Plant Pathology (2017) 66, 1472-1479

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H. Watanabe, H. Horinouchi, Y. Muramoto and H. Ishii (2017)
Occurrence of azoxystrobin-resistant isolates in Passalora fulva, the pathogen of tomato leaf mould disease
Plant Pathology 66 (9), 1472-1479
Abstract: Since 2007, serious damage to tomato from leaf mould caused by Passalora fulva has frequently been observed in commercial greenhouses in Gifu Prefecture, Japan. One of the factors relating to this damage was suspected to be a decrease in azoxystrobin sensitivity of the pathogen. Biological and molecular studies were conducted to characterize fungicide resistance. In in vitro sensitivity tests using mycelial homogenate placed on fungicide-amended medium, the minimum inhibitory concentrations (MIC) of azoxystrobin for mycelial growth of the isolates divided into two ranges, 0.031–0.5 mg L-1 and 8–32 mg L-1. Isolates with MICs within the two ranges were considered as sensitive and resistant, respectively, to azoxystrobin because, in in vivo tests, the percentage protection conferred by this fungicide (100 mg a.i. L-1) against these isolates was 89.7–100% and 4.5–31.1%, respectively. Resistant isolates had a replacement of phenylalanine with leucine at codon 129 (F129L) in cytochrome b. Forty-five percent of the 271 isolates collected from 63 tomato greenhouses from 2007 to 2008 were resistant to azoxystrobin. In many greenhouses where the isolation frequency of resistant isolates was 80% or more, azoxystrobin had been used twice per crop for approximately 6 years. In 2012, 27% of the 405 isolates collected were resistant to azoxystrobin, and there was a marked difference in the frequency of occurrence of resistant isolates in the field populations between the three locations sampled. The occurrence of azoxystrobin-resistant P. fulva isolates (F129L mutants) inflicted considerable damage on greenhouse tomatoes.
(The abstract is excluded from the Creative Commons licence and has been copied with permission by the publisher.)
Link to article at publishers website
Database assignments for author(s): Hideki Watanabe, Hideo Ishii

Research topic(s) for pests/diseases/weeds:
pesticide resistance of pest

Pest and/or beneficial records:

Beneficial Pest/Disease/Weed Crop/Product Country Quarant.


Fulvia fulva Tomato (Solanum lycopersicum) Japan
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