Genetic diversity of some Moringa oleifera Lam. cultivars available in South Africa.

Abstract

Moringa oleifera Lam. (Moringaceae) is a nutritious and high medicinal value tree. The species is native to India but grown globally due to its properties. The nutritional content of the species includes high levels of vitamins, minerals, calcium, magnesium and iron. It is now known that different cultivars of M. oleifera are grown throughout the world depending on the intended products. However, in South Africa, there is limited knowledge on the genetic variation of the cultivars most farmers and researchers are growing. In this study, a partial sequence of chloroplast atpB gene was used to determine genetic diversity of M. oleifera cultivars from different regions across the world but grown for research at the Agricultural Research Council, Vegetable and Ornamental Plants campus in Roodeplaat, Gauteng Province, South Africa. Thirteen cultivars were collected, of which three were domesticated cultivars from South Africa, eight were from Thailand, and one cultivar each was from Taiwan and the United States of America. Each cultivar consisted of six replicates. DNA extraction, PCR and gel electrophoresis were performed at the University of KwaZulu-Natal whereas DNA sequencing was done at Inqaba Biotec laboratory. DNA sequence analysis was done using BioEdit, MegaX, POPArT and DnaSP softwares. Based on the phylogenetic analysis, the average total length of the sequences was 404 nucleotides with the number of polymorphic segregating sites and mutation of 21 and 24, respectively. From the maximum likelihood tree and neighbour-joining tree, South African domesticated cultivars SH and Limpopo were more related to each other than to the domesticated cultivar, CHM (South African). The cluster which was well supported with 84% bootstrap value was between cultivars TOT 5077 (Thailand) and TOT 4100 (Taiwan). The polymorphic data indicated a nucleotide diversity of 0.01654 and average number of nucleotide difference (k) of 6.58095. The haplotype network also showed less genetic differences between the cultivars with some cultivars recorded as similar. The low genetic diversity observed in these cultivars suggests that the cultivars might have originated from a common ancestor. However, further study is necessary by collecting more cultivars of M. oleifera South Africa and other parts of the world to get a clear view on the genetic diversity. The results from this study will be an addition to the already existing knowledge of M. oleifera available in the world and new knowledge on genetic variation among South African cultivars, which may be relevant in cultivar development and conservation.