scholarly journals Benomyl Sensitivity of Isolates of Colletotrichum acutatum and C. gloeosporioides from Citrus

Plant Disease ◽  
2004 ◽  
Vol 88 (2) ◽  
pp. 125-130 ◽  
Author(s):  
N. A. R. Peres ◽  
N. L. Souza ◽  
T. L. Peever ◽  
L. W. Timmer
Keyword(s):  
Mycelial Growth ◽  
Colletotrichum Acutatum ◽  
Nucleotide Substitutions ◽  
Partial Sequencing ◽  
Research Fields ◽  
Fruit Drop ◽  
Highly Sensitive ◽  
Sensitive Isolate ◽  
Moderately Resistant

Postbloom fruit drop (PFD) of citrus, caused by Colletotrichum acutatum, produces orange-brown lesions on petals and results in premature fruit drop and the retention of calyces. C. gloeosporioides is common in groves and causes postharvest anthracnose on fruit. Both diseases are controlled effectively by the fungicide benomyl in research fields and commercial orchards. Highly sensitive and resistant isolates of C. gloeosporioides were found, whereas all isolates of C. acutatum tested were moderately resistant. In preliminary studies conducted in vitro with three isolates of each, mycelial growth of sensitive isolates of C. gloeosporioides was inhibited completely by benomyl (Benlate 50 WP) at 1.0 μg/ml, whereas resistant isolates grew well at 10 μg/ml. Growth of all isolates of C. acutatum was inhibited by about 55% at 0.1 μg/ml and by 80% at 1.0 μg/ml. Spore germination of C. acutatum was inhibited more at 0.1 μg/ml than at 1.0 μg/ml or higher concentrations. In all, 20 isolates of C. acutatum from 17 groves and 20 isolates of C. gloeosporioides from 7 groves were collected from locations with different histories of benomyl usage in São Paulo, Brazil, and Florida, United States. Benomyl at 1.0 μg/ml completely inhibited growth of 133 isolates of C. gloeosporioides, with the exception of 7 isolates that were highly resistant to the fungicide, whereas all isolates of C. acutatum were only partially inhibited at 0.1 and 1.0 μg/ml. Analysis of variance indicated that the sensitivity of the isolates of C. acutatum was not affected by benomyl usage or grove of origin, and country of origin had only minor effects. No highly resistant or sensitive isolate of C. acutatum was recovered. Partial sequencing of the β-tubulin gene did not reveal nucleotide substitutions in codons 198 or 200 in C. acutatum that usually are associated with benomyl resistance in other fungi.

scholarly journals Baseline Sensitivities of Fungal Pathogens of Fruit and Foliage of Citrus to Azoxystrobin, Pyraclostrobin, and Fenbuconazole

Plant Disease ◽  
2005 ◽  
Vol 89 (11) ◽  
pp. 1186-1194 ◽  
Author(s):  
S. N. Mondal ◽  
Alka Bhatia ◽  
Turksen Shilts ◽  
L. W. Timmer
Keyword(s):  
Mycelial Growth ◽  
Fungal Pathogens ◽  
Fungal Species ◽  
Brown Spot ◽  
Colletotrichum Acutatum ◽  
Fungicide Sensitivity ◽  
Fruit Drop ◽  
Coefficients Of Variation ◽  
Foliar Pathogens

The baseline sensitivities for mycelial growth of foliar fungal pathogens of citrus, Colletotrichum acutatum, Alternaria alternata, Elsinoe fawcettii, Diaporthe citri, and Mycosphaerella citri, the causal agents of postbloom fruit drop, brown spot of tangerine, citrus scab, melanose, and greasy spot, respectively, were determined in vitro for azoxystrobin, pyraclostrobin, and fenbuconazole. The effective dose to reduce growth by 50% (ED50 values) was determined for each pathogen-fungicide combination using five isolates from different citrus areas of Florida and eight fungicide concentrations. A discriminatory dose for each combination was selected near the ED50, and the range of sensitivity of 50 to 62 isolates of each fungal species was determined. The effect of salicylhydroxamic acid (SHAM) on the sensitivity of the five fungal species to azoxystrobin and pyraclostrobin was determined. Since mycelial growth of A. alternata was insensitive to azoxystrobin, the effect of that fungicide with and without SHAM on spore germination was assessed. The ED50 values for most fungal pathogens of citrus were relatively high compared with foliar pathogens of other tree crops. Values for azoxystrobin ranged from a low of 0.06 μg/ml with E. fawcettii to a high of >100 μg/ml with A. alternata. With pyraclostrobin, the values ranged from a low of 0.019 μg/ml with D. citri to a high of 0.87 μg/ml with A. alternata. With fenbuconazole, the lowest ED50 value was 0.21 μg/ml with M. citri and the highest was 1.01 μg/ml with C. acutatum, but A. alternata and D. citri were not tested. SHAM was inhibitory to all species and reduced growth of D. citri greatly. Inclusion of SHAM in the medium did not greatly affect the sensitivity of mycelial growth of these fungi to azoxystrobin or pyraclostrobin, nor did it affect the ED50 values for conidial germination of A. alternata. The coefficients of variation for the sensitivity of 50 to 62 isolates of each species to these fungi ranged from 7.3% with the pyraclostrobin-C. acutatum combination to a high of 55.0% with the fenbuconazole- M. citri combination. Discriminatory doses have been established for these pathogen- fungicide combinations that should be useful for detecting major shifts in fungicide sensitivity.

scholarly journals Effects of essential oils from thyme, cinnamon and clove on mycelial growth of Colletotrichum acutatum

2010 ◽  
Vol 25 (2) ◽  
pp. 151-156 ◽  
Author(s):  
Natasa Duduk ◽  
Aleksa Obradovic ◽  
Mirko Ivanovic
Keyword(s):  
Essential Oils ◽  
Mycelial Growth ◽  
Petri Dish ◽  
Control Treatment ◽  
Colletotrichum Acutatum ◽  
Dependent Manner ◽  
Cinnamon Oil ◽  
Volatile Phase ◽  
Vitro Effect

Effects of the volatile phase of thyme, cinnamon and clove essential oils on Colletotrichum acutatum were investigated. Mycelial disc was placed in the center of the Petri dish (V=66 ml) containing PDA. Different volumes of either non- or ethanol-diluted essential oils were placed on the inner side of the dish cover to obtain final concentrations of 153, 107, 76, 46, 15, 14, 12, 11, 7.6, 3.82, 1.53, 0.153 and 0.0153 ?l/L of air. The dishes were sealed with Parafilm and incubated in up-side-down position. After 7 days of incubation, mycelial growth was recorded by measuring the colony diameter. If no mycelial growth was recorded, the disc was transferred to a new PDA plate in order to evaluate whether the activity was either fungistatic or fungicidal. Mean growth values were obtained and then converted to inhibition percentage of mycelial growth compared with the control treatment. All the tested essential oils inhibited mycelial growth of C. acutatum in the dose dependent manner. Mycelial growth was totally inhibited by thyme oil in the concentration of 76 ?l/L of air. The same results were obtained by cinnamon and clove oil in the concentration of 107 ?l/L of air. Thyme and cinnamon oil had fungicidal effect in concentrations of 107 and 153 ?l/L respectively. The results obtained provide evidence on the antifungal in vitro effect of the tested essential oils as potential means for the control of C. acutatum.

scholarly journals Variations in the Sensitivity of Phytophthora infestans Isolates from Different Genetic Backgrounds to Dimethomorph

Plant Disease ◽  
2003 ◽  
Vol 87 (11) ◽  
pp. 1283-1289 ◽  
Author(s):  
J. M. Stein ◽  
W. W. Kirk
Keyword(s):  
Life Cycle ◽  
Phytophthora Infestans ◽  
Mycelial Growth ◽  
Hyphal Growth ◽  
Potato Leaf ◽  
Leaf Discs ◽  
Highly Sensitive ◽  
Significant Difference ◽  
Cyst Germination

The sensitivities of 11 isolates of Phytophthora infestans to dimethomorph were examined at all stages of the asexual life cycle and when inoculated onto potato leaf discs. In vitro zoospore encystment and cyst germination were highly sensitive to dimethomorph with 50% reduction of mycelial growth and cyst germination (EC50) values for most isolates <0.20 μg/ml, whereas direct sporangia germination and in vitro hyphal growth and sporulation were less sensitive (means of 0.45 and 0.22 μg/ml, respectively). Zoosporogenesis was not significantly inhibited at the maximum dimethomorph concentration examined, 10 μg/ml. Significant differences (Fisher's least significant difference, P = 0.05) in the EC50 values were present between isolates for all stages of the asexual life cycle, except direct sporangia germination and zoosporogenesis. Sensitivity ratios between the least- and most-sensitive isolates were 6.11, 12.14, 12.36, and 10.56 for hyphal growth, in vitro sporulation, zoospore encystment, and cyst germination, respectively. Application of dimethomorph at 1,000 μg/ml to potato leaf discs at 24 or 48 h before inoculation completely inhibited symptom incidence for most isolates, whereas application after inoculation generally was not significantly different from the untreated control, regardless of concentration. Sporulation from leaf discs treated with dimethomorph at 24 or 48 h after inoculation was completely inhibited for all isolates with dimethomorph at 1,000 μg/ml, even when symptom incidence was not significantly reduced.

scholarly journals Synthesis and Characterization of Novel Copper Nanoparticles for the Control of Leaf Spot and Anthracnose Diseases of Olive

Nanomaterials ◽  
2021 ◽  
Vol 11 (7) ◽  
pp. 1667
Author(s):  
Panagiota Ntasiou ◽  
Alexandra Kaldeli Kerou ◽  
Theodora Karamanidou ◽  
Afrodite Vlachou ◽  
George T. Tziros ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Mycelial Growth ◽  
Crop Protection ◽  
Attenuated Total Reflection ◽  
Colletotrichum Acutatum ◽  
In Planta ◽  
Colletotrichum Spp ◽  
Type 3

Olive crop is frequently treated with copper fungicides to combat foliar and fruit diseases such as olive leaf spot caused by Fusicladium oleagineum and anthracnose caused by Colletotrichum spp. The replacement of copper-based products with more eco-friendly alternatives is a priority. Metal nanoparticles synthesized in several ways have recently revolutionized crop protection with applications against important crop pathogens. In this study, we present the development of four copper-based nanoparticles (CuNP Type 1 to 4) synthesized with a wet chemistry approach. The CuNPs were characterized using Transmission Electron Microscopy, Dynamic Light Scattering, Laser Doppler Electrophoresis, and Attenuated Total Reflection measurements. In addition, the activity of the four CuNP types was tested in vitro and in planta against F. oleagineum and Colletotrichum spp. In vitro sensitivity measurements showed that for both pathogens, mycelial growth was the most susceptible developmental stage to the tested compounds. Against both pathogens, CuNP Type 1 and Type 2 were found to be more active in reducing mycelial growth compared to the reference commercial compounds of copper oxide and copper hydroxide. In planta experiments showed that CuNP Type 3 and CuNP Type 4 exhibited a strong protectant activity against both F. oleagineum and Colletotrichum acutatum with control efficacy values significantly higher than those achieved by the applications of either reference product.

scholarly journals In vitro fungicide testing for control of avocado fruit rots

2007 ◽  
Vol 60 ◽  
pp. 99-103 ◽  
Author(s):  
K.R. Everett ◽  
O.E. Timudo-Torrevilla
Keyword(s):  
Spore Germination ◽  
Mycelial Growth ◽  
Effective Concentration ◽  
Colletotrichum Acutatum ◽  
Copper Hydroxide ◽  
Copper Fungicides ◽  
Avocado Fruit

Avocado fruit rots are most commonly caused by five fungi Colletotrichum acutatum C gloeosporioides Botryosphaeria parva B dothidea and Phomopsis sp These rots are controlled by applying copper fungicides in the field on eight occasions during the season Alternatives to standard copper fungicides were screened in the laboratory against these five pathogens for inhibition of spore germination and mycelial growth In total seven fungicides were tested (boscalid boscalid/pyraclostrobin three formulations of copper hydroxide copper hydroxosulphate and dithianon) The effective concentration at which 50 of spore germination or mycelial growth was inhibited (EC50) was calculated for each fungicide The EC50 values for spore germination were lowest for boscalid/pyraclostrobin and dithianon and were le;185 g/ml against all five test fungi For boscalid/pyraclostrobin all EC50 values were le;7 g/ml Copper formulations effectively inhibited spore germination by 50 at concentrations ranging from 01 g/ml to 141 g/ml but were less effective against mycelial growth

scholarly journals Thiophanate-Methyl Resistance and Fitness Components of Colletotrichum musae Isolates from Banana in Brazil

Plant Disease ◽  
2017 ◽  
Vol 101 (9) ◽  
pp. 1659-1665 ◽  
Author(s):  
Willie Anderson dos Santos Vieira ◽  
Waléria Guerreiro Lima ◽  
Eduardo Souza Nascimento ◽  
Sami Jorge Michereff ◽  
Ailton Reis ◽  
...  
Keyword(s):  
Fungicide Resistance ◽  
Mycelial Growth ◽  
Postharvest Disease ◽  
Banana Fruit ◽  
Coding Region ◽  
Banana Production ◽  
Thiophanate Methyl ◽  
Moderately Resistant ◽  
Colletotrichum Musae

Anthracnose, caused by Colletotrichum musae, is the most important postharvest disease of banana and is widely distributed among the banana production regions in Brazil. Although thiophanate-methyl is a fungicide frequently used in Brazilian banana orchards to control Sigatoka leaf spot, Collettotrichum populations are also exposed, resulting in the evolution of fungicide resistance and the inability to manage banana anthracnose. We investigated 139 Brazilian isolates of C. musae for thiophanate-methyl sensitivity in vitro. The 50% mycelial growth inhibition (EC50) values varied between 0.003 and 48.73 μg/ml. One-hundred and thirty isolates were classified as sensitive, with EC50 values ranging from 0.003 to 4.84 μg/ml, while the remaining nine isolates were considered moderately resistant, with EC50 values ranging between 10.43 and 48.73 μg/ml. Resistant or highly resistant isolates (EC50 > 100 μg/ml) were not found. A substitution of TAC for TTC at codon 200 in a coding region of the β-tubulin gene was associated with the moderately resistant phenotype. Applications of thiophanate-methyl formulation to detached banana fruit at the label rate (500 μg/ml) showed low efficacy in controlling the moderately resistant isolates on banana fruits. However, there is no indication of a reduction in fitness associated with fungicide resistance as sensitive and moderately resistant isolates do not differ with respect to mycelial growth rate (P = 0.098), spore production (P = 0.066), spore germination (P = 0.366), osmotic sensitivity (P = 0.051), and virulence (P = 0.057). Our results revealed absence of adaptability cost for the moderately resistant isolates, suggesting that they can be dominant in population if the fungicide continue to be applied.

scholarly journals Sensitivity of Colletotrichum acutatum Isolates from Citrus to Carbendazim, Difenoconazole, Tebuconazole, and Trifloxystrobin

Plant Disease ◽  
2020 ◽  
Vol 104 (6) ◽  
pp. 1621-1628 ◽  
Author(s):  
Andre B. Gama ◽  
Juliana S. Baggio ◽  
Carolina S. Rebello ◽  
Silvia de Afonseca Lourenço ◽  
Maria Cândida de G. Gasparoto ◽  
...  
Keyword(s):  
Growth Inhibition ◽  
Mycelial Growth ◽  
Conidial Germination ◽  
Colletotrichum Acutatum ◽  
Dilution Method ◽  
Quinone Outside Inhibitor ◽  
Fruit Drop ◽  
Species Complexes ◽  
Before And After ◽  
Dmi Fungicides

Postbloom fruit drop (PFD) of citrus is caused by the Colletotrichum acutatum and C. gloeosporioides species complexes. The disease is important when frequent rainfall occurs during the flowering period of citrus trees. In Brazil, until 2012, PFD was mainly controlled by preventive applications of the methyl-benzimidazole carbamate (MBC) carbendazim and demethylation-inhibitor (DMI) fungicides such as difenoconazole. Since then, mixtures containing the DMI tebuconazole and the quinone-outside inhibitor (QoI) trifloxystrobin have been commonly used. Fungicides are often applied preventively, sometimes even when conditions are not conducive for PFD development. Excessive fungicide applications may favor the selection of resistant populations of Colletotrichum spp. In this study, we assessed the fungicide sensitivity of C. acutatum isolates collected during the two distinct periods of PFD management in Brazil: before and after the trifloxystrobin and tebuconazole mixture became widely employed. The sensitivity of 254 C. acutatum isolates to carbendazim and difenoconazole and of 164 isolates to tebuconazole and trifloxystrobin was assessed. Mycelial growth inhibition of these isolates was evaluated for all the fungicides using either serial dilution of fungicide rates or the spiral gradient dilution method. In addition, inhibition of conidial germination was also assessed for trifloxystrobin. Analysis of partial β-tub, cytb, and cyp51b gene sequences did not reveal any mutations related to resistance to MBCs, QoIs, and DMIs, respectively. In mycelial growth assays, mean EC50 values were 0.14, 0.11, and 0.21 μg/ml for difenoconazole, tebuconazole, and trifloxystrobin, respectively. The conidial germination inhibition by trifloxystrobin was similar among the tested isolates, and the mean EC50 value was 0.002 μg/ml. All isolates had similar mean mycelial growth inhibition for carbendazim, regardless of the fungicide concentrations. Therefore, based on similar EC50 values and molecular analyses, no shift in the sensitivity of isolates has been observed to the fungicides commonly used in different citrus-producing areas in Brazil.

Resistance to Phytophthora cinnamomi in callus tissue derived from three avocado cultivars

1991 ◽  
Vol 69 (9) ◽  
pp. 2026-2032 ◽  
Author(s):  
D. Phillips ◽  
G. Weste ◽  
J. M. Hinch
Keyword(s):  
Key Words ◽  
Mycelial Growth ◽  
Callus Tissue ◽  
Phytophthora Cinnamomi ◽  
Host Tissue ◽  
Plant Parts ◽  
Whole Plant ◽  
Moderately Resistant ◽  
Undifferentiated Callus

Calli induced from various plant parts of avocado cultivars Topa Topa (susceptible), Duke 7 (moderately resistant), and Martin Grande (resistant) were inoculated with the root and collar rotting pathogen Phytophthora cinnamomi and examined for expression of resistance. Resistance was assessed quantitatively by measuring the rate of hyphal extension across the callus surface from the point of inoculation. Resistance in the callus tissue was associated with sparse, limited mycelial growth, in contrast to prolific, dense growth on and within susceptible callus. Rates of hyphal extension on calli of the resistant ‘Duke 7’ and ‘Martin Grande’ ranged from 1–3 mm day−1 compared with 4–7 mm day−1 on calli of ‘Topa Topa’. This difference in growth was significant (P = 0.05). This is the first report of avocado callus exhibiting resistance to P. cinnamomi and it mirrors that recorded for the whole plant for the three avocado cultivars tested. Thus, the level of resistance expressed by each cultivar appears to be innate whether the host tissue remains in an organized state or is in the form of an undifferentiated callus mass. The basis of the resistance expressed appeared to be largely physiological and (or) biochemical rather than anatomical. Assessing rates of hyphal colonization on undifferentiated callus masses in vitro may provide a new and useful assay for screening and selecting host lines in avocado resistant to P. cinnamomi. Key words: callus, avocado, in vitro, resistance, Phytophthora cinnamomi, Persea.

scholarly journals Activity of Benomyl for Control of Postbloom Fruit Drop of Citrus Caused by Colletotrichum acutatum

Plant Disease ◽  
2002 ◽  
Vol 86 (6) ◽  
pp. 620-624 ◽  
Author(s):  
N. A. R. Peres ◽  
N. L. Souza ◽  
S. E. Zitko ◽  
L. W. Timmer
Keyword(s):  
Germ Tube ◽  
Good Control ◽  
Colletotrichum Acutatum ◽  
Disease Development ◽  
Mature Leaves ◽  
Fruit Drop ◽  
Fungal Propagules ◽  
Highly Sensitive ◽  
Subsequent Application ◽  
Colony Area

Postbloom fruit drop (PFD) of citrus caused by Colletotrichum acutatum produces orange-brown lesions on petals and induces the abscission of young fruitlets and the retention of the calyces. Despite the fact that C. acutatum is not highly sensitive to benomyl in culture, this fungicide provides good control of the disease under field conditions. This study was undertaken to determine the effect of benomyl on various stages of disease development to understand the basis for its effectiveness in the field. We found that benomyl at 1.0 μg/ml reduced colony area of C. acutatum by about 75% and completely inhibited growth of C. gloeosporioides. Benomyl did not prevent conidial germination even at 100 μg/ml, but reduced germ tube elongation at 10 and 100 μg/ml. When benomyl was applied to flower clusters on screenhouse-grown plants before inoculation, disease severity was greatly reduced. Applications at 24 and 48 h, but not at 72 h, after inoculation reduced PFD severity. Application of benomyl to symptomatic petals not bearing conidia did not prevent or reduce production of inoculum. Application to petals bearing conidia reduced viability of these fungal propagules by only about 50%. The viability of appressoria on mature leaves was not affected by benomyl application. Even when appressoria on mature leaves were stimulated to germinate by treatment with flower extracts, subsequent application of benomyl did not reduce propagule numbers below original levels. Benomyl appears to act by preventing infection and early development of the fungus in petals. However, once symptoms have developed, this fungicide has only minimal effects on further disease development and spread.

An Attempt at Biological Control of Blossom Blight of Rose Caused by Botrytis cinerea Using some Local Trichoderma spp. Strains

2020 ◽  
Vol 55 (1) ◽  
pp. 27-34
Author(s):  
G. Zadehdabagh ◽  
K. Karimi ◽  
M. Rezabaigi ◽  
F. Ajamgard
Keyword(s):  
Botrytis Cinerea ◽  
Mycelial Growth ◽  
Limiting Factor ◽  
Dual Culture ◽  
Trichoderma Spp ◽  
Khuzestan Province ◽  
Inhibitory Potential ◽  
Cut Rose

The northern of Khuzestan province in Iran is mainly considered as one of the major areas of miniature rose production. Blossom blight caused by Botrytis cinerea has recently become a serious limiting factor in rose production in pre and post-harvest. In current study, an attempt was made to evaluate the inhibitory potential of some local Trichoderma spp. strains against B. cinerea under in vitro and in vivo conditions. The in vitro results showed that all Trichoderma spp. strains were significantly able to reduce the mycelial growth of the pathogen in dual culture, volatile and non-volatile compounds tests compared with control, with superiority of T. atroviride Tsafi than others. Under in vivo condition, the selected strain of T. atroviride Tsafi had much better performance than T. harzianum IRAN 523C in reduction of disease severity compared with the untreated control. Overall, the findings of this study showed that the application of Trichoderma-based biocontrol agents such as T. atroviride Tsafi can be effective to protect cut rose flowers against blossom blight.

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