THE DURATION OF MEIOSIS IN A DIPLOID RYE, A TETRAPLOID WHEAT AND THE HEXAPLOID TRITICALE DERIVED FROM THEM

Meiosis and pollen development were timed in diploid rye, Secale cereale L. cv. Prolific; tetraploid wheat, Triticum turgidum L. var. durum cv. Stewart; and a hexaploid, Triticale hexaploide cv. 6A190, derived from them. At 20 C the duration of meiosis was about 51 hr in Prolific rye, 31 hr in Stewart wheat, and 37 hr in 6A190 triticale. Pollen development at 20 C lasted about 16 days in Prolific rye, about 9.5 days in Stewart wheat, and about 10 days in 6A190 triticale. These times are in close agreement with estimates previously made for diploid rye, cv. Petkus Spring; tetraploid Triticum dicoccum; and hexaploid triticale cv. RosnerThe high nuclear DNA content of rye pollen mother cells (PMC's) determines a longer meiotic time in both diploid and tetraploid rye than that determined by the lower nuclear DNA contents of PMC's in diploid and tetraploid wheat. The data available may be interpreted to indicate that the relative effect of the wheat and rye genomes in determining the rate of meiotic development in wheat/rye amphiploids varies according to the ratio of wheat to rye genomes. In diploid and tetraploid rye and in 6A190 triticale the proportion of the total meiotic time taken by zygotene and pachytene together (about 40%) differs from the proportion of meiosis which they take in hexaploid wheat and octoploid triticale (about 25%). This difference may be causally correlated with differences between the meiotic stability of rye chromosomes in wheat/rye amphidiploids at the hexaploid and octoploid levels.