Kernel-weight effects and transmission of a partial trisome involving the long arm of chromosome 5 in maize

Abstract

Effects of trisomy for a portion of the long arm of chromosome 5 of maize (Zea mays L.) were explored by using the B5La element derived from the B–A translocation TB-5La. In one family, the B5La chromosome was transmitted through the egg to half of the offspring; in two other families, the rate of transmission was 44 and 46%, respectively. From the reciprocal cross, only 5.6% of the progeny carried B5La. The presence of the allele Pr (purple aleurone) on the partial trisome made it possible to study the effect of trisomy for a portion of the long arm of chromosome 5 on kernel weight. The trisegmental kernels averaged 11% lighter than their disomic sibs on seven ears and were of the same weight on one ear. It appears that the particular alleles of genes on B5La originally reduced kernel weight, but one variant, presumably acquired by crossing over, did not. Crossover products involving an exchange between the translocation breakpoint on B5La and the pr locus occurred at a rate of 8.3%.