scholarly journals Efficacy and Baseline Sensitivity of Succinate-Dehydrogenase-Inhibitor Fungicides for Management of Colletotrichum Crown Rot of Strawberry

Plant Disease ◽  
2020 ◽  
Vol 104 (11) ◽  
pp. 2860-2865
Author(s):  
Michelle S. Oliveira ◽  
Leandro G. Cordova ◽  
Natalia A. Peres
Keyword(s):  
Succinate Dehydrogenase ◽  
Colletotrichum Gloeosporioides ◽  
Fungal Growth ◽  
Crown Rot ◽  
Baseline Sensitivity ◽  
Current Management ◽  
Qoi Fungicides ◽  
Dilution Assay ◽  
Succinate Dehydrogenase Inhibitor

The current management of Colletotrichum crown rot (CCR) of strawberry, caused by Colletotrichum gloeosporioides sensu lato, relies on the use of a few fungicide classes, particularly QoI fungicides. Since resistance to QoI fungicides has recently been detected, alternative fungicide groups are needed to control this disease. Our objective was to evaluate the efficacy of succinate-dehydrogenase-inhibitor (SDHI) fungicides in managing CCR. Five SDHI fungicides, fluopyram, isofetamid, penthiopyrad, fluxapyroxad, and benzovindiflupyr, were applied 2 days before or 1 day after inoculation of cultivar Strawberry Festival. SDHI treatments were compared with the most common fungicides used for CCR management, i.e., thiophanate-methyl, pyraclostrobin, and captan. Benzovindiflupyr applied 1 day after inoculation was effective in reducing plant mortality and disease development. The baseline sensitivity of C. gloeosporioides isolates was determined in vitro using a spiral gradient dilution assay. The EC50 for benzovindiflupyr and penthiopyrad varied from 0.08 to 1.11 and 0.45 to 3.17 µg/ml, respectively, whereas the other SDHI fungicides did not inhibit fungal growth. If registered, benzovindiflupyr could serve as an alternative to manage CCR in Florida.

scholarly journals Baseline Sensitivity of Cercospora zeae-maydis to Quinone Outside Inhibitor Fungicides

Plant Disease ◽  
2011 ◽  
Vol 95 (2) ◽  
pp. 189-194 ◽  
Author(s):  
C. A. Bradley ◽  
D. K. Pedersen
Keyword(s):  
United States ◽  
Leaf Spot ◽  
The United States ◽  
Gray Leaf Spot ◽  
Alternative Respiration ◽  
Baseline Sensitivity ◽  
Qoi Fungicides ◽  
Quinone Outside Inhibitor ◽  
Cercospora Zeae Maydis

Cercospora zeae-maydis, the causal agent of gray leaf spot on corn (Zea mays), can cause severe yield loss in the United States. Quinone outside inhibitor (QoI) fungicides are effective tools that can be used to manage gray leaf spot, and their use has increased in corn production in the United States. In total, 61 C. zeae-maydis isolates collected from fields in which QoI fungicides had never been applied were tested in vitro using azoxystrobin-, pyraclostrobin-, or trifloxystrobin-amended medium to determine the effective fungicide concentration at which 50% of the conidial germination was inhibited (EC50). The effect of salicylhydroxamic acid (SHAM) also was evaluated for seven isolates to determine whether C. zeae-maydis is capable of using alternative respiration in azoxystrobin-amended medium. All seven C. zeae-maydis isolates tested had significantly greater (P < 0.02) EC50 values when SHAM was not included in medium amended with azoxystrobin, indicating that C. zeae-maydis has the potential to utilize alternative respiration to overcome QoI fungicide inhibition in vitro. Baseline EC50 values of azoxystrobin ranged from 0.003 to 0.031 μg/ml, with mean and median values of 0.018 and 0.019 μg/ml, respectively. Baseline EC50 values of pyraclostrobin ranged from 0.0003 to 0.0025 μg/ml, with mean and median values of 0.0010 and 0.0010 μg/ml, respectively. Baseline EC50 values of trifloxystrobin ranged from 0.0004 to 0.0034 μg/ml, with mean and median values of 0.0023 and 0.0024 μg/ml, respectively. These baseline sensitivity values will be used in a fungicide resistance monitoring program to determine whether shifts in sensitivity to QoI fungicides are occurring in C. zeae-maydis populations.

scholarly journals Sensitivity ofRhizoctonia solanito Succinate Dehydrogenase Inhibitor and Demethylation Inhibitor Fungicides

Plant Disease ◽  
2017 ◽  
Vol 101 (3) ◽  
pp. 487-495 ◽  
Author(s):  
Olutoyosi O. Ajayi-Oyetunde ◽  
Carolyn J. Butts-Wilmsmeyer ◽  
Carl A. Bradley
Keyword(s):  
Succinate Dehydrogenase ◽  
The United States ◽  
Fungicide Sensitivity ◽  
Dmi Fungicides ◽  
Soybean Plants ◽  
Succinate Dehydrogenase Inhibitor ◽  
Collection Date ◽  
Demethylation Inhibitor

Soybean seedling diseases are caused by Rhizoctonia solani and can be managed with seed-applied fungicides that belong to different chemistry classes. To provide a benchmark for assessing a decline in sensitivities to these fungicide classes, R. solani isolates collected prior to 2001 were evaluated for their sensitivities to succinate dehydrogenase inhibitor (SDHI) (penflufen and sedaxane) and demethylation inhibitor (DMI) fungicides (ipconazole and prothioconazole). The effective concentration of each fungicide that reduced mycelial growth by 50% (EC50) was determined in vitro and compared with those of isolates recovered after 2011 from soybean plants with damping off and hypocotyl and root rot symptoms across different soybean-growing regions in the United States and Canada. All isolates, regardless of collection date, were extremely sensitive (EC50< 1 μg/ml) to the SDHI fungicides but were either extremely sensitive or moderately sensitive (1 ≤ EC50≤ 10 μg/ml) to the DMI fungicides. For all four active ingredients, variation in sensitivities was observed within and among the different anastomosis groups composing both isolate groups. Isolates collected after 2011, which also had varying in vitro sensitivities, were further evaluated for in vivo sensitivity to the four fungicides in the greenhouse. In vitro fungicide sensitivity did not always coincide with fungicide efficacy in vivo because all isolates tested, regardless of in vitro sensitivity, were effectively controlled by the application of the seed treatment fungicides in the greenhouse. Overall, our results indicate no shift in sensitivity to the fungicide classes evaluated, although considerable variability in the sensitivities of the two groups of isolates examined was present. Based on this research, continued monitoring of fungicide sensitivities of R. solani populations should occur to determine whether sensitivities become further reduced in the future.

In vitro and in vivo activity of QoI fungicides against Colletotrichum gloeosporioides causing fruit anthracnose in Citrus sinensis

2018 ◽  
Vol 236 ◽  
pp. 90-95 ◽  
Author(s):  
Giulio Piccirillo ◽  
Raffaele Carrieri ◽  
Giancarlo Polizzi ◽  
Antonino Azzaro ◽  
Ernesto Lahoz ◽  
...  
Keyword(s):  
Citrus Sinensis ◽  
Colletotrichum Gloeosporioides ◽  
Qoi Fungicides

scholarly journals Baseline Sensitivity of Botrytis cinerea to the Succinate Dehydrogenase Inhibitor Isopyrazam and Efficacy of this Fungicide

Plant Disease ◽  
2016 ◽  
Vol 100 (7) ◽  
pp. 1314-1320 ◽  
Author(s):  
Yingying Song ◽  
Zhengqun Zhang ◽  
Lele Chen ◽  
Leiming He ◽  
Hongbao Lu ◽  
...  
Keyword(s):  
Succinate Dehydrogenase ◽  
Botrytis Cinerea ◽  
Spore Germination ◽  
Mycelial Growth ◽  
Field Trials ◽  
Baseline Sensitivity ◽  
Control Efficacy ◽  
Frequency Distributions ◽  
Geographical Regions ◽  
Succinate Dehydrogenase Inhibitor

Isopyrazam is a new broad-spectrum, foliar-absorbed and -translocated succinate dehydrogenase inhibitor fungicide. In this study, 159 Botrytis cinerea isolates collected from different geographical regions of Shandong Province of China were characterized for baseline sensitivity to isopyrazam. Furthermore, the protective and curative activity of isopyrazam on strawberry fruit and the control efficacy in the field were also determined. In contrast to its mycelial growth, the spore germination of B. cinerea was inhibited completely by lower concentrations of isopyrazam, about 1 μg ml−1 on yeast-peptone-acetate medium. Frequency distributions of isopyrazam 50% effective concentration (EC50) values were unimodal curves, with mean EC50 values of 0.07 ± 0.04 (standard deviation) and 0.68 ± 0.36 μg ml−1 for the inhibition of spore germination and mycelial growth, respectively. In addition, there was no positive multiple resistance between isopyrazam and other classes of botryticides such as diethofencarb, iprodione, pyrimethanil, or SYP-Z048. In field trials conducted during 2014 and 2015, isopyrazam used at a concentration of active ingredient at 150 and 200 g ha−1 provided a control efficacy ranging from 76.7 to 87.8% on leaves and from 81.5 to 90.7% on fruit. These results suggest that isopyrazam has the potential to play an important role in the management of gray mold.

scholarly journals Baseline Sensitivity of Guignardia citricarpa Isolates from Florida to Azoxystrobin and Pyraclostrobin

Plant Disease ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 780-789 ◽  
Author(s):  
Martha Hincapie ◽  
Nan-Yi Wang ◽  
Natalia A. Peres ◽  
Megan M. Dewdney
Keyword(s):  
Mycelial Growth ◽  
Control Measure ◽  
Black Spot ◽  
Conidial Germination ◽  
Baseline Sensitivity ◽  
Qoi Fungicides ◽  
Resistance Risk ◽  
Guignardia Citricarpa ◽  
The Mean

Citrus black spot (CBS), caused by Guignardia citricarpa, is an emerging disease in Florida. Fungicide applications are the main control measure worldwide. The in vitro activity and baseline sensitivity of G. citricarpa isolates to quinone outside inhibitor (QoI) fungicides (azoxystrobin and pyraclostrobin) were evaluated. The effective concentration needed to reduce mycelial growth or spore germination by 50% (EC50) was determined for 86 isolates obtained from Florida counties where CBS is found. The effect of salicylhydroxamic acid (SHAM) plus azoxystrobin and pyraclostrobin was also assessed for mycelial growth and conidial germination. The mean EC50 for mycelial growth for azoxystrobin was 0.027 μg/ml and that for pyraclostrobin was significantly lower at 0.007 μg/ml (P < 0.0001). Similarly, the mean EC50 for conidial germination for azoxystrobin was 0.016 μg/ml and that for pyraclostrobin was significantly lower at 0.008 μg/ml (P < 0.0001). There was no effect of SHAM on inhibition of mycelial growth or conidial germination by the QoI fungicides but SHAM slightly affected mycelium inhibition by pyraclostrobin. Cytochrome b was partially sequenced and three group 1 introns were found. One intron was immediately post G143, likely inhibiting resistance-conferring mutations at that site. It is surmised that the QoI resistance risk is low in the Florida G. citricarpa population.

Multi-locus phylogenetic analyses of Colletotrichum gloeosporioides species complex causing crown rot on strawberry in Florida

2021 ◽  
Author(s):  
Michelle Souza Oliveira ◽  
Nan-Yi Wang ◽  
Natalia Peres
Keyword(s):  
Colletotrichum Gloeosporioides ◽  
Phylogenetic Analyses ◽  
Management Strategies ◽  
Morphological Characteristics ◽  
Crown Rot ◽  
Cultivated Plants ◽  
Complex Species ◽  
Colletotrichum Gloeosporioides Species Complex ◽  
Genomic Regions

Colletotrichum gloeosporioides is the causal agent of Colletotrichum crown rot of strawberry in the southern United States. Recent multi-gene studies defined C. gloeosporioides as a complex species comprised of 37 species. In our study, we phylogenetically characterized C. gloeosporioides isolates from strawberry and other non-cultivated plants around strawberry fields. One hundred and fifteen strawberry isolates and 38 isolates from non-cultivated hosts were sequenced for five genomic regions: internal transcribed spacer (ITS), actin (ACT), calmodulin (CAL), chitin synthase (CHS-1), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Phylogenetic analysis using the maximum likelihood and Bayesian inference methods, based on partition-specific models, revealed that most of the isolates in Florida (86%) were closely related to C. siamense, whereas 14 isolates were closely related to C. theobromicola (syn. C. fragariae), four isolates were C. fructicola, and three were C. clidemiae. However, only the first three species were pathogenic to strawberry. Morphological characteristics evaluated show that mycelial growth of all species is about 5 mm/day but colony morphology varies by species and incubation conditions. In vitro mating of the isolates demonstrated that C. fructicola is homothallic whereas C. siamense and C. theobromicola isolates are heterothallic. The biological importance of these different Colletotrichum species is currently being investigated to determine whether different management strategies are needed in strawberry production fields.

scholarly journals Occurrence, Distribution, and Characteristics of Boscalid-Resistant Corynespora cassiicola in China

Plant Disease ◽  
2019 ◽  
Vol 103 (1) ◽  
pp. 69-76 ◽  
Author(s):  
Fadi Zhu ◽  
Yanxia Shi ◽  
Xuewen Xie ◽  
Ali Chai ◽  
Baoju Li
Keyword(s):  
Growth Inhibition ◽  
Succinate Dehydrogenase ◽  
Frequency Distribution ◽  
Mycelial Growth ◽  
Corynespora Cassiicola ◽  
Baseline Sensitivity ◽  
Resistance Patterns ◽  
Moderately Resistant ◽  
Succinate Dehydrogenase Inhibitor ◽  
Important Disease

Corynespora blight, caused by Corynespora cassiicola (Berk. & M.A. Curtis) C.T. Wei, has become an important disease affecting cucumber in China. Its management mainly depends on fungicides; however, no research has been conducted to assess the sensitivity of C. cassiicola in China to boscalid, a succinate dehydrogenase inhibitor (SDHI). To facilitate boscalid resistance monitoring, baseline sensitivity was established. The EC50 value (i.e., the concentration that results in 50% mycelial growth inhibition) frequency distribution was unimodal with a right-hand tail; with the means 0.95 ± 0.51 μg/ml and the range 0.03 to 2.85 μg/ml. We then assessed the sensitivity of C. cassiicola to boscalid using discriminatory doses and EC50 values. In total, 27.8% of the 798 isolates were resistant, distributed in five provinces and two municipalities. Thirty-seven isolates with different resistance levels to boscalid were also evaluated for their sensitivity to carboxin, fluopyram, and penthiopyrad. Seven SDHI resistance patterns were observed (i.e., I: BosMRFluoMRPenLRCarSS; II: BosVHRFluoSSPenMRCarR; III: BosLRFluoMRPenLRCarR; IV: BosMRFluoMRPenMRCarR; V: BosHRFluoMRPenHRCarR; VI: BosHRFluoHRPenHRCarR; and VII: BosHRFluoSSPenLR CarR, VHR: very highly resistant; HR: highly resistant; MR: moderately resistant; LR: low resistant; R: resistant; SS: supersensitive), corresponding to seven mutations in sdhB/C/D genes, respectively.

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