Internal colonization pathways of potato plants by Erwinia carotovora ssp. atroseptica

Abstract

Transmission of pectinolytic Erwinia species from infected mother tubers to daughter tubers has been studied mainly through detection tests, carried out at harvest, on limited samples of tubers produced by plants grown from artificially inoculated mother tubers. However, detection has not been performed on samples collected at different stages of crop development, in order to follow the contamination progress in different organs through the plants to the progeny tubers. In this study the bacterial contamination of progeny tubers was investigated by detecting Erwinia carotovora ssp. atroseptica in different symptomless plant organs (stolons, stems, progeny tubers) and in the parts with or without symptoms of diseased stems, collected at various stages of crop development. Infection levels in below‐ and above‐ground organs of plants of two cultivars differing in their resistance to Erwinia, infected by either vacuum infiltration or sand wounding, were monitored throughout the growing season and at harvest using DAS‐ELISA and PCR. Detection tests showed that healthy organs from symptomless plants were less frequently contaminated than symptomless organs from diseased plants, and that stolons were precociously and more frequently contaminated than stems and daughter tubers, irrespective of the health of the plant. Stem infections were shown to progress latently in the stem, bacteria usually being recovered 10–15 cm past visible lesions. In many cases, typical aerial stem‐rot symptoms could be related to this upward movement of bacteria from the infected mother tuber. Daughter tubers without symptoms were shown to be frequently contaminated, usually at heel ends, suggesting internal contamination from mother tuber to progeny.

Effects of genetically modified potatoes with increased zeaxanthin content on the abundance and diversity of rhizobacteria with in vitro antagonistic activity do not exceed natural variability among cultivars

“…Because all the strains obtained for SR48 originated from the same plot, this might either be the result of a local infection or a consequence of the pooling of the root material. Pathogenic strains of the genera Dickeya and Pectobacterium typically produce a broad range of extracellular enzymes which were described as major pathogenicity factors and are expressed in a cell-density dependent manner (Hélias et al 2000;Kotoujansky 1987). The production of extracellular enzymes by the isolates might have contributed to their antagonistic activity.…”

Resistance Behaviour of Potato Cultivars and Advanced Breeding Clones to Tuber Soft Rot Caused by Pectobacterium atrosepticum

“…The relative ranking of cultivars generally differs between blackleg (stem) and tuber (soft rot) tests; however, the rate at which mother tubers rot may affect blackleg incidence (Allefs et al, 1995). Because latent infection is frequent in tubers (Pérombelon and Kelman, 1980;Hélias et al, 2000b), and because inoculum levels vary during the growing season in both rotting mother tubers and stems Bain et al, 1990;Pérombelon, 2002), the level of resistance that is necessary to prevent severe outbreaks is difficult to predict. Given the fact that cultivars now exist with high, but incomplete resistance to P. atrosepticum, these cultivars should now be used as a major component in integrated crop production systems also involving prophylactic measures during cropping (i.e., use of certified seed; sanitation through the management of cull piles (Harrison and Brewer, 1982); irrigation with clean water only) and in storage.…”

Use of repetitive DNA sequences to determine the persistence of enteropathogenicEscherichia coliin vegetables and in soil grown in fields treated with contaminated irrigation water

“…Isolates were grown overnight at 37°C on BHI agar (Merck). DNA extraction was carried out using the method described by Helias et al. (2000), and DNA concentration was estimated on agarose gel.…”