ADJACENT-II SEGREGATION PRODUCTS IN B-A TRANSLOCATIONS OF MAIZE

In maize (Zea mays L.), meiotic events in B-A translocations that cause the A chromosome to move to one pole and the A-B and B-A chromosomes to move to the opposite pole result in the production of balanced, functional microspores and megaspores. Meiotic events that allow other combinations of chromosomes to proceed to the two poles (A A-B and A B-A) lead to the production of both duplicate (A A-B) and deficient (B-A) spores. Microspores and often megaspores that are deficient for a segment of the A chromosome are expected to abort. Duplication-bearing gametes usually function through the egg but are less able to compete with the normal gametes in the pollen. Cytological data, and genetic data from pollen, kernel, and seedling counts, were used to identify the production of A A-B gametes by B-A translocation heterozygotes and hyperploids. Adjacent II segregation of the A and A-B chromosomes of B-A heterozygotes and hyperploids has been detected in stocks of several different B-A translocations. Some B-A translocations exhibited a frequency of adjacent 11 segregation as high as 23%.