First Report of Fludioxonil Resistance in Botrytis cinerea, the Causal Agent of Gray Mold, from Strawberry Fields in Maryland and South Carolina

Botrytis cinerea Pers. is the causal agent of gray mold and one of the most economically important plant-pathogenic fungi affecting strawberry (Fragaria × ananassa). Control of gray mold mainly depends on the use of site-specific fungicides, including the phenylpyrrole fludioxonil. This fungicide is currently registered in combination with cyprodinil in form of Switch 62.5WG (Syngenta Crop Protection, Greensboro, NC) for gray mold control of small fruits in the United States. In June 2013, strawberries affected with symptoms resembling gray mold were observed despite the application of Switch in one field located in Federalsburg, MD, and one located near Chesnee, SC. Ten single-spore isolates, each from a different fruit, were obtained from each location and confirmed to be B. cinerea using cultural and molecular tools as described previously (3). In vitro sensitivity to fludioxonil (Scholar SC, 20.4% [v/v] active ingredient, Syngenta Crop Protection, Greensboro, NC) was determined using a conidial germination assay as previously described (4). Eight of the 20 isolates (six from Maryland and two from South Carolina) were moderately resistant to fludioxonil, i.e., they grew on medium amended with 0.1 μg/ml fludixonil and showed residual growth at 10 μg/ml (4). The in vitro assay was repeated obtaining the same results. To assess in vivo sensitivity on fungicide-treated fruit, commercially grown strawberries were rinsed with water, dried, and sprayed 4 h prior to inoculation with either water or 2.5 ml/liter of Scholar SC to runoff using a hand mister. Fruit was stab-wounded with a sterile syringe and inoculated with a 30-μl droplet of conidia suspension (106 spores/ml) of either two sensitive or four resistant isolates (two isolates from Maryland and two isolates from South Carolina). Each isolate/treatment combination consisted of 24 mature but still firm strawberry fruit with three 8-fruit replicates. The fruit were kept at 22°C and lesion diameters were measured after 4 days of inoculation. The sensitive isolates developed gray mold symptoms on nontreated (2.5 cm lesion diameter) but not on Scholar SC-treated fruit. The resistant isolates developed gray mold on both, the water-treated control (2.3 cm lesion diameter), and the fungicide-treated fruit (1.8 cm lesion diameter). The experiment was performed twice. To our knowledge this is the first report of fludioxonil resistance in B. cinerea from strawberry fields in Maryland and South Carolina. Resistance to fludioxonil is still rare in the United States and has only been reported in B. cinerea isolates from a Virginia strawberry field (1). The increase in occurrence of resistance to fludioxonil may be a result of increased use of Switch following reports of resistance to other chemical classes in this pathogen in southern strawberry fields (2). References: (1) D. Fernández-Ortuño et al. Plant Dis. 97:848, 2013. (2) D. Fernández-Ortuño et al. Plant Dis. 96:1198, 2012. (3) D. Fernández-Ortuño et al. Plant Dis. 95:1482, 2011. (4) R. W. S. Weber and M. Hahn. J. Plant Dis. Prot. 118:17, 2011.

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First Report of Fludioxonil Resistance in Botrytis cinerea from a Blackberry Field in Georgia

Plant Disease ◽

10.1094/pdis-10-13-1020-pdn ◽

2014 ◽

Vol 98 (6) ◽

pp. 848-848 ◽

Cited By ~ 6

Author(s):

D. Fernández-Ortuño ◽

A. Grabke ◽

P. K. Bryson ◽

E. D. Beasley ◽

L. A. Fall ◽

...

Keyword(s):

South Carolina ◽

Botrytis Cinerea ◽

Crop Protection ◽

The United States ◽

Gray Mold ◽

Resistant Isolate ◽

Malt Extract ◽

First Report ◽

Control Fruit ◽

Lesion Diameter

Botrytis cinerea Pers. is an important plant-pathogenic fungi responsible for gray mold on more than 230 plant species worldwide, including blackberry (Rubus). One of the main strategies to control the disease involves the application of different classes of fungicides. The phenylpyrrole fludioxonil is currently marketed in combination with the anilinopyrimidine cyprodinil as Switch 62.5WG (Syngenta Crop Protection Inc., Greensboro, NC) for gray mold control. In August 2013, blackberries affected with symptoms resembling gray mold were collected from a field located in Berrien County (Georgia), where Switch 62.5WG had been used extensively over the last 5 years. Three single-spore isolates, each from a different fruit, were obtained and identified as B. cinerea on the basis of morphology and confirmed by a 238-bp PCR amplification product obtained with primer set G3PDH-F1 (5′-GGACCCGAGCTAATTTATGTCACGT-3′), G3PDH-F2 (5′-GGGTGTCAACAACGAGACCTACACT-3′), and G3PDH-R (5′-ACCGGTGCTCGATGGGATGAT-3′). In vitro sensitivity to fludioxonil (Scholar SC, Syngenta) was determined on 1% malt extract agar (MEA) using a conidial germination assay as previously described (4). One isolate was moderately resistant due to growth on medium amended with the discriminatory dose of 0.1 μg/ml fludioxonil and residual growth at 10 μg/ml (4). To assess performance of fludioxonil in detached fruit assays, commercially grown strawberries (24 in total for each isolate and treatment) were rinsed with water, dried, and sprayed 4 h prior to inoculation with either water (control fruit) or 2.5 ml/liter of Scholar SC to runoff using a hand mister. Scholar SC was used because fludioxonil was the sole active ingredient in this product and strawberries were used because latent infections in fresh blackberry fruit interfered with inoculation experiments. This dose reflects the rate recommended for postharvest gray mold control according to the Scholar label. Fruit was stab-wounded with a sterile syringe and inoculated with a 30-μl droplet of conidia suspension (106 spores/ml) of the two sensitive or the resistant isolate. After inoculation, the fruit were kept at 22°C for 4 days. The sensitive isolates developed gray mold on non-treated (2.7 cm lesion diameter) but not on Scholar SC-treated fruit (0.0 cm lesion diameter). The resistant isolate developed gray mold disease on the water-treated control fruit (2.5 cm lesion diameter) and the fungicide-treated fruit (1.8 cm lesion diameter). EC50 values were determined in microtiter assays as described previously (3) using the concentrations of 0.01, 0.04, 0.12, 0.37, 1.1, 3.3, and 10 μg/ml fludioxonil. Values were 0.02 and 0.05 μg/ml for the two sensitive isolates and 3.15 μg/ml for the resistant isolate. All experiments were performed twice. This is the first report of fludioxonil resistance in B. cinerea from blackberry in Georgia. Prior to this study, resistance to fludioxonil in B. cinerea was reported in France, Germany, and only a few states in the United States including Maryland, South Carolina, Virginia, and Washington (1,2). The emergence of resistance to fludioxonil emphasizes the importance of resistance management strategies. References: (1) D. Fernández-Ortuño et al. Plant Dis. 97:848, 2013. (2) D. Fernández-Ortuño et al. Plant Dis. 98:692, 2013. (3) M. Kretschmer et al. PLOS Pathog. 5:e1000696, 2009. (4) R. W. S. Weber and M. Hahn. J. Plant Dis. Prot. 118:17, 2011.

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Characterization of Botrytis cinerea Isolates from Strawberry with Reduced Sensitivity to Polyoxin D Zinc Salt

Plant Disease ◽

10.1094/pdis-02-16-0166-re ◽

2016 ◽

Vol 100 (10) ◽

pp. 2057-2061 ◽

Cited By ~ 5

Author(s):

Madeline E. Dowling ◽

Meng-Jun Hu ◽

Linus T. Schmitz ◽

Jennifer R. Wilson ◽

Guido Schnabel

Keyword(s):

United States ◽

South Carolina ◽

Botrytis Cinerea ◽

Tomato Fruit ◽

Resistance Management ◽

The United States ◽

Gray Mold ◽

Zinc Salt ◽

Malt Extract ◽

Action Committee

Polyoxin D is a Fungicide Resistance Action Committee (FRAC) code 19 fungicide that was recently registered for gray mold control of strawberry in the United States. In this study, we determined the sensitivity to polyoxin D zinc salt (hereafter, polyoxin D) of Botrytis cinerea isolates from 41 commercial strawberry farms in South Carolina, North Carolina, Maryland, Virginia, and Ohio and investigated the fitness of sensitive (S) and reduced sensitive (RS) isolates. Relative mycelial growth ranged between 0 and over 100% on malt extract agar amended with a discriminatory dose of polyoxin D at 5 μg/ml. Isolates that grew more than 70% at that dose were designated RS and were found in three of the five states. The 50% effective dose (EC50) values of three S and three RS isolates ranged from 0.59 to 2.27 and 4.6 to 5.8 μg/ml, respectively. The three RS isolates grew faster on detached tomato fruit treated with Ph-D WDG at recommended label dosage than S isolates (P < 0.008). In all, 25 randomly selected RS isolates exhibited reduced sporulation ability (P < 0.0001) and growth rate (P < 0.0001) but increased production of sclerotia (P < 0.0386) compared with 25 S isolates. Of 10 isolates tested per phenotype, the number of RS isolates producing sporulating lesions on apple, tomato, and strawberry was significantly lower compared with S isolates (P < 0.0001 for each fruit type). The results of this study indicate that resistance management is necessary for fungicides containing polyoxin D. To our knowledge, this is the first study demonstrating reduced sensitivity to FRAC 19 fungicides in B. cinerea isolates from the United States.

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First Report of Resistance to Mefenoxam in Phytophthora cactorum in the United States and Elsewhere

Plant Disease ◽

10.1094/pdis.2004.88.5.576a ◽

2004 ◽

Vol 88 (5) ◽

pp. 576-576 ◽

Cited By ~ 18

Author(s):

S. N. Jeffers ◽

G. Schnabel ◽

J. P. Smith

Keyword(s):

United States ◽

South Carolina ◽

Tap Water ◽

Southeastern United States ◽

Crop Protection ◽

The United States ◽

Crown Rot ◽

Phytophthora Cactorum ◽

Mycelium Growth ◽

First Report

Phytophthora cactorum causes crown rot of strawberry (Fragaria × ananassa) (2), a disease that has been particularly severe during the last 5 years in the southeastern United States. In the fall of 2001, strawberry plants (cv. Camarosa) in a field in Lexington County, South Carolina exhibited typical crown rot symptoms (2) 1 to 2 weeks after transplanting, even though plants had been drenched with mefenoxam (Ridomil Gold; Syngenta Crop Protection, Greensboro, NC) immediately after transplanting. Initially, we observed leaves that had marginal necrosis, were smaller than normal, and were discolored. Soon after, diseased plants appeared stunted and unthrifty compared with other plants in the field, and some of these plants eventually wilted and died. Severely affected plants had necrotic roots and decayed crowns. Ten symptomatic plants were collected for isolation. In the laboratory, root and crown tissues were rinsed in running tap water and blotted dry, small pieces of necrotic tissue were placed aseptically on PAR-V8 selective medium (1), and isolation plates were placed at 20°C in the dark for up to 7 days. P. cactorum was recovered from six plants. Isolates produced characteristic asexual and sexual structures directly on the isolation plates (i.e., papillate sporangia on sympodial sporangiophores and oospores with paragynous antheridia) (2). A single hypha of an isolate from each plant was transferred to fresh PAR-V8, and pure cultures were stored on cornmeal agar in glass vials at 15°C in the dark. All six isolates from the Lexington County field and nine other isolates of P. cactorum from strawberry (three from South Carolina, three from North Carolina, and three from Florida) were tested for sensitivity to mefenoxam on fungicide-amended medium. Mefenoxam was added to 10% clarified V8 juice agar (cV8A) after autoclaving so the concentration in the medium was 100 ppm. Agar plugs from active colonies were transferred to mefenoxam-amended and nonamended cV8A (three replicates per treatment), plates were placed at 25°C in the dark for 3 days, and linear mycelium growth was measured. All six isolates from Lexington County were highly resistant to mefenoxam with mycelium growth relatively unrestricted on mefenoxam-amended medium (73 to 89% of that on nonamended medium). In comparison, the other nine isolates were sensitive to mefenoxam with mycelium growth severely restricted by 100 ppm of mefenoxam (0 to 7% of that on nonamended medium). To our knowledge, this is the first report of mefenoxam resistance in P. cactorum on strawberry or any other crop in the United States and elsewhere. Because mefenoxam is the primary fungicide used to manage Phytophthora crown rot in the southeastern United States, resistance may limit use of this fungicide in strawberry production. References: (1) A. J. Ferguson and S. N. Jeffers. Plant Dis. 83:1129, 1999. (2) E. Seemüller. Crown rot. Pages 50–51 in: Compendium of Strawberry Diseases, 2nd ed. J. L. Maas, ed. The American Phytopathological Society, St. Paul, MN, 1998.

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Resistance to Cyprodinil and Lack of Fludioxonil Resistance in Botrytis cinerea Isolates from Strawberry in North and South Carolina

Plant Disease ◽

10.1094/pdis-06-12-0539-re ◽

2013 ◽

Vol 97 (1) ◽

pp. 81-85 ◽

Cited By ~ 51

Author(s):

Dolores Fernández-Ortuño ◽

Fengping Chen ◽

Guido Schnabel

Keyword(s):

South Carolina ◽

Multidrug Resistance ◽

Botrytis Cinerea ◽

The United States ◽

Gray Mold ◽

Cross Resistance ◽

Single Spore ◽

Moderately Resistant ◽

North And South

Chemical control of gray mold of strawberry caused by Botrytis cinerea is essential to prevent pre- and postharvest fruit decay. For more than 10 years, the anilinopyrimidine (AP) cyprodinil and the phenylpyrrole fludioxonil (Switch 62.5WG) have been available to commercial strawberry producers in the United States for gray mold control. Both active ingredients are site-specific inhibitors and, thus, prone to resistance development. In this study, 217 single-spore isolates of B. cinerea from 11 commercial strawberry fields in North and South Carolina were examined for sensitivity to both fungicides. Isolates that were sensitive (53%), moderately resistant (30%), or resistant (17%) to cyprodinil were identified based on germ tube inhibition at discriminatory doses of cyprodinil at 1 and 25 mg/liter at 10 of the 11 locations. None of the isolates was fludioxonil resistant. Phenotypes that were moderately resistant or resistant to cyprodinil were not associated with fitness penalties for mycelial growth rate, spore production, or osmotic sensitivity. Detached fruit assays demonstrated cross resistance between the two AP fungicides cyprodinil and pyrimethanil, and that isolates that were characterized in vitro as moderately resistant or resistant were equivalent in pathogenicity on fruit sprayed with pyrimethanil (currently the only AP registered in strawberry as a solo formulation). This suggests that the in vitro distinction of moderately resistant and resistant isolates is of little if any field relevance. The absence of cross-resistance with fludioxonil, iprodione, cycloheximide, and tolnaftate indicated that multidrug resistance in the form of multidrug resistance phenotypes was unlikely to be involved in conferring resistance to APs in our isolates. Implications for resistance management and disease control are discussed.

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First Report of Fludioxonil Resistance in Botrytis cinerea from a Strawberry Field in Virginia

Plant Disease ◽

10.1094/pdis-01-13-0012-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 848-848 ◽

Cited By ~ 12

Author(s):

D. Fernández-Ortuño ◽

P. K. Bryson ◽

A. Grabke ◽

G. Schnabel

Keyword(s):

South Carolina ◽

Botrytis Cinerea ◽

Disease Incidence ◽

Crop Protection ◽

Gray Mold ◽

Resistant Isolate ◽

Single Spore ◽

First Report ◽

Single Spore Isolate

Gray mold caused by Botrytis cinerea Pers.:Fr. is one of the most economically important diseases of cultivated strawberry (Fragaria × ananassa) worldwide. Control of gray mold mainly depends on fungicides, including the phenylpyrrole fludioxonil, which is currently marketed in combination with cyprodinil as Switch 62.5WG (Syngenta Crop Protection, Research Triangle Park, Raleigh, NC). In 2012, 790 strains of B. cinerea were collected from 76 strawberry fields in eight states, including Arkansas, Florida, Georgia, Kansas, Maryland, North Carolina, South Carolina, and Virginia. Strains were collected from sporulating flowers and fruit and sensitivity to fludioxonil was determined using a conidial germination assay as previously described (2). Only one isolate from a farm located in Westmoreland County, Virginia, grew on medium amended with the discriminatory dose of 0.1 μg/ml fludioxonil and was therefore considered low resistant. The isolate did not grow on 10 μg/ml. All other 789 isolates did not grow at either of the two doses. This assay was repeated twice with a single-spore culture of the same strain. In both cases, residual growth was observed on the fludioxonil-amended medium of 0.1 μg/ml. The single spore isolate was confirmed to be B. cinerea Pers. using cultural and molecular tools as described previously (1). To assess resistance in vivo, commercially grown ripe strawberry fruit were rinsed with sterile water, dried, placed into plastic boxes (eight strawberries per box for each of the three replicates per treatment), and sprayed 4 h prior to inoculation with either water or 2.5 ml/liter of fludioxonil (Scholar SC, Syngenta) to runoff using a hand mister. This dose reflects the rate recommended for gray mold control according to the Scholar label. Each fruit was stabbed at three equidistant points, each about 1 cm apart and 1 cm deep using a syringe tip. Wounds were injected with a 30-μl droplet of conidia suspension (106 spores/ml) of either 5 sensitive or the resistant isolate. Control fruit were inoculated with water. After inoculation, the fruit were kept at 22°C for 4 days. In two independent experiments, sensitive and low resistant isolates were indistinguishable in pathogenicity on detached, unsprayed fruit. The low resistant isolate developed gray mold disease on all treated and untreated fruit (100% disease incidence) as determined by the absence or presence of gray mold symptoms. The sensitive isolates only developed disease on untreated fruit. The EC50 values, determined in microtiter assays with concentrations of 0.01, 0.03, 0.1, 0.3, 1, 3, and 10 μg/ml fludioxonil, were 0.01 μg/ml for the sensitive isolates and 0.26 μg/ml for the resistant isolate. To our knowledge, this is the first report of fludioxonil resistance in B. cinerea from strawberry in North America. Our monitoring results indicate that resistance is emerging 10 years after the introduction of fludioxonil and stress the importance of chemical rotation for gray mold control. References: (1) X. P. Li et al. Plant Dis. 96:1634, 2012. (2) R. W. S. Weber and M. Hahn. J. Plant Dis. Prot. 118:17, 2011.

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First Report of Botrytis mali Causing Gray Mold on Strawberry in the United States

Plant Disease ◽

10.1094/pdis-01-17-0054-pdn ◽

2017 ◽

Vol 101 (6) ◽

pp. 1034 ◽

Cited By ~ 7

Author(s):

M. E. Dowling ◽

G. Schnabel

Keyword(s):

United States ◽

The United States ◽

Gray Mold ◽

First Report

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AVALIAÇÃO DO REAL POTENCIAL INIBIDOR DE EXTRATOS ETANÓLICOS DE Ottonia martiana SOBRE Cylindrocladium spathulatum E Botrytis cinerea

FLORESTA ◽

10.5380/rf.v43i2.20199 ◽

2013 ◽

Vol 43 (2) ◽

pp. 225

Author(s):

Miriam Machado Cunico ◽

Celso Garcia Auer ◽

Marlon Wesley Machado Cunico ◽

Obdulio Gomes Miguel ◽

Patricio Peralta Zamora ◽

...

Keyword(s):

Factorial Design ◽

Botrytis Cinerea ◽

Mycelial Growth ◽

Black Spot ◽

Gray Mold ◽

Causal Agent ◽

In Vitro Testing ◽

Ethanolic Extracts ◽

Antifungal Potential

Extratos etanólicos de anestesia, Ottonia martiana Miq., foram reavaliados quanto à inibição do crescimento micelial dos fungos Cylindrocladium spathulatum (pinta-preta da erva-mate) e Botrytis cinerea (mofo-cinzento do eucalipto), por meio do planejamento fatorial. A ocorrência de decomposição de bioativos no processo de autoclavagem também foi investigada, por meio de teste de eficiência de extratos filtrados (filtro Millipore) e esterilizados (autoclave) no controle dos fitopatógenos, nas concentrações de 1, 10, 100 e 1000 ppm. Os extratos etanólicos filtrado e esterilizado inibiram o crescimento micelial dos fungos e foram mais ativos frente a B. cinerea.O extrato filtrado exibiu maior potencial antifúngico que o extrato esterilizado. O processo de esterilização por autoclavagem causou pequena decomposição dos bioativos presentes no extrato de anestesia.Palavras-chave: Anestesia; mofo-cinzento; pinta-preta. Abstract Fungitoxic potential of ethanolic extracts of anestesia in the control of phytopathogenic diseases. The antifungal potential of anestesia, Ottonia martiana Miq. was reassessed by factorial design, in vitro testing of fungal mycelial growth compared to the pathogenic isolates Cylindrocladium spathulatum, causal agent of black spot onyerba mate, and Botrytis cinerea causal agent of gray-mold on eucalypts. Occurrence of decomposition of bioactive of the autoclaving process was investigated using foliar detached test compared to the pathogens (1000 ppm). Ethanolic extracts - EBEtOH (filtered and autoclaved) inhibited the mycelial growth of C. spathulatum and B. cinerea (1000 ppm) and were more pronounced against B. cinerea (43.6 % and 68.9 %). EBEtOH filtered (0.22 µm) presented higher activity than EBEtOH autoclaved (C. spathulatum: 52.8 % and 43.6 %, B. cinerea: 68.9 % and 43.6 %), suggesting little decomposition ofbioactive after autoclaving. EBEtOH filtrate presented potential inhibition of 28 % in eucalypt leaves against B. cinerea. Keywords: Ottonia martiana; black spot; gray-mold.

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First Report of Stem and Foliage Blight of Chrysanthemum Caused by Phytophthora drechsleri in the United States

Plant Disease ◽

10.1094/pdis-03-21-0631-pdn ◽

2021 ◽

Author(s):

Charles Krasnow ◽

Nancy Rechcigl ◽

Jennifer Olson ◽

Linus Schmitz ◽

Steven N. Jeffers

Keyword(s):

United States ◽

South Carolina ◽

Sequence Similarity ◽

Morphological Characteristics ◽

The United States ◽

Universal Primers ◽

Broad Host Range ◽

Pathogenicity Test ◽

First Report ◽

Foliage Blight

Chrysanthemum (Chrysanthemum × morifolium) plants exhibiting stem and foliage blight were observed in a commercial nursery in eastern Oklahoma in June 2019. Disease symptoms were observed on ~10% of plants during a period of frequent rain and high temperatures (26-36°C). Dark brown lesions girdled the stems of symptomatic plants and leaves were wilted and necrotic. The crown and roots were asymptomatic and not discolored. A species of Phytophthora was consistently isolated from the stems of diseased plants on selective V8 agar (Lamour and Hausbeck 2000). The Phytophthora sp. produced ellipsoid to obpyriform sporangia that were non-papillate and persistent on V8 agar plugs submerged in distilled water for 8 h. Sporangia formed on long sporangiophores and measured 50.5 (45-60) × 29.8 (25-35) µm. Oospores and chlamydospores were not formed by individual isolates. Mycelium growth was present at 35°C. Isolates were tentatively identified as P. drechsleri using morphological characteristics and growth at 35°C (Erwin and Ribeiro 1996). DNA was extracted from mycelium of four isolates, and the internal transcribed spacer (ITS) region was amplified using universal primers ITS 4 and ITS 6. The PCR product was sequenced and a BLASTn search showed 100% sequence similarity to P. drechsleri (GenBank Accession Nos. KJ755118 and GU111625), a common species of Phytophthora that has been observed on ornamental and vegetable crops in the U.S. (Erwin and Ribeiro 1996). The gene sequences for each isolate were deposited in GenBank (accession Nos. MW315961, MW315962, MW315963, and MW315964). These four isolates were paired with known A1 and A2 isolates on super clarified V8 agar (Jeffers 2015), and all four were mating type A1. They also were sensitive to the fungicide mefenoxam at 100 ppm (Olson et al. 2013). To confirm pathogenicity, 4-week-old ‘Brandi Burgundy’ chrysanthemum plants were grown in 10-cm pots containing a peat potting medium. Plants (n = 7) were atomized with 1 ml of zoospore suspension containing 5 × 103 zoospores of each isolate. Control plants received sterile water. Plants were maintained at 100% RH for 24 h and then placed in a protected shade-structure where temperatures ranged from 19-32°C. All plants displayed symptoms of stem and foliage blight in 2-3 days. Symptoms that developed on infected plants were similar to those observed in the nursery. Several inoculated plants died, but stem blight, dieback, and foliar wilt were primarily observed. Disease severity averaged 50-60% on inoculated plants 15 days after inoculation. Control plants did not develop symptoms. The pathogen was consistently isolated from stems of symptomatic plants and verified as P. drechsleri based on morphology. The pathogenicity test was repeated with similar results. P. drechsleri has a broad host range (Erwin and Ribeiro 1996; Farr et al. 2021), including green beans (Phaseolus vulgaris), which are susceptible to seedling blight and pod rot in eastern Oklahoma. Previously, P. drechsleri has been reported on chrysanthemums in Argentina (Frezzi 1950), Pennsylvania (Molnar et al. 2020), and South Carolina (Camacho 2009). Chrysanthemums are widely grown in nurseries in the Midwest and other regions of the USA for local and national markets. This is the first report of P. drechsleri causing stem and foliage blight on chrysanthemum species in the United States. Identifying sources of primary inoculum may be necessary to limit economic loss from P. drechsleri.

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First Report of Fludioxonil Resistance in Botrytis cinerea, the Causal Agent of Gray Mold, From Strawberry Fields in Spain

Plant Disease ◽

10.1094/pdis-02-16-0172-pdn ◽

2016 ◽

Vol 100 (8) ◽

pp. 1779-1779

Author(s):

D. Fernández-Ortuño ◽

J. A. Torés ◽

A. Pérez-García ◽

A. de Vicente

Keyword(s):

Botrytis Cinerea ◽

Gray Mold ◽

Causal Agent ◽

First Report

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First Report of Tobacco ringspot virus in Blackberry (Rubus sp.) in Alabama

Plant Disease ◽

10.1094/pdis-92-12-1708c ◽

2008 ◽

Vol 92 (12) ◽

pp. 1708-1708 ◽

Cited By ~ 3

Author(s):

E. Coneva ◽

J. F. Murphy ◽

R. Boozer ◽

N. Velásquez

Keyword(s):

United States ◽

North Carolina ◽

South Carolina ◽

Virus Infection ◽

The United States ◽

Negative Control ◽

Ringspot Virus ◽

First Report ◽

Tobacco Ringspot Virus ◽

Control Samples

In 2006, primocane stunted growth and crumbly berry development were observed on 4-year-old Kiowa and Apache blackberry cultivars grown at the Chilton Research and Extension Center, Clanton, AL. Samples from affected plants were tested for virus infection by ELISA kits (Agdia, Inc., Elkhart, IN) specific to each of 14 different viruses. Most samples tested positive for Tobacco ringspot virus (TRSV). TRSV was detected in blackberry samples from North Carolina and South Carolina (2). Bray et al. (1) studied the incidence of viruses in blackberry nursery stock in the United States and reported that 9% of the tested samples contained TRSV. Thus, a survey was conducted for TRSV incidence among commercial blackberry stands in eight counties in Alabama during July 2007. Blackberry plants were observed to express virus-like symptoms including chlorotic spots on leaves, leaf veinal chlorosis, stunting, and combinations thereof. Fruit-bearing plants sometimes had crumbly fruit symptoms characteristic of virus infection. Leaf samples that were collected from symptomatic and nonsymptomatic plants representing 14 cultivars were tested by TRSV ELISA (Agdia, Inc.). Of 180 blackberry samples, 68 tested positive for TRSV. Positive ELISA reactions for TRSV were on average 28 times greater than the reactions of known negative control samples considered negative for TRSV. Blackberry plants shown to be infected with TRSV during the 2007 survey were tested in July 2008 in an effort to confirm the presence of TRSV. Fifty-four percent of the samples tested positive by ELISA with the average positive ELISA value being 21 times higher than the average negative ELISA value for known negative control samples. To further confirm the occurrence of TRSV in Alabama-grown blackberry plants, leaf samples were tested by reverse transcription (RT)-PCR to amplify a 329-bp fragment of the viral coat protein gene (TRSV RNA 2 sequence accession no. NC_005096; primers TRSCP-F (5′-TCTGGCACTATAAGCGGAAG-3′) and TRSCP-R (5′-GAAAACATGGGAGGATGCAC-3′). A single band of the anticipated size was amplified (analyzed by agarose gel electorphoresis and visualized by ethidium bromide staining) from RNA samples extracted with a RNeasy Mini kit (Qiagen, Valencia, CA) from blackberry samples that tested positive for TRSV by ELISA and a known positive control. No amplified product resulted from a blackberry sample that tested negative for TRSV by ELISA. These results illustrate and confirm the presence of TRSV in blackberry leaf tissues grown in Alabama. To our knowledge, this is the first report of TRSV infection of blackberry plants in Alabama. References: (1) M. M. Bray et al. HortScience 40:874, 2005. (2) T. L. Guzmán-Baeny. Incidence, distribution, and symptom description of viruses in cultivated blackberry (Rubus subgenus Eubatus) in the southeastern United States. M.S. thesis, North Carolina State University, Raleigh, 2003.

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