A candidate recombination modifier gene for Zea mays L.

Maize meiotic mutant desynaptic (dy) was tested as a candidate recombinatio n modifier gene because its effect is manifested in prophase I. Recombinati on rates for desynaptic (dy) and its wild type were compared in two ways: ( I) segregation analysis using six linked molecular markers on chromosome 1L and (2) cytogenetic analysis using fluorescence in situ hybridization (FIS H)-aided meiotic configurations observed in metaphase I. Chromosome 1L map lengths among the six linked markers were 45-63 chi for five F-2 dy/dy plan ts, significantly lower than the wild-type F-2 map distance of 72 cM. Chrom osomes 2 and 6 were marked with rDNA FISH probes, and their map lengths wer e estimated from FISH-adorned meiotic configurations using the expectation- maximization algorithm. Chiasma frequencies for dy/dy plants were significa ntly reduced for both arms of chromosome 2, for chromosome arm 6L, and for eight unidentified chromosomes. There was a notable exception for the nucle olus-organizing region-bearing arm chromosome arm 6S, where dy increased ch iasma frequency. Maize meiotic mutant desynaptic is a recombination modifie r gene based on cytogenetic and segregation analyses.