Pectobacterium carotovorum subsp. carotovorum can cause potato blackleg in temperate climates

Abstract

It is well established that the pectinolytic bacteria Pectobacterium atrosepticum (Pca) and Dickeya spp. are causal organisms of blackleg in potato. In temperate climates, the role of Pectobacterium carotovorum subsp. carotovorum (Pcc) in potato blackleg, however, is unclear. In different western and central European countries plants are frequently found with blackleg from which only Pcc can be isolated, but not Pca or Dickeya spp. Nevertheless, tubers vacuum-infiltrated with Pcc strains have so far never yielded blackleg-diseased plants in field experiments in temperate climates. In this study, it is shown that potato tubers, vacuum-infiltrated with a subgroup of Pcc strains isolated in Europe, and planted in two different soil types, can result in up to 50% blackleg diseased plants. All three pathogens can cause tuber rot during storage, whereas infections of seed potatoes with Pca and Dickeya spp. can also result in the occurrence of various field symptoms, including reduced emergence, chlorosis, wilting, tuber and stem rot, blackleg, haulm desiccation and plant death (Pérombelon and Kelman 1980;Pérombelon 1992;Fraaije et al. 1996;Helias et al. 2000). These symptoms can be caused by Pca as well as by Dickeya spp., making identification of the causal organism by visual observation in the field unreliable. Regulatory field inspections in seed potatoes in many countries are therefore based on recognition of this 'blackleg complex' without discriminating between the various blackleg-causing organisms.

Pectobacterium carotovorum subsp. brasiliensis causing blackleg on potatoes in South Africa

“…Blackleg is mainly caused by Pectobacterium atrosepticum (Pba) but under certain conditions Pectobacterium carotovorum (Pbc) and Dickeya spp. can also cause similar symptoms , Oliveira et al 2003, De Haan et al 2008). These species were formerly known as the soft rot Erwinia spp., but they were recently reclassified into two new genera, namely Pectobacterium and Dickeya, on the basis of 16S rDNA sequences, their ability to grow at 39°C and host ranges (Hauben et al 1998, Garden et al 2003, Samson et al 2005, Laurila et al 2008.…”

“…are pathogenic under warm or warm-dry conditions (Elphinstone and Toth 2007). In Brazil, Pbcb causes disease in areas with a humid subtropical climate, but relatively cool temperatures (17-20˚C) during the growing season (Duarte et al 2004). De Haan et al (2008 stated that Pbc can cause typical blackleg symptoms in a temperate climate.…”

Distribution of Dickeya spp. and Pectobacterium carotovorum subsp. carotovorum in naturally infected seed potatoes

“…E. carotovora subsp. carotovora) (Pcc) (De Haan et al 2008) or by P. c. subsp. brasiliensis (Pcb) ( Duarte et al 2008).…”

“…with a relative low growth temperature maximum were also isolated from blackleg-diseased plants in temperate regions (Janse and Ruissen 1988). Pcc is considered to play a minor role in potato blackleg in temperate zones, although it has already been proven that tuber infections with virulent Pcc strains can result in true blackleg (De Haan et al 2008). To date, Pcb has only been found in subtropical regions (Duarte et al 2008) Blackleg symptoms vary depending on the initial bacterial concentrations in seed tubers, the susceptibility of the potato cultivar and environmental conditions, particularly temperature and soil moisture content (Perombelon 2002).…”

Survey: to assess the distribution and impact of potato blackleg and soft rot diseases in Zimbabwe

“…Blackleg and soft rot symptoms are not species specific but are dependent on climatic conditions (Hèlias et al, 2000;De Haan et al, 2008). The diseases are caused by soft rot bacteria formerly known as Erwinia species.…”