Simple sequence repeat (SSR)-based marker variation in Brassica nigra genebank accessions and weed populations

Brassica nigra, a weed and minor crop species, may be a source of useful tr aits for breeders of major Brassica crops. However, little is known about t he extent and distribution of genetic variation in B. nigra, and few marker s have been developed to describe this variation. In an initial survey of v ariation in B. nigra, we used five amplified DNA fragment markers based on SSRs to describe variation in 32 entries (genebank accessions and weed popu lations) from four regions: Europe/North Africa (the species' native range) , India, Ethiopia, and North America. Considerable variation was apparent b etween regions and between entries, but more than half of the total variati on was between plants within entries. Ethiopian entries formed the most dis tinct group. European and North American entries comprised the nost variati on and were generally grouped together. Unique variants were present in wee d populations from North America (where the species is introduced), but mar ker variation between the populations was not correlated with geographic di stance. In summary, SSR-based markers were informative descriptors of varia tion in a global sampling of B. nigra germplasm. The patterns of variation appear to be consistent with the species' agricultural history, and they ca n be used to design further studies and plan strategies for conserving B. n igra genetic resources.