CHARACTERISTICS OF INTERACTION OF BARLEY HORDEUM-DEPRESSUM (SCRIBN AND SM) RIBD (4X) WITH GENOMES OF RYE SECALE-CEREALE L (2X) AND BARLEY HORDEUM-VULGARE L (2X) IN MEIOSIS OF F1 HYBRIDS

Peculiarities of chromosome pairing in MI and variation in chromosome number in microsporocytes of reciprocal hybrids between Hordeum depres sum (4x) and cultivated barley H. vulgare (2x), haploid H. depressum ( n = 2x), hybrids between H. depressum (4x), and rye Secale cereale (2x ) were studied. It was shown that in reciprocal hybrids H. depressum x H. vulgare and haploid H, depressum, the frequency of chromosome pair ing is significantly lower (a mean of 0.78 - 3.00 bivalents per cell i n single plants) than in hybrids between H. depressum and rye (a mean of 6.27 - 6.50 bivalents per cell in single plants; 3.18 - 4.15 of the se are ring bivalents). It is suggested that H. depressum (4x) possess es a genetic system that suppresses homoeologous chromosome pairing of H. depressum genomes and is ineffective in the presence of the rye ge nome. In hybrids H. vulgare x H. depressum, in contrast to hybrids bet ween H. depressum and rye or haploid H. depressum, variation in chromo some number in the sporogenous tissue is observed: in various plants, 27 - 72% of microsporocytes possess an aneuploid chromosome complement . We assume that the cytogenetical instability of reciprocal hybrids H . depressum x H. vulgare results from interactions between the genomes of these species in the hybrid genome. On the basis of our results on chromosome pairing in hybrids with different genomic composition, we conclude that at the current stage of evolution, H. depressum (4x) is an allopolyploid containing two highly homologous genomes.