| Allelic variation at the crossability loci in wheat
(Triticum aestivum) L.A.SITCH1) and J.W. SNAPE Plant Breeding Institute, Cambridge, Great Britain The crossability of hexaploid wheat (Triticum aestivum) with rye (Secale cereale) has been shown to be controlled by three loci, designated Kr1, Kr2 (LEIN 1943) and Kr3 (KROWLOW 1970), located on chromosomes 5B, 5A (RILEY & CHAPMAN 1967) and 5D (KROWLOW 1970) respectively. LEIN (1943) demonstrated that the dominant alleles at the Kr1 and Kr2 loci reduced crossability, with Kr1 having a greater effect than Kr2. A high positive correlation between the crossability of wheat with rye and Hordeum bulbosum has also been demonstrated (FALK & KASHA 1981; SITCH et al. 1985; SNAPE et al. 1979) and genetic studies involving comparisons of the crossability of the Chinese Spring (Hope) single chromosome substitution lines (SNAPE et al. 1979) and of recombinant lines for the Kr1 locus, with rye and H. bulbosum (SITCH et al. 1985) confirm that the Kr loci control the crossability of wheat with both pollen parents. An examination of the H.bulbosum and the rye crossability of the single chromosome substitution lines of the non-crossable varieties, Hope, Atlas 66 and Cheyenne into Chinese Spring, for all the homoeologous group 5 chromosomes by FALK & KASHA (1983) indicated that there may be multiple alleles for reduced crossability on chromosomes 5A and 5B. However, no evidence was found for variation at the Kr3 locus on chromosome 5D of these varieties. The only significant evidence of a third crossability gene was obtained by FEDAK & JUI (1982), in pollinations of barley (Hordeum vulgare) cv. Betzes with the Chinese Spring (Hope) substitution lines. This paper describes an investigation designed to ascertain whether there is any evidence of multiple allelism at the Kr loci of the non-crossable varieties Hope and Cappelle-Desprez and to determine whether different Kr3 alleles exist in these varieties from that in Chinese Spring, from a study of the H. bulbosum crossability of the group 5 substitution lines of these varieties into Chinese Spring. |
| 1) Author's address: International Rice Research Institute (IRRI), P.O. Box 933, Manila, Philippines |
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