A new method for producing homozygous duplications in maize

Abstract

Translocations between the B chromosomes of maize and standard (A) chromosomes have been widely used to manipulate the dosage of A chromosome segments. The B chromosome frequently undergoes nondisjunction at the second pollen mitosis as part of its normal pattern of inheritance. BA chromosomes also undergo nondisjunction and, therefore, are used to produce duplications and deficiencies of A-chromatin. Duplications are useful in gene dosage studies and some may have agronomic value if they are associated with useful phenotypes. However, duplications produced by BA nondisjunction cannot be easily maintained during propagation. The BA undergoes nondisjunction each generation, destabilizing its inheritance. A new method is presented here for systematically duplicating segments of the maize genome using B–A translocations. The method uses meiotic segregation rather than nondisjunction to produce duplications. It employs AB chromosomes instead of BA chromosomes. As a test of the method, homozygous duplications (segmental tetrasomics) were constructed for a region on chromosome 3 and for another region on chromosome 9.Key words: maize, B chromosome, duplication.