Banana bunchy top virus in South Africa: the distribution, molecular relationship and transmission studies.

Abstract

The first report of Banana bunchy top virus (BBTV) in KwaZulu-Natal (KZN), South Africa in 2016 has raised the need to study the virus in South Africa. The aim of this research project was to conduct surveys across banana-producing provinces, including KwaZulu-Natal, Mpumalanga and Limpopo in South Africa, to determine the spread of BBTV in banana production regions across the country. To date, the virus has been localized within the province of KZN in the South Coast region. Once positive samples were obtained, the genetic relationships between the South African isolates and those collected globally was investigated. This was done by studying five (DNA-C, -S; -N; -M; -U3) of the six components of the BBTV genome. No major differences between the isolates were observed. As the virus is only transmitted through infected planting material and through the vector, Pentalonia nigronervosa, BBTV transmission studies were conducted. Such studies have been conducted in different countries on this topic with conflicting results and BBTV transmission studies were included here as well. Plant species namely Colocasia esculenta, Alocasia macrorrhizos, Alpinia zerumbet and Strelitzia reginae, that are usually found growing around banana plantations, were investigated to determine if these plants act as reservoirs of the virus vector and also to determine if these potential alternative host plant can be hosts of the virus. Banana plants were included as controls in the experiment. A qPCR was optimised to test for BBTV in the plants and aphids at low concentrations. BBTV was detected in all of the plants except A. macrorrhizos. It was concluded that A. zerumbet was an alternative host of the banana aphid while C.esculenta and S. reginae are assumed to be intermediary hosts of the virus vector while A. macrorrhizos is neither a host of the vector nor of the virus.