Assessment of recent outbreaks of Dickeya sp. (syn. Erwinia chrysanthemi) slow wilt in potato crops in Israel

Abstract

Suspected Dickeya sp. strains were obtained from potato plants and tubers collected from commercial plots. The disease was observed on crops of various cultivars grown from seed tubers imported from the Netherlands during the spring seasons of 2004-2006, with disease incidence of 2-30% (10% in average). In addition to typical wilting symptoms on the foliage, in cases of severe infection, progeny tubers were rotten in the soil. Six strains were characterised by biochemical, serological and PCR-amplification. All tests verified the strains as Dickeya sp. The rep-PCR and the biochemical assays showed that the strains isolated from blackleg diseased plants in Israel were very similar, if not identical to strains isolated from Dutch seed potatoes, suggesting that the infection in Israel originated from the Dutch seed. The strains were distantly related to D. dianthicola strains, typically found in potatoes in Western Europe, and were similar to biovar 3 D. dadanti or D. zeae. This is the first time that the presence of biovar 3 strains in potato in the Netherlands is described. One of the strains was used for pathogenicity assays on potato cvs Nicola and Mondial. Symptoms appeared 2 to 3 days after stem inoculation, and 7 to 10 days after soil inoculation. The control plants treated with water, or plants inoculated with Pectobacterium carotovorum, did not develop any symptoms with either method of inoculation. The identity of Dickeya sp. and P. carotovorum re-isolated from inoculated plants was confirmed by PCR and ELISA.

Cardinal temperature differences, determined in vitro, between closely related species and subspecies of pectinolytic bacteria responsible for blackleg and soft rot on potatoes

“…The species Dso presented an extremely broad temperature range with a high optimal temperature of +35 o C. These temperatures place Dso in its own group. This is contradictory to the results of Tsror et al (2009), which indicated that Dickeya spp. isolated from potatoes in Israel were not able to grow at temperatures above 41 o C in vitro.…”

“…to tropical environments and warm temperatures (Tsror et al 2009), was confirmed in this study. Significant differences were noted between Dickeya spp.…”

“…Temperature plays an important role in pathogenicity differentiation of soft rot and blackleg pathogens (Pérombelon and Kelman 1980;Pérombelon et al 1987;Pérombelon 1992 (Pérombelon and Kelman 1980;Elphinstone 1987;Pérombelon et al 1987;Pérombelon 1992;Tsror et al 2009Tsror et al , 2013. Each of these blackleg and soft rot bacterial species, however, prefer specific temperatures at which they cause disease.…”

“…It has been reported that Dickeya spp. can survive at elevated temperatures, growing weakly at 39°C, up to a maximum of 41°C (Tsror et al 2009). …”

Salicylic acid can reduce infection symptoms caused by Dickeya solani in tissue culture grown potato (Solanum tuberosum L.) plants

“…outbreaks have increased substantially since 2001, when the isolates of the new Dickeya species (D. solani) have been found in potato for the first time (Slawiak et al 2009ab). This pathogen has never before been observed in the European climate zone or elsewhere (van der Wolf et al 2014;Tsror et al 2009;Slawiak et al 2009;Laurila et al 2008). Since 2005, the presence of D. solani has been reported in potato in many European countries including The Netherlands, Finland, Poland, Germany, Belgium, France, United Kingdom and Sweden, as well as outside Europe, in Israel and Georgia.…”