The Journal of Heredity 1992:83(5):335-341
© 1992 The American Genetic Association 83:335-341
research-article |
Production of Aneuploid and Diploid Eggs by Meiotic Mutants of Maize
Department of Botany and Plant Sciences, University of California Riverside, CA 92521
The USDA-ARS, University of Missouri Columbia
Abstract
Mutations that affect meiosis in maize (Zea mays L.) have most often been discovered because of their negative effects on pollen fertility. Their precise effects during meiosis were confirmed subsequently through cytological studies of male meiosis. In our investigation, 11 such mutants (afd, am1, am2, dsy, dv, dy, pam1, pam2, po, va1, and va2) were analyzed for their effects on female meiosis. Since the cytological study of female meiosis is extremely difficult, an indirect approach was used. Homozygous mutant plants were crossed as females by a diploid inbred line and separately by an autotetraploid line. Chromosome constitutions of egg cells were deduced from chromosome constitutions of progeny. Aneuploid eggs can indicate chromosome nondisjunction or fragmentation during female meiosis; diploid (2n) eggs can indicate a failure of the first or second meiotic division. Differences between a meiotic mutation's inferred effects in megaspore mother cells (MMCs) and those observed directly in pollen mother cells (PMCs) were sometimes found. These differences suggest separate genetic control in PMCs and MMCs of certain meiotic functions. The potential of these mutations as sources of egg cells with unusual or novel chromosome constitutions was also considered. Two percent of small-sized kernels from variable sterile-1 (va1) and variable sterile-2 (va2) ears had telocentric chromosomes or isochromosomes. The frequency of aneuploids on va1 and va2 ears was 18-fold greater among small-sized kernels than among normal-sized kernels.
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