Table_1_Substitution Mapping of a Locus Responsible for Hybrid Breakdown in Populations Derived From Interspecific Introgression Line.pdf

Hybrid breakdown, a form of postzygotic reproductive barrier, has been reported to hinder gene flow in many crosses between wild and cultivated rice. Here, the phenomenon of hybrid breakdown was observed as low-tillering (i.e., low tiller number) in some progeny of an interspecific cross produced in an attempt to introduce Oryza meridionalis Ng (W1625) chromosomal segments into Oryza sativa L. ssp. japonica “Taichung 65” (T65). Low-tillering lines were obtained in BC4-derived progeny from a cross between W1625 and “Taichung 65,” but the locus for low-tillering could not be mapped in segregating populations. As a second approach to map the locus for low-tillering, we analyzed an F2 population derived from a cross between the low-tillering lines and a high-yielding indica cultivar, “Takanari.” A major QTL for low-tillering, qLTN4, was detected between PCR-based markers MS10 and RM307 on the long arm of chromosome 4, with a LOD score of 15.6. The low-tillering phenotype was associated with weak growth and pale yellow phenotype; however, low-tillering plant had less reduction of grain fertility. In an F4 population (4896 plants), 563 recombinant plants were identified and the low-tillering locus was delimited to a 4.6-Mbp region between markers W1 and C5-indel3729. This region could not be further delimited because recombination is restricted in this region of qLTN4, which is near the centromere. Understanding the genetic basis of hybrid breakdown, including the low-tillering habit, will be important for improving varieties in rice breeding.

杂交破裂，一种后配子生殖隔离形式，已被报道阻碍野生稻与栽培稻之间许多杂交的基因流动。在本研究中，杂交破裂现象表现为某些杂交后代中分蘖少（即分蘖数量低）的现象，该杂交后代是在尝试将 Oryza meridionalis Ng（W1625）染色体片段引入 Oryza sativa L. 野败亚种“台中65”（T65）的过程中产生的。在来自 W1625 与“台中65”杂交的 BC4 衍生后代中获得了分蘖少品系，但无法在分离群体中定位分蘖少的位点。为了定位分蘖少位点作为第二个方法，我们分析了来自分蘖少品系与高产印度品种“Takanari”杂交的 F2 群体。在 4 号染色体长臂上，基于 PCR 标记的 MS10 和 RM307 之间检测到一个主要的 QTL 位点 qLTN4，其 LOD 分数为 15.6。分蘖少表型与生长衰弱和淡黄色表型相关；然而，分蘖少的植株在种子产量上的降低较少。在 F4 群体（4896 株植物）中，确定了 563 株重组植株，并将分蘖少位点限定在标记 W1 和 C5-indel3729 之间的 4.6-Mbp 区域。由于重组在此 qLTN4 区域受限，该区域靠近着丝粒，因此无法进一步限定这一区域。了解杂交破裂的遗传基础，包括分蘖少习性，对于提高水稻育种中的品种改良具有重要意义。