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ARS Home » Plains Area » Lubbock, Texas » Cropping Systems Research Laboratory » Plant Stress and Germplasm Development Research » Research » Publications at this Location » Publication #327186
Title: Morphological characterization of a new and easily recognizable nuclear male sterile mutant of sorghum (Sorghum bicolor).

Author
item Xin, Zhanguo
item HUANG, JIAN - University Of Wisconsin
item SMITH, ASHLEY - University Of Wisconsin
item Chen, Junping
item Burke, John
item Sattler, Scott
item ZHAO, DAZHONG - University Of Wisconsin

Submitted to: PLOS ONE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/8/2016
Publication Date: 1/4/2017
Citation: Xin, Z., Huang, J., Smith, A., Chen, J., Burke, J.J., Sattler, S.E., Zhao, D. 2017. Morphological characterization of a new and easily recognizable nuclear male sterile mutant of sorghum (Sorghum bicolor). PLoS One. 12(1):1-14.

Interpretive Summary: Hybrids generally produce >20% increase in grain yield. Most sorghum varieties grown in the US are hybrids. All commercial sorghum (Sorghum bicolor L. Moench) hybrids are produced using A1 cytoplasmic male sterility (CMS) lines. However, this homogenous cytoplasm could predispose sorghum to devastating diseases. Furthermore, it is expensive to develop and maintain the CMS-based breeding system, because it requires a CMS male sterile (A) line, a maintainer (B) line, and a dominant R line. Thus, it is imperative to develop the two-line hybrid system using nuclear male sterility (NMS) to simplify breeding and enable hybrid combinations between any two lines. Here, we report a new, easily recognizable, NMS sorghum mutant male-sterile 8 (ms8) from an elite inbred BTx623 mutagenized by ethyl methane sulfonate (EMS). Our results show that the ms8 mutant was caused by a mutation on a single nuclear gene that is different from all available NMS loci reported in sorghum. In BTx623 and all other sorghum accessions, yellow anthers appeared first during anthesis, while in ms8 mutant, white hairy stigma emerged first. More importantly, ms8 mutant anthers were small and white, making the mutant plants easily recognizable at early flowering stage. We found that ms8 mutant anthers did not produce pollen grains. Further analysis revealed that ms8 anthers were defective in tapetum development, which led to the arrest of pollen formation. As a stable male sterile mutant across different environments, greenhouses, and fields in different locations, the ms8 mutant could be a useful breeding tool and holds a promise for engineering two-line breeding system in sorghum.

Technical Abstract: All commercial sorghum (Sorghum bicolor L. Moench) hybrids are produced using A1 cytoplasmic male sterility (CMS) lines. However, this homogenous cytoplasm could predispose sorghum to devastating diseases. Furthermore, it is expensive to develop and maintain the CMS-based breeding system, because it requires a CMS male sterile (A) line, a maintainer (B) line, and a dominant R line. Thus, it is imperative to develop the two-line hybrid system using nuclear male sterility (NMS) to simplify breeding and enable hybrid combinations between any two lines. Here, we report a new, easily recognizable, NMS sorghum mutant male-sterile 8 (ms8) from an elite inbred BTx623 mutagenized by ethyl methane sulfonate (EMS). Our results show that the ms8 mutant was caused by a mutation on a single nuclear gene that is different from all available NMS loci reported in sorghum. In BTx623 and all other sorghum accessions, yellow anthers appeared first during anthesis, while in ms8 mutant, white hairy stigma emerged first. More importantly, ms8 mutant anthers were small and white, making the mutant plants easily recognizable at early flowering stage. We found that ms8 mutant anthers did not produce pollen grains. Further analysis revealed that ms8 anthers were defective in tapetum development, which led to the arrest of pollen formation. As a stable male sterile mutant across different environments, greenhouses, and fields in different locations, the ms8 mutant could be a useful breeding tool.