Abstract

Cucurbit vegetables play important role as sources of vitamins, micronutrients and income. However, their production is constrained, inter alia, by the virus diseases. Cucumber mosaic virus (CMV; Cucumovirus), Zucchini yellow mosaic virus (ZYMV; Potyvirus) and Watermelon mosaic virus (WMV; Potyvirus) are the major causal agents of devastating virus diseases of the cucurbits. Disease symptoms similar to those caused by these viruses were observed in cucurbits in the coastal lowland of Tanzania. To determine what caused these symptoms, leaf samples were collected from 223 cultivated and wild cucurbit plants and virus infections detected using Double Antibody Sandwich Enzyme-linked immunosorbent Assay (DAS-ELISA). Visual incidence of virus disease symptoms ranged from 0.0 to 90.0% but ELISA test for CMV, ZYMV and WMV revealed the range of 0 to 80%. The highest incidence of the virus infections was that of WMV (33.0%) in Cucumis sativus. The highest incidence of ZYMV and CMV were 10.4 and 13.4% in Citrullus lanatus and Cucurbita pepo, respectively. These viruses were found infecting cucurbits in single, co- and triple infections. Moreover, these viruses were also detected in the wild plants, Cucumis hystrix and Luffa aegyptiaca and in cultivated Vigna unguiculata. ZYMV was the commonest virus in wild plants. Yield losses caused by virus diseases remain undetermined for cucurbits in Tanzania but co- and triple virus infections have implication on disease severity and evolution of these viruses and may pose challenge for breeding for resistance.

Key words: Cucurbit virus diseases, DAS-ELISA, virus mixed infections.