Hybrid sterility is a major obstacle to the development of superior inter-subspecific hybrids between indica and japonica subspecies of Asian-cultivated rice. To overcome hybrid sterility, we introduced four japonica alleles (S-j) at Sa, Sc, f5, and S32 loci from Nipponbare into 9311 through marker-assisted backcross breeding, and four improved lines were obtained. Three wide-compatibility lines 9311(S5-n), 9311(f5-n), and 9311(S5-n+f5-n) previously constructed were used as control and parental line of hybridization. By crossing with 9311(S5-n+f5-n), two pyramiding lines 9311(Sa+S5-n+f5-n) and 9311(S32+Sa+S5-n+f5-n) were obtained. To evaluate the gene effect of pollen fertility and spikelet fertility, the near-isogenic lines (NILs) harboring S5-n, f5-n, Sa, Sc, f5, or S32 and three pyramiding lines with S5-n+f5-n, Sa+S5-n+f5-n, or S32+Sa+S5-n+f5-n were testcrossed to six japonica varieties. The results showed that single-gene f5, f5-n, S32, and S5-n could significantly improve spikelet fertility in majority of indica-japonica hybrids. Single-gene Sa and Sc could significantly improve spikelet fertility in part of indica-japonica hybrids. Moreover, the pyramiding lines exhibited significantly higher spikelet fertility than the control in indica-japonica hybrids. A significant increase in spikelet fertility (31.4–55%) was observed in three- or four-gene pyramiding lines. Our results provide an effective approach to exploiting heterosis between indica and japonica subspecies, which had a profound implication in rice breeding.

杂种不育性是性出色亚种间杂种的发展的主要障碍籼稻和粳稻亚洲栽培稻的亚种。为了克服杂交不育，我们通过标记辅助回交育种，将来自日本晴的Sa，Sc，f5和S32位点的四个粳稻等位基因（Sj）引入了9311，获得了四个改良品系。三条宽兼容性线9311（S5-n），9311（f5-n）和9311（S5-n + f5-n先前构建的）用作杂交的对照和亲本系。通过与9311（S5-n + f5-n）相交，得到两条金字塔线9311（Sa + S5-n + f5-n）和9311（S32 + Sa + S5-n + f5-n）。为了评估花粉育性和小穗育的基因效果，近等基因系（近等基因系）窝藏S5-n的，F5-N ，萨，钪，F5，或S32和三个金字塔用线S5-N + F5-N ，萨将+ S5-n + f5-n或S32 + Sa + S5-n + f5-n与六个粳稻品种杂交。结果表明，单基因f5，f5-n，S32和S5-n可以显着提高大多数in粳杂交种的小穗繁殖力。单基因萨和钪能显著提高结实率中的一部分籼-粳杂种。此外，金字塔形线表现出比对照组中的小穗高得多的育性。印度-杂交粳稻。在三或四基因金字塔系中观察到小穗繁殖力显着增加（31.4-55％）。我们的研究结果提供了有效的方法来利用间杂种优势籼稻和粳稻亚种，其中有水稻育种的深厚意蕴。