多基因型並存現象發生變異，與部分台農71號原種出現特異基因型。最後建議藉由延後一季單株選拔，在F5 世代仍進行單株選拔，待F6 (F5:6) 世代才混合收穫，其種子整齊度將由87.5%提升至93.75%，避免日後逐年進行去偽去雜的工作。 Objective of this study is to determine the genetic consistency of seeds produced under three-step propagation system. Twenty-three simple sequence repeat (SSR) markers which have full discrimination power on 22 superior rice varieties produced in Taiwan during 2004 and 2005 were used in this study. Breeder’s seeds and foundation seeds of these 22 varieties were used to establish standard genetic profiles for each variety. The result shows that allelic composition of foundation seeds possessed single genotype and was identical with breeder’s seeds in most varieties. But allelic composition of TK11, TK16, KH139, KH145 and TNGS22 contained more than one genotype. Cluster analysis of 77 registered samples in 2005 first season and their predecessors, breeder’s seed, reveals high genetic consistency except TK9, TNG71 and TK16. In final, it is suggested to extend one more generation for plant selection until F5 gneration, in order to increase seed identical ratio from 87.5% to 93.5%