Chromosome elimination in different meristematic regions of hybrids between Hordeum vulgare L. and H. bulbosum L..

Abstract

Cytological observations were made on spike primordia and root and leaf meristems of hybrids between H. vulgare and H. bulbosum (2.times.) to elucidate mechanism of chromosome elimination. High frequencies of cells with micronuclei were observed in spike primordia of the hybrids examined. The average percentages of cells with micronuclei in 3 different hybrids were 16.8 (R25788), 12.9 (S92-201) and 7.9% (S130-200). About 40% of spike primordium cells of R25788 had fewer chromosomes than the 14 expected in a diploid hybrid. In root and leaf meristems of R25788, percentages of cells with micronuclei were 2.3 and 2.4%, respectively. Of root meristem cells of R25788, 94.6% had the expected hybrid chromosome number. Thus, chromosome elimination in hybrids between H. vulgare and H. bulbosum apparently is a tissue-dependent phenomenon, perhaps related to the extent of differentiation required. Disturbances in nuclear division were also examined. Percentages of cells with non-congressed chromosomes at metaphase and lagging chromosomes at anaphase were 15.2 and 20.7%, respectively, in spike primordia of R25788. These percentages are similar to those of cells with micronuclei in spike primordia of R25788. Failure of congression of some chromosomes during prometaphase is probably the main mitotic disturbance leading to chromosome elimination.