| Chromosomal location of a gene for male sterility in
wheat (Triticum aestivum) G. KLEIJER and A. FOSSATI Federal Agricultural Research Station, CH-1260 Nyon, Switzerland In 1970, FOSSATI and INGOLD isolated in M2 a male sterile mutant of the variety Probus after applying 24 kR of X-rays to seed. The sterility is due to a single recessive gene, which is normally inherited. They proposed the designation msa1 for this gene. Chromosomal location of a recessive gene can be done in F1 from crosses between a monosomic serie and in this case plants heterozygous for the msa1 gene. For 20 chromosomes, there will be no segregation in F1. The critical chromosome will be segregated in about 35% of sterile plants. To locate this gene, crosses are made between the 21 monosomics of Probus, a part of the monosomics of Cappelle (kindly provided by Dr. C.N. LAW, Cambridge) with male fertile plants, heterozygous for the msa1 gene. The F1 is cultivated on the fleld. Observations are made during flowering time. The florets of the male sterile plants remain broadly open. The anthers are typically thin and slightly curved, staying mostly in the flower and are not dehiscent. The results of the analyses in F1 are given in Table 1. In two cases, male sterile plants were found : in the F2 of the cross male sterile plants with Probus and in the F1 of the cross mono 4A with heterozygous male fertile plants. Microscopical examination of the anthers of these plants showed nearly only empty pollen. Thus, this recessive gene for male sterility is located on chromosome 4A. The segregation ratios of the F2 and chromosome 4A do not very well fit in with the expected values. An explanation of this is difficult to give. A lot of plants were lost with an attack by the larvae of an insect (Agriotes sp.). As chromosome 4A is one of the chromosomes carrying a gene or genes for male fertility (SEARS, cited by DRISCOLL, 1973), it might be possible that the male. sterility of this mutant is due to a small deletion, behaving as a recessive gene. (Received August 15, 1975) |