Chromosomal Location of Genetic Male Sterility Genes in Four Mutants of Hexaploid Wheat

of the 4BS chromosome arm (Endo et al., 1991). The dominant male-sterile genes Ms2 and Ms3 are located Few genetic male sterility (GMS) genes have been mapped in in chromosome arms 4DS and 5AS, respectively (Mchexaploid wheat (Triticum aestivum L.). Our objective was to locate to chromosomes the GMS genes in mutants FS2, FS3, FS20, and FS24. Intosh et al., 1998). The Ms4 gene is a dominant maleWe crossed each mutant to the Cornerstone male sterile, which has sterility gene that recently has been located by Maan the ms1c allele, to determine allelic relationships. We crossed the and Kianian (2001) to chromosome arm 4DS. FS20 mutant to ‘Chris’ monosomics, and observed segregation in the Franckowiak et al. (1976) treated seeds of alloplasmic F2 and backcrosses to FS20. After observing the results, we made Chris (which has the cytoplasm of T. tauschii L.) with appropriate crosses to Chinese Spring (CS) ditelosomic lines to locate ethyl methanesulfonate in an attempt to induce mutaand map the genes to chromosome arms. The allelism test to Cornertions of a cytoplasmic male-sterility gene in chromostone indicated that the mutants FS2, FS3, and FS24 were allelic to ms1. In the monosomic analysis of the mutated FS20 gene, half of some 1D. All of the induced mutations proved to be the monosomic 3A plants were male sterile. Therefore, the mutated cytoplasmic nonspecific (Sasakuma et al., 1978). Five gene in FS20 was located in chromosome 3A. This conclusion was of these mutants were of particular interest. The FS6 confirmed by analyzing segregation ratios in backcross populations mutation was conditioned by a dominant gene subseinvolving chromosome 3A. The FS20 mutant was crossed with CS quently assigned the gene symbol Ms3. The mutations ditelosomic 3AS and 3AL, and the monotelodisomic 3AS plants were in FS2, FS3, FS20, and FS24 were each inherited as male sterile. Therefore, the FS20 gene was in chromosome arm 3AL. monogenic-recessive genes. These four mutants had low A backcross of monotelodisomic 3AL plants to FS20 was used to levels of self-fertility in bagged spikes, and high levels 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 of female fertility as indicated by seed set following centromere of chromosome 3A. The gene symbol ms5 was assigned hybridization. On the basis of segregation patterns in to the mutated gene in FS20, and gene symbols ms1d, ms1e, and ms1f the F1 of intercrosses, Sasakuma (1978) concluded that were assigned to the mutations in FS2, FS3, and FS24, respectively. mutations in FS2, FS3, and FS24 were allelic, but the FS20 mutant was nonallelic to the other mutations. Sasakuma et al. (1978) did not establish the chromosomal M sterility may be conditioned by either cytolocation of the mutant genes or determine the allelic plasmic specific or genetic (chromosomal) male relationship to ms1, which is the only mapped monosterility (GMS) genes. Cytoplasmic male sterility has genic-recessive locus for GMS in wheat. Determining been more extensively studied than GMS for hybrid the chromosomal location of these genes is the first step wheat production. However, there have been proposals in further genetic studies including gene cloning. The to use GMS for producing hybrid wheat (Driscoll, 1972; objective of our study was to determine the allelic relaTrupp, 1971). In addition, GMS may be used in populationship of FS2, FS3, FS20, and FS24 relative to ms1 tion improvement by facilitating crosses in recurrent and to determine the chromosomal locations of these selection schemes (Krishna Rao et al., 1990). GMS genes. There have been many reports of GMS in the literature, but only four GMS loci have been located to wheat MATERIALS AND METHODS chromosomes. There are three known mutants of the ms1 locus in chromosome arm 4BS (previously 4A ) Mutant Stocks which are inherited as monogenic-recessive genes. These Male sterile (msms) alloplasmic Chris plants carrying the mutants were named Pugsley’s (ms1a; Suneson, 1962), FS2, FS3, FS20, and FS24 mutant genes were crossed to Chris Probus (ms1b; Fossati and Ingold, 1970), and Corner(MsMs) to produce heterozygous male-fertile (Msms) F1 stone (ms1c; Driscoll, 1977). Because the mutations in plants which were backcrossed to respective male-sterile Probus and Cornerstone were radiation induced, these plants of each mutant. The resulting populations segregated mutants are presumed to result from a terminal deletion one heterozygous male fertile to one homozygous male sterile. of chromosome arm 4BS. The Pugsley’s mutant was Each mutant population was then maintained by mating maleisolated as a spontaneous mutant, and it likely has an sterile females with male-fertile sibs. Maintaining the populations in this fashion has the advantage that male-sterile plants intact 4BS arm. The location of the ms1 gene has been occur at a 1:1 rather than a 3:1 ratio, and that all male-fertile physically mapped to a region comprising the distal 16% plants in the population are known heterozygotes. D.L. Klindworth, USDA-ARS, Northern Crop Science Lab., P.O. Allelism Tests Box 5677, State University Station, Fargo, ND 58105; N.D. Williams, Deceased; S.S. Maan, Dep. of Plant Sciences, North Dakota State The Cornerstone (PI409014) mutant, which carries the ms1c Univ. Fargo ND 58105. Received 29 Oct. 2001. *Corresponding author allele, was obtained from the National Small Grains Collec([email protected]). Abbreviations: GMS, genetic male sterile; CS, Chinese Spring. Published in Crop Sci. 42:1447–1450 (2002).