Baack Eric J, Sapir Yuval, Chapman Mark A, Burke John M, Rieseberg Loren H
Department of Botany, University of British Columbia, 6270 W University Blvd, Vancouver, BC, Canada V6T 1Z4.
Mol Ecol. 2008 Jan;17(2):666-77. doi: 10.1111/j.1365-294X.2007.03596.x. Epub 2007 Dec 20.
The strength and extent of gene flow from crops into wild populations depends, in part, on the fitness of the crop alleles, as well as that of alleles at linked loci. Interest in crop-wild gene flow has increased with the advent of transgenic plants, but nontransgenic crop-wild hybrids can provide case studies to understand the factors influencing introgression, provided that the genetic architecture and the fitness effects of loci are known. This study used recombinant inbred lines (RILs) generated from a cross between crop and wild sunflowers to assess selection on domestication traits and quantitative trait loci (QTL) in two contrasting environments, in Indiana and Nebraska, USA. Only a small fraction of plants (9%) produced seed in Nebraska, due to adverse weather conditions, while the majority of plants (79%) in Indiana reproduced. Phenotypic selection analysis found that a mixture of crop and wild traits were favoured in Indiana (i.e. had significant selection gradients), including larger leaves, increased floral longevity, larger disk diameter, reduced ray flower size and smaller achene (seed) mass. Selection favouring early flowering was detected in Nebraska. QTLs for fitness were found at the end of linkage groups six (LG6) and nine (LG9) in both field sites, each explaining 11-12% of the total variation. Crop alleles were favoured on LG9, but wild alleles were favoured on LG6. QTLs for numerous domestication traits overlapped with the fitness QTLs, including flowering date, achene mass, head number, and disk diameter. It remains to be seen if these QTL clusters are the product of multiple linked genes, or individual genes with pleiotropic effects. These results indicate that crop trait values and alleles may sometimes be favoured in a noncrop environment and across broad geographical regions.
基因从作物流入野生种群的强度和范围，部分取决于作物等位基因以及连锁位点上等位基因的适合度。随着转基因植物的出现，人们对作物 - 野生基因流动的兴趣增加了，但非转基因作物 - 野生杂种可为理解影响渐渗的因素提供案例研究，前提是已知位点的遗传结构和适合度效应。本研究利用作物和野生向日葵杂交产生的重组自交系（RILs），在美国印第安纳州和内布拉斯加州两个不同环境中评估对驯化性状和数量性状位点（QTL）的选择。由于恶劣天气条件，在内布拉斯加州只有一小部分植株（9%）结籽，而印第安纳州的大多数植株（79%）进行了繁殖。表型选择分析发现，在印第安纳州，作物和野生性状的混合受到青睐（即有显著的选择梯度），包括更大的叶片、更长的花期、更大的花盘直径、减小的舌状花大小和更小的瘦果（种子）质量。在内布拉斯加州检测到有利于早花的选择。在两个田间地点的连锁群六（LG6）和九（LG9）末端都发现了适合度的QTL，每个解释总变异的11 - 12%。LG9上作物等位基因受青睐，但LG6上野生等位基因受青睐。许多驯化性状的QTL与适合度QTL重叠，包括开花日期、瘦果质量、头状花序数量和花盘直径。这些QTL簇是多个连锁基因的产物，还是具有多效性的单个基因，还有待观察。这些结果表明，作物性状值和等位基因有时可能在非作物环境和广泛的地理区域中受到青睐。
