An assessment of genetic diversity within and between Brassica napus and Brassica juncealines from International germplasm collections

Germplasm collections are valuable gene pools providing diverse genetic material that may be applied for the improvement of cultivars and advanced agronomic productivity. An assessment of genetic diversity in crop germplasm collections can assist in the choice of parents for genetic mapping populations and subsequent marker-assisted selection. Genotyping individuals and cultivars within germplasm collections can help breeders narrow the search for new alleles at loci of interest and assist in the identification of 'perfect' marker alleles from candidate genes that can then be introduced into new varieties along with their associated desirable traits. Genotypic information from germplasm collections can be used to assign lines and populations to heterotic groups; to study the evolutionary history of wild relatives; to verify pedigrees and fill in the gaps in incomplete pedigree or selection history and to monitor changes in allele frequencies in cultivars or populations. Towards the application of genetic diversity analysis to germplasm improvement, we have characterised within and between line genetic diversity in an international germplasm collection, consisting of over 100 B. napus and B. juncea lines, using genomic and EST (expressed sequence tag) derived Simple Sequence Repeat (SSR) molecular markers. Further genetic diversity analysis has been performed on related germplasm from 17 lines maintained in the UK along with 30 B. napus cultivars grown commercially in Australia. Analysis of the resulting data indicates clustering associated with geographical origin and breeding history as well as association with valuable agronomic traits.