Sensitivities of various Oomycetes to hymexazol and metalaxyl

Kato, Shigehiro; Coe, R.; New, Laura; Dick, M.W.

doi:10.1099/00221287-136-10-2127

Cited by 23 publications

(16 citation statements)

References 20 publications

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“…Currently, the effects of subinhibitory doses of fungicides on fungal plant pathogens are unknown. The evidence gathered from literature indicates that stimulation of fungi and oomycetes by sub-inhibitory doses of fungicides has been observed in ascomycetes (64,65,67,68), basidiomycetes (2,69,74), as well as in oomycetes (66,70,71,72,73,74). Several fitness factors could be affected for the benefit of pathogens, including mycelial growth, spore germination, toxin production and pathogenicity (66,67,68,74).…”

Section: Why Is Chemical Hormesis Relevant For Crop Management?mentioning

confidence: 99%

Hormesis: Biphasic Dose-Responses to Fungicides in Plant Pathogens and Their Potential Threat to Agriculture

Garzón¹,

Flores²

2013

Fungicides - Showcases of Integrated Plant Disease Management From Around the World

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Section: Why Is Chemical Hormesis Relevant For Crop Management?mentioning

confidence: 99%

Hormesis: Biphasic Dose-Responses to Fungicides in Plant Pathogens and Their Potential Threat to Agriculture

Garzón¹,

Flores²

2013

Fungicides - Showcases of Integrated Plant Disease Management From Around the World

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“…Landry et al (23) observed significantly increased radial growth of Lyophyllum palustre (Peck) Singer on media amended with low concentrations of propamocarb compared with the fungicide-free control. With regard to oomycete plant pathogens, Phytophthora undulate could be stimulated by low doses of hymexazol (21). Metalaxyl-resistant P. infestans growth and virulence was stimulated by low concentrations of metalaxyl (37).…”

mentioning

confidence: 97%

Stimulatory Effects of Sublethal Doses of Dimethachlon on Sclerotinia sclerotiorum

Zhou

Liang

et al. 2014

Plant Disease

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A b s t r a c t -X. 2014. Stimulatory effects of sublethal doses of dimethachlon on Sclerotinia sclerotiorum. Plant Dis. 98:1364-1370.Growth and virulence stimulations of sublethal doses of fungicides on plant-pathogenic fungi and oomycetes have been reported and the stimulatory effects are potentially relevant to plant disease manage ment. Sclerotinia sclerotiorum is one of the most devastating and eco nomically important necrotrophic fungal phytopathogens, capable of infecting more than 400 species of plants worldwide. In order to study stimulatory effects of sublethal doses of fungicides on S. sclerotiorum, 55 dimethachlon-sensitive isolates and 3 dimethachlon-resistant iso lates of S. sclerotiorum were assayed to determine effects of sublethal doses of dimethachlon on mycelial growth rate on potato dextrose agar (PDA) media and virulence on oilseed rape plants. Results showed that all 3 dimethachlon-resistant isolates and 13 of the 55 sensitive isolates exhibited stimulatory responses to sublethal doses of dimethachlon.Dimethachlon-resistant isolates grew significantly (P < 0.05) faster on PDA media amended with dimethachlon at 0.5 to 4 pg/ml than on fungicide-free PDA media. As for virulence on detached leaves of oilseed rape plants, lesion diameters of dimethachlon-resistant isolates after growth on PDA media amended with dimethachlon at 0.5 to 2 pg/ml were significantly larger (P < 0.05) than the control. The maxi mum stimulatory effects were 42.40 to 59.80%. In pot experiments, for both dimethachlon-sensitive and -resistant isolates, significant (P < 0.05) virulence stimulations were observed after spraying with di methachlon at a concentration of 2 pg/ml. After growing on dimethachlon-amended PDA media, H20 2 sensitivity of S. sclerotiorum de creased significantly (P < 0.05) compared with the nonamended PDA control.At present, fungicides still play an essential and, in most cases, maybe the most important role in successful and effective plant disease management. When controlling fungal and oomycete plant pathogens by application of fungicides, a small amount of phyto pathogens will inevitably be exposed to sublethal doses of fungi cides. Exposure to sublethal doses of fungicides can occur under diverse circumstances, such as inappropriate fungicide applica tions, in combination with other fungicides with different active ingredient, and emergence of fungicide-resistant strains (16,26). Normal doses of fungicides for sensitive phytopathogen strains are perhaps sublethal doses for fungicide-resistant strains. In most experiments, researchers are mainly interested in effects of normal (high) doses of fungicides on plant pathogens, and effects of suble thal doses of fungicides have been largely ignored.In experiments to test in vitro sensitivity of Sclerotinia scleroti orum (Lib.) de Bary to fungicide, we noticed that some isolates grew faster on potato dextrose agar (PDA) media amended with sublethal doses of fungicides than on fungicide-free PDA media. There have been some reports of plant pathogen growth...

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“…Considering first the effect of individual antimicrobials in NARH on the growth of Phytophthora : hymexazol above 12.5 ppm inhibited P. gondwanensis and above 25 ppm, P. cinnamomi . Previously, its use at 50 ppm has been reported to be inhibitory to mycelial growth of P. cactorum (Tay et al ., 1983; Harris and Bielenin, 1986; Jeffers and Martin, 1986; Ho, 1987), P. cinnamomi (Tay et al ., 1983), P. infestans (Shen and Tsao, 1983; Ho, 1987), P. capsici (Papavizas et al ., 1981; Jeffers and Martin, 1986), P. palmivora (Jeffers and Martin, 1986; Kato et al ., 1990), P. sojae (Jeffers and Martin, 1986), P. hibernalis (Ho, 1987), and P. lateralis (Hansen et al ., 1979; Ho, 1987). To avoid the harmful effect of hymexazol on Phytophthora species, we selected a concentration of 12.5 ppm for further testing.…”

Section: Discussionmentioning

confidence: 99%

Antimicrobials in Phytophthora isolation media and the growth of Phytophthora species

et al. 2020

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Many recently described Phytophthora species detected using high‐throughput sequencing have never been isolated into culture. NARH is a commonly used isolation medium containing cornmeal agar with nystatin 22.72 ppm, ampicillin 100 ppm, rifampicin 10 ppm, and hymexazol 50 ppm. We investigated whether the antimicrobial compounds in this medium selectively inhibit growth of some Phytophthora species. Growth of 10 Phytophthora species from 10 Phytophthora clades was tested in NARH medium with antimicrobials in a range of concentrations, singly and in combination: nystatin 12.5–100 ppm, ampicillin 62.5–500 ppm, rifampicin 5–40 ppm, hymexazol 12.5–100 ppm and in addition, chloramphenicol 5–40 ppm. Two combinations of antimicrobials that supported good growth of the greatest number of species were selected: (a) nystatin 12.5 ppm, ampicillin 250 ppm, rifampicin 10 ppm, and hymexazol 12.5 ppm, and (b) these compounds with the addition of chloramphenicol 5 ppm. Subsequently the growth of 47 Phytophthora species from all clades was tested in media with these two combinations and standard NARH, both in aseptic culture and in plates with leaf baits infected from soils known to be infested with Phytophthora. Although growth of some Phytophthora species was better with the new combinations of antimicrobials in aseptic culture, suppression of competing microorganisms was best in standard NARH. Sensitivity to the NARH antimicrobials is not the reason for the difficulty or failure of isolating many species detected using high‐throughput sequencing. NARH is a robust and appropriate medium for isolation of Phytophthora species from all clades.

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Sensitivities of various Oomycetes to hymexazol and metalaxyl

Cited by 23 publications

References 20 publications

Hormesis: Biphasic Dose-Responses to Fungicides in Plant Pathogens and Their Potential Threat to Agriculture

Hormesis: Biphasic Dose-Responses to Fungicides in Plant Pathogens and Their Potential Threat to Agriculture

Stimulatory Effects of Sublethal Doses of Dimethachlon on Sclerotinia sclerotiorum

Antimicrobials in Phytophthora isolation media and the growth of Phytophthora species

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