Third Dominant Male Sterility Gene in Common Wheat

The mutants producing dominantly inherited male sterility (Ms) survive in the polyploid species. Hexaploid wheat (Triticum aestivum L.) has two Ms genes, Ms2 on chromosome 4D and Ms3 on chromosome 5A. Our objective was to determine the identity of a putative third Ms gene. First, we crossed an euploid Msms plant to double-ditelosomic 5A (dDt; 2n=44; 20''+2t'') of Chinese Spring (CS), a monoditelosomic 5A (mDt) Msms Fi (2n=43; 20''+tlt''' 5A) to numsomic 5A-tetrasomic 5D [(5A) 5D; 2n=42; 19''+1I supIV ] of CS, a 43-chromosome Msms plant (19''+1''5D+2t'5A) to CS, and produced a 1:1 ratio of fertile and sterile plants, showing that Ms was not located on chromosome 5A. Second, we crossed an euploid Msms plant to (4D)4A of CS, a tri 4A-mono 4D Msms (2n=43; 19''+1'''+ 1') plant to dDt 4D of CS, and produced Msms plants (20''+t1t'''4D) or dMt (20''+2t'4D) and fertile Dt plants (20''+ 2t') or Mt (20''+t'), showing that Ms is located on chromosome 4D. Third, a Msms dMt 4DL (20''+1t'') plant was crossed to CS and produced 21 sterile plants with 21'', 21 fertile plants with 20+lt4DL but no recombinants (msms with 21'' or Msms with 20''+1t''), showing that Ms is located in the short-arm of chromosome 4D (4DS). Fourth, two Msms mDt 4D (20''+t1t''') plants (one with Ms in whole chromosome 4D and the other with Ms in telo 4DS) were crossed to CS and produced 1:1 ratios of fertile and sterile plants with 21'' as well as 20''+t1t'', indicating that the new Ms (Ms4) gene is located in the distal portion of 4DS, while 4DS also has Ms2 with 31.16 crossover units from the centromere.