Scientific Opinion on the assessment of the risk of solanaceous pospiviroids for the EU territory and the identification and evaluation of risk management options

Abstract

Following a request from the EU Commission, the EFSA PLH Panel conducted a risk assessment for the EU territory of pospiviroids affecting solanaceous crops, identified and evaluated risk reduction options and evaluated the EU provisional emergency measures targeting Potato spindle tuber viroid (PSTVd). The risk assessment included PSTVd, Citrus exocortis viroid, Columnea latent viroid, Mexican papita viroid, Tomato apical stunt viroid, Tomato chlorotic dwarf viroid, Tomato planta macho viroid, Chrysanthemum stunt viroid and Pepper chat fruit viroid. Four entry pathways were identified, three involving plant propagation material, with moderate probability of entry, and one involving plant products for human consumption, with low probability of entry. The probability of establishment was considered very high. Spread was considered likely within a crop and moderately likely between crop species, with exception of spread to potato, rated as unlikely. The probability of long distance spread within vegetatively propagated crops was estimated as likely/very likely. The direct consequences were expected to be major in potato and tomato, moderate in pepper, minimal/minor in other vegetables and minimal in ornamentals. Main risk assessment uncertainties derive from limited knowledge on pospiviroids other than PSTVd, although all pospiviroids are expected to have similar biological properties. Management options to reduce risk of entry, spread and consequences were identified and evaluated. No management options can prevent establishment. Examples of successful PSTVd eradication are linked to timely and strict implementation of measures. Uncertainty exists on the effectiveness of risk reduction strategies targeting only one pathway. The EU provisional emergency measures appeared to have significantly reduced PSTVd incidence in Solanum jasminoides and Brugmansia sp., even though eradication from the EU is so far incomplete. The low PSTVd incidence in food crops did not permit to conclude whether the reduction in PSTVd prevalence in ornamentals led to a reduction in outbreaks in food crops.

Viroid-infected Tomato and Capsicum Seed Shipments to Australia

“…Others have argued that commercially produced vegetable seeds are unlikely to be responsible for most outbreaks of pospiviroids [10,52]. We believe that the evidence [1,2,3,4,5,6,7,8,9,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31,32,42,43] indicates infected seed is responsible for long-distance transport of pospiviroids and for moving these pathogens to areas where previously they were not present, even though the rate of seed-transmission is probably low. Our study added another dimension to the weight of evidence by indicating a route of transport that is active, and indicating the potential for invasion is real.…”

“…The testing reported here was done on a commercial basis, not as a research project, and the test results and related data are not entirely complete, as they were not always systematically collected. Regardless, the data is sufficient to show that traded seed lots were contaminated with pospiviroid-infected seeds (‘infected seed lots’) and the trade in infected seed lots was more significant than previously understood [31]. We know of only one other survey of a similar scale [32].…”

A Review of the Most Common and Economically Important Diseases That Undermine the Cultivation of Tomato Crop in the Mediterranean Basin

“…Although a wide spread of PSTVd infections has never occurred on tomatoes (it has been eradicated from five EU countries) [316], a high risk of disease spread always persists due to the PSTVd transmission by seeds, aphids (in coinfection with Potato leafroll virus), mechanical transmission by contaminated working tools during cultivation activities, and due to the recent identification of this viroid in ornamental plants, mainly asymptomatic [311,[317][318][319][320].…”

“…Disease management strategies consist in the use of certified planting material, elimination of infected plants or any suspected infected source, control of aphid vectors and spontaneous plants, hygiene practices and disinfection of cutting tools and agricultural machines between different crops, early diagnosis of the pathogen and symptom monitoring [311,316,321].…”

Pest categorisation of non‐EU viruses and viroids of potato

“…The following viruses and viroids have been addressed by EFSA in previous scientific opinions: beet curly top virus (EFSA PLH Panel, 2017), capsicum chlorosis virus (EFSA PLH Panel, 2012a), cherry rasp leaf virus (EFSA PLH Panel, 2013a,b, 2019a, chrysanthemum stunt viroid (EFSA PLH Panel, 2011, 2012b, groundnut bud necrosis virus (EFSA PLH Panel, 2012a), groundnut ringspot virus (EFSA PLH Panel, 2012a), tomato chlorotic spot virus (EFSA PLH Panel, 2012a), tomato planta macho viroid (EFSA PLH Panel, 2011), tomato ringspot virus (EFSA PLH Panel, 2013a, tomato yellow leaf curl virus (EFSA PLH Panel, 2013b, 2014, tomato yellow ring virus (EFSA PLH Panel, 2012a), tomato zonate spot virus (EFSA PLH Panel, 2012a). Following exchange with the European Commission, it was decided that they will not be further considered in the present categorisation.…”