Is maize B chromosome preferential fertilization controlled by a single gene?

In previous work, genotypes for high and low B chromosome transmission rate were selected from a native race of maize. It was demonstrated that the B transmission is genetically controlled. The present work reports the fourth and fifth generations of selection and the F-1 hybrids between the lines. The native B is characterized by a constant behaviour, with normal meiosis and nondisjunction in 100% of postmeiotic mitosis. It is concluded that gen etic variation for B transmission between the selected lines is due to the preferential fertilization process. The F-1 hybrids show intermediate B tra nsmission rate between the lines. They are uniform, the variance of the sel ected character being one order of magnitude lower than that of the native population. In addition, 0B x 2B and 2B x 2B crosses were made to study the effect of the presence of B chromosomes in the female parent, resulting in non-significant differences. Several crosses were made both in Buenos Aire s and in Madrid to compare the possible environmental effect, but significa nt differences were not found. Our results are consistent with the hypothes is of a single major gene controlling B transmission rate in maize, which a cts in the egg cell at the haploid level during fertilization. It is also h ypothesized that maize Bs use the normal maize fertilization process to pro mote their own transmission.