Abstract
The crossability between Hordeum vulgare L. and diploid H. bulbosum L. (which was estimated by embryo differentiation and haploid production) was assessed in two separate experiments with 13 Japanese two-rowed barleys and six F1 hybrids. Percentages of embryo differentiation (embryos obtained / florets crossed) and haploid production (haploids obtained / florets crossed) varied among the cultivars from 11.1 to 59.8% and from 3.4 to 29.5%, respectively in experiment I (1988). In experiment II (1989), the percentages varied from 1.7 to 72.7% and from 0.6 to 26.5%, respectively. Barley cultivar 'Kanto Nijo 25' showed uniquely high crossability with H. bulbosum in both experiments, showing that there was varietal difference of crossability between H. vulgare and H. bulbosum. F1 hybrids having a parent of 'Kanto Nijo 25' in their parentage had high crossability as that of 'Kanto Nijo 25', showing that the gene(s) for crossability was dominant. Powdery mildew resistance selection was made in haploids obtained from F1 hybrids. There was deviation from the expected 1:1 ratio to resistance in haploids obtained from F1 hybrid having 'Kanto Nijo 25' in their parentage.
