Registration of BTx623 _dw5 , a new sorghum dwarf mutant

The USDA-ARS has released a new dwarf sorghum [Sorghum bicolor (L.) Moench) mutant BTx623 _dw5 (Reg. No. GS-787, PI 688506). Dwarf genes have been an important driving force in breeding since the Green Revolution. Single dwarf locus is used to breed high-yielding semidwarf wheat (Triticum aestivum L.) and rice (Oryza sativa L.) cultivars. However, in sorghum, any of the known dwarf loci alone are insufficient to breed semidwarf grain sorghum fitting for modern farm practices. Therefore, four dwarf loci have been traditionally used collectively in combinations to breed sorghum cultivars of the desired plant height for machine harvesting. Here we register a new sorghum dwarf mutant isolated from a mutagenized BTx623 mutant library, which is genetically different from those currently known controlling the dwarf phenotype in sorghum. Therefore, we designated this newly identified dwarf genotype as dwarf 5 (dw5). The dwarf phenotype of dw5 was evaluated in two environments: the Puerto Rico winter nursery with short days and mild temperature conditions and the Lubbock, TX, summer field with long days and high temperature conditions. The dw5 mutation reduced the plant height of BTx623 from 155 to 74 cm in Puerto Rico and from 113 to 72 cm in Lubbock. The dwarf phenotype in dw5 mutant is caused by a single nuclear gene mutation and is inherited in a recessive manner. It can be easily identified and bred into other sorghum lines through recurrent backcrossing. The dw5 mutation provides a new way to control sorghum height.