Identification and genetic mapping for <Emphasis Type="Italic">rht-DM</Emphasis>, a dominant dwarfing gene in mutant semi-dwarf maize using QTL-seq approach

Semi-dwarfism is an agronomically important trait in breeding for stable high yields and for resistance to damage by wind and rain (lodging resistance). Many QTLs and genes causing dwarf phenotype have been found in maize. However, because of the yield loss associated with these QTLs and genes, they have been difficult to use in breeding for dwarf stature in maize. Therefore, it is important to find the new dwarfing genes or materials without undesirable characters. The objectives of this study were: (1) to figure out the inheritance of semi-dwarfism in mutants; (2) mapping dwarfing gene or QTL. Maize inbred lines ‘18599’ and ‘DM173’, which is the dwarf mutant derived from the maize inbred line ‘173’ through ⁶⁰Co-γ ray irradiation. F₂ and BC₁F₁ population were used for genetic analysis. Whole genome resequencing-based technology (QTL-seq) were performed to map dwarfing gene and figured out the SNP markers in predicted region using dwarf bulk and tall bulk from F₂ population. Based on the polymorphic SNP markers from QTL-seq, we were fine-mapping the dwarfing gene using F₂ population. In F₂ population, 398 were dwarf plants and 135 were tall plants. Results of χ² tests indicated that the ratio of dwarf plants to tall plants was fitted to 3:1 ratio. Furthermore, the χ² tests of BC₁F₁ population showed that the ratio was fitted to 1:1 ratio. Based on QTL-seq, the dwarfing gene was located at the region from 111.07 to 124.56 Mb of chromosome 9, and we named it rht-DM. Using traditional QTL mapping with SNP markers, the rht-DM was narrowed down to 400 kb region between SNP-21 and SNP-24. The two SNPs were located at 0.43 and 0.11 cM. Segregation analysis of F₂ and BC₁F₁ indicated that the dwarfing gene was likely a dominant gene. This dwarfing gene was located in the region between 115.02 and 115.42 Mb on chromosome 9.