GENETIC-ANALYSIS OF MORPHOLOGICAL VARIATION IN BRASSICA-OLERACEA USING MOLECULAR MARKERS

A cross between the open-pollinated Brassica oleracea cabbage cultivar 'Wisconsin Golden Acre' and the hybrid broccoli cultivar 'Packman' wa s used with molecular markers to investigate the genetic control of mo rphological variation. Twenty-two traits derived from leaf, stem, and flowering measurements were analyzed in 90 F-2 individuals that were a lso classified for genotype by restriction fragment length polymorphis m (RFLP) markers. Seventy-two RFLP loci, which covered the mapped geno me at an average of 10 map-unit intervals on all nine linkage groups, were tested individually for associations to phenotypic measurements b y single factor ANOVA, and markers with significant associations (P < 0.05) were used to develop multilocus models. These data were utilized to describe the location, parental contribution of alleles, magnitude of effect, and the gene action of trait loci. Single marker loci that were significantly associated (P < 0.05) with trait measurements acco unted for 6.7-42.7% of the phenotypic variation. Multilocus models des cribed as much as 60.1% of the phenotypic variation for a given trait. In some cases, different related traits had common marker-locus assoc iations with similar gene action and genotypic class ranking. The numb ers, action, and linkages, of genes controlling traits estimated with marker loci in this population corresponded to estimates based on clas sical genetic methods from other studies using similar, or similarly-w ide, crosses. There was no evidence that genome duplication accounted for a significant portion of multiple genes controlling trait loci ove r the entire genome, but possible duplications of trait loci were iden tified for two regions with linked, duplicated marker loci.