Raherison Elie, Majidi Mohammad Mahdi, Goessen Roos, Hughes Nia, Cuthbert Richard, Knox Ron, Lukens Lewis
Department of Plant Agriculture, University of Guelph, Ontario, Canada.
Department of Agronomy and Plant Breeding, College of Agriculture, Isfahan University of Technology, Isfahan, 84156-83111, Iran.
G3 (Bethesda). 2020 Nov 5;10(11):4001-4011. doi: 10.1534/g3.120.401269.
Plant breeding leads to the genetic improvement of target traits by selecting a small number of genotypes from among typically large numbers of candidate genotypes after careful evaluation. In this study, we first investigated how mutations at conserved nucleotide sites normally viewed as deleterious, such as nonsynonymous sites, accumulated in a wheat, , breeding lineage. By comparing a 150 year old ancestral and modern cultivar, we found recent nucleotide polymorphisms altered amino acids and occurred within conserved genes at frequencies expected in the absence of purifying selection. Mutations that are deleterious in other contexts likely had very small or no effects on target traits within the breeding lineage. Second, we investigated if breeders selected alleles with favorable effects on some traits and unfavorable effects on others and used different alleles to compensate for the latter. An analysis of a segregating population derived from the ancestral and modern parents provided one example of this phenomenon. The recent cultivar contains the green revolution semi-dwarfing allele and compensatory alleles that reduce its negative effects. However, improvements in traits other than plant height were due to pleiotropic loci with favorable effects on traits and to favorable loci with no detectable pleiotropic effects. Wheat breeding appears to tolerate mutations at conserved nucleotide sites and to only select for alleles with both favorable and unfavorable effects on traits in exceptional situations.
植物育种是通过在大量候选基因型中经过仔细评估后挑选少量基因型，从而实现目标性状的遗传改良。在本研究中，我们首先调查了通常被视为有害的保守核苷酸位点（如非同义位点）的突变是如何在一个小麦育种系中积累的。通过比较一个有150年历史的祖先品种和现代品种，我们发现近期的核苷酸多态性改变了氨基酸，并且在保守基因中出现的频率是在没有纯化选择的情况下预期的频率。在其他情况下有害的突变可能对育种系中的目标性状影响非常小或没有影响。其次，我们研究了育种者是否选择了对某些性状有有利影响而对其他性状有不利影响的等位基因，并使用不同的等位基因来补偿后者。对来自祖先亲本和现代亲本的分离群体的分析提供了这一现象的一个例子。现代品种含有绿色革命半矮化等位基因和补偿性等位基因，这些等位基因减少了其负面影响。然而，除株高以外的性状改良是由于对性状有有利影响的多效性位点以及对性状没有可检测到的多效性影响的有利位点。小麦育种似乎能够容忍保守核苷酸位点的突变，并且仅在特殊情况下才选择对性状有有利和不利影响的等位基因。
