Selection of a core collection from the US castor bean germplasm collection

Castor bean (Ricinus communis L.) is a medicinal, industrial and biodiesel crop that is adapted to marginal soils in hot, dry and semi-arid environments, but its genetic potential is not fully exploited. Genetic variation exists in different castor bean genebanks, which hold many germplasm accessions. Since there are large numbers of accessions (normally over 1,000 accessions) in any genebank, the efficient way to exploit genetic diversity is to establish a core collection (i.e. 10% of the collection, but maximally representing the genetic diversity of the entire collection). There are 1,033 accessions in the United States Department of Agriculture (USDA) castor genebank, but a castor bean core collection was not available. For assessment of the genetic variation, we evaluated up to 347 accessions with available morphological and seed production data in the Germplasm Resources Information Network (GRIN) for seven qualitative and quantitative descriptors (plant height, maturity, raceme length, seed colour, seed size, stem colour and seed numbers) and then analyzed seeds chemically using nine quantitative traits (oil percentage, palmitic acid, stearic acid, oleic acid, linoleic acid, linolenic acid, gadoleic acid, ricinoleic acid and dihydrosterculic acid content).