Atypical late blight symptoms following first recorded infections by Phytophthora infestans genotype EU_39_A1 in UK vine tomatoes

New disease reports

S.O.L. John^1¹  G.J. Keane^1²  T.R. Pettitt^1³ 

[1] Agricultural Institute of Slovenia, Hacquetova ulica 17, 1000 Ljubljana, Slovenia^3;The James Hutton Institute, Invergowrie, Dundee DD2 5DA, UK^2;University of Worcester, Henwick Grove, Worcester, WR2 6AJ, UK^1

关键词: lateral flow device;    oomycete;    Solanum lycopersicum;   

DOI  :  10.5197/j.2044-0588.2019.039.016

学科分类：生物科学（综合）

来源: British Society for Plant Pathology

【 摘 要 】

Early in 2018, Phytophthora late blight was recorded on young plants in at least five large UK vine-tomato nurseries. Infection (as high as 20%) appeared limited to some batches of plants. Initially, affected plants showed some foliar and girdling stem lesions with a high rate of mortality. These were rogued and no secondary infection appeared to occur. Some infected plants (24 sites in Slovenia, on tomatoes in two gardens in Belgium, on two potato crops in Germany and a single potato crop in an allotment in south Wales. All subsequent UK records of EU_39 have been on potatoes: a single crop in Fife, Scotland in 2016 and once in a Bristol allotment, twice in eastern Scotland and once in Staffordshire in 2017. In the previous tomato cases in Belgium and Slovenia, EU_39 symptoms were more consistent with normal late blight, with high mortality and abundant sporulation on leaves and fruits (Fig. 5). The presence of the pathogen was confirmed by sporulation from the cut ends of excised stems, divided into 50 mm segments and incubated at 100% relative humidity (RH) and 20°C for 36 hours. Cut stem segments were also incubated at a range of RH from 82-100%, with sporulation seen at RH >95%. Sporulation was determined by stereo microscopy and by swabbing small areas with 0.1% agar solution with cotton wool swabs for direct microscope observation and detection by immunodiagnostic assay lateral flow device (LFD) tests (Pettitt et al ., 2018). Most sporulation was observed on cut stem ends, although increasing amounts were seen on stem surfaces at RH increasing from 95%. LFD tests were more sensitive than microscope assessments. LFD results of swabs were compared with those from scrape samples (0.1-0.2 g surface tissue) from in situ stem lesions. Scrape samples mostly tested positive for Phytophthora and swab samples were mostly negative, confirming a general lack of sporulation throughout the largely dry tomato growing season in 2018. The potential for secondary disease spread as a consequence of sporulation was a major concern and LFD swab tests proved useful in assessing this and confirming the efficacy of sanitation at the end of the season.

【 授权许可】

CC BY