Stability of deletion, insertion and point mutations at the bronze locus in maize

Phenotypic revertants from several kinds of mutations, including deletions, have been detected by pollen analysis at the wx and Adh loci in maize. Mutations in these genes give phenotypic revertants with median frequencies of 0.7 and 0.5×10(-5), respectively. However, the nature of such revertants can only be analyzed following their recovery from conventional matings. In the current study large seed populations derived from crosses involving several bz (bronze) locus mutations in maize were examined for reversion to a Bz (purple) expression. Deletion, insertion and point mutations were included in the study. Principally, over 2 million gametes of the bz-R mutation, which is shown here to be associated with a 340 base pair deletion within the transcribed region of the gene, have been screened for reversion. No revertants from it or any of the other bz mutations have been recovered, even though a total of almost 5 million gametes from homoallelic crosses have been examined to date. Results from seed analysis are discussed in reference to those from pollen analysis in maize.