Proliferation of Recombinant PVY Strains in Two Potato-Producing Regions of Canada, and Symptom Expression in 30 Important Potato Varieties with Different PVY Strains

Abstract

Potato virus Y (PVY) exists as several strains with distinct symptomology and tuber yield effects in different potato varieties. Recently, new recombinant strains have proliferated and dominated local populations around the world. In this study, PVYO, PVYN:O, PVYN-Wi, and PVYNTN strains were tracked across Canada from 2014 to 2017, showing rapid evolution of populations away from the traditionally dominant PVYO to recombinants PVYN-Wi (western Canada) and PVYNTN (eastern Canada). Simultaneously, 30 potato varieties were inoculated with PVYO, PVYN:O, and PVYNTN in controlled greenhouse experiments. Foliar symptoms of primary (mechanical inoculation mimicking aphid infection) and secondary (tuber seedborne) infection were cataloged, and tuber yield measured. On average, and generally similar in primary and secondary infection, symptom expression and yield reduction were most severe with PVYO, followed by PVYN:O and PVYNTN. Strong mosaic symptoms were most commonly expressed with PVYO infection, and only seen with PVYN:O or PVYNTN in 15 and 3 varieties, respectively. Across variety–strain combinations, yield reduction was correlated with symptom severity, most strongly in PVYO-infected plants (e.g., AC Chaleur, Beljade, Envol, Norland, and Pacific Russet), and four varieties exhibited tuber necrotic ringspot disease with PVYNTN (AC Chaleur, Envol, Pacific Russet, and Yukon Gold).

Molecular Characterization of Potato Virus Y (PVY) Using High-Throughput Sequencing: Constraints on Full Genome Reconstructions Imposed by Mixed Infection Involving Recombinant PVY Strains

“…Recombination, together with mutation, increases the genetic variability of the given taxa, which can result in higher viral fitness or survival of the virus population in a previously nonviable environment, sometimes leading to the emergence of new resistance-breaking strains [36,37]. Indeed, a change in the PVY strain prevalence from a non-recombinant to recombinant one during the last few decades was generally observed [6,38,39] suggesting a better adaptation of current recombinant strains over non-recombinant ones. Similarly, the latest reports of PVY strain characterization in infected plants point to a growing incidence of recombinant PVY strains [40].…”

Characterization of Potato Virus Y Isolates and Assessment of Nanopore Sequencing to Detect and Genotype Potato Viruses

“…Certain PVY recombinants are often associated with the induction of potato tuber necrotic ringspot disease (PTNRD) in susceptible potato cultivars [13,32,33], which can make tubers unmarketable. Among them, PVY NTN genotypes have been reported from many areas of the world [24,30,31,[33][34][35][36][37][38][39] and represent a relevant concern for potato production. PVY O used to be the predominant strain infecting potatoes, but recently the recombinant genotypes, once a minor part of the PVY complex, became prevalent in many regions of the world [19,33,34,36,37,[39][40][41][42][43][44][45][46][47][48].…”

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“…According to [15], the N strain induces systemic vein necrosis in tobacco, but generally causes no hypersensitive reaction and only mild or zero symptoms in potato leaves. However, [16] report symptoms on the aerial part of the plant include leaf mosaicing, mottling, crinkling, and vein necrosis. In general, PVX and PVS are reported to cause mild mosaicing, while PVS and PVY NTN cause intermediate mosaicing, and PVY NTN +PVX and PVY O +PVS/PVX co-infections cause severe leaf deformation/necrosis/drop symptoms [12].…”