多環境下的水稻穀粒長寬及白堊質 數量性狀基因座定位

Abstract

本研究以台稉2號與台中秈10號雜交分離產生的F2:4家系族群，於98年度1期作與2期作栽培於高雄、台中與台北三地區，並以多重區間定位法分析水稻穀粒長寬與白堊質比率外觀性狀的數量性狀基因座 (QTL) 位置及遺傳效應。白堊質比率在絕大部分的家系都低於5%，在所有環境下均呈現極度偏歪分佈，因此白堊質比率以對數轉換為近似常態分布後進行後續的QTL分析。在所有的環境中，穀粒長、寬間均無相關性，而穀粒寬與白堊質比率之間均呈現相當程度的正相關，此與多數前人研究之觀察一致。本試驗採用R/qtl程式進行QTL定位，共得到26個QTLs：穀粒長有7個，外表型變異解釋量介於3.7~19.1 %；穀粒寬有7個，外表型變異解釋量介於3.7~32.1 %；白堊質有12個QTLs，外表型變異解釋量介於3.1~19.6 %。穀粒長寬的主效QTL位在不同染色體上，但穀粒寬與白堊質的主效QTLs可能存在緊密連鎖或基因多效性。本研究所定位到的穀粒寬主效基因qGW5與前人所發表的GW5基因位置相近，白堊質比率qLC7基因座與前人發表的qPGWC-7數量性狀基因座位置相近，應為相同的基因座。qLC7基因座來自台中秈10號的對偶基因可降低白堊質比率，且此基因座與穀粒寬QTL之間並無連鎖關係，透過分子標誌輔助選種可將此一秈稻染色體片段導入至稉稻的染色體組中，將可有效降低稉稻中的白堊質比率，並提升台灣優良水稻品種的外觀品質。

Quantitative trait loci (QTLs) controlling grain length, grain width and percentage of grain chalkiness of rice were mapped with F2:4 lines derived from a cross between TK2 and TCS10, using multiple interval mapping method implemented in R/qtl package. Phenotypic data were collected from multi-environment trials conducted at Kaohsiung, Taichung and Taipei under two growing seasons in 2009. Since the percentages of grain chalkiness were lower than 5% for most of the lines and thus showed skewed distributions in all environments, measurements were log-transformed before further analysis. In all environments, grain width was not correlated with grain length, but positively correlated with percentage of grain chalkiness. Twenty-six QTLs were identified on eleven chromosomes which included 7 QTLs controlling grain length, with phenotypic variation explained from 3.7 to 19.1 %; 7 QTLs controlling grain width, with phenotypic variation explained from 3.7 to 32.1 %; and 12 QTLs controlling grain chalkiness, with phenotypic variation explained from 3.1 to 19.6 %. While major QTLs for grain width and grain length were located at different chromosomes or regions of chromosome, some of the major QTLs for grain width and chalkiness may be linked or pleiotropic. QTLs qGW5 and qLC7 identified in this study, which controlling grain width and percent grain chalkiness respectfully, located at the same regions with recently published GW5 and qPGWC-7. The qLC7 allele originated from the indica parent TCS10 has a negative effect on grain chalkiness and is the only QTL identified in this study not correlated with reduced grain width, may be a useful source for fourthly reducing grain chalkiness for premium japonica rice varieties through marker assisted selection.