Abstract
As part of a routine screening for the possible presence of the necrotic strains of potato virus Y affecting potatoes in Mexico, five PVY isolates were submitted to biological and molecular analysis. Considering their serological properties, two belong to the common strain (O) and three to the necrotic strain (N). All the isolates induced vein necrosis in Nicotiana tabacum. To characterize the isolates, 5' NTR and P1 genes were sequenced and compared with sequences from GenBank database. Nucleotide sequence similarity ranged from 47–100% in the 5' NTR and from 63–100% in the P1 coding region. The lowest amino acid similarity between sequences of P1 gene was 55%. In phylogenetic trees of 5'NTR analysis, two PVYO Mexican isolates clustered with other PVYO isolates. In turn, the three PVYN isolates grouped with PVYN-NTN isolates. The phylogenetic analysis of P1 sequences (nucleotide and amino acid) showed two PVYO isolates grouping next to N-NTN cluster. A detailed analysis of the PVYO isolates showed two potential recombination regions in the P1 gene, in contrast to 5'NTR where no recombination was detected.
Highlights
Potato virus Y (PVY), the type member of the family Potyviridae, can infect potato, tobacco, tomato and pepper as well as wild species, especially those in the Solanaceae family [1]
It produces veinal necrosis in tobaco leaves and is referred as PVYNTN [NTN = isolates belonging to the necrotic group (N) of PVY and inducing tuber necrosis (TN)], according to a decision of the European Association of Potato Research Virology Section [4,5]
Three isolates belonging to the N strain, Pic1, Vic6 and Vic15 (Table 1), inoculated in plants of N. tabacum induced typical necrotic symptoms; i.e. vein necrosis 7–10 days after inoculation
Summary
Potato virus Y (PVY), the type member of the family Potyviridae, can infect potato, tobacco, tomato and pepper as well as wild species, especially those in the Solanaceae family [1]. Isolates belonging to the PVYN strain induce severe vein necrosis on Nicotiana tabacum leaves. This strain has been divided into two groups: the first one causing mild mosaic in most potato cultivars, while the second one provokes "potato tuber necrotic ring disease" (PTNRD) and severe chlorotic mosaic in the leaves [3]. The PVYO strain isolates induce non-necrotic mosaics on tobacco leaves but more severe symptoms on potato, such as crinkling, leaf dropping or severe necrotic mosaic. The PVYC strain causes stipple streak on potato cultivars carrying the Nc resistance gene and non-necrotic symptoms, similar to those of PVYO, on N. tabacum leaves [6]. The symptoms of mosaic are masked in temperatures out of the normal rank from 10°C to 25°C
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