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The gene for mildew resistance has been succesfully transferred into the cultivated oat from the wild oat species Avena barbata by means of an irradiation-induced translocation. The translocation has been shown to involve the long arm of chromosome ST21 of A. sativa, the short arm, the centromere and a segment of the long arm of the barbata chromosome.

A disomic addition line in which a pair of chromosomes of the tetraploid wild oat Avena barbata have been added to the cultivar Manod is resistant to all the prevalent races of mildew. The gene for mildew resistance is located on the particular A. barbata chromosome involved in the addition line. Seeds of the disomic addition line were irradiated in an attempt to introduce this source of resistance into the cultivated oat by an induced translocation involving the A. barbata chromosome.

The pattern of chromosome association at first metaphase of meiosis in interspecific hybrids of the natural hexaploid Festuca arundinacea and the diploid Lolium perenne was examined in order to investigate the relationship between a pairing control system previously isolated in L. perenne and that present in the hexaploid F. arundinacea. The pairing pattern at meiosis in the hybrids was clearly modified by the genotype of L. perenne and by the presence of B chromosomes. Whereas chromosome association (homoeologous) in F. arundinacea × L. perenne genotype Lp10 without B chromosomes was extensive it was almost absent in the hybrids involving L. perenne genotype Lp19 containing B chromosomes. Two alternative interpretations are suggested for the relationship between the two pairing control systems.Heredity (1986) 56, 97–103; doi:10.1038/hdy.1986.13

The genetic basis of the control system responsible for suppressing the association of homoeologous chromosomes at first metaphase of meiosis in interspecific hybrids of Lolium was investigated by means of cytological and genetical analyses of a test cross between L. temulentum and L. perenne. It is concluded that more than one gene is involved. Linkage to a gene which codes for an Esterase enzyme of low electrophoretic mobility is clearly identified with the possibility that a second gene is associated with another Esterase locus. The phenotypic effect of individual pairing genes in relation to the distance between them and linked markers is discussed.Heredity (1987) 59, 129–134; doi:10.1038/hdy.1987.104

MILDEW (Erysiphe graminis, F.sp. avenae) can reduce the yield of cultivated oats by 30% (ref. 1) and is the most important disease of the crop in the UK. The ability of the pathogen to change either by mutation or recombination, giving rise to strains which can effectively attack previously resistant cultivars, leads to a continuous search for further sources of resistance. Genotypes of related weed species of Avena have been isolated that are completely resistant to mildew. A genotype of the tetraploid species Avena barbata (2n = 28) collected in Algeria is resistant to all the prevalent races of mildew and would form a valuable source of resistance to the pathogen. We now report the successful transfer of this source of mildew resistance into the cultivated oat. This provides the oat breeder with a new source of mildew resistance to use in breeding programmes.