Developing DNA barcoding (matK) primers for marama bean [Tylosema esculentum (Burchell) Schreiber]

Abstract

DNA barcoding is based on the premise that a short standardized DNA barcoding sequence can distinguish individuals of a species because the genetic variation between species exceeds that within species. Information on genetic variation of breeding materials helps to maintain genetic diversity and sustains long term selection gain. This information is a prerequisite for the genetic improvement of any plant species for effective use of germplasm in breeding and for conservation. Marama bean [Tylosema esculentum (Burchell) Schreiber] is found in the arid, dry parts of Southern Africa and due to the high nutrient value of the seeds and tubers, richness in protein, oil and starch, it is a potential crop for arid areas where few conventional crops can survive. The effective conservation and use of marama bean genetic resources for domestication involves investigating the extent of genetic variation. The matK gene, formerly known as orfK, is emerging as a DNA barcoding gene with potential contribution to plant molecular systematics and evolution. The gene matK, approximately 1500 base pairs (bp), is believed to code for a maturase-related protein based on structural similarities to other such genes. This gene was investigated for potential contribution in genetic variation studies of marama bean and also establishing a barcode for T. esculentum. The matK gene was amplified in marama bean and we reported herein, the first record of sequences of this gene for the species that were found to be related to other legume matK sequences deposited in GenBank. The homology found with Tylosema fassoglensis (trnK gene) and Pisum sativum (matK gene) suggests that an identical region was amplified for Tylosema esculentum. A phylogenetic tree was constructed based on the matK sequences and the results suggest that the matK region can also be used in determining levels of genetic variation and for barcoding.

Key words: Marama bean, DNA barcoding, genetic variation, maturase kinase.