Use of core and mini core collections in preservation and utilization of genetic resources in crop improvement.

Plant genetic resources are the most valuable and essential basic raw material to meet the current and future needs of crop improvement programmes and the demands of increasing populations. The International Crops Research Institute for the Semi-Arid Tropics (ICRISAT, established in 1972) responded to this need by establishing a Genetic Resources Unit (GRU) for assembling, characterizing, evaluating, maintaining, conserving, documenting and distributing germplasm of the mandate crops (sorghum, pearl millet, chickpea, pigeonpea and groundnut) and their wild relatives, and six small millets (finger millet, foxtail millet, barnyard millet, kodo millet, little millet and proso millet). The efforts have yielded the assembly of 113 849 germplasm accessions in the ICRISAT genebank and over 5.5 million accessions globally. Unfortunately, only a small proportion of this large collection has been used in improving crops. Developing core collection (about 10% of the entire collection) has been suggested as a method of enhancing the use of the germplasm. However, even this number could be large and unmanageable if the entire accession is several thousands. A methodology to reduce the size further and select a mini-core that is about 1% of the entire collection, yet represents full diversity of the species has been developed. Core collections of sorghum, pearl millet, chickpea, pigeonpea, groundnut, and finger millet and mini-core collection of groundnut and chickpea have also been developed. The core and mini-core collections of chickpea and groundnut have been evaluated and diverse sources for early maturity, traits related to drought tolerance and large seed size in kabuli chickpea, and early maturity, tolerance to low temperature, and traits related to drought tolerance in groundnut have been identified. Their use in breeding will broaden the genetic base of the cultivars