Less-than-additive epistatic interactions of quantitative trait loci in tomato.
Less-than-additive epistatic interactions of quantitative trait loci in tomato.
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作者：
Y. Eshed;D. Zamir
上位性在决定表型中发挥着重要作用，但数量性状基因座 (QTL) 作图却没有发现多少证据。为了解决这一明显的矛盾，我们分析了渗入到 L. esculentum（cv. M82）的同质遗传背景中的单个番茄染色体片段之间的相互作用。十个不同的纯合基因渗入系，每个含有 4 至 58 cM 的基因渗入 DNA，以半双等位基因方案进行杂交。在田间对 45 个衍生双杂合子以及 10 个单杂合子和 M82 的四个产量相关性状进行了评估。在 180 (45 x 4) 项测试的相互作用中，28% 在线性和几何尺度上都是上位的 (P < 0.05)。检测到的上位性主要是小于加性的，即双杂合子的效应小于相应的单杂合子的效应之和。还发现影响果实质量和总可溶性固形物的纯合连锁 QTL 具有上位性。尽管上位性频率很高，但加性性是QTL对相互作用的主要组成部分。我们认为，当涉及更多基因座时，QTL 效应的可加性递减会被放大；这种上位模式可能是表型管道化和育种的重要因素。
Epistasis plays a role in determining the phenotype yet quantitative trait loci (QTL) mapping has uncovered little evidence for it. To address this apparent contradiction, we analyzed interactions between individual Lycopersicon pennellii chromosome segments introgressed into an otherwise homogeneous genetic background of L. esculentum (cv. M82). Ten different homozygous introgression lines, each containing from 4 to 58 cM of introgressed DNA, were crossed in a half diallele scheme. The 45 derived double heterozygotes were evaluated in the field for four yield-associated traits, along with the 10 single heterozygotes and M82. Of 180 (45 x 4) tested interactions, 28% were epistatic (P < 0.05) on both linear and geometric scales. The detected epistasis was predominantly less-than-additive, i.e., the effect of the double heterozygotes was smaller than the sum of the effects of the corresponding single heterozygotes. Epistasis was also found for homozygous linked QTL affecting fruit mass and total soluble solids. Although the frequency of epistasis was high, additivity was the major component in the interaction of pairs of QTL. We propose that the diminishing additivity of QTL effects is amplified when more loci are involved; this mode of epistasis may be an important factor in phenotype canalization and in breeding.