A critique of selection methodology of core collections and their use in crop improvement

Abstract

Growth in large germplasm collections in most important crops has led to the development of the concept of core collection or a smaller set of germplasm representing most spectrum of variability of total collections to facilitate their easy management, evaluation and use in crop improvement. In the last two decades, significant efforts have been made in this direction, following nearly identical sampling or selection strategies in most crops. The present article has tried to analyze critically the selection methodologies followed to assess how far core collections in different crops have succeeded in meeting the objectives, particularly those of crop genetic improvement. An attempt has also been made to address the possible ways for improvement in the selection strategy with additional steps to overcome the lacunas. Groundnut cores have been critically analyzed as a case study. This has revealed that cores have been able to capture only around 70% of variability, which has limited the value of core with non-capture of rare alleles. To overcome present lacunas, a modified stratification method has been suggested based on biogeographical distribution, and integration of gene pools (sets) of various desirable traits in the selection of accessions to formulate the core set. Greater emphasis needs to be given to genomics and characterization of accessions, particularly in relation to desired traits, using molecular markers associated with these traits to avoid masking effect caused by environment factors.