Development and evaluation of a mini core collection for the US peanut germplasm collection

A core collection (831 accessions) has been developed to represent the U.S. Arachis hypogaea L. germplasm collection. This core collection has been shown to be effective in improving the efficiency of identifying genes of interest in the entire germplasm collection. However, an even smaller subset of germplasm is needed for traits which are difficult and/or expensive to measure. The objectives of this study were to select a core of the core collection and to evaluate the usefulness of this subset of germplasm to identify genes of interest in peanut. Data for eight above ground and eight below ground morphological characteristics were measured for each accession in the core collection. Cluster analysis was used on these data to partition the core accessions into groups which, theoretically, are genetically similar. Random sampling was then used to select a 10% sample from each group. The result was a core of the core collection (mini core) consisting of 112 accessions. Examination of morphological data indicated that the majority of genetic variation expressed in the core collection has been preserved in this core of the core collection. Data on disease resistances for accessions in the core collection were collected and used to determine retrospectively how effective the use of a mini core collection would have been in identifying sources of resistance in the core collection. Results indicated that the mini core collection can be used to improve the efficiency of identifying desirable traits in the core collection. For resistance to late leaf spot (Cercosporidium personatum (Berk. & M. A. Curtis), the use of a mini core collection would have improved the efficiency of identifying resistant accessions in the entire collection. The core of the core approach should be particularly useful for traits which are difficult and/or expensive to measure.