Epidemiology and control of Septoria pyricola in pear leaf and fruit

The susceptibility of pear leaf and fruit at their early development stages to Septoria pyricola and the chemical control of the disease were studied. Unfolded or fully expanded leaves and young fruit were susceptible to infections,when artificially inoculated. With an average temperature of 14�C,relative humidity of 70% and increased leaf wetness for at least 6 hours during the night,the characteristic disease symptoms,on both leaves and fruits,were developed within two to three weeks. Pycnidia were not formed on fruit and their infection was confirmed by applying Koch’s postulates. Surveys in pear orchards during 2010 revealed the predominance of isolates highly resistant to the benzimidazole fungicide carbendazim. Some isolates exhibited 10-fold reduced sensitivity to bitertanol (sterol demethylation inhibitors; DMI’s) but they were sensitive to kresoxim-methyl (quinone outside inhibitors; QoI’s) and to boscalid (succinate dehydrogenase inhibitors; SDHI’s). Bitertanol and flusilazole (DMI’s),azoxystrobin,kresoxim-methyl and trifloxystrobin (QoI’s) and the mixture of pyraclostrobin (QoI) plus boscalid (SDHI) controlled Septoria effectively when they were applied on five occasions,commencing at the stage of ‘inflorescence emergence’. The disease progress was ceased even in cases of only one application with either azoxystrobin or flusilazole at ‘inflorescence emergence’ stage. Carbendazim failed to control the disease when BenHR-resistant propagules were enclosed in the primary inoculum. The results indicate that the pear leaf and fruit are vulnerable to S. pyricola at early stages of development,whereas secondary formed inocula on leaves expanded the disease only within the tree canopy. � 2016,Edizioni ETS. All rights reserved

Control of bottom rot in hydroponic lettuce, caused by strains of botrytis cinerea with multiple fungicide resistance

Summary. For two consecutive growing periods, fungicide-resistant Botrytis cinerea strains were detected in high proportions in glasshouse-grown lettuce, but at variable frequencies. Pre-transplanting fungicide sprays applied on two successive occasions reduced disease severity and increased the number of healthy plants without leaving detectable residues above accepted MRLs at harvest. In some instances, the disease was further decreased when pre-transplanting applications were combined with one or two further sprays applied soon after transplanting. The fungicide mixture of fludioxonil + cyprodinil was the most effective against the disease and provided better control of B. cinerea isolates in situ. These treatments gave satisfactory disease control despite the predominance of multi-fungicide resistant B. cinerea populations. © 2019

Detection of Venturia inaequalis Isolates with Multiple Resistance in Greece

The excessive use of fungicides against Venturia inaequalis, the causal agent of apple scab, has led to the emergence of resistant populations to multiple fungicides over the years. In Greece, there is no available information on fungicide resistance, despite the fact that control failures have been reported on certain areas. An amount of 418 single-spore isolates were collected from three major apple production areas and tested for their sensitivity to eight commonly used fungicides from unrelated chemical groups. The isolates were tested on malt extract agar media enriched with the discriminatory dose of each fungicide using the point inoculation method. To define the discriminatory dose for assessing the levels of resistance, EC50 values on both spore germination and mycelial growth assays were previously determined. Isolates exhibiting high resistance to trifloxystrobin (92% in total) and difenoconazole (3%); and moderate resistance to cyprodinil (75%), dodine (28%), difenoconazole (36%), boscalid (5%), and fludioxonil (7%) were found for the first time in Greece. A small percentage of the isolates were also found less sensitive to captan (8%) and dithianon (6%). Two isolates showed various levels of resistance to all eight fungicides. Despite the occurrence of strains with multiple resistances to many fungicides, we concluded that this practical resistance in the field arose mainly due to the poor control of apple scab with trifloxystrobin and difenoconazole. © 2022 by the authors

Effcient control of apple scab with targeted spray applications

For two consecutive growing seasons (2017 and 2018), three different fungicide spray programs, each with five sprays from unrelated chemical groups, were evaluated for their effectiveness against apple scab (causal agent: Venturia inaequalis) in an experimental trial in Greece. The targeted application programs consisted of five sprays with protective and systemic fungicides from unrelated chemical groups, in alternation. The applications were started at the pink bud stage (a copper-based fungicide had previously been applied at the green bud stage) and completed at the second fruit fall to arrest the primary infections by ascospores. These five-spray programs were compared to the standard farmer practice (12 sprays per season), whereas untreated plots were used as controls. The timing of the applications was based: A) on the critical growth stage of the crop, and b) on the risk analysis for infection calculated by the software Field Climate, which incorporated meteorological data from the trial site. All the five-spray programs were of very high efficacy against apple scab, showing disease severity ratings on leaves and fruits below 1.88%. In both years, in the untreated control, the disease incidence and severity on leaves ranged from 96.5% to 99.3% and from 65.2% to 75.93%, respectively. The five-spray programs showed similar efficacy to the standard 12-application program in all cases. From the results, it becomes apparent that apple scab can be controlled effectively by five targeted applications with selected fungicides at critical growth stages of the crop. © 2020 by the authors

High-Resolution Melting approaches towards plant fungal molecular diagnostics (vol 43, pg 265, 2015)

Reliable and early molecular detection of phytopathogenic fungi is crucial in an era where the expansion of global trade in plant material is undoubtedly increasing the risk of invasive outbreaks, with devastating effects in crop production. Genetic variation within and between fungal species or strains is also important for screening isolates regarding various resistance attributes. Until today many approaches have been employed in fungal diagnostics which are either labor- and time-consuming or costly and of reduced sensitivity. Here, we demonstrate and review recent advances on high-resolution melting (HRM) analysis as a rapid, accurate and powerful tool, capable of differentiating even closely related fungal isolates. HRM technique is based on monitoring the melting of PCR amplicons, using saturating concentrations of a fluorescent intercalating dye that binds to double-stranded DNA. Additionally, we discuss the four case studies inferring applications of HRM analysis towards either genotyping of closely related fungal species or screening for fungicide resistance. We focus on the promising results of these studies, giving some technical considerations and describing the advantages of the application of this approach. Finally, we discuss current prospects and applications for research and development related to this innovative HRM technique in plant fungal diagnostics

Sensitivity of Septoria pyricola isolates to carbendazim, DMI and QoI based fungicides and to boscalid, in Greece

The sensitivity of 36 Septoria pyricola single spore isolates, obtained from isolated pear orchards, to carbendazim, bitertanol, flusilazole, myclobutanil, azoxystrobin, kresoxim-methyl, pyraclostrobin, trifloxystrobin and boscalid, was studied in vitro. Spore suspensions were point-inoculated on media amended with various concentrations of fungicides and the minimum inhibitory concentration (MICs) of the fungicides was determined. Most isolates were highly resistant to carbendazim, forming colonies even at concentrations of 100 mg L(-1) of the fungicide. A few isolates failed to form colonies with carbendazim concentrations of 0.1 and 10 mg L(-1); these isolates were designated carbendazim-sensitive and moderately carbendazim-resistant respectively. The MIC of DMI fungicides was up to 1 mg L(-1) with some isolates, and the mean MICs of bitertanol, flusilazole and myclobutanil were 0.133 +/- 0.036, 0.075 +/- 0.044 and 0.230 +/- 0.038 mg L(-1) respectively. The MIC of the QoI fungicides was up to 0.1 mg L(-1) with most isolates, but some isolates were 100-fold less sensitive to azoxystrobin. The mean MICs of azoxystrobin, kresoxim-methyl, pyraclostrobin and trifloxystrobin were 0.177 +/- 0.040, 0.075 +/- 0.035, 0.067 +/- 0.063, and 0.073 +/- 0.065 mg L(-1) respectively. Overall, the MIC of boscalid was 1 mg L(-1), and the mean MIC was 0.111 +/- 0.044 mg L(-1). The ED(50) values of representative isolates are also presented, as determined by colony formation with dispersed spore inoculation on a medium amended with fungicides. The results show that the benzimidazoles are ineffective against S. pyricola isolates in Greece and suggest that the future effectiveness of the DMIs is at risk

Comparative genomics of Botrytis cinerea strains with differential multi-drug resistance

[No abstract available

High-Resolution Melting (HRM) Analysis Reveals Genotypic Differentiation of Venturia inaequalis Populations in Greece

During the recent years, High Resolution Melting (HRM) analysis has been developed as a rapid and accurate tool in plant disease diagnostics, species identification and SNP genotyping. This approach has been applied to analyze the genetic diversity in several plant species with molecular markers, including single sequence repeats (SSR). However, no studies have been carried out to investigate the variation of SSR in plant pathogenic fungi by using the HRM technology. In this report, the genetic structure of Venturia inaequalis populations in Greece was investigated for the first time by using six microsatellite markers. The developed HRM protocol was able to generate genotype-specific melting curves, consistent with the haploid nature of the fungus. Unknown samples were genotyped using standard samples as reference controls among multiple runs. Compared to the more complex genome of diploid plants, several limitations were avoided. The shape of the melting curves revealed differences between the genotypes in each SSR marker and showed that all the genotypes could be easily distinguished. The genetic analysis of apple scab populations revealed high genetic variation within the populations (96%), while only 4% of the total gene diversity was attributed to among-population variation. The isolates were grouped into three higher-level populations according to the principal coordinate analysis (PCoA). © Copyright © 2019 Chatzidimopoulos, Ganopoulos, Moraitou-Daponta, Lioliopoulou, Ntantali, Panagiotaki and Vellios

High-Resolution Melting approaches towards plant fungal molecular diagnostics

Reliable and early molecular detection of phytopathogenic fungi is crucial in an era where the expansion of global trade in plant material is undoubtedly increasing the risk of invasive outbreaks, with devastating effects in crop production. Genetic variation within and between fungal species or strains is also important for screening isolates regarding various resistance attributes. Until today many approaches have been employed in fungal diagnostics which are either labor- and time-consuming or costly and of reduced sensitivity. Here, we demonstrate and review recent advances on high-resolution melting (HRM) analysis as a rapid, accurate and powerful tool, capable of differentiating even closely related fungal isolates. HRM technique is based on monitoring the melting of PCR amplicons, using saturating concentrations of a fluorescent intercalating dye that binds to double-stranded DNA. Additionally, we discuss the four case studies inferring applications of HRM analysis towards either genotyping of closely related fungal species or screening for fungicide resistance. We focus on the promising results of these studies, giving some technical considerations and describing the advantages of the application of this approach. Finally, we discuss current prospects and applications for research and development related to this innovative HRM technique in plant fungal diagnostics

Detection and characterization of fungicide resistant phenotypes of Botrytis cinerea in lettuce crops in Greece

The development of resistance to chemical control agents needs continuous monitoring in Botrytis cinerea. 790 isolates from lettuce and other vegetable crops were collected from six widely separated sites in Greece and tested for their sensitivity to 11 fungicides from nine unrelated chemical groups. 44 of the isolates exhibited multiple resistance to fenhexamid (hydroxyanilides), azoxystrobin and pyraclostrobin (QoI's), boscalid (SDHI's), cyprodinil and pyrimethanil (anilinopyrimidines), fludioxonil (phenylpyrroles), carbendazim (benzimidazoles) and iprodione (dicarboximides). Thirty per cent of such phenotypes were detected in an experimental glasshouse with lettuce crops, the third year after commencing fungicide applications. The average resistance factor (R-f) for mycelial growth to fenhexamid, pyraclostrobin, boscalid, cyprodinil and fludioxonil, was over 40, 1,000, 100, 700 and 50, respectively. Some strains with high resistance to anilinopyrimidines (14 %) or moderate to fludioxonil (7 %) were detected even in isolates collected from vegetable crops prior to commercial use of these fungicides in Greece. Isolates with fludioxonil moderate resistance and fenhexamid high resistance, were detected for the first time in Greece. The results suggested the high risk in chemical control of grey mould due to development of resistance to most fungicides with site-specific modes of action. Isolates with resistance to fluazinam (phenylpyridinamines) and to chlorothalonil (phthalonitriles) were not found. The inclusion of appropriate multi-site inhibitors like chlorothalonil in fungicide anti-resistance strategies was indispensable