Taxonomic identification of Nigerian Terminalia superba and Terminalia ivorensis Combretaceae) using AFLP molecular markers

Abstract

Terminalia superba and T. ivorensis are difficult to identify with morphological markers. Molecular characterization is very effective to correct the delimitation of timber species, especially when the discriminatory power of morphological markers is weak. In this study, four amplified fragment length polymorphism (AFLP) marker combinations were used to determine the taxonomic relationship among a total of 33 accessions of the genus Terminalia, consisting of two species, Terminalia ivorensis (12 accessions) and T. superba (21). The primer combinations produced a total of 740 fragments out of which 619 (83.6%) were polymorphic. Among all the primer combinations used, E-ACT/M-CTC was the most informative, which generated 11 unique markers for clear identification of the two species. The average polymorphic information content (PIC) ranged from 0.24 (E-ACT/M-CAT) to 0.28 (E-ACT/M-CTC) while the resolving power (RP) varied from 40.73 (E-AAC/M-CTA) to 63.76 (E-ACT/M-CTC). The genetic difference between the two species was significant (PhiPT = 0.610, p<0.001). All 33 accessions were delimited by both the UPGMA cluster and principal component analysis. Based on the results, it was concluded that E-ACT/M-CTC is the best among the marker combinations used for molecular study of the two tree species and used significantly to distinguish them. STRUCTURE analysis identified two accessions of Terminalia superba with alleles derived from T. ivorensis as well as revealed five putative hybrid accessions, which requires further genetic investigation to substantiate the finding.