TaqMan real-time RT-PCR for detection of cowpea aphid-borne mosaic virus and epidemiological aspects of passion fruit woodiness disease

Brazil is the world’s largest producer and consumer of passion fruit; however, productivity is restricted by phytosanitary factors, mainly viruses. Passion fruit woodiness disease (PWD) is the major viral disease of the crop, caused in Brazil by the cowpea aphid-borne mosaic virus (CABMV), and non-persistently transmitted by aphids. In this study, a protocol was developed and validated using real-time RT-PCR with a specific TaqMan probe combined with a direct sample preparation method for the detection of CABMV. The new protocol is 100 times more sensitive than the PTA-ELISA in detecting CABMV in passion fruit. The nucleotide sequence of the CABMV isolates from Santa Catarina (SC), had high identity (above 99%) in the capsid protein (CP) genome region, with isolates from São Paulo (SP). CABMV isolates from SC formed a monophyletic cluster with 99% bootstrap support containing CABMV isolates and strains from SP and Sergipe (SE). The logistic model showed a better fit to the virus incidence data compared to the Gompertz and monomolecular models and was able to predict that half of the orchard would be infected in about 110 days after transplantation (DAT). The TaqMan assay will be used for the detection of CABMV in propagation plant material and insect vectors, contributing to avoiding the dissemination of PWD.