Mapping and breeding value evaluation of a semi-dominant semi-dwarf gene in upland rice

Plant height is an important trait related to yield potential and plant architecture. A suitable plant height plays a crucial role in improvement of rice yield and lodging resistance. In this study, we found that the traditional upland landrace 'Kaowenghan' (KWH) showed a special semi-dwarf phenotype. To identify the semi-dwarf gene from KWH, we raised BC₂F₄ semi-dwarf introgression lines (IL) by hybridization of the japonica rice cultivar 'Dianjingyou1' (DJY1) and KWH in a DJY1 background. The plant height of the homozygous semi-dwarf IL (IL-87) was significantly reduced compared with that of DJY1. The phenotype of the F₁ progeny of the semi-dwarf IL-87 and DJY1 showed that the semi-dwarf phenotype was semi-dominant. QTL mapping indicated that the semi-dwarf phenotype was controlled by a major QTL qDH1 and was localized between the markers RM6696 and RM12047 on chromosome 1. We also developed near-isogenic lines (NIL) from the BC₃F₃ population, and found that the yield of homozygous NIL (NIL-2) was not significantly different compared to DJY1. Breeding value evaluation through investigation of the plant height of the progeny of NIL (NIL-2) and cultivars from different genetic background indicate that the novel semi-dwarf gene shows potential as a genetic resource for rice breeding.