Pest categorisation of the Ralstonia solanacearum species complex

Abstract

Following a request from the European Commission, the EFSA Panel on Plant Health performed a pest categorisation of the Ralstonia solanacearum species complex (RSSC), a distinguishable cosmopolitan group of bacterial plant pathogens (including R. solanacearum, Ralstonia pseudosolanacearum and two subspecies of Ralstonia syzygii) of the family Burkholderiaceae. The RSSC causes bacterial wilt in solanaceous crops, such as potato, tomato and pepper, but can also cause wilts in other important food crops such as fruit banana, plantain banana and cassava. The pest survives in the soil, and a number of weed species can also be infected by the pest, often asymptomatically. The RSSC is regulated in Council Directive 2000/29/EC (Annex IAII) (indicated by its former name R. solanacearum, as delimited by Yabuuchi et al.) as a harmful organism whose introduction into the EU is banned. In addition, Council Directive 1998/57/EC (amended by Commission Directive 2006/63/CE) concerns the measures to be taken within EU Member States (MS) against the RSSC to (a) detect it and determine its distribution, (b) prevent its occurrence and spread, and (c) control it with the aim of eradication. The pest is present in several EU MS, but in all cases with a restricted distribution and under official control. New phylotypes of the RSSC could enter the EU primarily via host plants for planting (including seed tubers). The pest could establish in the EU, as climatic conditions are favourable, hosts are common and the pathogen has high adaptability. Spread is mainly via plants for planting. Substantial crop losses in the EU would occur in the presence of RSSC epidemics. The RSSC is regarded as one of the world's most important phytopathogenic bacteria due to its broad geographical distribution, large host range, aggressiveness, genetic diversity and long persistence in soil and water. The list of hosts and commodities for which the pest is regulated is incomplete due to the high diversity of hosts and the lack of knowledge of the complete host range. Moreover, the comparative epidemiology of the different pathogen species has not yet been studied. The criteria assessed by the Panel for consideration of the RSSC as potential quarantine pest are met, while, for regulated non-quarantine pests, the criterion on the widespread presence in the EU is not met.

Mitigation of tobacco bacteria wilt with microbial degradation of phenolic allelochemicals

“…It may be caused by the inadequate degradation of PAs in soil or the simple combination degradation mode. Another reason may lie in that TBW is caused by many factors including climatic conditions, physicochemical properties of soil and the structure and physiology of the rhizosphere microbial community, hence degradation of PAs alone is not enough to completely wipe out TBW 50 . Next, we will optimize the ratio among the six strains and develop additives, such as bacteria carrier, humectant, dispersant and stabilizer, to help growth and colonization of degrading strains to tobacco roots.…”

Bacteriophages and Food Production: Biocontrol and Bio-Preservation Options for Food Safety

“…The environmentally present pathogenic species Ralstonia solanacearum is the causative agent of bacterial welt in many crops, and is therefore, a pest of economic and environmental importance in the EU [ 55 ]. The studies of on 3 isolated phages named vRsoP-WF2, vRsoP-WM2, and vRsoP-WR2, against R. solanacearum in environmental water achieved excellent bacterial death of 5 log cfu in less than 10 h at 24 °C [ 56 ].…”

Dose-response relationship of Ralstonia solanacearum and potato in greenhouse and in vitro experiments

“…Nevertheless, infected progeny tubers were only found at high inoculum densities (>10 7 CFU) but not when irrigated with low doses. This is an important outcome as trading of latently infected seed tubers poses a high risk spreading brown rot disease internationally (EFSA et al, 2019). While the greenhouse experiments simulated irrigation with contaminated water under natural conditions, in vitro experiments allowed to study the dose-response relationship under conditions (high temperature, availability of water and nutrients, absence of competition by other micro-organisms) expected to be optimal for the multiplication of R. solanacearum and for disease expression at very low inoculation concentrations.…”

“…The emergence of brown rot has predominantly been associated with the use of (latently) infected seed tubers. Trading of seed and ware potatoes forms the highest risk of disease spread internationally (EFSA et al, 2019). For example, the first occurrence of brown rot in the Netherlands was detected in a ware potato field in 1992, presumably introduced through infected non-certified seed tubers (Janse et al, 1998).…”

“…For example, the first occurrence of brown rot in the Netherlands was detected in a ware potato field in 1992, presumably introduced through infected non-certified seed tubers (Janse et al, 1998). Natural dispersal of brown rot is mainly caused by contaminated irrigation water as surface water used in irrigation can become contaminated with run-off water from R. solanacearum infected agricultural fields or through contact with effluent water coming from potato processing industry (EFSA et al, 2019). R. solanacearum has been repeatedly detected in surface waters in the Netherlands and other European countries and disease outbreaks were directly linked to the use of contaminated surface water in irrigation (Janse, 1996;Wenneker et al, 1999).…”