GENETIC-CONTROL OF B-CHROMOSOME TRANSMISSION RATE IN ZEA-MAYS SSP MAYS (POACEAE)

We selected genotypes of high and low B chromosome transmission rate ( TR) in a native race of maize (Pisingallo) from northwest Argentina. W e made 20 female 0B x male 1B and 20 f.1B x m.0B crosses. The former ( G0m) showed a large variation of B TR, with a mean of TR +/- SE = 0.52 +/- 0.06, ranging from 0.17 to 0.98. In the latter (G0f) the mean was TR = 0.47 +/- 0.02 ranging from 0.31 to 0.58. Plants showing the high est and the lowest TR were selected to constitute the progenitors of t he G1 generations. We made 19 f.0B x m.2B crosses, studying 24-30 plan ts per cross. The TR of the high (H) and low (L) lines in G1m (G1mH an d G1mL) significantly differed (TRH = 0.65 +/- 0.03, TRL = 0.40 +/- 0. 01), indicating that the H and L lines are different groups. The large variation in male TR suggests that preferential fertilization of game tes carrying B chromosomes does not always occur. We also selected pla nts showing high and low TR in the progenies of f.1B x m.0B crosses (G 0f), and made 24 f.1B x m.0B crosses, studying 23-30 plants per cross. The TRs of the H and L lines in G1f (G1fH and G1fL) were significantl y different (TRH = 0.48 +/- 0.025, TRL = 0.40 +/- 0.02). The TRs in G0 f and G1fL were significantly different (TR = 0.47 +/- 0.02 and 0.40 /- 0.02, respectively), while this was not the case between G0f and G1 fH. Our results demonstrate the existence of genotypes controlling B T R in this native population of maize.