Distribution of potato viruses in Uganda

Abstract

Viral diseases are among the major factors affecting potato ( Solanum tuberosum L.) production in Uganda. Knowledge of the types of viruses and their distribution levels in the country is vital for targeting sound management strategies. The objective of this study was to assess the prevalence and distribution of potato viruses in different potato growing areas in Uganda. Virus diagnostic surveys were conducted across the main potato producing regions and virus detection was done using DAS-ELISA and RT-PCR techniques. The study showed that the most widely distributed and economically important potato viruses were: PVS (31-90.9%), PLRV (2.6-81.3%), PVY (7.1-54.5%) and PVX (8.3 -53.3%); while the least detected viruses were PVM (18.2%) and PVA (9%). The viruses were prevalent either singly or in mixtures. Up to 42.8% of the samples were infected with one virus, 20.9% with two viruses and 4.2% with three viruses; while no virus was detected in 31.3% of the samples. Of the double infections, the PVY+PVS combination was the most common and widely distributed (2.1-18.2%) in 12 districts; followed by PVY+PLRV (1.8-21.3%) occurring in six districts, PVM+PVS (7.9-16.7%), PLRV+PVX (2.4-14.3%) in 5 districts and PVY+PVX (2.4-4.4%) in 3 districts. Triple infections involving PVY+PLRV+PVS were recorded at prevalence levels of 2.2-18.6% in six district. Altitude, temperature, varieties and seed sources showed relationships with the variation in the prevalence of the viruses. There were high virus prevalence and disease severity levels in low altitude areas (1088-1334 m.a.s.l) of mid-western sub-region (Mbarara and Lwengo), Central (Kibaale, Mubende) and Mid Northern (Pader) sub region compared to high altitude areas (>1600 m.a.s.l). The Virus risk Area Modeling results showed the largest area (48.6%; 1,308,160 ha) at moderate risk of virus infection; while 27.3% (732,305 ha) was at high risk of virus infection. Based on the distribution level of the viruses, potato production could be intensified in areas with less virus pressure mainly, in parts of West Nile and Rwenzori regions.Les maladies virales sont l\u2019un des principaux facteurs affectant la production de pommes de terre ( Solanum tuberosum L.) en Ouganda. La connaissance des types de virus et de leurs niveaux de distribution en Ouganda est essentielle pour cibler des strat\ue9gies de gestion rationnelles. L\u2019objectif de cette \ue9tude \ue9tait d\u2019\ue9valuer la pr\ue9valence et la distribution des virus de la pomme de terre dans diff\ue9rentes zones de culture de la pomme de terre en Ouganda. Des enqu\ueates de diagnostic viral ont \ue9t\ue9 men\ue9es dans les principales r\ue9gions productrices de pommes de terre et la d\ue9tection des virus a \ue9t\ue9 effectu\ue9e \ue0 l\u2019aide des techniques DAS-ELISA et RT-PCR. L\u2019\ue9tude a montr\ue9 que les virus de la pomme de terre les plus largement r\ue9pandus et les plus importants sur le plan \ue9conomique \ue9taient: PVS (31-90,9%), PLRV (2,6-81,3%), PVY (7,1-54,5%) et PVX (8,3% -53,3%); tandis que les virus les moins d\ue9tect\ue9s \ue9taient le PVM (18,2%) et le PVA (9%). Ces virus \ue9taient r\ue9pandus seuls ou en m\ue9langes. Jusqu\u2019\ue0 42,8% des \ue9chantillons \ue9taient infect\ue9s par un virus, 20,9% par deux virus et 4,2% par trois virus; alors qu\u2019aucun virus n\u2019a \ue9t\ue9 d\ue9tect\ue9 dans 31,3% des \ue9chantillons. Parmi les doubles infections, la combinaison PVY + PVS \ue9tait la plus courante et la plus r\ue9pandue (2,1 \ue0 18,2%) dans 12 districts; suivi de PVY + PLRV (1,8-21,3%) survenant dans six districts, PVM + PVS (7,9-16,7%), PLRV + PVX (2,4-14,3%) dans 5 districts et PVY + PVX (2,4-4,4%) dans 3 les quartiers. Des infections triples impliquant PVY + PLRV + PVS ont \ue9t\ue9 enregistr\ue9es \ue0 un niveau de pr\ue9valence de 2,2 \ue0 18,6% dans six districts. L\u2019altitude, la temp\ue9rature, les vari\ue9t\ue9s et les sources de semences ont montr\ue9 une relation avec la variation de la pr\ue9valence des virus. La pr\ue9valence du virus et la gravit\ue9 de la maladie virale \ue9taient \ue9lev\ue9es dans les zones de basse altitude (1088-1334 m d\u2019altitude) de la sous-r\ue9gion du centre-ouest (Mbarara et Lwengo), du centre (Kibaale, Mubende) et du centre-nord (Pader) par rapport aux zones de haute altitude (> 1600 m d\u2019altitude). Les r\ue9sultats de la mod\ue9lisation des zones \ue0 risque viral ont montr\ue9 que la plus grande zone (48,6%; 1 308 160 ha) pr\ue9sente un risque mod\ue9r\ue9 d\u2019infection virale; tandis que 27,3% (732 305 ha) \ue9taient \ue0 haut risque d\u2019infection virale. Sur la base du niveau de distribution des virus, la production de pommes de terre pourrait \ueatre intensifi\ue9e dans les zones o\uf9 la pression virale est moindre, principalement dans certaines parties des r\ue9gions du Nil occidental et de Rwenzori