The genus Annona is a genus of flowering plants in the sugar apple family, Annonaceae. It is the second largest genus in the family after Guatteria, containing approximately 166 species of mostly Neotropical and Afrotropical trees and shrubs. It is a traditional food plant in Africa. There have been some taxonomic difficulties in identifying the species within this genus using morphological traits alone. To understand the taxonomic affinity of this genus, there is a need for molecular discrimination. This study was therefore designed to check the possibilities of molecular markers in identifying the species within the genus Annona.
Thirty-three sequences (33), which represents three barcode loci (matK, rbcL and trnL), were retrieved from the NCBI website. They were combined and aligned using the ClustalW component in MEGA 11 software. The aligned sequences were evaluated, and this provided the genetic characteristics, match identification rate, barcoding gaps, haplotype diversity and nucleotide diversities of the markers. A phylogenetic tree was also constructed using the Neighbor-Joining tree-based method of MEGA 11.
The results showed the number of variable sites for all single and combined markers ranging from 2 (trnL) to 1077 (matK+trnL+rbcL) and the Parsimony informative sites ranging from 2 (rbcL) to 630 (matK+trnL+rbcL). The average intraspecific distance was discovered to be zero (0) for all single and combined markers, while the interspecific distance ranged from 0.002 (rbcL) to 0.990 (matK+trnL+rbcL). The results of this study showed that matK+trnL had the highest for best match (71.42%), while matK had the highest value for the best close match (38.46%). The phylogenetic tree generated revealed that only three species (Annona glabra, A. sengalensis and A. stenophylla ) are paraphylletic