Prevalence And Co-infection Of Cassava With Cassava Mosaic Geminiviruses And Cassava Brown Streak Virus In Popular Cultivars In Western Kenya

Cassava mosaic geminiviruses (CMGs) and Cassava brown streak virus (CBSV) cause diseases of major economic significance to cassava in Kenya. The Western region of Kenya contributes about 60% of cassava production in the country. Currently CBSD distribution is being newly reported in the Western region where over 90% CMD incidences have been observed. Transmission studies have confirmed that B. tabaci transmits both CMGs and CBSV. The co-occurrence of the vector, CMGs and the newly reported CBSV undoubtedly raises the alarming possibility of a „dual pandemic‟. This study was designed to investigate the dual virus spread, the possible interactions of CMGs and CBSV on the host plant and their effect on the development of symptoms on the popular cassava varieties. To evaluate the status of the two viruses on the local popular varieties in terms of incidence, prevalence and severity, a survey was conducted in Kakamega, Teso, Bungoma, Siaya and Busia districts in Western Kenya and 273 samples collected from 67 farmer‟s fields. The CMGs and CBSV were confirmed by polymerase chain reaction (PCR) and reverse transcriptase polymerase chain reaction (RT- PCR) respectively. The CMD incidence among the varieties was highest in Embwanatereka 89%, Serere 87%, Adhiambolera 86%, and lowest in Kibandameno 83% while CBSD incidence was highest in Serere 73%, Adhiambolera 69%, and Kibandameno 56% and lowest in Embwanatereka 51%. To assess the possible interactions of the two viruses, 10 Nicotiana benthamiana plants were sap inoculated with CMGs and CBSV singly and in combination in two trials. A highly significant difference (P