Molecular marker-based characterization of Ecuadorian dry forest tamarind plus trees.

To improve the potential of tamarind as an economically valued domesticated species it is important to characterize its variability in Ecuador for breeding purposes. Our aim was to investigate the genetic diversity of 32 tamarind plus trees using inter-simple sequence repeat (ISSR) markers. Eighty four loci were examined using 12 markers, with a mean number of 4.42 loci per primer; 8 loci (9.52 %) were monomorphic and 76 (90.48 %) polymorphic, revealing genetic variability among the individuals. Polymorphic information content (PIC) values varied from 0.29 (ISSR_808) to 0.93 (ISSR_HB12), whereas the marker index ranged from to 26.4 (ISSR_814) to 62.5 (ISSR_17899A). Primers ISSR_HB11, ISSR_836, ISSR_842, ISSR_848, ISSR_860, ISSR_17899A and ISSR_17899B were useful to discriminate the grouping of the accessions according to their PIC values. Ward cluster analysis grouped accessions into two major groups with five subgroups with 46 % similarity according to Jaccard distance. The genotypes from Loja, Manabi and Guayas provinces were grouped in the first cluster; while only individuals from Manabi located in the other group, indicating major diversity in the latter province. Genotypes T1-ECUM-001 and T1-ECUM-002 presented 76 % similarity, while T1-ECUM-008, T1-ECUM-010, T1-ECUM-012, T1-ECUM-017 and T1-ECUM-018 shared 60 %. All materials from Loja grouped with 65 % similarity. Other genotypes clustered with similarity of 54 %. The cophenetic correlation coefficient (0.634) showed a good fit between the data matrix and the dendrogram results. A reasonable degree of diversity was found among tamarind genotypes potentially useful to select plus trees for clonal propagation as well as to identify diverse parents for hybridization programs.