Variation for crossability in a reciprocal,interspecific cross involvingHordeum vulgare andH. lechleri

Summary Several crossing series including the hexaploid (2n=6x=42), South American speciesHordeum lechleri and diploid (2n=2x=14) cultivated barley (H. vulgare) were performed. Barley functioned better as the paternal than as the maternal parent in all cases. Viable offspring were only obtained from one hybrid combination when barley was used as the maternal parent. There was an environmental influence on the success of crosses. A high seed set was counteracted by a lower germination frequency. The outcome is that different crossing series give similar results. As a result of chromosome elimination and in a few cases duplication of especially the barley chromosomes, the chromosome numbers of the offspring (239 plants) varied from 2n=21 (trihaploids ofH. lechleri) to 2n=30. Fifty-five % of the plants were euploid with the number expected for a hybrid (2n=28). The frequency of hyperploids, euploids, hypoploids (2n=22–27) and trihaploids varied by year, locality, type (winter/spring) of barley,H. lechleri population, and crossing direction.