Sampling Strategies for Composing a Core Collection of Cultivated Barley (Hordeum vulgare s. Iat.) Collected in China

Abstract

Using 96 accessions of Chinese barley landraces with reliable passport data, alternative methods for composing a core collection have been compared. The relative success of the different methods was assessed by counting the number of isozymic variants in the resulting core collections; the larger the number of alleles in the core collection, the more successful the method. Clustering on the basis of the location of the collection site was compared with clustering on the basis of qualitative and quantitative morphological characteristics. The collection site data proved to be the best basis for clustering, followed by the qualitative descriptive data, i.e., row number, presence of awns or hoods, and kernel covering. Clustering based on quantitative data, i.e., heading date and plant height, did not improve sampling efficiency. The optimal number of clusters obtained using the collection site data was eight, and corresponds to the number of geographical regions where the germplasm was collected. Alternatives for allocating the accessions to the groups after clustering were also compared, but seemed to have little effect; in general, proportional and logarithmic allocation scored better than constant representation, but this was not always the case.