DIVERSITY IN NATURAL-POPULATIONS OF WILD BRASSICA-OLERACEA AS ESTIMATED BY ISOZYME AND RAPD ANALYSIS

Naturally occurring populations of wild Brassica oleracea were collect ed in Spain, France, and Great Britain. Allele frequencies at four iso zyme loci were determined for 18 populations, while five populations w ere screened using five random primers to generate RAPDs. Levels of ho mozygosity and gene diversity, H, were computed for each population us ing isozyme data and RAPD data when applicable. Homozygosity levels te nded to be higher in smaller populations, which could also be observed as increased numbers of homozygous loci in smaller populations. Gene diversity values based on isozymes indicated considerable within popul ation variation regardless of population size. The RAPID based gene di versities were significantly higher and the two exceptional population s displayed diversity levels more in keeping with the rest. The coeffi cient of gene differentiation, G(ST), for populations in each region s howed that the Spanish populations were more homogeneous than the Fren ch or British. When the G(ST) for all populations was calculated using isozymes vs. RAPD data, the RAPD data gave a significantly lower valu e, a plausible result of the higher within population variation detect ed using RAPDs. Genetic distances between populations from different r egions were also calculated from both data sets and used to produce ph enograms. Clustering according to geographic region was not evident us ing either isozyme or RAPD data.