DISTRIBUTION OF CHLOROPLAST DNA DIVERSITY WITHIN AND AMONG POPULATIONS IN GYNODIOECIOUS BETA-VULGARIS SSP. MARITIMA (CHENOPODIACEAE)

With the recent technical advances in molecular biology chloroplast DN A (cpDNA) has become a marker used for the study of cytoplasmic differ entiation of natural populations of plants. As chloroplasts are matern ally inherited in most plant species, the seed component of gene flow is thus made accessible. We present here a study of cpDNA polymorphism within the maritima sub species of the gynodioecious Beta vulgaris in which we try to assess the impact of such a reproductive system on se ed flow. One hundred and eighty-eight wild beets were sampled from 20 hermaphroditic and 20 gynodioecious (i.e. containing both hermaphrodit ic and female plants) populations from the Atlantic coast of Europe. c pDNA variability in these populations was characterized with a rapid r estriction fragment length polymorphism (RFLP) method. Eight cpDNA hap lotypes were found. Strong differentiation among populations was obser ved (F-ST = 0.43) and was consistent with isolation by distance, altho ugh most of the cpDNA haplotypes were ubiquitous. Gynodioecy seems to affect the distribution of cpDNA diversity: gynodioecious populations of Beta vulgaris ssp. maritima contained a greater number of cpDNA typ es but were less differentiated among themselves than hermaphroditic o nes.