Abstract
Passion fruit green spot and passion fruit sudden death are two reportedly distinct viral diseases that recurrently affect passion fruit (Passiflora spp.) groves in Brazil. Here we used a systematic approach that interconnects symptoms, transmission electron microscopy, RT-PCR detection assays followed by Sanger sequencing, and high-throughput sequencing of the RNA of affected passion fruit plants to gain insights about these diseases. Our data confirmed not only the involvement of cileviruses in these two pathologies, as previously suggested, but also that these viruses belong to the same tentative species: passion fruit green spot virus (PfGSV). Results revealed that PfGSV has a positive-sense RNA genome split into two molecules of approximately 9 kb (RNA1) and 5 kb (RNA2), which share about 50–70% nucleotide sequence identity with other viruses in the genus Cilevirus. Genome sequences of five PfGSV isolates suggest that they have more conserved RNA1 (<5% of nucleotide sequence variability) compared to RNA2 (up to 7% of variability) molecules. The highest nucleotide sequence divergence among PfGSV isolates and other cileviruses is in the genomic segment covering from the 5′-end of the RNA2 until the 5′-end of the open reading frame (ORF) p61, which includes the ORF p15 and the intergenic region. This genomic stretch also harbors a novel orphan ORF encoding a 13 kDa protein presenting a cysteine-rich domain. High variability of 5′-end of the RNA2 in cileviruses is discussed in an evolutionary context assuming that they share putative common ancestors with unclassified arthropod-infecting single-strand positive RNA viruses, including mosquito-specific viruses of the group Negevirus (clades Nelorpivirus and Sandwavirus), and other viruses in the family Kitaviridae.
Highlights
Passion fruit (Passiflora spp.) crops can be severely affected by viral infections that may cause up to 100% of production losses and limit their commercial expansion around the tropical and neartropical regions of the world (Fischer and Rezende, 2008; Santos et al, 2015; Atukunda et al, 2018)
We have revealed the genome of five novel bipartite viruses found in passion fruit plants affected by either passion fruit green spot (PfGS) or passion fruit sudden death (PfSD) diseases
Our results complement previous works that suggested the presence of cileviruses as causal agents of these pathologies (Kitajima et al, 2003; Antonioli-Luizon, 2010), and indicate that these viruses belong to the same tentative cilevirus species, previously named as passion fruit green spot virus (PfGSV) (Kitajima et al, 1997)
Summary
Passion fruit (Passiflora spp.) crops can be severely affected by viral infections that may cause up to 100% of production losses and limit their commercial expansion around the tropical and neartropical regions of the world (Fischer and Rezende, 2008; Santos et al, 2015; Atukunda et al, 2018). In PfGS disease, spots of approximately 5 mm showing brilliant green borders with or without a central necrotic dip develop on the peel of yellow mature fruits, and necrotic lesions appear on the stems. These stem wounds, which sometimes exhibit deep slits, may coalesce and encircle the branch leading to the death of the distal end. As a consequence of PfSD disease, affected plants display the major symptoms of PfGS, but they rapidly progress toward death, passing through abundant necrosis, branch death, and the orchard’s collapse (Antonioli-Luizon et al, 2009)
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