GENETIC-CONTROL OF THE RATE OF TRANSMISSION OF RYE B-CHROMOSOMES .2. 0BX2B CROSSES

Twenty female OB x male 2B crosses were made in which a single male wa s crossed with four different females, and the character 'mean number of Bs per giant in the progeny' was analysed. The 2B plants used as ma les and the OB females belonged either to low or to high transmission rate lines, previously selected. The genetic basis of the difference b etween the high and low transmission rate lines was statistically test ed. The male group (high or low class of the 2B male) has a significan t effect on the progeny, while the female group (high or low class of the OB female) has no significant effect. The genes controlling the tr ansmission rate of B chromosomes affect the proportion of OB vs. 2B pl ants in the OB x 2B cross, but this is not a result of any effect on t he nondisjunction mechanism, since the proportion of 1B plants is low in all cases. Structural variants of B chromosomes appeared de novo at a high frequency.