ASSOCIATION OF ISOZYME MARKER-GENES ON CHROMOSOME-6 WITH RESISTANCE TO MDMV IN MAIZE

In order to determine the precise position of Mdm1 on the maize chromo some map, isozymes of the chromosome 6 were used as genetic markers. P arental homozygous lines were chosen by both divergence in MDMV resist ance and presence of segregating isozyme markers. Two resistant (R: 38 -11, B84) and 2 susceptible (S: Mo17, Oh43) lines and BC (F1 x S paren t) progenies of 4 crosses (R x S) were analysed. Resistance scoring of mechanically inoculated plants was performed visually. The obtained r atio of R vs S plants showed that the degree of resistance depended on the susceptible parent genotype. Recombination percentage between Mdm 1 and chromosome 6 isozyme loci showed apparent association only with the Pgd1 (6-phosphogluconate dehydrogenase) locus. The distance betwee n these 2 loci is 14-22 recombination units.