Cowpea aphid-borne mosaic virus (CABMV) in Passiflora by qPCR analysis reveals asymptomatic plants with viruses and new species with immunity

Abstract The passion fruit woodiness disease (Cowpea aphid-borne mosaic virus – CABMV) causes socioeconomic problems for Brazilian passion fruit crop. Understanding the temporal progress of the disease and identifying resistance sources to CABMV are essential steps to develop resistant varieties. The objective of the study was to evaluate temporal progress of passion fruit woodiness disease, identify Passiflora genotypes with CABMV resistance and to detect virus infection in asymptomatic plants by qPCR. The experiment was conducted in a greenhouse using 128 genotypes belonging to 12 species and three hybrids (inter and intraspecific) of Passiflora evaluated in five periods after inoculation. The symptoms severity was quantified from the disease index (DI%). The CABMV infection in symptomatic plants was confirmed by RT-PCR and in asymptomatic plants by qPCR. Progress rates and disease severity were lower in the species P. cincinnata, P. gibertii, P. miersii e P. mucronata compared to P. edulis, P. alata, Passiflora sp. and hybrids. Of the evaluated genotypes, 20.31% were resistant, with emphasis on the accessions of P. suberosa, P. malacophylla, P. setacea, P. pohlii e P. bahiensis that did not show symptoms of virus. The absence of symptoms does not imply immunity of plants to the virus, as the qPCR analysis confirmed infection by the virus in asymptomatic plants of P. cincinnata, P. gibertii, P. miersii, P. mucronata, P. setacea, P. malacophylla e P. suberosa. Even after four inoculations, the virus was not detected by qPCR in the upper leaves in plants of P. pohlii and P. bahiensis indicating that these species are immune to CABMV.