Biological characterization of French Potato virus Y (PVY) isolates collected from PVY‐susceptible or ‐resistant tobacco plants possessing the recessive resistance gene va

Abstract

Improved tobacco cultivars introgressed with alleles of the recessive resistance va gene have been widely deployed in France to limit agronomical consequences associated with Potato virus Y (PVY) infections. Unfortunately, necrotic symptoms associated with PVY have been reported on these cultivars suggesting that PVY is able to overcome the resistance. A field survey was performed in France in 2007 to (i) estimate the prevalence of PVY in tobacco plants showing symptoms and (ii) characterize PVY isolates present in susceptible and va‐derived tobacco cultivars. A serological typing procedure, applied to 556 leaves collected from different French tobacco growing areas, was performed using polyclonal antisera raised against different viral species including PVY. Viral species were detected in 80·8% of leaves and PVY was present in 83·5% of infected samples. However, statistical analysis confirmed that the probability of a tobacco plant being infected with PVY is reduced in va hosts. Eighty‐six PVY isolates were mechanically inoculated on one susceptible and three va‐derived tobacco cultivars used as indicator hosts to define virulence of these isolates against alleles 0, 1 and 2 of the va gene. Both qualitative and quantitative analyses showed that 55 PVY isolates were able to overcome the three va alleles. Moreover, the monitored biological diversity of PVY isolates was higher in the susceptible tobacco hosts than in the va‐derived ones. This study helps to understand consequences of the deployment of the va gene in tobacco on diversity and virulence of PVY isolates.

A complex eIF4E locus impacts the durability of va resistance to Potato virus Y in tobacco

“…The PVY isolates used to challenge the different tobacco accessions belong to the clade N (CSA1, LA7, CSA6, MaSan4, 1108) and the clade O (O139, LA4, SN3 and SAV8), depending on their ability to induce (N) or not (O) systemic veinal necrosis symptoms in tobacco (Jakab et al , ; Moury, ; Singh and Singh, ) (Table ). Those isolates were selected according to their pathogenic and biological properties in tobacco after a field survey carried out in tobacco plots in France in 2007 (Janzac et al , ; Lacroix et al , ). The other PVY isolates listed in Table belong to the C clade, more specifically to the C1 (SON41, Alger1, Marti3, LYE84.2, CAA157, CAA141, CAA16, LYE72‐Puc2Pl3) or C2 (Cadgen, LYE90v) groups.…”

“…The two lastly developed leaves were inoculated with 100 µL of the calibrated viral inoculum supplemented with carborundum. Evaluation of PVY infection in non‐inoculated leaves was performed by DAS enzyme‐linked immunosorbent assay (ELISA) (Clark and Adams, ; Lacroix et al , ) at 15 and 30 dpi. Absorbance values at 405 nm ( A 405 ) with the background subtraction of buffer samples were considered for analysis.…”

“…PVY isolates are distributed into three biotypes, with the PVY N and PVY O biotypes separated by their ability or inability, respectively, to cause systemic veinal necrosis on tobacco (Moury, ; Singh et al , ). Although mosaic symptoms impact less dramatically the yield and quality of tobacco crops, severe leaf necrosis induced by PVY N isolates are a major concern for tobacco producers (Lacroix et al , ; Rolland et al , ; Tian et al , ).…”

The amino acid 419 in HC-Pro is involved in the ability of PVY isolate N605 to induce necrotic symptoms on potato tubers

“…Xanthi. This inoculation step was carried out by a standard mechanical inoculation procedure as described by Lacroix et al (2010). Briefly, leaf tissue (+/-1 g) was ground in the presence of 4 ml of inoculation buffer (50 mM Na 2 HPO 4 ·12H 2 O; 50 mM KH 3 PO 4 ; 40 mM sodium diethyldithiocarbamate, pH 7.2) supplemented with 1.5 g of activated charcoal and 2.5 g of carborundum.…”

Specific detection and quantification of virulent/avirulent Phytophthora infestans isolates using a real-time PCR assay that targets polymorphisms of the Avr3a gene

“…) or at the macromolecular level (e.g., use of monoclonal antibodies; Lacroix et al . ). Recent advances in next‐generation sequencing technologies (Shendure and Ji ) provided new alternative methods to detect/describe specific genotypes in mixtures using, for example, barcodes (Smith et al .…”