Research Faculty of Agriculture, Hokkaido University, Kita-9 Nishi-9, Kita-ku, Sapporo, 060-8589, Japan.
Faculty of Agriculture, Ryukoku University, 1-5 Yokotani, Seta Oe-cho, Otsu, Shiga 520-2194, Japan.
G3 (Bethesda). 2019 May 7;9(5):1655-1662. doi: 10.1534/g3.119.201011.
Transgressive segregation produces hybrid progeny phenotypes that exceed the parental phenotypes. Unlike heterosis, extreme phenotypes caused by transgressive segregation are heritably stable. We examined transgressive phenotypes of flowering time in rice, and revealed transgressive segregation in F populations derived from a cross between parents with similar (proximal) days to heading (DTH). The DTH phenotypes of the A58 × Kitaake F progenies were frequently more extreme than those of either parent. These transgressive phenotypes were maintained in the F and F populations. Both A58 and Kitaake are rice cultivars adapted to Hokkaido, Japan, which is a high-latitude region, and have a short DTH. Among the four known loci required for a short DTH, three loci had common alleles in A58 and Kitaake, implying there is a similar genetic basis for DTH between the two varieties. A genome-wide single nucleotide polymorphism (SNP) analysis based on the F population identified five new quantitative trait loci (QTL) associated with transgressive DTH phenotypes. Each of these QTL had different degrees of additive effects on DTH, and two QTL had an epistatic effect on each other. Thus, a genome-wide SNP analysis facilitated the detection of genetic loci associated with extreme DTH phenotypes, and revealed that the transgressive phenotypes were produced by exchanging the complementary alleles of a few minor QTL in the similar parental phenotypes.
越界分离产生的杂种后代表型超过亲本表型。与杂种优势不同，越界分离引起的极端表型是遗传稳定的。我们研究了水稻开花时间的越界表型，并揭示了来自具有相似（近端）抽穗期（DTH）的亲本杂交的 F 群体中的越界分离。A58×Kitaake F 后代的 DTH 表型通常比任何一个亲本都更为极端。这些越界表型在 F 和 F 群体中得以维持。A58 和 Kitaake 都是适应日本北海道的水稻品种，北海道是一个高纬度地区，DTH 较短。在四个已知的短 DTH 所需的基因座中，A58 和 Kitaake 有三个基因座具有共同的等位基因，这表明这两个品种之间存在相似的 DTH 遗传基础。基于 F 群体的全基因组单核苷酸多态性（SNP）分析鉴定出与越界 DTH 表型相关的五个新的数量性状基因座（QTL）。这些 QTL 中的每一个对 DTH 都有不同程度的加性效应，并且两个 QTL 之间存在上位性效应。因此，全基因组 SNP 分析有助于检测与极端 DTH 表型相关的遗传基因座，并揭示了越界表型是由几个少数 QTL 的互补等位基因在相似的亲本表型中交换产生的。
