Increasing Accuracy and Throughput in Large-Scale Microsatellite Fingerprinting of Cacao Field Germplasm Collections

Abstract

In this study we report on increasing the rate and accuracy of microsatellite fingerprinting of accessions in Theobroma cacao L. field germplasm collections with a medium-throughput capillary sequencing system. We examined the use of a reduced number of microsatellite loci to decrease the time and materials required for fingerprinting and determined the best available microsatellite loci for accurately separating accessions. A subset of nine informative loci that could separate sixty accessions into the same genetic groupings as a complete set of 37 loci was found. Stringent probability of identity values (i.e. chance of unique accession) was highly influenced (r = −0.996; P < 0.001) by the number of alleles utilised in the fingerprinting set but the composition of the primer set was more important when choosing discriminatory loci. DNA pooling to reduce the number of samples was also investigated. There was a relatively high level of mixture within plots (59% of 54 plots examined) of the field genebank, which opposed the use of a pooling strategy to fingerprint the multiple trees of an accession plot in the collection.