ABERRANT MEIOTIC DIVISIONS IN A HORDEUM-LECHLERI X HORDEUM-VULGARE HYBRID

Five plants produced in a H. lechleri x H. vulgare cross comprised fou r trihaploids of H. lechleri with 2n = 21 and one aneuploid interspeci fic hybrid with 2n = 25 26. Somatic cells of the hybrid lacked H. vulg are chromosomes nos 1 and 6 and one, or two H. lechleri chromosomes, b ut had two representatives of H. vulgare chromosome no- 7. Chromosome numbers of meiotic metaphases ranged from 4 to 54 with peaks at or jus t below euploid numbers corresponding to the prevalent aneuploid chrom osome number of the hybrid. The cause of chromosome numbers at and aro und 2n = 14 and 2n = 7 is proposed to be intraspecific, intergenomic e limination of one and two H. lechleri genomes, respectively, in additi on to the elimination of all H. vulgare chromosomes. It is suggested t hat intraspecific, intergenomic elimination occurs in allopolyploids i n nature, thereby causing reduction in chromosome number within specie s. Numbers above 2n = 29 are ascribed to spontaneous chromosome doubli ng- Meiotic irregularities such as misdivisions, ''budding'', telocent rics, fragmentation of the whole chromosome set, and non-synchronized divisions were common. The production of ''buds'', generally with few chromosomes, may have added to the variability in chromosome numbers.