| Popis: |
The virome of Nigerian vineyards was assessed via diagnostic surveys for viruses/viroids in 40 sites across six states during 2016. Leaf tissues from 360 grapevines were preserved dried under CaCl2. High throughput sequencing of total RNA extracts from two composite dry leaf samples resulted in the detection of grapevine leafroll-associated virus 1 (GLRaV-1), hop stunt viroid (HSVd), grapevine yellow speckle viroid 1 (GYSVd-1), and GYSVd-2. The incidences and distribution of these agents were assessed via RT-PCR with specific primers and two additional primer pairs targeting grapevine rupestris stem pitting-associated virus (GRSPaV) and grapevine red blotch virus (GRBV). Approximately 47% (169/360) of the samples had mixed infections of two to five agents, ~22% (78/360) had single infections, and ~31% (113/360) tested negative. HSVd was the most common with its occurrence in ~53% (192/360; 39 sites) of samples, followed by GYSVd-2 (~43%; 155/360; 34 sites), GYSVd-1 (~33%; 120/360; 26 sites), GLRaV-1 (~24%; 85/360; 26 sites), and GRSPaV (~3%; 10/360; 7 sites). All 360 samples were negative for GRBV. In pairwise comparisons, GLRaV-1 isolates from Nigeria shared 97-100% nucleotide (nt) and amino acid identities among themselves based on partial HSP70h and complete p24 sequences. The nearly complete genome (18,689 nt) of one GLRaV-1 isolate was determined and it shared 76.5-94.5% identity with other fully sequenced GLRaV-1 isolates. The results revealed a simpler virome of Nigerian vineyards and underscores the need to strengthen phytosanitary measures and promote propagation of clean plant materials for vineyard establishment in Nigeria to forestall the introduction of additional viruses/viroids. |
