scholarly journals Stem Canker of Cabbage Seed Stalks Caused by Botrytis cinerea in Western Washington

Plant Disease ◽  
2001 ◽  
Vol 85 (5) ◽  
pp. 559-559
Author(s):  
D. Inglis ◽  
M. Derie ◽  
T. Hsiang
Keyword(s):  
Brassica Oleracea ◽  
Botrytis Cinerea ◽  
Mechanical Damage ◽  
Tween 80 ◽  
Stem Canker ◽  
The United States ◽  
Gray Mold ◽  
Freezing Injury ◽  
Razor Blade ◽  
Western Washington

Stem cankers were observed during 1998 on bolting stalks of cabbage (Brassica oleracea var. capitata L.) in seed production fields in western Washington. In 1999, approximately 4 ha of cabbage hybrid 'Wk 121, was severely affected. Lesions occurred at the base of seed stalks after they emerged from heads of plants overwintered in the field, or on flower branches and seed-bearing stalks that developed during the growing season. Lesions girdled a branch or stalk, and killed or weakened it so that it broke during pod fill. Isolates of Botrytis cinerea Pers.:Fr. were obtained by plating spores from lesions onto potato dextrose agar. To confirm pathogenicity, stems of 12-day-old seedlings of ‘Wk 121’ were scraped with a razor blade or left intact, atomized with sterile 0.01 % Tween 80 or a suspension of Botrytis cinerea at 1.0 × 106 conidia/ml, and kept at 20°C in a dew chamber in plastic bags. The fungus was reisolated from small lesions on wounded stems inoculated with B. cinerea after 3 days. No lesions developed on non-wounded or wounded control plants. B. cinerea is reported to cause storage rot of cabbage (2) and gray mold on Brassica oleracea L. (cabbage, kale, kohlrabi, wild cabbage) in Washington (1) but not stem canker. This new seed crop disease may be the result of predisposition to infection by freezing injury or mechanical damage on a highly susceptible cultivar grown under cool, wet weather. References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society. St. Paul, MN. (2) O. C. Yoder and M. L. Whalen. Can. J. Bot. 53:691, 1975.

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

Plant Disease ◽  
2016 ◽  
Vol 100 (10) ◽  
pp. 2057-2061 ◽  
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.

scholarly journals Gray Mold of Green Shiso (Perilla frutescens), Caused by Botrytis cinerea, in California

Plant Disease ◽  
2012 ◽  
Vol 96 (6) ◽  
pp. 908-908 ◽  
Author(s):  
S. T. Koike ◽  
O. Daugovish
Keyword(s):  
Botrytis Cinerea ◽  
Pathogenic Fungi ◽  
The United States ◽  
Gray Mold ◽  
Early Spring ◽  
Perilla Frutescens ◽  
Foliar Blight ◽  
Plastic Bags ◽  
Initial Symptoms ◽  
Blight Disease

Shiso (Perilla frutescens) is a leafy herb in the Lamiaceae family and is widely used in Japanese and other Asian cuisine for cooking, pickling, oil (from the seeds), and garnish. A number of shiso types are used, though the most common are green shiso (ao-shiso) and red shiso (aka-shiso). In the winter months of 2010 and early spring 2011, a foliar blight disease developed on greenhouse-grown green shiso produced in Ventura County, CA. Initial symptoms were angular, dull green leaf lesions on older foliage. Such lesions often were initiated along leaf edges. As the disease progressed, lesions turned gray green, expanded, and could affect most of the leaf surface. Lesion tissue became dry and papery in texture; signs of a pathogen were not present. Tests for bacterial agents were negative. However, a fungus was consistently isolated from symptomatic leaves. Isolates of this fungus were grown on potato dextrose agar (PDA) in petri plates incubated under fluorescent lights and were identified as Botrytis cinerea (1). On PDA, mycelial growth was gray brown and conidiophores measured 2 mm or longer and were branched at the terminals. Conidia were aseptate, hyaline, ellipsoidal, and measured (6.5–) 8.4 to 9.2 (–12.0) × (6.1–) 6.8 to 8.0 (–9.5) μm. Sclerotia were not present. Pathogenicity of four isolates was tested by spraying conidial suspensions (1 × 105 conidia/ml) until runoff onto sets of potted green and red shiso plants. Each set consisted of six wounded (leaf tips cut) and six unwounded plants. Plants were enclosed in plastic bags for 48 h and then maintained at 22 to 24°C in a greenhouse. After 4 days, leaf lesions developed on both wounded and unwounded leaves of green and red shiso. The resulting symptoms were similar to those observed in commercial production and B. cinerea was recovered from symptomatic tissue. Non-inoculated, wounded, and unwounded red and green shiso plants were sprayed with distilled water and did not develop symptoms. This experiment was conducted two times and results were the same. To our knowledge, this is the first report of gray mold of shiso in the United States caused by B. cinerea. The disease caused significant damage to the shiso crop because symptomatic leaves are unacceptable for market. In 2010, the greenhouse facility that contained the diseased shiso had numerous leaks in the roof; winter rains that occurred during this time therefore resulted in higher free moisture and humidity in the growing area, which likely provided optimum environmental conditions for the pathogen to infect and cause disease on shiso. Reference: (1) M. B. Ellis and J. M. Waller. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 431, 1974.

scholarly journals Fungicide Resistance Profiling in Botrytis cinerea Populations from Blueberry in California and Washington and Their Impact on Control of Gray Mold

Plant Disease ◽  
2016 ◽  
Vol 100 (10) ◽  
pp. 2087-2093 ◽  
Author(s):  
S. Saito ◽  
T. J. Michailides ◽  
C. L. Xiao
Keyword(s):  
Botrytis Cinerea ◽  
Fungicide Resistance ◽  
Resistance Management ◽  
Central Valley ◽  
Gray Mold ◽  
Postharvest Disease ◽  
Quinone Outside Inhibitor ◽  
Development Of Resistance ◽  
Western Washington ◽  
Moderately Resistant

Gray mold caused by Botrytis cinerea is a major postharvest disease of blueberry grown in the Central Valley of California and western Washington State. Sensitivities to boscalid, cyprodinil, fenhexamid, fludioxonil, and pyraclostrobin, representing five different fungicide classes, were examined for 249 (California) and 106 (Washington) B. cinerea isolates recovered from decayed blueberry fruit or flowers. In California and Washington, 7 and 17 fungicide-resistant phenotypes, respectively, were detected: 66 and 49% of the isolates were resistant to boscalid, 20 and 29% were moderately resistant to cyprodinil, 29 and 29% were resistant to fenhexamid, and 66 and 55% were resistant to pyraclostrobin. All isolates from California were sensitive to fludioxonil, whereas 70% of the isolates from Washington showed reduced sensitivity to fludioxonil. In California, 26 and 30% of the isolates were resistant to two and three classes of fungicides, respectively. In Washington, 31, 14, 16, and 9% of the isolates were resistant to two, three, four, and five classes of fungicides, respectively. Inherent risk of the development of resistance to quinone outside inhibitor (QoI) fungicides was assessed by detecting the presence of the Bcbi-143/144 intron in gene cytb. The intron was detected in 11.8 and 40% of the isolates in California and Washington, respectively, suggesting that the risk of QoI resistance is higher in California than in Washington. On detached blueberry fruit inoculated with 11 isolates exhibiting different fungicide-resistant phenotypes, most fungicides failed to control gray mold on fruit inoculated with the respective resistant phenotypes but the mixture of cyprodinil and fludioxonil was effective against all fungicide-resistant phenotypes tested. Our findings would be useful in designing and implementing fungicide resistance management spray programs for control of gray mold in blueberry.

scholarly journals Independent Emergence of Resistance to Seven Chemical Classes of Fungicides in Botrytis cinerea

2015 ◽  
Vol 105 (4) ◽  
pp. 424-432 ◽  
Author(s):  
Dolores Fernández-Ortuño ◽  
Anja Grabke ◽  
Xingpeng Li ◽  
Guido Schnabel
Keyword(s):  
United States ◽  
Botrytis Cinerea ◽  
Target Genes ◽  
Management Strategies ◽  
Resistance Management ◽  
Monitoring Program ◽  
Gene Mutations ◽  
The United States ◽  
Gray Mold ◽  
Development Of Resistance

Gray mold, caused by the fungal pathogen Botrytis cinerea, is one of the most destructive diseases of small fruit crops and control is largely dependent on the application of fungicides. As part of a region-wide resistance-monitoring program that investigated 1,890 B. cinerea isolates from 189 fields in 10 states of the United States, we identified seven isolates (0.4%) from five locations in four different states with unprecedented resistance to all seven Fungicide Resistance Action Committee (FRAC) codes with single-site modes of action including FRAC 1, 2, 7, 9, 11, 12, and 17 registered in the United States for gray mold control. Resistance to thiophanate-methyl, iprodione, boscalid, pyraclostrobin, and fenhexamid was based on target gene mutations that conferred E198A and F200Y in β-tubulin, I365N/S in Bos1, H272R/Y in SdhB, G143A in Cytb, and T63I and F412S in Erg27. Isolates were grouped into MDR1 and MDR1h phenotypes based on sensitivity to fludioxonil and variations in transcription factor mrr1. MDR1h isolates had a previously described 3-bp deletion at position 497 in mrr1. Expression of ABC transporter atrB was increased in MDR1 isolates but highest in MDR1h isolates. None of the isolates with seven single resistances (SR) had identical nucleotide variations in target genes, indicating that they emerged independently. Multifungicide resistance phenotypes did not exhibit significant fitness penalties for the parameters used in this study, but MDR1h isolates produced more sclerotia at low temperatures and exhibited increased sensitivity to salt stress. In this study we show that current resistance management strategies have not been able to prevent the geographically independent development of resistance to all seven site-specific fungicides currently registered for gray mold control in the United States and document the presence of MDR1h in North America.

scholarly journals Sources of Primary Inoculum of Botrytis cinerea and Their Impact on Fungicide Resistance Development in Commercial Strawberry Fields

Plant Disease ◽  
2017 ◽  
Vol 101 (10) ◽  
pp. 1761-1768 ◽  
Author(s):  
Michelle Souza Oliveira ◽  
Achour Amiri ◽  
Adrian I. Zuniga ◽  
Natalia A. Peres
Keyword(s):  
United States ◽  
Botrytis Cinerea ◽  
Fungicide Resistance ◽  
Integrated Approach ◽  
The United States ◽  
Gray Mold ◽  
Resistance Development ◽  
Primary Inoculum ◽  
Potential Source ◽  
Northern United States

Strawberry transplants produced in nurseries across Canada, northern United States, and California are shipped annually to other strawberry-growing regions, including Florida. Botrytis cinerea, the causal agent of gray mold, causes latent infections on transplants which are suggested as a potential source of primary inoculum in strawberry fields. In this study, we investigated the survival of B. cinerea isolates over the summer in Florida, the presence of B. cinerea in transplants from 14 nurseries from Canada and the United States in 2011, 2012, and 2013, and the sensitivity of nursery population to several botryticides. Botrytis cinerea was detected on dead strawberry plants sampled from commercial strawberry fields between March and June but not in July and August, suggesting that the fungus does not over-summer in strawberry fields in Florida. Nursery transplants surveyed in 2011, 2012, and 2013 showed B. cinerea incidences of 20 to 37, 20 to 83, and 2.5 to 92.5%, respectively. In total, 409 isolates were tested for sensitivity to pyraclostrobin, boscalid, pyrimethanil, fenhexamid, iprodione, penthiopyrad, fluopyram, and fludioxonil. Overall, respective resistance frequencies were 91.7, 79.3, 33.2, 20.7, 2.4, 0.2, 0.2, and 0.0%. A majority of isolates tested were resistant to either 3 or 4 fungicides simultaneously. These findings reinforce the need for an integrated approach between strawberry nurseries and production fields to improve gray mold management and mitigate future risks of resistance development in B. cinerea.

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

Plant Disease ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 848-848 ◽  
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.

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

Plant Disease ◽  
2014 ◽  
Vol 98 (5) ◽  
pp. 692-692 ◽  
Author(s):  
D. Fernández-Ortuño ◽  
A. Grabke ◽  
P. K. Bryson ◽  
R. J. Rouse ◽  
P. Rollins ◽  
...  
Keyword(s):  
United States ◽  
South Carolina ◽  
Botrytis Cinerea ◽  
Crop Protection ◽  
The United States ◽  
Gray Mold ◽  
Causal Agent ◽  
First Report ◽  
Lesion Diameter

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.

scholarly journals Evidence that Cercospora carotae Causes Leaf Spot on Carrot in Western Washington

Plant Disease ◽  
2001 ◽  
Vol 85 (5) ◽  
pp. 559-559
Author(s):  
D. A. Inglis ◽  
M. L. Derie ◽  
K. C. Volker
Keyword(s):  
Leaf Spot ◽  
Leaf Tissue ◽  
Tween 80 ◽  
The United States ◽  
Cercospora Leaf Spot ◽  
Disease Symptoms ◽  
Daucus Carota L ◽  
Clear Plastic ◽  
Western Washington ◽  
Cercospora Carotae

During 1999, a leaf spot on carrot (Daucus carota L. subsp. sativus [Hoffm.] Arcang.) was observed on nearly every plant in a 20-ha field of carrots (cv. Red Chantenay) grown for processing in western Washington. Circular to elongate, light brown lesions surrounded by chlorosis were present on leaflet margins and petioles of affected plants. Conidia of Cercospora carotae (Pass.) Solheim were present in the lesions. Small pieces of surface-sterilized leaf tissue were placed onto potato dextrose agar plates and incubated at room temperature to obtain fungal isolates. Koch's postulates were completed by atomizing the upper and lower leaves of carrot seedlings at the three to four leaf stage with sterile water or C. carotae at 1.0 × 104 conidia/ml in sterile 0.01% Tween 80. Treatments were replicated five times using single plants. The plants were bagged in clear plastic and placed in a greenhouse at 25°C for 72 h. Disease symptoms developed within 10 days as light brown lesions on leaflet margins and petioles, and were similar to those found in the field. The fungus was reisolated as described above. Symptoms did not develop in control plants sprayed with water. Farr et al. (1) report that C. carotae occurs in several states but not Washington, and Shaw (2) lists C. carotae only from British Columbia and Oregon. To our knowledge, this is the first report of Cercospora leaf spot on carrot in Washington. References: (1) D. F. Farr et al. 1989. Fungi on Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN. (2) C. G. Shaw. W.S.U. Agric. Exp. Sta. Bull. 765, 1969.

scholarly journals First Report of Botrytis cinerea Causing Gray Mold of Pomegranate (Punica granatum) in Greece

Plant Disease ◽  
2009 ◽  
Vol 93 (12) ◽  
pp. 1346-1346 ◽  
Author(s):  
G. A. Bardas ◽  
G. D. Tzelepis ◽  
L. Lotos ◽  
G. S. Karaoglanidis
Keyword(s):  
Botrytis Cinerea ◽  
Morphological Characteristics ◽  
Punica Granatum ◽  
The United States ◽  
Gray Mold ◽  
Fruit Rot ◽  
American Phytopathological Society ◽  
First Report ◽  
Surface Sterilization ◽  
Food Agric

Pomegranate is rapidly increasing in production in Greece. During August of 2008 in the region of Larisa (central Greece), preharvest fruit rot was observed on pomegranate (cv. Kapmaditika) that caused losses estimated at 10%. Symptoms first appeared as small spots on the fruits that later increased in size and developed into expanded, dark brown lesions. Internally, tissues were soft and brown with gray mycelia and conidiophores observed. Affected fruits decayed completely during 2 months of storage (5 to 6°C), causing yield losses of up to 20%. To isolate the casual agent, conidia and conidiophores were scraped aseptically from the internal tissues, suspended in sterile water, and streaked onto the surface of potato dextrose agar (PDA). Single hyphal tips were transferred to PDA, and the isolated fungus was identified as Botrytis cinerea Pers.:Fr. on the basis of morphological characteristics (2). B. cinerea was consistently isolated from symptomatic tissues. Colonies of B. cinerea on PDA were at first colorless and became gray to brown with the development of lemon-shaped conidia (average 7.5 × 9 μm). Sclerotia were black and varied in size (1.4 to 4.5 × 1.5 to 2.7 mm) and shape (2). Pathogenicity of the isolated fungus was tested by wound inoculating five mature pomegranate fruits (cv. Kampaditika) after surface sterilization with 5% sodium hypochlorite. Plugs of the fungus (5 mm in diameter) obtained from the colony margins were transferred onto a 3- × 3-mm wound on the surface of sterilized fruit. Sterile PDA plugs were used to inoculate five control pomegranate fruits. Fruit were incubated at 22°C and 80% relative humidity in the dark. Extensive decay, similar to that observed on diseased fruits in the field, was observed on inoculated fruits 7 days after inoculation, whereas control fruits showed no decay. The pathogen was reisolated from internal rotten tissues of inoculated fruit, but not from the noninoculated control fruits. Fruit rot of pomegranate caused by B. cinerea has been reported previously in the United States (1) and China (3). However, to our knowledge, this is the first report of B. cinerea causing gray mold of pomegranate in Greece. References: (1) A. M. French. California Plant Disease Host Index. Calif. Dept. Food Agric., Sacramento, 1989. (2) W. B. Hewitt. Compendium of Grape Diseases. American Phytopathological Society, 1994. (3) Z. Zhang. Flora Fungorum Sinicorum 26:277, 2006.

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

Plant Disease ◽  
2013 ◽  
Vol 97 (1) ◽  
pp. 81-85 ◽  
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.

Sign in / Sign up

Export Citation Format

Share Document