Registration of two novel grain sorghum nuclear male sterile mutants: BTx623ms9-1 and BTx623ms9-3

Authors: Chen, Junping; LAZA, HAYDEE - Texas Tech University; Burow, Gloria; Hayes, Chad; Burke, John; Emendack, Yves; Xin, Zhanguo

Submitted to: Journal of Plant Registrations
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/24/2022
Publication Date: 9/22/2022
Citation: Chen, J., Laza, H., Burow, G.B., Hayes, C.M., Burke, J.J., Emendack, Y., Xin, Z. 2022. Registration of two novel grain sorghum nuclear male sterile mutants: BTx623ms9-1 and BTx623ms9-3. Journal of Plant Registrations. https://doi.org/10.1002/plr2.20251.
DOI: https://doi.org/10.1002/plr2.20251

Interpretive Summary: Breeding hybrid varieties plays a major role in increasing sorghum yield. However, a major problem in the current hybrid production technique requires scientists to breed three different sorghum lines at same time, which is complicated, labor-intensive, and expensive. In contrast, two-line systems are much easier and cheaper to use and have dramatically improved hybrid production while also significantly cutting breeding time and expense in crops such as rice and wheat. In this study, ARS scientists from Lubbock, Texas identified and characterized a novel sorghum male sterility mutant gene, named Ms9, that can be used in a two-line breeding system. This new two-line breeding system for sorghum will not only improve hybrid breeding efficiency, but also will significantly broaden genetic sources for breeding resulting in new, higher yielding sorghum hybrids. Two unique mutant lines, ms9-1 and ms9-3, are being submitted for registration and public use.

Technical Abstract: The USDA-ARS has released a new sorghum Sorghum bicolor (L.) Moench) nuclear male sterile (NMS) mutant BTx623ms9-1 and BTx623ms9-3 (Reg. No______, PI ######; Reg. No______, PI ######). The BTx623ms9 mutants were isolated from an ethylmethane sulfonate (EMS) mutanized BTx623 sorghum line and evaluated under different day-length and temperature conditions. Results showed that the male sterile phenotype of BTx623ms9 is stable in a variety of environments. The male sterility of BTx623ms9 is controlled by a single nuclear gene (Sobic.002G221000) and inherited in a recessive manner. Allelism testing indicated that the genetic control of male sterility in BTx623ms9 differs from those of currently available known nms sorghum lines (ms1, ms2, ms3, ms7 and ms8). Therefore, this nms mutant was named consecutively as ms9 and the corresponding locus as Ms9 in sorghum. Both ms9-1 and ms9-3 have been backcrossed to the original BTx623 wild type for four generations. Phenotypical characterization showed that, except for the sterility phenotype of sorghum panicle at anthesis, the backcrossed BTx623ms9 has no morphological or developmental difference from those of the wild type plant at both vegetative and reproductive stages. The homozygous BTx623ms9 panicle produces normal ovaries but small pale-colored empty anthers with no mature pollen grains, therefore, making it easy to identify the sterile panicles from the fertile ones at the starting of anthesis. The seed pools of this registration were generated by crossing the BC4F2ms (ms9/ms9) panicles with pollen of the BC5F1 (Ms9/ms9) plants. Therefore, they are self-complementing population where 50% plants are male sterile (ms9/ms9) and the rest of the 50% plants are heterozygous fertile plants at the Ms9 locus (Ms9/ms9). Thus, the seed pools of this registration can be maintained by pollinating the ms9 panicles with pollen from the heterozygous fertile plants within the population. The MS9 gene has been identified. The BTx623ms9-1 contains a C-to-T substitution at nucleotide 1207 of Ms9 and BTx623ms9-3 contain a (G-to-A) mutation at the splicing site of intron II and Exon III. Thus, the male sterile mutations in BTx623ms9 can be introduced into any other sorghum accessions and breeding lines through recurrent backcrosses via marker-assisted selection (MAS). The resulting male sterile plant in these accession can serve as female parent in creating new mapping populations for genetic study as well as new hybrids, hence broadening and accelerating the utility of the BTx623ms9 in the sorghum breeding program.