Genetic Fingerprinting of Sweet Potato [Ipomoea batatas (L.) Lam] as Revealed by Isozyme Electrophoresis Analysis
Sweet potato is an important staple crop and many varieties have been released into farmers’ fields in Nigeria, but no reliable means in tracking their identity, thus causing multiple naming of these varieties among farmers. The objective of the study is to establish objectively and reliable means of identifying released, local and elite sweet potato genotypes available in farmers’ fields. Thirty genotypes of sweet potato (Ipomoea batatas) species comprised IITA elites, local landraces and adaptable farmers’ varieties were planted at a space of 1m x 1m in a randomized complete block design in two replications. High genetic diversity was observed among the sweet potato genotypes examined. The morphological data revealed three distinctive clusters. In cluster I, purple vine, green petiole and light pink storage root colour were the dominant traits. While cluster II had dark green leaf at emergence and later changed to light green when fully expanded and the root cortex and pulp were white and cream colour, respectively. Cluster III exhibited different morphological characters. Two of the four isozyme markers examined, Aspartate amino transferase (AAT) and 6-phosphogluconate dehydrogenase (6 PGD) were more effective to discriminate sweet potato genotypes. AAT had 9 loci while 6-PGD had 10 loci and polymorphism ranged from 10.0% - 90.0% for AAT and 10.0% - 96.7% for 6-PGD. Isozyme data analysis revealed four clusters and insignificant correlations were observed between the isozyme and morphological analyses. The results could assist breeders in genetic diversity study of this crop and for its improvement.
Keywords: Electrophoresis, isozyme markers, sweet potatos, morphology and polymorphisms