Strains of Moroccan watermelon mosaic virus isolated from Lagenaria breviflorus and Coccinia barteri in Calabar, Southeastern Nigeria
Virus infection of Lagenaria breviflora and Coccinia barteri were observed in Calabar, Nigeria during the 2005/2006 growing season. The viruses causing the diseases were characterized in this study. Diagnostic tools were host range, transmission studies, cytopathology, electron microscopy, Immunosorbent Electron Microscopy (ISEM), serology and coat protein gene sequencing. Evidence from biological, serological and sequence data confirmed that both viruses belong to the genus Potyvirus, family Potyviridae. Both were mechanically transmissible and also transmitted by Myzus persicae and Aphis gossyppi in a fore-gut manner. They also induced cytoplasmic inclusions in infected leaf tissues. The Lagenaria virus isolate has a coat protein molecular weight of 32.5 kDa and 35.0 kDa for Coccinia isolate. Of the two viruses only Lagenaria virus isolate showed cross reactivity with MWMV in DAS-ELISA. Both viruses reacted negatively with antisera to some notable cucurbit viruses in the same test, showed weak to moderate decorations with antisera to PRSV, TuMV and TeMV in immunosorbent electron microscopy (ISEM) tests. The Coccinia virus was, however, strongly decorated by antiserum to MWMV but no decoration with the Lagenaria virus. Comparison of the amino acid sequence data of the N-terminal regions of the coat proteins to that of MWMV reported from Sudan indicated 92% and 93% identities for the Coccinia and Lagenaria viruses, respectively. It is suggested that the virus isolates reported in the study be considered strains of the MWMV Sudan isolate. This is the first report of the occurrence of MWMV in Nigeria.