GENETIC DIVERSITY AND SELECTION OF A CORE COLLECTION FOR LONG TERM CONSERVATION OF COCOA (Theobroma cacao L)

Ninety-nine accessions of the Cocoa Germplasm Bank in the Rosario Izapa Experimental Station, INIFAP, Mexico, were studied in order to evaluate the genetic diversity and thus lay the foundation for a long-term conservation program of materials representative of diversity through a core collection. Fourteen microsatellite (SSR's) markers were used. To analyze polymorphism the absence/presence (0/1) of bands for each locus was recorded, and a binary matrix was generated with the information generated with all the primers. Diversity parameters were obtained with the GenAlex 6.5 program and an algorithm based on K-i%fFANS and FFT was used for the development of Core Collection CorColl ver. 2.3; Windows executable of a Python implementation of the original algorithm in FreeMat. Overall analysis of the 99 accessions and the use of 14 combinations of SSR's, allowed to ampler 75 bands, of which 79.7% were polymorphic. The number of different alleles was two for all the primers, while the number of effective alleles varied from 1.105 to 1.384 (average - 1.213). The Shannon index varied from 0.167 to 0.407 (average= 0.267), which are considered to be low values. The above agrees with the expected heterozygosity, which varied from 0.085 to 0.255 (average= 0.153). However, with the observed diversity it was possible to obtain a dendrogram with several groups. The core collection was constructed with values of K= 16, 18, 20 and 22 and the best proposal was with K= 22 because it efficiently represents the diversity of the original collection and can be proposed for long-term conservation by cryopreservation.