利用SSR分子標誌分析水稻F3族群之遺傳重組

Abstract

本研究以19個F3品系共包含230個單株為材料，而這19個F3品系係利用SSR DNA分子標誌分析由水稻秈稻品種台中秈十號(母本)與稉稻品種越光(父本)雜交之93株F2單株，選擇同源染色體分別具有完整母本與父本分子標誌組成之個體，將選獲植株自交以產生F3世代分離族群作為試驗材料，試驗主要目的為探討F3族群之偏差分離、遺傳重組、親本遺傳成分貢獻及同結合基因型比例，並且與本研究室先前分析F2世代之結果比較。 試驗結果顯示，遺傳重組分析顯示在F2世代繁殖至F3世代過程中，各對染色體平均發生交換次數為1.47次，而一個個體約有17.64個(1.47 × 12)交換點，其中第七對染色體發生交換之平均頻度最低，為0.93次，而第二對染色體發生交換之平均頻度最高，為2.11次，與F2世代結果大致相符。在第二對染色體的OSR26、第六對染色體的RM340及OSR21與第十一對染色體的RM202等四個分子標誌基因座呈現偏差分離現象，佔F3族群所分析的80個基因座中的5%，與F2世代偏差分離比率(46.08%)相比，可發現偏差分離比率大幅下降，此結果支持大多數偏差分離並非由單一基因座所控制之理論。而水稻分離族群往秈稻遺傳成份偏離現象，F3世代中明顯減少。RM340及OSR21基因座異常分離的主要原因是同結合的基因型偏離，而OSR26及RM202基因座異常分離的主要原因則是異結合基因型的數目增加。 本研究係利用分子標誌綜合探討秈稻與稉稻雜交後代F2與F3族群之遺傳重組及基因型分離行為，將可提供秈稻與稉稻雜交族群早世代選拔之參考。

A total of 230 individuals attributed to 19 F3 lines, were used to study segregation distortion, genetic recombination, genetic contribution from female or male parent, and homozygosity in the F3 population. In addition, comparison of genetic recombination between F3 and F2 (previous study) was discussed. The 19 lines with at least one pair of entire homologous chromosomes from each parent were identified using SSR DNA markers from 93 F2 plants of an inter-subspecific cross population, Taichung-Sen 10 (indica type) x Koshihikari (japonica type). The experimental results indicated that the averaged crossing over frequency was 1.47 times for a pair of homologous chromosomes and 17.64 (1.47 x 12) times for an F3 individual bred through F2 generation. The chromosomes 2 and 7 respectively had the highest (2.11 times) and the lowest (0.93) frequencies of crossing over in the F3 generation, and similar results were found in the F2 generation of the same cross. Four SSR DNA loci, including OSR26 on chromosome 2, RM340 and OSR21 on chromosome 6, and RM202 on chromosome 11, accounted for 5% of 80 analyzed loci were detected. In comparison with the F2 generation (46.08%), apparent decline in the frequency of segregation distortion was observed in the F3 generation. This result supports the hypothesis that the segregation distortion is not controlled by a single gene. Segregation distortion to indica genetic background in the F2 generation was obviously reduced in the F3 generation. The segregation distortion in the RM340 and OSR21 loci was mainly caused from the deviation of homozygous genotypes. However, segregation in the OSR26 and RM202 loci was mostly resulted from the increase of heterozygous genotypes. The systematic study results of genetic recombination and genotypic segregation in the F2 and F3 generations of an inter-subspecific cross population would provide information for early generation selection in rice breeding.