Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2002
Publication Date: 10/1/2002
Citation: KLINDWORTH, D.L., WILLIAMS, N.D., MAAN, S.S. CHROMOSOMAL LOCATION OF GENETIC MALE-STERILITY GENES IN FOUR MUTANTS OF HEXAPLOID WHEAT. CROP SCIENCE. 2002. VOL. 42(5):1447-1450. Interpretive Summary: Male-sterility in wheat is important for production of hybrid wheat and as a tool to make a large number of crosses for recurrent selection schemes. Four mutant wheat lines that had a single gene for male-sterility had been previously identified. These four mutants were known to be controlled by genes at only two loci. Determining the chromosomes on which these two loci are located is the first step in more detailed genetic studies. Our objective was to map the genes for male-sterility in the four mutants. We first crossed the mutants to Cornerstone, which is a line in which a male-sterility gene had previously been mapped to chromosome arm 4BS. We determined that the mutations in FS2, FS3, and FS24 were located in the same region of chromosome arm 4BS as is the Cornerstone mutant. To map the mutated gene in the FS20 mutant, we crossed FS20 to a set of wheats lacking one of each of the 21 wheat chromosomes and observed the hybrids and their offspring. We found that the mutant gene in FS20 was located in chromosome 3A. We then crossed FS20 to wheat genetic stocks lacking either chromosome arm 3AS or 3AL and observed the hybrids. We found that the gene in FS20 was located in chromosome arm 3AL. Finally, we mapped the FS20 gene relative to the 3A centromere by crossing a plant in which chromosome 3A was marked by lacking chromosome arm 3AS, and carrying a single copy of this male-sterility gene, to male-sterile plants of the FS20 mutant. By observing the hybrids, we determined that the male-sterility gene in FS20 was in a location of chromosome arm 3AL which was not near the centromere. This new male-sterility locus of wheat is assigned the gene symbol ms5.
Technical Abstract: Few genetic male-sterility (GMS) genes have been mapped in hexaploid wheat (Triticum aestivum L.). Our objective was to locate to chromosomes the GMS genes in mutants FS2, FS3, FS20, and FS24. We crossed each mutant to the Cornerstone male-sterile, having the ms1c allele, to determine allelic relationships. We crossed the FS20 mutant to Chris monosomics, and observed segregation in the F2 and backcrosses to FS20. After observing the results, we made appropriate crosses to Chinese Spring (CS) ditelosomic lines to locate and map the genes to chromosome arms. The allelism test to Cornerstone indicated that the mutants FS2, FS3 and FS24 were allelic to ms1. The cross to CS dimonotelocentric 4BL confirmed that the mutant genes in FS2 and FS24 were located in chromosome arm 4BS. In the monosomic analysis of the mutated FS20 gene, half of the monosomic 3A plants were male-sterile. Therefore, the mutated gene in FS20 was located in chromosome 3A. This conclusion was confirmed by analyzing segregation ratios in backcross populations involving chromosome 3A. The FS20 mutant was crossed with CS ditelosomic 3AS and 3AL, and the monotelodisomic 3AS plants were male-sterile. Therefore, the FS20 gene was in chromosome arm 3AL. A backcross of monotelodisomic 3AL plants to FS20 was used to map the mutated gene in FS20 relative to the centromere. The linkage chi-square test indicated that the FS20 gene was not linked to the centromere of chromosome 3A. The gene symbol ms5 is assigned to the mutated gene in FS20.