LOCALIZATION OF THE GENES-CONTROLLING B-CHROMOSOME TRANSMISSION RATE IN MAIZE (ZEA-MAYS SSP. MAYS, POACEAE)

In previous papers we found that the frequency of B chromosomes in nat ive races of maize varies considerably in different populations. Moreo ver, we found genotypes that control high and low transmission rates ( TR) of B chromosomes in the Pisingallo race. In the present work cross es were made to determine whether the genes controlling B-TR are locat ed on the normal chromosome set (As) or on the B chromosomes (Bs). We made female f.0B X male m.2B crosses between and within high (H) and l ow (L) B-TR groups. The Bs were transmitted on the male side in all ca ses. The mean B-TR from the progeny of f.0B (H) X m.2B (H) and f.0B (H ) X m.2B (L) crosses was significantly higher than that from f.0B (L) X m.2B (L) and f.0B (L) X m.2B (H) crosses. The results show that the B-TR of the crosses corresponds to the H or L B-TR of the 0B female pa rents irrespective of the Bs of the male parent. This indicates that B -TR is genetically controlled by the 0B female parent and that these g enes are located on the A chromosomes.