Molecular characterization of boscalid‐ and penthiopyrad‐resistant isolates of <i>Didymella bryoniae</i> and assessment of their sensitivity to fluopyram

Avenot, Hervé F.; Thomas, Anna; Gitaitis, R. D.; Langston, David B.; Stevenson, K. L.

doi:10.1002/ps.2311

Cited by 97 publications

(64 citation statements)

References 15 publications

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“…However, it should be emphasized that different levels of sensitivity to SDHIs were found in closely related species D. bryoniae. [32][33][34][35] The EC 50 values of fluopyram, established by Avenot et al [32] were homogeneous and far lower (0.020-0.189 mg L ¡1 ) than these obtained in the present study. In terms of sensitivity to boscalid, Thomas et al [33,34] found 82 very highly resistant and seven highly resistant D. bryoniae isolates using the discriminatory concentration of 3 mg L ¡1 .…”

Section: Discussioncontrasting

confidence: 68%

Toxicity of mancozeb, chlorothalonil, captan, fluopyram, boscalid, and difenoconazole toDidymella applanataisolates from Serbia

Mirković

Tanović

Stević

et al. 2015

Journal of Environmental Science and Health, Part B

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Field isolates of Didymella applanata, the causal agent of spur blight of raspberry, were evaluated in vitro for their sensitivity to mancozeb, chlorothalonil, captan, fluopyram, boscalid and difenoconazole. A total of 10 isolates, collected during 2013 at five localities in the major raspberry growing region in Serbia, and characterized as copper hydroxide, dithianon, and tebuconazole (sensitive), pyraclostrobin (sensitive or highly resistant) and fluazinam (sensitive or moderately resistant), were used in this study. The EC50 values for the isolates ranged from 1.33 to 2.88 mg L(-1) for mancozeb, from 3.18 to 6.65 mg L(-1) for chlorothalonil, from 15.75 to 24.69 mg L(-1) for captan and from 1.80 to 8.20 mg L(-1) for fluopyram. The narrowest range of EC50 values was recorded for difenoconazole (0.23-0.49 mg L(-1)), whereas the widest range was obtained for boscalid (4.49-49.25 mg L(-1)). The calculated resistance factors showed that all D. applanata isolates were sensitive to mancozeb, chlorothalonil, captan, and difenoconazole. Four isolates were moderately resistant to boscalid, while three of them were also moderately resistant to fluopyram. This finding of moderately resistant isolates to these SDHI fungicides indicates a possible cross-resistance which should be clarified in further investigations.

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Section: Discussioncontrasting

confidence: 68%

Toxicity of mancozeb, chlorothalonil, captan, fluopyram, boscalid, and difenoconazole toDidymella applanataisolates from Serbia

Mirković

Tanović

Stević

et al. 2015

Journal of Environmental Science and Health, Part B

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“…To date, S. cucurbitacearum has been identified only in temperate regions and is more often associated with Cucurbita species (Stewart et al 2015). Although S. citrulli is the dominant gummy stem blight species worldwide, both S. caricae and S. citrulli have been found within watermelon fields in Georgia, USA, where the two species vary in sensitivity to different fungicides (Avenot et al 2012;Li et al 2015). Leaf spot and fruit and stem rot of papaya, also caused by S. caricae (syn.…”

Section: Introductionmentioning

confidence: 96%

Two Stagonosporopsis species identified as causal agents of gummy stem blight epidemics of gherkin cucumber (Cucumis sativus) in Karnataka, India

Garampalli

Gapalkrishna

et al. 2015

Eur J Plant Pathol

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Since 2008, severe disease epidemics with symptoms resembling gummy stem blight have occurred on gherkin cucumbers (Cucumis sativus) in Karnataka, India. Three morphologically identical, but genetically distinct, Stagonosporopsis species, namely: Stagonosporopsis cucurbitacearum (syn. Didymella bryoniae), Stagonosporopsis citrulli, and Stagonosporopsis caricae, can cause gummy stem blight of cucurbits. Our objective was to use molecular techniques to identify if one or more of these species caused the recent epidemics on gherkin. It is not known which of these species is causing gummy stem blight of cucurbits in India. Based on the original host species, disease symptoms, fulfilment of Koch's postulates, and macroscopic and microscopic morphological analysis, the causal agent was tentatively identified as Stagonosporopsis sp. To identify which species was responsible, nine isolates were obtained from the outbreaks on gherkin in two regions of Karnataka in October and November 2014. The internal transcribed spacer region (ITS) of the ribosomal DNA was sequenced, and a previously developed PCR-based marker for distinguishing species causing gummy stem blight was used to identify the species of the isolates. We determined that seven of the isolates were S. caricae and two were S. citrulli. This is the first account in India that at least two Stagonosporopsis species are causing gummy stem blight of cucurbits, and are substantial threats to gherkin productivity and other cucurbits in India.

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“…Although there are multiple benefits of using modern techniques for testing fungicide sensitivity, a standard protocol for boscalid has not been established yet due to the complex responses of many fungi exposed to the fungicide. Indeed, for some fungi, the most critical stage for testing boscalid is the spore germination and germ tube elongation (28,41) whereas, for others, the most sensitive stage is the mycelial growth (6,9).…”

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confidence: 99%

Sensitivity of Alternaria alternata from Citrus to Boscalid and Polymorphism in Iron-Sulfur and in Anchored Membrane Subunits of Succinate Dehydrogenase

Vega

Dewdney

2015

Plant Disease

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Vega, B., and Dewdney, M. M. 2015. Sensitivity of Alternaria alternata from citrus to boscalid and polymorphism in iron-sulfur and in anchored membrane subunits of succinate dehydrogenase. Plant Dis. 99:231-239.Boscalid, a succinate dehydrogenase inhibitor (SDHI), was registered in 2011 to control Alternaria brown spot (ABS) of citrus, caused by Alternaria alternata. In this study, the effect of boscalid on mycelial growth, conidial germination, and resazurin reduction was established in a subset of 16 sensitive isolates using three different media. Conidial germination and mycelial growth inhibition were not suppressed even at higher concentrations of boscalid, although effective concentration to inhibit 50% growth (EC 50 ) values were established with each method. Resazurin reduction produced the lowest EC 50 values and was selected for further sensitivity tests. In total, 419 isolates, never exposed to boscalid and collected from Florida tangerine orchards between 1996 to 2012, were tested for boscalid sensitivity. The sensitivity distribution was a unimodal curve with a mean EC 50 value of 0.60 µg/ml and a range of 0.07 to 5.84 µg/ml. The molecular characterization of the succinate dehydrogenase (SDH) genes were also determined in a subset of 15 isolates, exhibiting great variability in boscalid sensitivity, by cloning and sequencing the sdhB, sdhC, and sdhD genes. Sequence comparisons of the SDH complex revealed the presence of mutations in 14 of 15 isolates. In total, 21 mutations were identified. Double and multiple mutations were observed in SDHC and SDHD, respectively. In SDHB, 4 mutations were observed while, in SDHC and SDHD, 5 and 12 mutations were detected, respectively. No mutations were found in the highly conserved histidine residues at positions 277 in SDHB, 134 in SDHC, and 133 in SDHD, typically observed in SDHI-resistant isolates. Our findings suggest that A. alternata populations from Florida are sensitive to boscalid and it could be used in ABS spray programs. Boscalid resistance is currently not a problem, although further monitoring for resistance is advisable.Alternaria brown spot (ABS), caused by Alternaria alternata (Fr.) Keissl., is the most important foliar fungal disease of tangerine plants (Citrus reticulata Blanco) and their hybrids (34,35). The disease affects the leaves, twigs, and young fruit. The first symptoms observed on young leaves is the presence of small brown to black spots surrounded by a yellow halo. Lesions expand rapidly, due to the production of the host-specific ACT toxin (1,46,47), and form irregular necrotic areas. On mature fruit, blemishes that reduce marketability can vary from small necrotic spots to large and depressed dark brown areas (12,51). Although cultural practices such as disease-free nursery stock, wide tree spacing, avoidance of excessive vegetative growth, and the elimination of overhead irrigation (15,47) can help to reduce disease severity, multiple fungicide applications are essential to achieve optimal disease control.Over the last decade, qui...

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Molecular characterization of boscalid‐ and penthiopyrad‐resistant isolates of Didymella bryoniae and assessment of their sensitivity to fluopyram

Abstract: The genotype-specific cross-resistance relationships between the SDHIs boscalid and penthiopyrad and the lack of cross-resistance between these fungicides and fluopyram should be taken into account when selecting SDHIs for gummy stem blight management.

Cited by 97 publications

References 15 publications

Toxicity of mancozeb, chlorothalonil, captan, fluopyram, boscalid, and difenoconazole toDidymella applanataisolates from Serbia

Toxicity of mancozeb, chlorothalonil, captan, fluopyram, boscalid, and difenoconazole toDidymella applanataisolates from Serbia

Two Stagonosporopsis species identified as causal agents of gummy stem blight epidemics of gherkin cucumber (Cucumis sativus) in Karnataka, India

Sensitivity of Alternaria alternata from Citrus to Boscalid and Polymorphism in Iron-Sulfur and in Anchored Membrane Subunits of Succinate Dehydrogenase

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