Detection of Dickeya spp. latent infection in potato seed tubers using PCR or ELISA and correlation with disease incidence in commercial field crops under hot‐climate conditions

Abstract

Over a 5-year period (2006)(2007)(2008)(2009)(2010), 277 certified, visually healthy potato seed lots, imported from Europe to Israel for commercial use, were tested for Dickeya spp. latent infection by PCR analysis (277 seed lots) and ELISA (154 seed lots). Seeds from these lots were grown in commercial potato fields which were inspected twice a season by Plant Protection and Inspection Services (PPIS). Stem samples were tested for the presence of Dickeya spp. by PCR analysis. PCR and ELISA results from seed lot testing correlated with disease expression in 74 and 83AE8% of the cases, respectively. Positive laboratory results with no disease symptoms in the field ('+lab ⁄ )field' results) comprised 24AE7 and 9AE7% of the PCR and ELISA analyses, respectively, whereas negative laboratory results with disease symptoms in the field results (')lab ⁄ +field') were obtained in 1AE3 and 6AE5%, of cases respectively. Maximum disease incidence, as well as the number of cultivars expressing disease symptoms, increased over the years of this study, indicating an increase in the prevalence of the disease. Severe disease incidence was observed on cvs Dita, Rodeo, Desiree, Mondial, Tomensa and Jelly. Of the 55 imported seed lots from which disease was recorded in the field, 49 originated from the Netherlands, four from Germany and two from France. None originated from Scotland.

Characterization of Dickeya strains isolated from potato grown under hot‐climate conditions

“…A 5‐year study (2006–2010) of Dickeya spp. detected in certified potato seed lots imported from Europe to Israel indicated a high correlation between results obtained by PCR seed lot testing and disease expression in the field (Tsror et al ., ). Dickeya sp.…”

“…This could be explained by an increase in virulence during plant development which favours the multiplication of highly virulent ‘ D. solani ’ strains or by a reduction in virulence during storage of the seeds, or both. These findings are in accordance with the suggestion that ‘ D. solani ’ biovar 3 is more aggressive than D. dianthicola at higher temperatures, as determined by greenhouse studies and experiments in high‐temperature regions (Laurila et al ., ; Sławiak et al ., ; Tsror et al ., ; Czajkowski et al ., ), and might be affected by climate change (Toth et al ., ; Tsror et al ., ). ‘ Dickeya solani ’ was reported as a better colonizer of potato plants compared to D. dianthicola under high temperature conditions, although total pectinolytic enzyme production was not significantly different, suggesting that ‘ D. solani ’ possesses more virulence factors than D. dianthicola (Czajkowski et al ., ).…”

“…latent infection as described in Tsror et al . (). The stolon ends of tubers from each subsample (including both the vascular bundles and the peel) were incubated in 50 mL polypectate enrichment broth (Pérombelon & van der Wolf, ) at 28°C for 48 h. PCR was conducted for Dickeya spp.…”

“…‘ Dickeya solani ’ possesses features that allow more efficient plant colonization than D. dianthicola at high temperatures (Czajkowski et al ., ). Therefore, development and expression of the disease in field crops may be particularly favoured under hot‐climate conditions (Toth et al ., ; Tsror et al ., ). Recent outbreaks of ‘ D. solani ’ in Israel in potato plants grown from imported seed tubers are of great concern because of the warm climatic conditions during the spring growing season.…”

“…The most important means of dissemination for ‘ D. solani ’ is the movement of latently infected potato seed tubers (Czajkowski et al ., ; Tsror et al ., ; Toth et al ., ). The pathogen is currently causing increasing economic damage in potato in a number of countries in Europe (van der Wolf & de Boer, ), including Spain (Palacio‐Bielsa et al ., ), Finland (Laurila et al ., , ), Poland (Sławiak et al ., ), Georgia (Tsror et al ., ) and Israel (Tsror et al ., , ).…”