Sinapis alba L. is a major specialty crop grown as a condiment in western Canada, but little is known about its genetic diversity. The objective of this study was to assess the level and pattern of genetic diversity in a collection of 127 S. alba accessions held at Plant Gene Resources of Canada using amplified fragment length polymorphism (AFLP) markers. Five AFLP primer pairs were applied, and 134 polymorphic bands were scored for each accession. These scored bands had frequencies of occurrence ranging from 0.02 to 0.99 with an average of 0.69. More AFLP variation was found within single (79.1%) than between (20.9%) S. alba accessions. A small degree of AFLP difference (1.7%) was observed among the accessions of various regions, while relatively large variation (9.2%) existed among the accessions of various countries. A large AFLP difference (15.6%) also existed between the yellow- and brown-seeded accessions, but only 6.2% difference was observed between the cultivar and landrace accessions. Two distinct groups of S. alba germplasm were identified on the basis of the seed colour (yellow or brown), although a few mixtures also existed. No apparent ‘duplicated’ accessions were observed. The most diverse accessions were from Italy, Spain, France and Greece. Among the most genetically distinct accessions were SA97 from Portugal, SA89 and SA88 from France, SA83 from Russia and SA57 from Italy. These findings are significant not only for managing S. alba germplasm, but also for identifying diverse germplasm that can be used by plant breeders to improve S. alba seed yield and quality parameters.

Out-crossing between genetically modified herbicide-tolerant (GMHT) and non-GM rape cultivars was studied using GMHT source field plots of approximately 0.8 ha. Levels of cross-pollination between adjacent fully fertile rape varieties declined rapidly with increasing distance from the interface between plots. A varietal association with low levels of male sterility showed higher levels of out-crossing than other varieties. Out-crossing data were used to compare negative exponential and inverse power-law models for their fit to describe the observed relationship between cross-pollination and distance from source. Results showed that the inverse power-law model provided a better fit of the data.

Isozyme data were used to assess genetic diversity within and among a subdivided population of the salt-tolerant Batini barley landrace. Population diversity and its components were estimated on the basis of 12 isozymes scored on 450 single plants representing seven subpopulations. Two principal components, based on mean gene diversity, Shannon's diversity index, percentage polymorphic loci, genetic identity and genetic distance among subpopulations accounted for 91.7% of total variation and separated the subpopulations into four distinct groups. Contributions to total diversity by individual subpopulations were partitioned into intra- and inter-population components. The level of population differentiation indicates that a large percentage of total genetic diversity was apportioned within subpopulations. The presence of valuable genetic diversity in this landrace was confirmed.

Molecular characterization of ex situ plant germplasm, although more attainable than before, has rarely been applied to a whole germplasm collection of 2000 accessions or larger. The benefits of screening large numbers of accessions have not been well recognized for germplasm management and utilization. Challenges also exist in identifying duplicated and genetically related accessions and in validating developed core subsets. Here we show how a new approach using an average marker-based dissimilarity of an accession in a collection can be applied to identify both redundancy and distinctness in a plant germplasm collection. Application of this dissimilarity measure to 2727 flax accessions genotyped by 149 randomly amplified polymorphic DNA (RAPD) markers revealed that up to 22% of accessions could be deemed to be redundant. Up to 500 of the most distinct flax accessions were identified and these can be directly screened for traits of interest to broaden the genetic base in a flax improvement programme. These results demonstrate that molecular screening of a large number of accessions with an informative diversity analysis can facilitate the management and utilization of ex situ plant germplasm.

Molecular investigations of qualitative and quantitative changes in the genetic diversity of cultivated crops are useful for plant breeding and the management of crop genetic resources. A genotyping study, based on 28 genomic (g-SSR) and 13 expressed sequence tag-derived (e-SSR) microsatellite markers uniformly distributed across the barley genome, was conducted on samples of cultivated barley (Hordeum vulgare L.) collected at intervals of 40–50 years in three comparable geographical regions in Austria, Albania and India. The analysis indicated an absence of any significant differences either in the total number of alleles per locus or in g-SSR and e-SSR polymorphic information content (PIC) values from the Indian and Austrian materials. However, a slight reduction in genetic diversity was noted among the materials collected in Albania. The trend in numbers of collection mission-specific SSR alleles suggests significant allele flow over the time interval sampled. The g-SSRs yielded a higher mean number of alleles per locus and a superior PIC than the e-SSR markers. We conclude that a qualitative, rather than a quantitative shift in diversity has taken place over time, and that g-SSR markers detect more diversity than do e-SSR markers.

A collection of 120 Ethiopian tetraploid wheat accessions was analysed for high-molecular weight (HMW) glutenin subunit, low-molecular weight (LMW) glutenin subunit and omega gliadin composition by SDS–PAGE. For the HMW glutenin subunits, a new allelic variant, 2****, was detected which has not been previously described at the Glu-A1 locus. A high proportion of Glu-A1x banding pattern was observed in durum wheat. For the Glu-B1 locus four different banding patterns were detected. Among those HMW glutenin subunits, 7+8 were the most common, while subunits 14+15 and 6+8 were found to be rare. A high degree of variation was evident for the LMW glutenin subunits and D-zone omega gliadins. The association of the composition of the gluten with quality has been discussed. This wide variation can be used in improving the quality of wheat and to widen its genetic base.

We present here the first large-scale genetic characterization of grape cultivars from Transcaucasia and Anatolia. These regions where wild grapes still grow in nature have been cultivating wine and table grapes for thousands of years and are considered the cradles of viticulture. Using 12 nuclear microsatellite markers, we genotyped 116 accessions of traditional grape cultivars from Armenia, Georgia and Turkey and we detected 17 identical genotypes and six homonymy cases, mainly within each national germplasm. Neighbour-joining analysis of genetic distance showed that each germplasm could have multiple origins and although they are now separated, they might have some common ancestors. In addition, four varieties from Western Europe included as outgroups turned out to be more related to Georgian cultivars than other germplasms, suggesting a possible ancient origin in Georgia. This work represents a first step towards germplasm management of this rich ampelographic heritage.