Evaluation of genetic relationship among varieties of Capsicum annuum L. and Capsicum frutescens L. in West Africa using ISSR markers

The taxonomic identity of two closely related Capsicum species; Capsicum annuum and Capsicum frutescens in West Africa has not been clarified because they have overlapping morphological traits. Effective control and management measures as well as improvement of crop plants in any breeding programme can only be implemented when plant species are correctly identified. The genetic relationships of the varieties of these Capsicum species were assessed using 10 ISSR primers for the first time. The varieties and species used include C. annuum var. abbreviatum; C. annuum var. acuminatum; C. annuum var. grossum and C. frutescens var. baccatum. PCR amplification of the isolated DNA from the four varieties of Capsicum revealed a total of 75 loci out of which 14 were found to be polymorphic. Average polymorphism information content (PIC) and heterozygosity (He) of the 10 ISSR markers were estimated as 0.67 and 0.78 respectively. The relatedness among the varieties assessed by Unweighted Pair Group Method with Arithmetic Mean (UPMGA) cluster analysis did not separate C. frutescens var. baccatum from the three cultivated varieties of C. annuum. The result from the principal component analysis (PCA) further supports the genetic relatedness and groupings obtained from the cluster analysis. Overall, the study indicated that ISSR markers were effective in assessing the genetic relatedness and revealed genetic homogeneity of the four varieties. Our results, therefore, support the inclusion of C. frutescens var. baccatum as a variety of C. annuum species.