scholarly journals Rapid Detection of Fungicide Resistance Phenotypes Among Populations of Nothopassalora personata in South Carolina Peanut Fields

2020 ◽  
Vol 21 (2) ◽  
pp. 123-132 ◽  
Author(s):  
Misbakhul Munir ◽  
Hehe Wang ◽  
Paula Agudelo ◽  
Daniel J. Anco
Keyword(s):  
South Carolina ◽  
Fungicide Resistance ◽  
Site Specific ◽  
Thiophanate Methyl ◽  
Phenotypic Resistance ◽  
Detached Leaf ◽  
Binary Event ◽  
Routine Monitoring ◽  
Control Failure ◽  
Successful Control

We evaluated the occurrence of fungicide resistance phenotypes in populations of Nothopassalora personata, the causal agent of late leaf spot (LLS), sampled from South Carolina peanut fields in 2018 using a modified detached leaf assay (DLA). Spore suspensions obtained from each of 72 groups of LLS-symptomatic leaves collected from nine counties were used in the DLA to examine phenotypic resistance to four site-specific fungicides (azoxystrobin, benzovindiflupyr, prothioconazole, and thiophanate-methyl) and one multisite contact fungicide (chlorothalonil). Lesion development was measured as a binary event in which presence of a lesion indicated control failure (phenotypic resistance) and absence of a lesion indicated successful control (sensitivity). Phenotypic resistance probabilities of N. personata samples to each site-specific fungicide were compared against the control fungicide (chlorothalonil). Variation in phenotypic resistance probabilities to the four single-site fungicides was observed from most counties (6 of 9), with frequencies of phenotypic resistance having differed among counties. The DLA facilitated rapid evaluation of N. personata phenotypic resistance to azoxystrobin, benzovindiflupyr, prothioconazole, and thiophanate-methyl. This assay has potential to be used as an alternative method for routine monitoring of phenotypic resistance, identification of populations to test for the presence of resistance genes, and improving reliability of current fungicide recommendations.

scholarly journals First Report of Thiophanate-Methyl Resistance in Botrytis cinerea on Strawberry from South Carolina

Plant Disease ◽  
2012 ◽  
Vol 96 (11) ◽  
pp. 1700-1700 ◽  
Author(s):  
D. Fernández-Ortuño ◽  
G. Schnabel
Keyword(s):  
South Carolina ◽  
Botrytis Cinerea ◽  
Fungicide Resistance ◽  
Pathogenic Fungi ◽  
Gray Mold ◽  
Resistant Isolate ◽  
Conidial Suspension ◽  
Strawberry Fruit ◽  
Single Spore ◽  
Thiophanate Methyl

Botrytis cinerea Pers.:Fr. is the causal agent of gray mold disease and one of the most important plant-pathogenic fungi affecting strawberry (Fragaria× ananassa). Control of gray mold mainly depends on fungicides, including the methyl benzimidazole carbamate (MBC) thiophanate-methyl. In 2011, strawberries with gray mold symptoms were collected from commercial fields near Chesnee, Florence, Lexington, McBee, Monetta, and North Augusta, all in South Carolina. MBC fungicides were used in most of these fields for gray mold control during the last 3 years. A total of 124 single spore B. cinerea isolates were obtained, each from a different fruit. Resistance to thiophanate-methyl (Topsin M 70WP, Cerexagri-Nisso LLC, King of Prussia, PA) was determined using a conidial germination assay as described previously (1). The majority of isolates (81.4%) were resistant; the rest were sensitive. Resistant isolates were found in all locations with some populations (Chesnee, McBee, and Lexington) revealing no sensitive isolates. Genomic DNA from 35 resistant isolates (representing all locations) and 10 sensitive isolates (from Chesnee, Monetta, and North Augusta, SC) was extracted, and the molecular basis of MBC fungicide resistance was determined as described previously (2). All MBC-resistant isolates possessed the E198A mutation known to confer high levels of MBC fungicide resistance in many fungi, including B. cinerea (2,3). Disease was assessed using a detached strawberry fruit assay. Commercially grown strawberry fruit (24 in total for each isolate and fungicide treatment) were rinsed with water, dried, and sprayed 4 h prior to inoculation with either water or 2.4 g/liter of Topsin M to runoff using a hand mister. Fruit was stab-wounded with a sterile syringe and inoculated with a 30-μl droplet of a conidial suspension (106 spores/ml) of either a sensitive or resistant isolate. After inoculation, the fruit were kept at 22°C for 4 days. The sensitive isolate developed gray mold disease in untreated but not Topsin M-treated fruit. The resistant isolate developed gray mold disease of equal severity in both, the control and fungicide-treated fruit. This experiment was repeated once. The results of the study show that resistance to MBC fungicides is common and widespread in B. cinerea from strawberry in South Carolina. Prior to this study, resistance to MBCs has only been reported in B. cinerea from ornamental crops grown in greenhouses in South Carolina (4). References: (1) J. E. Luck and M. R. Gillings. Mycol. Res. 99:1483, 1995. (2) R. W. S. Weber and M. Hahn. J. Plant Dis. Prot. 118:17, 2011. (3) O. Yarden and T. Katan. Phytopathology 83:1478, 1993. (4) L. F. Yourman and S. Jeffers. Plant Dis. 83:569, 1999.

scholarly journals Location-Specific Fungicide Resistance Profiles and Evidence for Stepwise Accumulation of Resistance in Botrytis cinerea

Plant Disease ◽  
2014 ◽  
Vol 98 (8) ◽  
pp. 1066-1074 ◽  
Author(s):  
Xingpeng Li ◽  
Dolores Fernández-Ortuño ◽  
Shuning Chen ◽  
Anja Grabke ◽  
Chao-Xi Luo ◽  
...  
Keyword(s):  
South Carolina ◽  
Botrytis Cinerea ◽  
Fungicide Resistance ◽  
Gene Mutations ◽  
Thiophanate Methyl ◽  
Resistance Profile ◽  
New Genotype ◽  
Resistant Population ◽  
Resistance Patterns ◽  
Medium Resistance

The fungicide resistance profiles to seven chemical classes of fungicides were investigated in 198 Botrytis cinerea isolates from five blackberry fields and 214 B. cinerea isolates from 10 strawberry fields of North and South Carolina. Populations of B. cinerea tended to have a single dominant, location-specific resistance profile that consisted of resistance to multiple fungicides in fields sprayed weekly with site-specific fungicides. The most prevalent profile in blackberry fields consisted of resistance to thiophanate-methyl, pyraclostrobin, and boscalid. The most prevalent resistance profile found in conventional strawberry fields consisted of resistance to thiophanate-methyl, pyraclostrobin, boscalid, and cyprodinil. A statistical model revealed that multifungicide resistance patterns did not evolve randomly in populations from both crops. Instead, strains resistant to thiophanate-methyl were more likely to acquire resistance to pyraclostrobin, the resulting dual-resistant population was more likely to acquire resistance to boscalid, the resulting triple-resistant population was more likely to acquire resistance to cyprodinil, and the resulting quadruple-resistant population was more likely to acquire resistance to fenhexamid (strawberry population only) compared with random chance. Resistance to iprodione and fludioxonil evolved from a pool of strains with different fungicide resistance profiles. Resistance to thiophanate-methyl, pyraclostrobin, boscalid, and fenhexamid in blackberry isolates was, without exception, based on target gene mutations, including E198A and E198V in β-tubulin, G143A in cytochrome b, H272Y and H272R in SdhB, and F412I in Erg27, respectively. A new genotype associated with fenhexamid resistance was found in one strain (i.e., Y408H and deletion of P298). Fungicide-resistant strains were present but rare in an unsprayed blackberry field, where some unique phenotypes, including low and medium resistance to fludioxonil, had emerged in the absence of fungicide pressure. The isolates resistant to fludioxonil had effective dose that inhibited 50% of mycelial growth values of 0.16 μg/ml (low resistance) and 0.32 and 0.38 μg/ml (medium resistance) and were also resistant to the anilinopyrimidine fungicide cyprodinil, indicating that this and similar phenotypes will eventually be selected by continued applications of the fludioxonil + cyprodinil premixture Switch. This study shows that multifungicide-resistant phenotypes are common in conventionally maintained strawberry and blackberry fields and that resistance to multiple fungicides evolved from stepwise accumulation of single resistances.

scholarly journals Fungicide Resistance in Botrytis fragariae and Species Prevalence in the Mid-Atlantic United States

Plant Disease ◽  
2018 ◽  
Vol 102 (5) ◽  
pp. 964-969 ◽  
Author(s):  
Madeline E. Dowling ◽  
Meng-Jun Hu ◽  
Guido Schnabel
Keyword(s):  
United States ◽  
North Carolina ◽  
South Carolina ◽  
Fungicide Resistance ◽  
The United States ◽  
Gray Mold ◽  
Thiophanate Methyl ◽  
Entire Collection ◽  
Field Samples ◽  
Fruit Samples

Botrytis fragariae was recently described causing gray mold of strawberry in Germany and the United States. The goal of the present study was to determine its prevalence, distribution, and sensitivity to fungicides in strawberry fields of five states. In total, 188 Botrytis isolates were obtained from flowers and fruit collected from the states of Maryland (n = 35), Virginia (n = 38), North Carolina (n = 46), South Carolina (n = 41), and Georgia (n = 28). Only 13 of these were fruit samples and came from South Carolina (n = 5) and Georgia (n = 8). B. fragariae made up 35.1% of the entire collection, and composed close to half of the Botrytis population in North Carolina (43.4%), South Carolina (61.0%), and Georgia (42.9%). One isolate of B. mali was also found, and the rest of the isolates were B. cinerea (sensu lato). B. fragariae and B. cinerea were found coexisting in 11 fields, while other field samples consisted of only B. fragariae (n = 3) or only B. cinerea (n = 10) isolates. B. fragariae isolates with resistance to one or more fungicides were found, and resistance profiles differed from those of B. cinerea, in that no resistance to cyprodinil (FRAC 8) or boscalid and other FRAC 7 botryticides was detected. We detected B. fragariae resistance to the active ingredients thiophanate-methyl, iprodione, fludioxonil, and fenhexamid. We also detected B. fragariae isolates with resistance to up to four chemical classes of fungicides, though most isolates were resistant to one or two chemical classes. In conclusion, isolates of the newly detected species B. fragariae were commonly found on strawberry flowers in the Mid-Atlantic United States, and have developed resistance to many of the most commonly used botryticides. Though the relevance of this species to pre- and postharvest fruit infections is unknown, fludioxonil applications may give this species a competitive advantage over B. cinerea. Controlling this fungus with FRAC 7 fungicides may be an effective way of limiting its spread in strawberry fields.

scholarly journals Resistance to Benzimidazole and Dicarboximide Fungicides in Greenhouse Isolates of Botrytis cinerea

Plant Disease ◽  
1999 ◽  
Vol 83 (6) ◽  
pp. 569-575 ◽  
Author(s):  
L. F. Yourman ◽  
S. N. Jeffers
Keyword(s):  
South Carolina ◽  
Botrytis Cinerea ◽  
Active Ingredient ◽  
Disease Incidence ◽  
Correlation Coefficients ◽  
Effective Concentration ◽  
Mycelium Growth ◽  
Thiophanate Methyl ◽  
Conidium Germination ◽  
The Mean

In 1996 and 1997, 325 isolates of Botrytis cinerea were collected from 35 commercial greenhouses growing ornamental crops in South Carolina to determine the incidence of resistance to benzimidazole and dicarboximide fungicides. Conidium germination was assessed on a defined agar medium amended with either thiophanate-methyl (a benzimidazole) or vinclozolin (a di-carboximide). A total of 53 representative isolates were evaluated further for conidium germination and mycelium growth on fungicide-amended medium and for infection of geranium seedlings treated with thiophanate-methyl or vinclozolin at label rates. Isolates were considered sensitive to thiophanate-methyl or vinclozolin when the effective concentration of the fungicide active ingredient resulting in 50% inhibition of germination (EC50-germ) was ≤5 μg/ml or when the effective concentration of fungicide active ingredient resulting in 50% inhibition of mycelium growth (EC50-growth) was ≤1 μg/ml. Of all isolates, 81% (262/325) were resistant to thiophanate-methyl and 69% (223/325) were resistant to vinclozolin. Four phenotypes were observed: sensitive to both fungicides (17%), resistant to both fungicides (67%), resistant only to thiophanate-methyl (14%), and resistant only to vinclozolin (2%). Isolates resistant to at least one fungicide were found in 33 of the 35 locations from which samples were taken. Disease incidences on geranium seedlings treated with 600 μg/ml of thiophanate-methyl and then inoculated with isolates sensitive and resistant to this fungicide were 1.4 and 96.1%, respectively. Disease incidences on geranium seedlings treated with 600 μg/ml of vinclozolin and then inoculated with isolates sensitive and resistant to this fungicide were 0.3 and 91.9%, respectively. With thiophanate-methyl, correlation coefficients (r) between disease incidence and log EC50-germ or log EC50-growth were 0.987 and 0.992, respectively. With vinclozolin, correlation coefficients between disease incidence and log EC50-germ and log EC50-growth were 0.975 and 0.893, respectively. Correlation coefficients between the two EC50 values for thiophanate-methyl were 0.989 and for vinclozolin were 0.900. Isolates sensitive to thiophanate-methyl had a mean EC50-germ value of 0.93 μg/ml and a EC50-growth value of 0.11 μg/ml. For isolates sensitive to vinclozolin the mean EC50-germ value was 1.63 μg/ml and the mean EC50-growth value was 0.26 μg/ml. Thiophanate-methyl-resistant isolates had mean EC50-germ and EC50-growth values greater than 500 μg/ml while vinclozolin-resistant isolates had a mean EC50-germ value greater than 500 μg/ml and a mean EC50-growth value of 3.18 μg/ml.

First Report of Resistance to Boscalid in Podosphaera xanthii, Cucurbit Powdery Mildew, in South Carolina

2018 ◽  
Vol 19 (3) ◽  
pp. 220-221 ◽  
Author(s):  
Anthony P. Keinath ◽  
Gabriel Rennberger ◽  
Chandrasekar S. Kousik
Keyword(s):  
South Carolina ◽  
Powdery Mildew ◽  
Fungicide Resistance ◽  
Southern United States ◽  
Podosphaera Xanthii ◽  
Powdery Mildew Fungus ◽  
Action Committee ◽  
Summer Squash ◽  
Laboratory Bioassays ◽  
Cucurbit Powdery Mildew

Resistance to boscalid, one of the older succinate-dehydrogenase inhibitors (SHDI) in Fungicide Resistance Action Committee (FRAC) code 7, was detected in Podosphaera xanthii, the cucurbit powdery mildew fungus, in South Carolina in July 2017. Resistance to the field rate (682 ppm) of boscalid was confirmed in greenhouse experiments and laboratory bioassays conducted on summer squash plants and cotyledons, respectively, that had been treated with a range of boscalid concentrations. This report is the first documentation of resistance to boscalid in P. xanthii in the southern United States.

scholarly journals Resistance in Colletotrichum siamense From Peach and Blueberry to Thiophanate-Methyl and Azoxystrobin

Plant Disease ◽  
2015 ◽  
Vol 99 (6) ◽  
pp. 806-814 ◽  
Author(s):  
Meng-Jun Hu ◽  
Anja Grabke ◽  
Madeline E. Dowling ◽  
Helen J. Holstein ◽  
Guido Schnabel
Keyword(s):  
South Carolina ◽  
Field Resistance ◽  
Fruit Rot ◽  
Nucleotide Sequence Analysis ◽  
Cytb Gene ◽  
Single Spore ◽  
Peach Fruit ◽  
Thiophanate Methyl ◽  
Colletotrichum Siamense ◽  
Commercial Operation

Anthracnose fruit rot was observed in some late-season peach cultivars in South Carolina in the 2012 and 2013 production seasons as well as increased anthracnose leaf spot of blueberry in a commercial operation of the same state in 2012. Single-spore isolates of Colletotrichum siamense were either sensitive or resistant to both thiophanate-methyl and azoxystrobin with the concentration of the fungicide at which fungal development is inhibited by 50% of ≥100 μg/ml. Resistant isolates revealed the E198A mutation in β-tubulin and the G143A mutation in cytochrome b. Nucleotide sequence analysis of the complete CYTB gene from genomic DNA of C. siamense isolates revealed an intronless genotype (CsI) and a genotype revealing two introns (CsII) at amino acid positions 131 and 164. Resistance to thiophanate-methyl or azoxystrobin was not found in isolates of C. fructicola collected from peach fruit. The CYTB gene of isolates of this species was of the CfII genotype or revealed a unique CfIIa genotype. Phylogenetic analysis of C. siamense isolates from different locations and different crops showed that the resistant isolates were genetically closer to each other than to sensitive isolates, suggesting that field resistance to thiophanate-methyl and azoxystrobin fungicides is derived from a common ancestor.

scholarly journals Relationship Between Fungicide Sensitivity and Control of Gummy Stem Blight of Watermelon Under Field Conditions

Plant Disease ◽  
2012 ◽  
Vol 96 (12) ◽  
pp. 1780-1784 ◽  
Author(s):  
A. Thomas ◽  
D. B. Langston ◽  
H. F. Sanders ◽  
K. L. Stevenson
Keyword(s):  
Fungicide Resistance ◽  
Field Experiments ◽  
In Vitro Assays ◽  
Didymella Bryoniae ◽  
Fungicide Sensitivity ◽  
Thiophanate Methyl ◽  
Stem Blight ◽  
Gummy Stem Blight ◽  
And Control

Gummy stem blight (GSB), caused by the fungus Didymella bryoniae, is the most destructive disease of watermelon and is managed primarily with fungicides. D. bryoniae has developed resistance to many fungicides that were once very effective, including azoxystrobin, boscalid, and thiophanate-methyl. Field experiments were conducted in Tifton (TN) and Reidsville (RV), GA in 2009 and 2010 to establish a relationship between frequency of resistance to a fungicide based on in vitro assays and its efficacy in the management of GSB. Frequency of resistance to boscalid, thiophanate-methyl, and azoxystrobin was >0.80 in isolates collected from nontreated plots in both locations and years. All isolates collected after six applications of boscalid, thiophanate-methyl, or azoxystrobin were resistant to the respective fungicide. All isolates collected from treated and nontreated plots were sensitive to tebuconazole and difenoconazole. GSB severity was assessed on a weekly basis from 63 days after planting. GSB severity in plots treated with boscalid, thiophanate-methyl, or azoxystrobin was not significantly different from that in the nontreated plots (39%, TN-2009; 45%, TN-2010; and 16%, RV-2010). GSB severity in tebuconazole-treated plots (27%, TN-2009; 14%, TN-2010; and 4%, RV-2010) was significantly lower than all other treatments and the nontreated control. There was a consistent negative association between frequency of fungicide resistance and disease control in the field. Thus, knowledge of the frequency of fungicide resistance in the pathogen population will be helpful in selecting the most effective fungicides for the management of GSB in watermelon fields.

scholarly journals Identification of Resistance to Multiple Fungicides in Field Populations of Venturia inaequalis

Plant Disease ◽  
2011 ◽  
Vol 95 (8) ◽  
pp. 921-926 ◽  
Author(s):  
Kimberly S. Chapman ◽  
George W. Sundin ◽  
Janna L. Beckerman
Keyword(s):  
Fungicide Resistance ◽  
Mycelial Growth ◽  
Venturia Inaequalis ◽  
Apple Scab ◽  
Field Resistance ◽  
Single Spore ◽  
Mycelium Growth ◽  
Thiophanate Methyl ◽  
Development Of Resistance

Venturia inaequalis, the causal agent of apple scab, is controlled primarily by fungicides. Long-term, extensive fungicide use has led to the development of resistance to multiple fungicides. To assess fungicide resistance, isolates of V. inaequalis were collected from Indiana and Michigan orchards. Single-spore derived isolates were evaluated by mycelium growth assays with previously determined discriminatory doses on media containing dodine, kresoxim-methyl, myclobutanil, or thiophanate-methyl. Of 195 isolates tested, 5.2, 0.7, 57.0, and 92.6% of isolates were found to be resistant to dodine, kresoxim-methyl, myclobutanil, and thiophanate-methyl, respectively. This is the first report of kresoxim-methyl field resistance in these states. Isolates resistant or shifted to a single fungicide were often found to have multiple fungicide resistance. Of all isolates tested, 38% were identified as resistant or shifted to two fungicides, and 12% were resistant or shifted to all four fungicides tested. No fitness penalty was found for isolates resistant to multiple fungicides based on a statistical analysis of mycelial growth and conidial production.

Does Erosion Corrosion Account for Intriguing Damage to the Civil War Submarine H.L. Hunley?1

2012 ◽  
Vol 46 (6) ◽  
pp. 38-48 ◽  
Author(s):  
Maria Jacobsen ◽  
Vincent Y. Blouin ◽  
William Shirley
Keyword(s):  
South Carolina ◽  
Civil War ◽  
Marine Environment ◽  
Combined Effects ◽  
Site Specific ◽  
Erosion Corrosion ◽  
Ballast Tanks

AbstractExcavation of the Civil War submarine H.L. Hunley, raised from the seabed off Charleston, South Carolina, has revealed large hull breaches in the fore and aft sections of the vessel. Initially, the damage was thought to have occurred the night the pioneering submarine sank in 1864, but recent hull forensic studies indicate that the two largest breaches in the submarine’s ballast tanks occurred due to natural and site-specific seabed conditions and did not contribute to the submarine’s demise. To reconstruct and interpret these conditions, a new methodology has been developed that utilizes forensic data embedded in the marine concretion covering the iron hull. Results from an experiment conducted to test the theory further support the notion that the largest breaches were likely caused by the combined effects of erosion and corrosion of the iron hull in the marine environment.

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