The production of fertile triploid hybrids from crosses between Hordeum vulgare L. (2n = 4x = 28) and H. bulbosum L. (2n = 2x=14)

Triploid interspecific hybrids (2n = 3 x = 21) combining two sets of chromosomes from Hordeum vulgare and one from H. bulbosum have twice been reported previously, with differing accounts, of chromosome pairing at meiotic metaphase I. In attempts to produce large numbers of these hybrids, reciprocal crosses were made between two tetraploid cultivars of barley ( H vulgare , 2n = 4x = 28) and four diploid genotypes of H. bulbosum (2a = 2x= 14) in an environment known to promote increased retention of the H bulbosum chromosomes. Forty‐five putative hybrids were regenerated after embryo culture from H. vulgare (♀) × H. bulbosum (♂). Their chromosome numbers ranged from 19 to 22. At metaphase 1 seven bivalents plus varying numbers of univalents were frequently observed. Trivalents were rarely seen and probably arose from autosyndetic pairing of H, vulgare chromosomes Of 36 hybrids inoculated with three fungal pathogens (powdery mildew, net blotch, and scald), 13 were resistant, but progeny from hybrids were susceptible. The lack of allosyndetic pairing makes it doubtful whether the hybrids will be of practical value for gene introgression from H bulbosum to H vulgare . From the leciprocal cross three plants were obtained which were similar morphologically to H. bulbosum but two of these had reduced height. As all three showed lower pairing at metaphase I than H. bulbosum . they may have arisen parthenogenetically.