J. Amer. Soc. Hort. Sci. 131(5):667-673. 2006.

Inflorescence identity gene alleles are poor predictors of inflorescence type in broccoli and cauliflower.

Joanne A. Labate, Larry D. Robertson, and Angela M. Baldo
United States Department of Agriculture, Agricultural Research Service, Plant Genetic Resources Unit,
New York State Agricultural Experiment Station, Geneva, NY 14456-0462

Thomas Björkman
Department of Horticultural Sciences, New York State Agricultural Experiment Station, Cornell University, Geneva, NY 14456

ABSTRACT Broccoli (Brassica oleracea L. var. italica Plenck) and cauliflower (B. oleracea var. botrytis DC) are closely related botanical varieties. The underlying genetic bases of their phenotypic differences from each other are not well understood. A molecular genetic marker enabling B. oleracea germplasm curators and breeders to predict phenotype from seeds or seedlings would be a valuable tool. Mutant alleles at flower developmental pathway loci BoAP1-a, BoCAL-a, and glucosinolate biosynthetic pathway locus BoGSL-ELONG have been reported to be associated with a cauliflower phenotype. We surveyed mutant alleles at these three loci in a genetically diverse sample of broccoli and cauliflower accessions from the U.S. Department of Agriculture, Agricultural Research Service (USDA-ARS) Plant Genetic Resources Unit (PGRU) and the University of Warwick, Genetic Resources Unit of Warwick HRI (HRI). Phenotypic and genotypic data were collected for multiple plants per accession during two field seasons. Simple genetic models assuming dominance or codominance of alleles were analyzed. Goodness-of-fi t tests rejected the null model that the mutant genotype was associated with a cauliflower phenotype. A correlation analysis showed that BoAP1-a and BoCAL-a alleles or loci were signifi cantly correlated with phenotype but the fraction of variation explained was
low, 4.4% to 6.3%. Adding BoGSL-ELONG to the analysis improved predictive power using the linear regression
procedure, Maximum R-square Improvement (max R2). In the best three-variable model, only 24.8% of observed
phenotypic variation was explained. Because tested genetic models did not hold robustly for the surveyed accessions,
it is likely that there are multiple genetic mechanisms that infl uence whether the phenotype is broccoli or caulifl ower.
Our results in commercial cultivars indicate that other genetic mechanisms are more important in determining the
horticultural type than are BoAP1-a and BoCAL-a. 

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