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Assessment of genetic drift in ex situ conserved seeds of rocket (Eruca vesicaria) after regeneration

Abstract:

Four accessions of rocket of wild origin held at the Universidad Polite'cnica de Madrid germplasm bank were regenerated in isolated cages with bumblebees as pollinators. The genetic diversity of parental (P) and regenerated (R) populations was studied by means of molecular markers: RAPD and two Brassica rapa SSR loci. From RAPD markers, UPGMA cluster analysis was performed; diversity was estimated using Shannon's index and AMOVA. Differences in marker frequency between P and R populations of each accession were analysed through the χ2 test. Frequencies of SSR alleles, genetic diversity estimators (FST, FIS) and AMOVA were calculated. The results obtained with RAPD markers were in accordance with those from SSRs and indicate that the regeneration process had only minor effects on the genetic diversity of samples in three out of four studied accessions. Detected changes in the frequency of markers were in most cases negligible and do not seem to constitute either a significant loss of genetic variability or risk of genetic erosion, except when seed dormancy or other factors involving selection are acting, as it might have happened in Ev9107. It has been demonstrated that Brassica rapa SSR markers can be effectively used for Eruca vesicaria.