Monitoring the Distribution of Banana Bunchy Top Virus in South Africa: A Country-Wide Survey

Banana bunchy top disease (BBTD) is the most devastating viral disease of bananas worldwide and is caused by the banana bunchy top virus (BBTV). The disease is spread by the banana aphid Pentalonia nigronervosa Coquerel (Hemiptera: Aphididae ) and through infected propagation material. In 2015, the virus was detected in an isolated area in the South Coast region of the KwaZulu-Natal Province (KZN), South Africa. The aim of this study was to conduct surveys across three banana-producing regions in South Africa, viz. KwaZulu-Natal, Mpumalanga and Limpopo provinces. Over 1700 plant and aphid samples were collected from commercial farms and rural households in the three provinces and more intense sampling was done in the affected KZN region. A BBTV-specific polymerase chain reaction (PCR), targeting the putative replicase gene, was performed to detect virus-infected samples. The amplicons that yielded an expected band size of 349 bp, were sequenced. Comparative phylogenetic analyses showed that the South African BBTV isolates clustered within the Pacific Indian Ocean genomic group that included isolates from India and other regions in Africa with a bootstrap value of 94% . To date, the virus has been identified only in the South Coast region of the KwaZulu-Natal province. Intense management strategies, including scouting, removal of infected plants and control of aphids, have been implemented in areas where positive samples were identified to minimize the spread of the virus. Findings from this study emphasize the need to continue monitoring and containing the spread in the KZN South Coast region.