A hybrid sterile locus leads to the linkage drag of interspecific hybrid progenies.

Interspecific hybridization plays an important role in rice breeding by broadening access to desirable traits such as disease resistance and improving yields. However, interspecific hybridization is often hindered by hybrid sterility, linkage drag, and distorted segregation. To mine for favorable genes from , we cultivated a series of BC introgression lines (ILs) of in the rice variety background (Dianjingyou 1) in which the IL-2769 (BCF) showed longer sterile lemmas, wider grains and spreading panicles compared with its receptor parent, suggesting that linkage drag may have occurred. Based on the BCF population, a hybrid sterility locus, , a long sterile lemma locus, , and a new grain width quantitative trait locus (QTL), , were mapped in the linkage region about 15 centimorgan (cM) from the end of the short arm of chromosome 7. The hybrid sterility locus from eliminated male gametes of , and male gametes carrying the alleles of in the heterozygotes were aborted completely. In addition, the homozygotes presented a genotype of , and homozygous were not produced. Surprisingly, the linked traits and showed similar segregation distortion. These results indicate that was responsible for the linkage drag. As a large number of detected hybrid sterility loci are widely distributed on rice chromosomes, we suggest that hybrid sterility loci are the critical factors for the linkage drag in interspecific and subspecific hybridization of rice.