scholarly journals First Report of In-Vitro Boscalid-Resistant Isolates of Alternaria solani Causing Early Blight of Potato in Idaho

Plant Disease ◽  
2012 ◽  
Vol 96 (3) ◽  
pp. 454-454 ◽  
Author(s):  
P. Wharton ◽  
K. Fairchild ◽  
A. Belcher ◽  
E. Wood
Keyword(s):  
Early Blight ◽  
Cultural Practices ◽  
Potato Crop ◽  
Plant Stress ◽  
Leaf Tissue ◽  
Alternaria Solani ◽  
Spore Morphology ◽  
First Report ◽  
The Impact

Early blight of potato (Solanum tuberosum) is caused by Alternaria solani and occurs annually to some degree in Idaho. The timing of its appearance and rate of disease progress determine the impact on the potato crop. Though losses rarely exceed 20%, they can be higher and occur in stored potatoes if the disease is not controlled. Early blight is managed mainly by cultural practices such as plant nutrition, water management, and avoidance of plant stress, but also with the use of foliar fungicides. Currently, the main fungicides labeled for control of early blight are in the carboxamide and strobilurin fungicide groups. Development of resistance to some fungicide groups may contribute to the loss of control of early blight. Isolates of A. solani from Idaho potatoes were tested for resistance to boscalid in the carboxamide group. Diseased potato leaves with early blight symptoms were collected from fields near Parma, Rupert, and Aberdeen in southern Idaho in 2009 and 2010 and Bonners Ferry in northern Idaho in 2010. To obtain A. solani isolates from leaves, small pieces of leaf tissue (5 × 5 mm) were taken from the center of early blight lesions and streaked across the surface of a thin layer (3 mm) of water agar. Plates were incubated at 25°C overnight to allow spores to germinate. Single germinated A. solani spores were transferred to acidified potato dextrose agar and incubated in the dark at 25°C. Germinated spores were identified based on spore morphology. Spores of A. solani can be easily distinguished from other Alternaria spp. found on potato because they are ellipsoid to oblong and taper to a long beak that is usually as long as the spore body. The identity of cultures grown from single spores was confirmed by colony and spore morphology. Sensitivity of A. solani isolates to boscalid was determined by the spiral gradient endpoint method (2). For all isolates, the effective concentration for 50% reduction in growth was outside the range of the spiral plate dilution series (i.e., isolates were either completely insensitive or completely sensitive to boscalid). In total, 46 isolates (20 collected in 2009 and 26 collected in 2010) were tested against boscalid. Experiments were carried out twice with 2009 isolates using mycelial strips and conidial suspensions. Experiments with 2010 isolates were carried out three times using only conidial suspensions. Of the isolates from 2009, 15% were insensitive. There was no difference between the use of mycelial strips or conidial suspensions. In 2010, 62% of isolates were insensitive. By location, 72% of isolates from Parma, 73% from Rupert, 63% from Aberdeen, and 44% from Bonners Ferry were insensitive. Resistance to boscalid has been reported in A. alternata isolates from pistachio (1,3). However, to our knowledge, this is the first report of resistance to boscalid in isolates of A. solani on potato. These data suggest that resistance to boscalid is widespread in Idaho, even in areas like Bonners Ferry where potato cultivation is limited. Boscalid insensitivity in vitro may not translate directly to commercial production and currently there is no evidence to suggest that boscalid has failed to control early blight in Idaho. However, the discovery of insensitive isolates suggests that boscalid should be considered at high risk of resistance development. References: (1) H. Avenot et al. Plant Dis. 91:1345, 2007. (2) H. Förster et al. Phytopathology 94:163, 2004. (3) N. Rosenzweig et al. (Abstr.) Phytopathology 93(suppl.):S75, 2003.

scholarly journals First Report of Boscalid and Penthiopyrad-Resistant Isolates of Alternaria solani Causing Early Blight of Potato in Michigan

Plant Disease ◽  
2013 ◽  
Vol 97 (12) ◽  
pp. 1655-1655 ◽  
Author(s):  
T. D. Miles ◽  
K. L. Fairchild ◽  
A. Merlington ◽  
W. W. Kirk ◽  
N. Rosenzweig ◽  
...  
Keyword(s):  
Early Blight ◽  
Fungal Growth ◽  
Leaf Tissue ◽  
Alternaria Solani ◽  
Cross Resistance ◽  
First Report ◽  
Primer Sets ◽  
Michigan Potato ◽  
Moderately Resistant ◽  
Succinate Dehydrogenase Inhibitor

Early blight of potato (Solanum tuberosum) is caused by Alternaria solani and occurs annually in Michigan. If left uncontrolled, it can result in yield losses exceeding 20% and impact stored potatoes. The disease is commonly managed using succinate dehydrogenase inhibitor (SDHI) fungicides (1). Unfortunately, recent studies have shown that SDHI resistance has increased dramatically over the past 2 years in A. solani populations (1,2). To investigate the occurrence of SDHI resistance in Michigan, potato leaves with early blight symptoms were collected from fields in Montcalm and Ionia counties, MI, in 2012. To obtain A. solani isolates from leaves, small pieces of leaf tissue (5 × 5 mm) were excised from the center of lesions and transferred on to water agar. Plates were incubated at 25°C overnight to allow conidia to germinate. Single germinated A. solani conidia were transferred to potato dextrose agar (PDA) and incubated at 25°C for 7 days. The identity of cultures was confirmed by colony and conidial morphology (3). Nineteen A. solani isolates were obtained and each was screened for sensitivity to the SDHI fungicides boscalid, penthiopyrad, and fluopyram, using a 50 ppm discriminatory dose based on EC50 values previously determined (2). Mycelial plugs (~5.5 mm) were transferred to amended and non-amended PDA plates that were incubated at 25°C for 7 days. An isolate was considered highly resistant if fungal growth relative to control plates exceeded 50%, moderately resistant if it was between 35 and 50%, and sensitive if it was less than 35% (2). A sensitive A. solani isolate (AS11) from Bonners Ferry, ID, was used as a control in these experiments. Of all isolates tested, 11% were highly resistant to both boscalid and penthiopyrad and 5% were moderately resistant to both fungicides, 21% were moderately resistant to penthiopyrad alone, and the remaining isolates (84 and 68% respectively) were sensitive to the two fungicides. None of the isolates tested were resistant to fluopyram. Recently, two major mutations, H227R in SdhB and H133R in SdhD, have been identified in highly resistant A. solani isolates in Idaho (2). Because the majority of the identified mutations occur near the 3′ end of each subunit, this region was amplified and sequenced using the following primer sets: SdhB (5′-TACTGGTGGAACCAGGAGGAGTA-3′ and 5′-CATACCACTCTAGGTGAAG-3′), SdhC (5′-CCAAATCACCTGGTACGCCTCG-3′ and 5′-TCATCCGAGGAAGGTGTAGTAAAGGCTG-3′), and SdhD (5′-CCGACTCTATTCTCTGCGCCCT-3′ and 5′-CTCGAAAGAGTAGAGGGCAAGACCCA-3′). In this study, all of the isolates that were highly resistant to both boscalid and penthiopyrad were found to contain the H133R mutation in SdhD, which correlated with the strongest resistance phenotype. To our knowledge, this is the first report of resistance to SDHI fungicides in populations of A. solani on potato in Michigan. These data are concerning as they indicate that the highly resistant isolates have already developed cross-resistance between boscalid and penthiopyrad, despite penthiopyrad not yet having regular use in Michigan. Although all of the isolates tested were sensitive to fluopyram, the discovery of isolates resistant to boscalid and penthiopyrad suggests that all SDHI fungicides should be considered at high risk of resistance development in Michigan. References: (1) K. Fairchild et al. Crop Prot. 49:31, 2013. (2) T. Miles et al. Plant Pathol. doi: 10.1111/ppa.12077, 2013. (3) P. Wharton et al. Plant Dis. 96:454, 2012.

scholarly journals Interrupted Wet Period (IWP) to Forecast the Aerial Alternaria in Potato Crops of A Limia (Spain)

Agronomy ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 585 ◽  
Author(s):  
Meno ◽  
Escuredo ◽  
Rodríguez-Flores ◽  
Seijo
Keyword(s):  
Early Blight ◽  
Potato Crop ◽  
Alternaria Solani ◽  
Weather Conditions ◽  
Economic Losses ◽  
Risk Of Infection ◽  
Climate Conditions ◽  
Crop Cycle ◽  
Minimal Environmental Impact ◽  
Potato Crops

Potato early blight caused by Alternaria solani generates significant economic losses in crops worldwide. Forecasting the risk of infection on crops is indispensable for the management of the fungal disease, ensuring maximum economic benefit but with minimal environmental impact. This work aimed to calculate the interrupted wet periods (IWP) according to the climate conditions of A Limia (Northwest of Spain) to optimize the prediction against early blight in potatoes. The study was performed during nine crop cycles. The relative hourly humidity and Alternaria concentration in the crop environment were taken into account. Alternaria levels were monitored by aerobiological techniques using a LANZONI VPPS-2000 volumetric trap. The relationships between weather conditions and airborne Alternaria concentration were statistically analyzed using Spearman correlations. To establish the effectiveness of wetness periods, the first important Alternaria peak was taken into account in each crop cycle (with a concentration greater than 70 spores/m3). Considering the six interrupted wet periods of the system, it was possible to predict the first peak of Alternaria several days in advance (between 6 and 38 days), except in 2007 and 2018. Automated systems to predict the initiation of early blight in potato crop, such as interrupted wet periods, could be an effective basis for developing decision support systems. The incorporation of aerobiological data for the calculation of interrupted wet periods improved the results of this system.

scholarly journals A Novel Rhizospheric Bacterium, Bacillus Velezensis NKMV-3 as a Biocontrol Agent against Alternaria Leaf Blight in Tomato

2021 ◽  
Author(s):  
Vignesh Murthy ◽  
VedhaHari BodethalaNarayanan ◽  
MubarakAli Davoodbasha ◽  
MadhanShankar ShankarRamakrishanan
Keyword(s):  
Early Blight ◽  
Plant Pathogens ◽  
Alternaria Solani ◽  
Inhibitory Effect ◽  
Rrna Gene ◽  
Bacillus Velezensis ◽  
Bacterium Bacillus ◽  
Blight Disease ◽  
Molecular Sequencing

Abstract A novel strain of Bacillus isolated from rhizosphere has shown to be excellent biocontrol agents against various plant pathogens. In this study, a first report of a Bacillus strain NKMV-3 which effectively controlling Alternaria solani, which cause the Early Blight disease in tomato. Based on the cultural and molecular sequencing of 16S rRNA gene sequence, the identity of the strain was confirmed as Bacillus velezensis NKMV-3. The presence of the lipopeptide which are antibiotic synthesis genes namely Iturin C, Surfactin A, Fengycin B and D were confirmed through gene amplification. In addition, lipopetides was also confirmed through liquid chromatography. The extract showed inhibitory effect against A.solani in-vitro and detached tomato leaf assays. Bacillus velezensis strain NKMV-3 based formulations may provide an effective solution in controlling early blight disease in tomato and other crops.

scholarly journals Antifungal activity against Alternaria solani and control of early blight in tomato by essential oil of bergamot orange

2020 ◽  
pp. 1861-1874
Author(s):  
Camila Hendges ◽  
José Renato Stangarlin ◽  
Márcia de Holanda Nozaki ◽  
Eloisa Lorenzetti ◽  
Odair José Kuhn
Keyword(s):  
Essential Oil ◽  
Mycelial Growth ◽  
Early Blight ◽  
Culture Media ◽  
Alternaria Solani ◽  
Maximum Growth ◽  
Tomato Crop ◽  
Toxic Activity ◽  
Progress Curve

The early blight (caused by the fungus Alternaria solani) results in significant damage to the tomato crop, directly affecting productivity. An alternative to the frequent use of pesticides is the use of essential oils, which can act in defense against phytopathogens. The objective of this work was to evaluate the toxic activity in vitro of the bergamot orange (Citrus aurantium ssp. bergamia) essential oil against A. solani, the control of the early blight, and the activity of defense enzymes in tomatoes treated with this oil and inoculated with A. solani. Mycelial discs of A. solani were added to dishes with V8 culture media to which essential oil at concentrations of 0, 500, 1000, 1500, 2000, and 2500 µL L-1, in addition to a standard fungicide treatment (azoxystrobin + difenoconazole, 200 + 125 g L-1, respectively) was added. The Petri dishes were incubated at 25 °C in the dark. Mycelial growth was evaluated daily for 19 days, when all treatments reached maximum growth. Sporulation analysis was performed thereafter. Tomato plants were treated with bergamot essential oil, 30 days after transplanting, in the concentrations and fungicide mentioned, in the second pair of leaves. After 72 hours, the pathogen was inoculated using a spray bottle, on treated leaves (second pair of leaves) and untreated leaves (third pair of leaves). The area under the disease progress curve (AUDPC) was calculated based on five severity assessments. The activity of peroxidase (POX), polyphenol oxidase (PPO), and phenylalanine ammonia-lyase (PAL) was evaluated in leaves treated with the concentration of 2500 µL L-1 of essential oil. The concentration of 2500 ?L L-1 reduced mycelial growth and sporulation of the pathogen by 68.15% and 29.48%, respectively. In treatments with application of essential oil, lower AUDPC was observed for a concentration of 2500 ?L L-1, which was statistically similar to that observed for fungicide application, both in treated and untreated leaves. A greater activity of PPO, POX, and PAL was found locally and systemically, both in the second and third leaves, at concentration of 2500 ?L L-1. The essential oil of bergamot can be an alternative for the control of early blight in tomato.

scholarly journals In-vitro evaluation of fungicides at different concentrations against Alternaria solani causing early blight of potato

2020 ◽  
Vol 9 (4) ◽  
pp. 1874-1878
Author(s):  
Arshad Husain ◽  
Md Mahtab Rashid ◽  
Nishar Akhtar ◽  
Abdul Muin ◽  
Gufran Ahmad
Keyword(s):  
Early Blight ◽  
Alternaria Solani ◽  
In Vitro Evaluation

scholarly journals Fenugreek extract application improves plant performance of Alternaria solani infected tomato plants

2021 ◽  
Vol 58 (04) ◽  
pp. 1263-1275
Author(s):  
Rashid Iqbal Khan
Keyword(s):  
Plant Extracts ◽  
Fungal Pathogens ◽  
Early Blight ◽  
Growth Parameters ◽  
Alternaria Solani ◽  
Plant Performance ◽  
Total Phenolic ◽  
Tomato Plants ◽  
Chlorophyll Pigments

Plant extracts (PE’s) has emerged as a safer alternative to manage the fungal pathogens affecting tomato productivity. The current study aimed to evaluate the antimicrobial potential of methanolic fenugreek extract against Alternaria solani, a causal agent of early blight disease in tomato. Fenugreek extract was used at different concentrations of 5%, 10%, 15%, 20% and 25% under in vitro conditions. Results concluded that 25% fenugreek extract significantly reduced the radial growth (2.5 cm) of A. solani under in vitro conditions. Based on in vitro results, three concentrations (5%, 15% and 25%) of fenugreek extract was examined under greenhouse and field conditions. The outcomes expressed that 5% fenugreek extract reduced the disease severity up to 30.19% under greenhouse conditions and up to 40.53% under field trials. Although, application of fenugreek extract had exhibited non-significant impact on vegetative and reproductive growth parameters. However, its application had proved better results as compared to those plants which are infected with A. solani but received zero application of fenugreek extract. Furthermore, the effectiveness of plant extracts was evaluated by variant photosynthetic, antioxidative, polyphenolic and hypersensitive response of A. solani affected tomato plants. The 25% fenugreek extract application had augmented the chlorophyll pigments along with the significant increment of superoxide dismutase (174.16 U mg-1 protein), peroxidase (7.61 µmol min-1 g-1 protein) and catalase activity (4.73 nmol min-1 g-1 protein). Similar outcomes were observed regarding phenolic compounds, where 5% fenugreek extract application had enhanced flavonoid levels (26.62 mg QuE g-1), tannins (1.28 mg TE g-1 extract) and total phenolic contents (2.39 mg GAE g-1) in tomato leaves demonstrating its protective effect against early blight. In dose response, 25% fenugreek extract was most effective in reducing lipid peroxidation and enhancing H2O2 levels. The outcomes of study exhibited the fenugreek extract as an effective strategy to be used against A. solani to control early blight infection in tomato plants. Thus, it can serve as suitable fungicide alternative for resource-poor agriculture areas mainly in developing countries.

scholarly journals INFLUENCE OF VARIOUS MEDIA AND NUTRIENT SOURCES ON ALTERNARIA SOLANI CAUSE EARLY BLIGHT DISEASE IN TOMATO

2021 ◽  
Vol 21 (no 1) ◽  
Author(s):  
B. Rex ◽  
G. Rajasekar
Keyword(s):  
Mycelial Growth ◽  
Leaf Extract ◽  
Early Blight ◽  
Carbon Sources ◽  
Nitrogen Sources ◽  
Alternaria Solani ◽  
Dry Weight ◽  
Potato Dextrose Broth ◽  
Nutrient Sources

Early blight of tomato (Solanum lycopersicum L.) incited by Alternaria solani is highly destructive causing yield loss up to 78 per cent. The fungus was tested with different media along with the host extract and different nutrient sources for their growth and development in in vitro. Twelve different media were tested on the growth of A. solani, among them potato dextrose agar + host leaf extract recorded maximum radial mycelial growth of A. solani (89.57mm) and potato dextrose broth + leaf extract has maximum mycelial dry weight (613mg). Six carbon and nitrogen sources amended media were tested. Among carbon sources, glucose recorded maximum radial mycelial growth (74.65mm) and mycelia dry weight (709.17mg). Among the nitrogen sources, ammonium nitrate has the enhanced the radial mycelail growth (84.56 mm) and high mycelial dry weigh (654.27mg). This study will be helpful for further investigations on the physiology of the fungus and management of the disease.

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