Abstract
In most developing countries, farmers lack sufficient supply of certified or healthy potato seed tubers. Hence, they often plant their own saved ware potato tubers, a practice that is known to contribute to spread and increase the prevalence of plant viruses. In this study, we proposed options for managing the virus based on the knowledge obtained from surveys of virus prevalence and distribution in potato cultivars grown under such conditions. Potato leaf samples randomly collected from 354 farms in five major potato-growing counties in Kenya were tested for six potato viruses; potato virus Y (PVY), potato leaf roll virus (PLRV), potato virus X (PVX), potato virus M (PVM), potato virus A (PVA) and potato virus S (PVS) through DAS-ELISA. Virus prevalence in the fields was high; 72.9% of the samples were positive for at least one of the six viruses; and 55.9% showed multiple infections. A follow-up survey conducted during three consecutive seasons, in two of the five counties, revealed that virus prevalence fluctuated across seasons. This suggested that updated information on virus prevalence might be of value for designing a virus control strategy. Distribution maps showed the presence of the viruses restricted to specific geographic regions, an indication of where control efforts should be directed. Four cultivars, Sherekea, Shangi, Kenya Karibu and Asante, grown at a high virus-prevalent area, showed low values of average ELISA absorbance (OD), suggest a field resistance to the viruses. This study demonstrated that knowledge of prevalence and distribution may be of value to identify and recommend virus resistant cultivars to replace susceptible ones, especially in the virus hotspot areas.
Highlights
Potato (Solanum tuberosum L.) is globally ranked as the fourth most important food crop after wheat, rice and maize
Virus prevalence was found to be changing over time especially with potato virus X (PVX) and potato virus S (PVS) which was found to occur with the highest overall prevalence
In Kenya, the first organised field survey on potato viruses was conducted during the potato-growing seasons of 1996 and ELISA optical density (OD) values at 405 nm 1998 in four regions (Nyamira, Kisii, Meru and Kiambu) on 80 leaf samples which were tested in ELISA only for potato leaf roll virus (PLRV)
Summary
Potato (Solanum tuberosum L.) is globally ranked as the fourth most important food crop after wheat, rice and maize. In Kenya, potato is the second most important food crop after maize and plays an important role in ensuring food security of the country (MoALF 2016). Viruses are among the most important vector and seed-borne diseases of the potato crop (Salazar 1996). Out of over 40 viruses which can infect potato (Whitfield et al 2015), the six best known viruses: potato virus Y (PVY, genus Potyvirus), potato leaf roll virus (PLRV, Polerovirus), potato virus X (PVX, Potexvirus), potato virus A (PVA, Potyvirus), potato virus S (PVS, Carlavirus) and potato virus M (PVM, Carlavirus) have been reported to be most important in Kenya (Were et al 2003; Muthomi et al 2009; Were et al 2013) and even in the neighbouring countries Ethiopia, Uganda and Tanzania (Gildemacher et al 2011; Priegnitz et al 2019)
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