油菜含油量性状QTL关联分析及有利等位基因在品种中的构成分析

Validation of QTL for Oil Content in a Population of Worldwide Rapeseed Cultivars by Association Analysis

【目的】验证不同遗传背景下7个含油量QTL的稳定性、通用性和实用性,检测QTL连锁标记辅助选择提高含油量的可行性,发掘可能实质性影响油菜含油量性状的候选基因。【方法】利用已发表的SG群体在11种环境下的QTL结果,在7个主效QTL峰值或置信区间内选择14个油脂形成相关候选基因标记对81份核心种质两年度的含油量数据进行关联分析,并鉴定各QTL位点高油等位基因在不同品种中的分布。【结果】4个QTL(OilA1、OilA5、OilA7和OilC8-1)位点的6个连锁标记在81个品种高、低2种等位基因间平均含油量差异达到显著或极显著;对其中4个标记Ra2E04、ZAAS919、ZAAS828和ZAAS441的跟踪选择和聚合,可相应提高含油量5个以上百分点;根据标记基因型推测,OilA1和OilC8-1位点,超过80%的欧洲春、冬油菜品种中已含Sollux高油等位基因,但中国品种中则80%和60%的品种含低油等位基因;OilA5和OilA7位点上,几乎所有被检欧洲材料均不含Gaoyou高油等位基因,而中国双低和双高品种中也只有约20%—30%含此有利等位基因。【结论】与4个QTL连锁的6个拟南芥油脂相关同源基因(At3g51830、At2g42450、At2g44620、At1g73600、At1g73480和At1g13560)有可能实质性参与油菜种子油分累积;当聚合了包括OilA7在内的3个或3个以上QTL位点高油等位基因时,含油量可相应提高5个百分点;所揭示的4个QTL高油等位基因在中国尚有较大利用空间而OilA5和OilA7的Gaoyou等位基因可能尤为欧洲油菜育种家们关注。

[Objective] The objective of this study is to validate the genetic stability of 7 major QTL for oil content, which were detected in authors＇ previous researches, and to assess the feasibility of marker assisted selection for improving seed oil content using closely linked functional makers. [Method] Fourteen lipid related candidate gene markers located in the 7 QTL regions were chosen to amplify 81 core collections ofBrassica napus and then a linkage disequilibrium was estimated by marker-trait association analysis. Meanwhile, the allelic distribution among 81 world-wide cultivars in each QTL was investigated. [Result] By association analysis, significant differences in oil content were detected between favorable and unfavorable allele genotypes in each of six linked markers flanking four QTL （OilA1, OilA5, OilA7 and OilC8-1）, respectively. Over 5 percentage in oil content could be increased by assembling favorable alleles together through four QTL linked markers Ra2E04, ZAAS919, ZAAS828 and ZAAS441. According to the marker genotypes, in the loci of OilA1 and OilCS-1, higher than 80% of European cultivars have carried positive alleles from ＂Sollux＂, while 80% and 60% Chinese materials contain unfavorable alleles. On OilA5 and OilA7, almost all the tested European varieties did not show favorable alleles from ＂Gaoyou＂ and for Chinese materials, also only around 20%-30% cultivars carrying these positive alleles. [ Conclusion ] Six orthologous gene markers （corresponding to At3g51830, At2g42450, At2g44620,Atl g73600, Atlg73480 and Atlg13560）, which closely link to OilA1, OilA5, OilA7 and OilCS-1 might be functional important in the accumulation of oil content in rapeseed. When favorable alleles from three QTL including OilA 7 or all four selected QTL combined together, the oil content could be increased more than 5 percentages. The results showed that the positive alleles in screened out 4 QTL loci are potentially interesting for present breeding programs in China, while the Chinese alleles from OilA5 and OilA7 should be also attractive to rapeseed breeders in European countries.