Molecular resolution of the genetic variability of major viruses infecting sweet potato (Ipomoea batatas L.) in the province of KwaZulu-Natal in the Republic of South Africa

The genetic variability of the three major viruses infecting sweet potato (Ipomoea batatas Lam.) in KwaZulu-Natal (KZN), South Africa was determined in this study. A total of 16 virus isolates originating from three different locations (Umbumbulu. Umfume and Umphambanyomi River) in KZN were analyzed. These comprised of 10 isolates of Sweet potato feathery mottle virus (SPFMV), five isolates of Sweet potato virus G (SPVG) and one isolate of Sweet potato chlorotic stunt virus (SPCSV). The phylogenetic relationships of the SPFMV, SPVG and SPCSV isolates from KZN relative to isolates occurring in SA and different parts of the world were assessed. The division of SPFMV into four genetic groups (strains) according to restriction fragment length polymorphism analysis as well as phylogenetic analysis of coat protein encoding sequences revealed mixed infections of the 0 (ordinary) and C (common) strains in sweet potato crops from KZN. All SPFMV isolates showed close lineage with isolates from South America, East Asia and Africa. The SPVG isolates showed high relatedness to each other and close lineage with other isolates, especially those from China and Egypt. Analysis of the partial sequence of the Heat shock protein 70 homologue (Hsp70) gene indicated that the SPCSV isolate from KZN belongs to the West African (WA) strain group of SPCSV and showed close relatedness to an isolate from Argentina. The knowledge of specific viral diversity is essential in developing effective control measures against sweet potato viruses in KZN. (C) 2012 Elsevier Ltd. All rights reserved.