Data from: Hybrid breakdown caused by epistasis-based recessive incompatibility in a cross of rice (Oryza sativa L.)

Viability and fertility in organisms depend on epistatic interactions between loci maintained in lineages. Here, we describe reduced fitness of segregants (hybrid breakdown, HB) that emerged in an F2 population derived from a cross between 2 rice (Oryza sativa L.) cultivars, “Tachisugata” (TS) and “Hokuriku 193” (H193), despite both parents and F1s showing normal fitness. Quantitative trait locus (QTL) analyses detected 13 QTLs for 4 morphological traits associated with the HB and 6 associated with principal component scores calculated from values of the morphological traits in the F2 population. Two-way analysis of variance of the putative QTLs identified 4 QTL pairs showing significant epistasis; among them, a pair on chromosomes 1 and 12 made the greatest contribution to HB. The finding was supported by genetic experiments using F3 progeny. HB emerged only when a plant was homozygous for the TS allele at the QTL on chromosome 1 and homozygous for the H193 allele at the QTL on chromosome 12, indicating that each allele behaves as recessive to the other. Our results support the idea that epistasis is an essential part of hybrid fitness.生物体的生存力与繁殖力，依赖于谱系中保留的基因座间的上位互作。本研究报道了两个水稻（Oryza sativa L.）品种"Tachisugata（TS）"与"Hokuriku 193（H193）"杂交获得的F₂群体中分离株的生存适合度下降现象——即杂种衰败（hybrid breakdown, HB）；尽管双亲与F₁群体均表现出正常的生存适合度。针对与HB相关的4个形态性状，数量性状基因座（quantitative trait locus, QTL）分析共检测到13个QTL，另有6个QTL与基于F₂群体形态性状值计算得到的主成分得分显著相关。针对候选QTL开展双因素方差分析，鉴定出4个存在显著上位性（epistasis）的QTL位点对；其中，位于1号与12号染色体上的位点对对HB的贡献度最高。该结论得到了F₃后代遗传实验的验证。研究发现，仅当植株在1号染色体QTL位点携带TS等位基因（allele）纯合基因型，且在12号染色体QTL位点携带H193等位基因纯合基因型时，才会出现HB现象，表明二者的等位基因互为隐性等位基因。本研究结果支持"上位性是调控杂种适合度的核心环节"这一学术观点。