Genetic diversity in ICRISAT sorghum collection using random vs non-random sampling procedures. A large collection, such as the sorghum (Sorghum bicolor (L.) Moench) landrace collection held at the International Crops Research Institute for the Semi-Arid Tropics (ICRISAT), represents a challenge for the maintenance of both the accessions of and the information documented for the germplasm collection. The accessibility and knowledge of the landrace collection are the essential factors for an efficient utilization of the genetic resources by both breeders and farmers.

Hence, the large size of the sorghum landrace collection maintained by ICRISAT led to the establishment of a core collection. The core collection concept has used to define a limited set of accessions derived from an existing germplasm collection, chosen to represent the genetic spectrum in the whole collection. The core should contain the maximum genetic diversity available in the collection. Accessions in the core should be chosen primarily to be representative of the whole collection, to be ecologically or genetically distinct from one another, and to maximize genetic diversity. The core collection serves as an entry point to the whole collection. Identification of core collections also simplifies the process of multiplication and distribution to potential users by substantially reducing the number of accessions that need to be maintained in active collections. Core collections can be formed on the basis of characterization information available on germplasm accessions, which can be further used to determine cluster groups of similar accessions together. A series of investigations, reported below, were under taken to define sorghum core collections and to compare each of their sampling procedures.

During this research, an assessment was also made, according to geographic and taxonomic classification, to determine the diversity pattern maintained in the landrace collection and its adequacy. This assessment indicates that the sorghum collection held in trust at ICRISAT was under represented for the race bicolor and for accessions from China. Furthermore, this assessment highlighted redundancies especially in races caudatum and durra, as well as in the germplasm acquired from East Africa and the Indian subcontinent.