scholarly journals Fungicide Resistance of Two Species of Alternaria from Potato in the Columbia Basin of Washington

Plant Disease ◽  
2014 ◽  
Vol 98 (12) ◽  
pp. 1648-1653 ◽  
Author(s):  
Lydia Tymon ◽  
Dennis A. Johnson
Keyword(s):  
Spore Germination ◽  
Fungicide Resistance ◽  
Mycelial Growth ◽  
Alternaria Solani ◽  
Threshold Concentration ◽  
Brown Spot ◽  
Cellular Respiration ◽  
Columbia Basin ◽  
Growth Ratio ◽  
Fungal Populations

Fungicides are extensively used in the Columbia Basin of Washington in an effort to manage early blight and brown spot on potato caused by Alternaria solani and A. alternata, respectively. Azoxystrobin and boscalid interfere with cellular respiration, and fungicide resistance is expected to occur in fungal populations due to the narrow modes of action dictated by each fungicide. The objective of this research was to assess A. solani and A. alternata populations in the Columbia Basin of Washington for azoxystrobin and boscalid resistance by initially screening isolates at a threshold concentration using mycelial growth and spore germination. Fifty isolates of A. solani and 58 of A. alternata were randomly selected for screening from 671 isolates collected from potato in the Columbia Basin from 2009 to 2011. Screening at a threshold concentration was done to estimate the range of fungicide resistance within the populations of A. solani and A. alternata in the region. Resistance of five isolates that differed in sensitivity to azoxystrobin and boscalid were then assessed for mycelial growth and spore germination at three fungicide concentrations in order to determine where rates were no longer effective. A. solani mycelial growth ratios and percent spore germination on azoxystrobin-amended media did not change from 2010 to 2011. A slight decrease in resistance of mycelial growth to azoxystrobin was exhibited among A. alternata isolates collected between 2010 and 2011. No change in sensitivity to azoxystrobin was observed in mycelial growth ratios among A. alternata isolates collected between 2010 and 2011. Resistance to boscalid by A. solani increased as indicated by a significant increase in mean mycelial growth ratio from 2010 to 2011, whereas A. alternata showed no change. Spore germination of A. solani was less at 100 μg/ml than at 1 or 10 μg/ml azoxystrobin. Spore germination of A. alternata did not differ among 1, 10, or 100 μg/ml azoxystrobin. Spore germination of A. solani and A. alternata did not differ among 0.5, 5, or 50 μg/ml boscalid. Resistance to azoxystrobin and boscalid in A. solani and A. alternata populations was shown to be present in the Columbia Basin and will likely become widespread with continued used of site-specific fungicides.

scholarly journals Evaluation of Phenamacril and Ipconazole for Control of Rice Bakanae Disease Caused by Fusarium fujikuroi

Plant Disease ◽  
2018 ◽  
Vol 102 (7) ◽  
pp. 1234-1239 ◽  
Author(s):  
Meixia Li ◽  
Tao Li ◽  
Yabing Duan ◽  
Ying Yang ◽  
Jian Wu ◽  
...  
Keyword(s):  
Antifungal Activity ◽  
Spore Germination ◽  
Fungicide Resistance ◽  
Mycelial Growth ◽  
Fusarium Fujikuroi ◽  
Rice Cultivars ◽  
Bakanae Disease ◽  
Field Isolates ◽  
High Antifungal Activity ◽  
Selection Of

This study evaluated the use of phenamacril and ipconazole, alone and in mixtures, for the control of rice bakanae disease caused by Fusarium fujikuroi. Mixtures were studied with the goal of reducing the selection of fungicide-resistant field isolates of the fungus. When tested alone, both phenamacril and ipconazole exhibited high antifungal activity against F. fujikuroi mycelial growth; the average EC50 value for 19 field isolates was 0.1544 μg/ml for phenamacril and 0.0472 μg/ml for ipconazole. A 2:1 mixture of phenamacril and ipconazole caused a slightly synergistic (greater than additive) inhibition of mycelial growth. Inhibition of F. fujikuroi sporulation was highest for ipconazole alone, intermediate with the 2:1 mixture, and lowest for phenamacril alone. Inhibition by phenamacril and ipconazole alone or by the 2:1 mixture was substantially lower for spore germination than for mycelial growth or sporulation. When the total fungicide concentration was <24 g of a.i./100 kg of treated rice seeds, the fungicides, whether alone or in the 2:1 mixture, were not phytotoxic to seeds or seedlings of two rice cultivars. In a greenhouse experiment, the 2:1 mixture of phenamacril and ipconazole at 6 g of a.i./100 kg of treated seeds provided 100% control of rice bakanae disease on two cultivars. Overall, the results indicate that the use of a 2:1 mixture of phenamacril and ipconazole should control rice bakanae disease while reducing the occurrence of fungicide resistance in F. fujikuroi.

scholarly journals Pathogenicity and Aggressiveness of Three Alternaria spp. on Potato Foliage in the U.S. Northwest

Plant Disease ◽  
2016 ◽  
Vol 100 (4) ◽  
pp. 797-801 ◽  
Author(s):  
Lydia S. Tymon ◽  
Thomas F. Cummings ◽  
Dennis A. Johnson
Keyword(s):  
Alternaria Solani ◽  
Russet Burbank ◽  
Brown Spot ◽  
Columbia Basin ◽  
Russet Norkotah ◽  
Expansion Curve ◽  
Detached Leaves ◽  
Potato Foliage ◽  
Whole Plants ◽  
Umatilla Russet

Alternaria spp. were collected from potato foliage showing symptoms of early blight and brown spot in the Columbia Basin, WA and Bonners Ferry and Rupert, ID between 2009 and 2011. The aggressiveness of three Alternaria spp. on potato was quantified on nonwounded and wounded detached leaves of ‘Russet Norkotah’ potato; wounded detached leaves of ‘Alturas’, ‘Ranger Russet’, ‘Russet Burbank’, and ‘Umatilla Russet’; and whole plants of Russet Norkotah. Mean infection frequencies (MIF) and area under the lesion expansion curve (AULEC) were significantly greater for Alternaria solani (P = 0.0072 and 0.0002, respectively) than for A. arborescens or A. arbusti on nonwounded leaves. Wounding of tissue significantly increased MIF and AULEC for A. arbusti (P = 0.008 and 0.0047, respectively) and AULEC for A. arborescens (P = 0.01) relative to nonwounded tissue. AULEC did not differ significantly among the three Alternaria spp. when inoculated onto wounded foliage of whole plants (P = 0.34); the AULEC of whole plants was positively and significantly correlated with AULEC on detached leaves (P = 0.03). Umatilla Russet was the most susceptible and Russet Burbank was the least susceptible based on MIF and AULEC for all three pathogen species. Results indicate that A. solani was the more aggressive pathogen of potato in the Columbia Basin, because both A. arborescens and A. arbusti require wounds and A. arbusti lesions do not expand significantly in comparison with A. solani or A. arborescens following inoculation.

scholarly journals Combination of Suspension Array and Mycelial Growth Assay for Detecting Multiple-Fungicide Resistance in Botrytis cinerea in Hebei Province in China

Plant Disease ◽  
2019 ◽  
Vol 103 (6) ◽  
pp. 1213-1219
Author(s):  
Zehua Su ◽  
Xin Zhang ◽  
Jianjiang Zhao ◽  
Wenqiao Wang ◽  
Lei Shang ◽  
...  
Keyword(s):  
Botrytis Cinerea ◽  
High Throughput ◽  
Fungicide Resistance ◽  
Mycelial Growth ◽  
Accurate Method ◽  
Hebei Province ◽  
Combination Method ◽  
Major Type ◽  
Suspension Array ◽  
Growth Assay

To provide a high-throughput, efficient, and accurate method to monitor multiple-fungicide resistance of Botrytis cinerea in the field, we used the suspension array, sequencing, and mycelial growth assay in our research. Discriminating-dose bioassays for detecting carbendazim, diethofencarb, boscalid, and iprodione resistance (CarR, DieR, BosR, and IprR, respectively) were used to analyze 257 isolates collected from Hebei Province in China during 2016 and 2017. High resistance frequencies to carbendazim (100%), diethofencarb (92.08%), and iprodione (86.59%) were detected. BosR isolates accounted for 11.67% of the total. In addition, 103 isolates were randomly selected for phenotype and genotype detection. The high-throughput suspension array was utilized to detect eight genotypes simultaneously, including BenA-E198, BenA-198A, SdhB-H272, SdhB-272Y, BcOS1-I365, BcOS1-365S, erg27-F412, and erg27-412S, which were associated with resistance toward carbendazim or diethofencarb, boscalid, iprodione, and fenhexamid (FenR), respectively. Most of the benzimidazole-resistant isolates (81.55%) possessed the E198V mutation in the BenA gene. Ninety-three isolates with dual resistance to carbendazim and diethofencarb showed the E198V/K mutation. All BosR isolates carried the H272R mutation in the SdhB gene. The I365S and Q369P+N373S (66.99%) mutations in the BcOS1 gene were more frequently observed. No mutation was detected in the erg27 gene in Hebei isolates. There were 13 resistance profile phenotypes. Phenotypes with triple resistance were the most common (83.50%), and CarRDieRBosSIprRFenS was the major type. CarR isolates that carried E198V/K/A were all highly resistant (HR) and only one F200Y mutant was moderately resistant (MR) to carbendazim. Isolates that possessed E198V/K were MR or HR to diethofencarb. BosR isolates that possessed H272R mutation were lowly resistant (LR). IprR isolates were all LR or MR. The distribution of half maximal effective concentrations of CarR isolates with E198V/K mutations and IprR isolates with Q369P+N373S mutations significantly increased from 2016 to 2017. Combined with our observations, a combination method of the high-throughput suspension array and the mycelial growth assay was suggested to accurately monitor multiple resistance of B. cinerea in the field.

Screening of Existing and New Boxwood Cultivars for Disease Resistance and In Vitro Fungicide Screening to Manage Boxwood Dieback Caused by Colletotrichum theobromicola

2021 ◽  
Author(s):  
Harleen Kaur ◽  
Monique DeSouza ◽  
Raghuwinder "Raj" Singh
Keyword(s):  
Active Ingredient ◽  
Spore Germination ◽  
Mycelial Growth ◽  
Management Practices ◽  
Management Strategies ◽  
Host Susceptibility ◽  
Germination Inhibition ◽  
Industry Professionals ◽  
The U.S

Boxwood is one of the most common and widely planted perennial ornamentals in both home gardens and commercial landscapes. Recently reported boxwood dieback, a fungal disease caused by Colletotrichum theobromicola, has been spreading at an alarming rate within the U.S. Boxwood breeders, nursery growers, and landscape professionals have shown great concerns regarding the lack of effective management practices. Therefore, the primary objectives of this study were to devise effective disease management strategies including screening cultivars to determine their susceptibility to boxwood dieback and screening various fungicides to determine their effectiveness in managing the disease. Host range studies were conducted by screening a wide variety of boxwood cultivars under greenhouse conditions. Although, boxwood cultivar ‘Little Missy’ showed much delayed symptom expression as compared to rest of the cultivars but none of the 11 cultivars were found to be resistance to boxwood dieback. In vitro screening of nine fungicides was conducted to determine mycelial growth as well as spore germination inhibition of eight isolates of C. theobromicola collected from eight states in the U.S. Of the nine fungicides, difenoconazole+pydiflumetofen showed maximum mycelial growth and spore germination inhibition at 1 ppm active ingredient followed by fluxapyroxad+pyraclostrobin, and pyraclostrobin+boscalid at 5 ppm active ingredient. Azoxystrobin+benzovindiflupyr significantly inhibited mycelial growth at 1 ppm but reduced spore germination at 10 ppm active ingredient. This study provides the boxwood industry professionals with critical and applied information pertaining to host susceptibility and fungicide efficacy to effectively mitigate boxwood dieback and to reduce its further spread.

Effects of Potassium Sorbate on Growth and Aflatoxin Production by Aspergillus parasiticus and Aspergillus flavus1

1983 ◽  
Vol 46 (11) ◽  
pp. 940-942 ◽  
Author(s):  
LLOYD B. BULLERMAN
Keyword(s):  
Aspergillus Flavus ◽  
Yeast Extract ◽  
Aflatoxin B1 ◽  
Spore Germination ◽  
Mycelial Growth ◽  
Aspergillus Parasiticus ◽  
Aflatoxin Production ◽  
Potassium Sorbate ◽  
Mycelial Mass ◽  
Yeast Extract Sucrose

Growth and aflatoxin production by selected strains of Aspergillus parasiticus and Aspergillus flavus in the presence of potassium sorbate at 12°C were studied. Potassium sorbate at 0.05, 0.10 and 0.15% delayed or prevented spore germination and initiation of growth, and slowed growth of these organisms in yeast-extract sucrose broth at 12°C. Increasing concentrations of sorbate caused more variation in the amount of total mycelial growth and generally resulted in a decrease in total mycelial mass. Potassium sorbate also greatly reduced or prevented production of aflatoxin B1 by A. parasiticus and A. flavus for up to 70 d at 12°C. At 0.10 and 0.15% of sorbate, aflatoxin production was essentially eliminated. A 0.05% sorbate, aflatoxin production was greatly decreased in A. flavus over the control, but only slightly decreased in A. parasiticus.

scholarly journals Antifungal Efficacy of Plant Oils Containing Thymol and Carvacrol in Controlling Botrytis cinerea, the Causal Agent of Grape (Vitis vinifera) GrayMould

2018 ◽  
Vol 16 (02) ◽  
pp. 15-24
Author(s):  
Zaker M ◽  
Zaker L
Keyword(s):  
Essential Oils ◽  
Botrytis Cinerea ◽  
Spore Germination ◽  
Mycelial Growth ◽  
Germ Tube ◽  
Plant Diseases ◽  
Plant Oils ◽  
Horticultural Products ◽  
Antifungal Efficacy ◽  
Germ Tube Elongation

The efficacy of a large number of plant extracts and essential oils in controlling plant diseases has been proven worldwide. Botrytis cinerea has attacked a wide host range causing severe loss in the field and at storage. In this study the antifungal efficacy of essential oils of three medicinal plants namely wild marjoram (Zataria multifolia), wild savory (perennial) (Satureja mutica) and savory (annual) (Satureja hortensis) possessing these compounds at three concentrations: 50, 100 and 200 ppm were evaluated in controlling the mycelial growth, spore germination and germ tube elongation of B. cinerea. All treatments except savory (annual) essential oil at 50 ppm showed significant differences with the control in inhibiting the mycelial growth as well as spore germination and germ tube elongation of B. cinerea (p=0.01). It was also noted that wild marjoram at 100 ppm and wild savory (perennial) essential oils at 200 ppm could completely (100%) inhibit the growth of the fungus. Essential oils from wild marjoram and wild savory had higher antifungal activity than annual savory. Their suitable formulations could be prepared and used as safe alternatives for controlling moulds of horticultural products during storage. The Agriculturists 2018; 16(2) 15-24

Sensitivity of Ulocladium atrum, Coniothyrium minitans, and Sclerotinia sclerotiorum to benomyl and vinclozolin

2002 ◽  
Vol 80 (8) ◽  
pp. 892-898 ◽  
Author(s):  
G Q Li ◽  
H C Huang ◽  
S N Acharya
Keyword(s):  
Growth Inhibition ◽  
Sclerotinia Sclerotiorum ◽  
Spore Germination ◽  
Mycelial Growth ◽  
Germination Rate ◽  
Effective Concentration ◽  
Coniothyrium Minitans ◽  
Inhibition Concentration ◽  
Maximum Inhibition ◽  
Germ Tubes

Assays on mycelial growth and spore germination were carried out to determine the sensitivity of the biocontrol agents Ulocladium atrum and Coniothyrium minitans and the plant pathogen Sclerotinia sclerotiorum to benomyl and vinclozolin. Ulocladium atrum was more tolerant to these fungicides than C. minitans and S. sclerotiorum. The 50% effective concentration (EC50) of U. atrum based on the mycelial growth inhibition was 1467.3 µg active ingredient (a.i.)/mL for benomyl and 12.6 µg a.i./mL for vinclozolin, and the maximum inhibition concentration was higher than 4000 µg a.i./mL for both fungicides. For C. minitans and S. sclerotiorum, however, the EC50 based on mycelial growth inhibition was lower than 1 µg a.i./mL. After incubation for 24 h at 20°C, the germination rate of U. atrum conidia was 90–99% on potato dextrose agar (PDA) amended with benomyl at 100–500 µg a.i./mL or vinclozolin at 10–500 µg a.i./mL. At these concentrations, germ tubes of U. atrum developed into long, branched hyphae in benomyl treatments, but they remained short and clustered in vinclozolin treatments. Pycnidiospores of C. minitans and ascospores of S. sclerotiorum germinated on PDA amended with benomyl at 100–500 µg a.i./mL, but the germ tubes did not grow further. Spore germination of C. minitans and S. sclerotiorum was less than 3.2% on PDA amended with vinclozolin at 10–500 µg a.i./mL after 24 h. This is the first report on the sensitivity of U. atrum and C. minitans to benomyl and vinclozolin. The results suggest that it is possible to control S. sclerotiorum using a combination of U. atrum and benomyl or vinclozolin.Key words: fungicides, mycelial growth, spore germination, integrated pest management.

scholarly journals Sensitivity of Bipolaris oryzae Isolates Pathogenic on Cultivated Wild Rice to the Quinone Outside Inhibitor Azoxystrobin

Plant Disease ◽  
2019 ◽  
Vol 103 (8) ◽  
pp. 1910-1917 ◽  
Author(s):  
Claudia V. Castell-Miller ◽  
Deborah A. Samac
Keyword(s):  
Cytochrome B ◽  
Fungicide Resistance ◽  
Wild Rice ◽  
Brown Spot ◽  
Bipolaris Oryzae ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Group I ◽  
Mitochondrial Cytochrome B

The occurrence of fungal brown spot, caused by Bipolaris oryzae, has increased in cultivated wild rice (Zizania palustris) paddies in spite of the use of azoxystrobin-based fungicides. The active ingredient blocks electron transfer at the quinone outside inhibitor (QoI) site in the mitochondrial cytochrome b within the bc1 complex, thus obstructing respiration. The in vitro averaged EC50 of baseline isolates collected in 2007 before widespread fungicide use was estimated to be 0.394 µg/ml with PROBIT and 0.427 µg/ml with linear regression analyses. Isolates collected during 2008, 2015, and 2016 had a range of sensitivity as measured by relative spore germination (RG) at a discriminatory dose of 0.4 µg/ml azoxystrobin. Isolates with a higher (≥80%) and lower RG (≤40%) had the wild type nucleotides at amino acid positions F129, G137, and G143 of cytochrome b, sites known to be associated with QoI fungicide resistance. Two Group I introns were found in the QoI target area. The splicing site for the second intron was found immediately after the codon for G143. A mutation for fungicide resistance at this location would hinder splicing and severely reduce fitness. B. oryzae expresses an alternative oxidase in vitro, which allows the fungus to survive inhibition of respiration by azoxystrobin. This research indicates that B. oryzae has not developed resistance to QoI fungicides, although monitoring for changes in sensitivity should be continued. Judicious use of QoI fungicides within an integrated disease management system will promote an effective and environmentally sound control of the pathogen in wild rice paddies.

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