Article Summary

User Generated

wnlznb2

Science

Description

Write an half page summary of this article, as simple as you can, double space. Fewer complex characters.

Unformatted Attachment Preview

MANAGEMENT OF SCLEROTINIA WHITE ROT OF BEANS WITH ANTAGONISTIC MICROORGANISMS Journal of Animal and Plant Sciences. 27.2 (Apr. 30, 2017): p542. From General OneFile. Copyright: COPYRIGHT 2017 Asianet-Pakistan http://thejaps.org.pk/ Full Text: Byline: Basheer A. Alsum, Mohamed Elsheshtawi, Maged T. Elkahky, Abdallah M. Elgorban, Marwah M. Bakri and Manal M. Alkhulafi ABSTRACT In the present study, antagonistic activity of locally isolated bio agents including five fungi and three bacteria was evaluated against Sclerotinia sclerotiorum (Lib.) de Bary casual of white rot of snap beans. All tested biocontrol agents were able to inhibit radial growth and sclerotia viability in dual culture assay. Trichoderma hamatum (Bonorden) Bainier was the most effective agent in suppressing the mycelial growth of S. sclerotiorum by 93% compared to control. Whereas, tested isolates of Trichoderma viride Pers and Coniothyrium minitans Campbell were able to completely deactivating all treated sclerotia. In field trial, same isolates were tested in comparison of other commercial bio products. Naturally infested soil with S. sclerotiorum treated with local isolated bio agents as well as some commercial bio agents. Local isolate of C. minitans was the most effective in reducing disease incidence and the disease severity by 94.6% living plants (5.4 % mortality) and 13.0, respectively. Trichoderma hamatum and Contans(r) (commercial product C. minitans) also minimized disease severity by 14 and 16.2%, respectively when compared to untreated control. Among tested bacterial bicontrol agents, Pseudomonas fluoroscens was the best in reducing disease severity by 21.3% compared to controls. Yield data showed that Trichoderma hamatum increased total yield (10.485 ton/ha) Conversely, C. minitans was the best in increasing quality of yield in terms of exportable yield that giving 9.729 ton/ha. Keywords: Coniothyrium minitans; white rot; low tunnel; beans. INTRODUCTION Sclerotinia sclerotiorum (Lib.) de Bary, considers one of the most destructive soil borne pathogens. It has been reported that this pathogen affects a wide range of wild and cultivated cops. It can infect over 408 species and 42 subspecies of plants at all stages of growth in field, moreover the infectioncould be developed during transit and storage of the product during postharvest stages (Barari et al., 2010). The resulted disease is commonly known as white mold, sclerotinia wilt or stalk rot. White rot considers one of the most important limitation factor in producing green beans in Egypt. S. sclerotiorum has been isolated from soil samples obtained from greenhouses and protected agricultural areas. These areas - where bean plants are grown-usually known to be very moist and cool. Such conditions seemed to be subsidizing factors to incidence of white rot disease. One of the major problems in controlling this disease, that the pathogen produces large numbers of sclerotia which could stay viable for a long time in the soil. During the growing season, depending on various diverse environmental factors, sclerotia start to germinate and produce either mycelium or ascospores by developing an apothecium (Elgorban et al., 2013). Ascospores are the primary inoculum for epidemics in many crops. They can move for a long distance to neighboring fields and infect plants in adhering fields. The fungus is capable of infecting flowers, leaves, fruits or stems. Wide host range of S. sclerotiorum make the control process more difficult. According to FAO STAT database Egypt exported about 37597 thousand ton of green beans in 2013. Most of this yield were exported to European Union fresh market. Beside known problems of using chemical control of white rot in beans such human health concerns, environmental pollution, and development of resistant isolates, most exporting regulation restrict using chemical pesticides for controlling white rot of snap beans. Biological control as a disease management strategy in protected agricultural areas could be economical and durable. It helps in reducing potential inoculum, which will lead to decreasing amount of disease produced by the pathogenic fungus. Several biocontrol agents have been screened for the control of S. sclerotiorum. For instance, Ulocladium atrum found to be a successful bio agent to management of S. sclerotiorum (Fernando et al., 2007). Furthermore, Trichoderma and Bacillus species seemed to be effective bio agents against S. sclerotiorum (Zhang et al., 2004; Fernando et al., 2007;). The aim of this study was to evaluate the effectiveness of some local isolates of antagonistic fungiand bacteria in controlling white rot of snap beans and compare their controlling level to other available commercial bio and chemical pesticides taking in consideration the impact of that control level on the quantity and quality of green beans yield. MATERIALS AND METHODS Pathogenic fungus: Sclerotinia sclerotiorum used in this study was retrieved from sclerotia collected from diseased bean plants (Phaseolus vulgaris L.). Infected plants samples showing typical symptoms of white rot were collected from Ismailia governorate, Egypt. Collected sclerotia were surface sterilized with NaOCl solution then plated on PDA and incubated at 25 degC for 7 days. The purified fungal isolates were identified by Department of Plant Pathology, College of Agriculture, Mansoura University according to Kora et al., 2005. PDA slants from isolated fungus were kept at 4 oC for further studies. Isolation, purification and identification of antagonistic fungi: Soils from 20 different fields of Ismailia, Egypt were collected in sterile polyethylene bags. Standard serial dilution method was used for isolation of antagonistic soil fungi. The soil suspensions were done by suspending 1 g of each soil sample in 9 mL of 0.1 % peptone solution. Serial dilution has been done by transferring 1mL of the previous suspension to 9 mL of 0.1 % peptone to be diluted to 1/10. 0.1 mL from each dilution was plated onto PDA supplemented with 300 mg/L of chloramphenicol. Petri plates were incubated at 25+-2oC for 7 days until sporulation was observed. Individual colonies with typical Trichoderma characters such as green, velvety mycelia were transferred separately onto new PDA plates, incubated at 25+-2 oC for 3-5 days. The isolates that grew rapidly and formed greenish to white concentric circles were transferred to the Trichoderma-selective medium Rose Bengal agar (Williams, et al., 2003) (Magnesium sulphate heptahydrate 0.2 gm/L; Dipotassium hydrogen phosphate 0.9 gm/L; Ammonium nitrate 1.0 gm/L; Potassium chloride 0.15 gm/L; Glucose 3.0 gm/L; Rose Bengal 0.15 gm/L; and Agar 20 gm/L). The isolates were confirmed as having the same morphotype as on PDA and then stored as purified isolates in 50 % (v/v) glycerol at -80 oC. Trichoderma spp. and Clonostachys rose were identified by microscopic observations according to identification keys of Bissett (Bissett, 1991a; Bissett, 1991b; Rifai, 1969). Conothyrium minitans Campbell, Isolate, the commercials product Trifender(r) (Trichoderma asperellum Samuels, Lieckf. and Nirenberg) and Contans(r) (C. minitans Campbell) were obtained from Plant Pathology Department, Plant Protection Research Institute, Budapest, Hungary. Spore suspensions of antagonistic fungi were prepared by subculture each fungus on PDA then incubated for 15 days at 25+-2 oC in the dark then adding 5 ml of sterilized distilled water and 2 drops of tween 20 to each plate and scrap the surface with sterilized spatula to harvest the spores. The resulted suspension has been transferred to sterilized baker through two layers of sterilized cheese cloth to get rid of mycelial fragments. Concentration of spore suspension was adjusted to 1x106 using hemocytometer slide to count spores and sterilized distilled water to dilute the suspension Isolation and Identification of antagonistic bacteria: Pseudomonas fluorescens was isolated from the rhizosphere of healthy green beans obtained from farmland in Ismailia, Egypt, using King's B medium. The identification of P. fluorescens was based on morphology, Gram staining, physiological and biochemical tests (Krieg and Holt, 1984). Locally isolated Bacillus subtilis was obtained from Center Laboratory Organic Agriculture, Agricultural Research Center, Egypt, where the commercial product Mycostop(r) (lyophilized spores of Streptomyces griseoviridis) obtained as a kind gift from the Kemira OY(r) of Finland. B. subtilis and P. fluorescens were grown on Nutrient Agar medium (NA), while Streptomyces griseoviridis was used as spore suspension from the commercial product Mycostop(r). Effect of antagonistic fungi on mycelial growth of Sclerotinia sclerotiorum in vitro: One mycelial discs 5 mm in diameter from 7 days old culture of antagonistic fungi (Trichoderma harzianum, Trichoderma viride, Trichoderma hamatum, Clonostachys rosea, and Coniothyrium minitans) were placed in facing 5 mm disc of S. sclerotiorum on in 90 mm Petri dish containing PDA, with four replicates. Control treatments conducted same as in treatments but without antagonistic fungi disc. All plates were incubated at 25+-2 oC for 15 days. Percentage of mycelial growth inhibition was calculated after 3 and 15 days by comparing the radial growth in treatments plates to control. Effect of antagonistic bacteria on Sclerotinia sclerotiorum (Lib.) de Bary: One disc, 5 mm in diameter of mycelial growth of S. sclerotiorum was placed in side of Petri dish and antagonistic bacteria were spot inoculated at 3 cm distance from pathogen's disc on a PDA. The inhibition zone was observed after 3 and 15 days of incubation at 25+2 oC. Viability of Sclerotinia sclerotiorum-sclerotia treated with antagonistic microorganisms: Sclerotia were collected from 21 day old culture of S. sclerotiorum grown on PDA and incubated at 25+-2 oC then dipped into a spore suspension 1x106 cfu/ml in case of antagonistic fungi or bacterial cell suspension 1x103 cfu/ml in case of antagonistic bacteria for 5 min. After that, all sclerotia were dried on sterilized filter paper in an air current for two hours under laminar flow hood. Untreated sclerotia used as the control were dipped in sterilized distilled water. The sclerotia were placed on the bottom of Petri plates, incubated at 20+-2 oC in a sterile humidity chamber (100% Rh). After 30 days, the viability of S. sclerotiorum-sclerotia was estimated by placing them on WA for 48 h at 25degC and counting the number of emerging hyphae with phase contrast microscopy (100x). The sclerotia viability was assessed on a scale from 0 to 4, and sclerotia viability index (VI) was calculated according to Jager and Velvis, 1988. One hundred sclerotia were used for each treatment. Low tunnels experiments: Soil preparation: The experiment was performed on loamy sand soil (pH 7.16) at the protected agricultural area of exportable green bean var. Paulista under low tunnel conditions. This experiment was established at Gamal Ahmed Farm, Faid city, Ismailia governorate, where fields were naturally infested with S. sclerotiorum. Fertilizers were applied according to the recommendation of Agricultural extension department in that area, in amount per hectare were as follows, 168 kg agriculture sulfur, 480 kg calcium phosphate Ca(H2PO4)2, 240kg Ammonium sulfate (NH4)2SO4, and 120kg K2SO4, while the organic amendments were 24m3 chicken manure and 12 m3 livestock manure. All fertilizers were applied at the beginning of the first season. The experiment had randomized complete block design. The plots were 0.75x5.0 meter, 10 cm distance between plants, with three replicates per treatment. Effect of antagonistic microorganisms on disease incidence and disease severity of white rot in beans: This test was done to evaluating antagonistic ability of five fungal antagonists and two bacterial antagonists in addition to three commercial biofungicides products; Contans(r) (C. minitns Campbell, 1x109 cfu/mL) and Trifender(r) (T. asperllium 1x106 cfu/mL) and Mycostop(r) (S. griseoviridis, 1x106 cfu/gm) in controlling whit rot of green beans under natural infestation conditions. Antagonistic fungi were applied as spore suspensions (1x 106 cfu/ml) through drenching soil at 5 days after sowing (DAS) at rate 50 ml spore suspension per plant. The control treatments were naturally infested soil without any treatment. Three chemical pesticides were used as chemical check at recommended dose. Chemical pesticides were also applied with same method (soil drenching 50 ml/ plant). Used pesticides were Topsin M-70(r) (2 gm/L), Rizolex(r) and Captan(r) (3 gm/L). The disease incidence calculated as average of dead plants numbers. The number of surviving plants after 15, 45 and 60 DAS were recorded. Disease severity (DS) was assessed on 0 to 4 scale. At the end of the season, plants were removed and washed to be free of soil then roots were visually assessed for percentage of affected root area that was due to Sclerotinia rot and each plant was assigned a root disease score 0-4 as follows:-0=lesions and necrosis absent from roots; 1= 1-25 % of total root area necrotic; 2 = 26-50 % of total root area necrotic; 3 = 51-75 % of total root area necrotic; 4 = 76-100 % of total root area necrotic. The DS was calculated with the following formula: Disease sevarity = Sum of all rating / Total number of plants x Maximun score x 100 In addition, number of branches, plant height, total yield and exportable yield were recorded as indicators for non-direct impact on controlling the pathogen. Statistical analysis: Collected data were statistically analyzed using the Statistic Analysis System Package (SAS institute, Cary, NC, USA). Differences between treatments were studied using Fisher's Least Significant Difference (LSD) test and Duncan's Multiple Range lest (Duncan, 1955). All analysis was performed at P: 5 % level. RESULTS Effect of the antagonistic fungi on Sclerotinia sclerotiorum: After 3 days, C. minitans Campbell was the most effective against S. sclerotiorum with 74.4% reduction in the mycelial growth. This was followed by T. hamatum (Bonorden) Bainier that cause 60.0% inhibition in the mycelial growth (Table 1). Conversely, T. hamatum (Bonorden) Bainier was the most effective against the radial growth of S. sclerotiorum after 15 days, with 93.0%, followed by T. viride Pers, T. harzianum Rifai and C. minitans Campbell that causing 91.9, 91.7 and 91.1% reduction in the mycelia growth, respectively. Effect of the antagonistic bacteria on Sclerotinia sclerotiorum: Data in Table 2 show the tested antagonistic bacterial strains significantly reduced pathogens growth in comparison to the control. P. fluoroscens was the most effective against S. sclerotiorum that giving 40.2 and 61.9% inhibition at 3 and 15 days, respectively. Viability of Sclerotinia sclerotiorum-sclerotia inoculated with antagonistic fungi: Germination of S. sclerotiorum-sclerotia was extremely reduced by antagonistic fungi (Table 3). S. sclerotiorum-sclerotia inoculated with T. viride Pers and C. minitans Campbell were completely deactivated, while non-inoculated sclerotia showed 85.8% viability index. Viability of Sclerotinia sclerotiorum sclerotia inoculated with antagonistic bacteria: The effect of antagonistic bacteria on sclerotia viability is presented in Table 4. Treatment of sclerotia by antagonistic bacteria caused comparable results in VI of the sclerotia ranging from 19.5% VI in case of P. fluorescens to 20.5% in case of Mycostop(r), while the control was 85.8% VI.
Purchase answer to see full attachment
User generated content is uploaded by users for the purposes of learning and should be used following Studypool's honor code & terms of service.

Explanation & Answer

Attached.

Surname 1
Name
Course
Instructor
Date
Article Summary
Alsum, B. A., Elsheshtawi, M., Elkahky, M. T., Elgorban, A. M., Bakri, M. M., &
Alkhulafi, M. M. (2017). MANAGEMENT OF SCLEROTINIA WHITE ROT OF
BEANS WITH ANTAGONISTIC MICROORGANISMS. JAPS: Journal of Animal
& Plant Sciences, ...


Anonymous
Great! 10/10 would recommend using Studypool to help you study.

Studypool
4.7
Trustpilot
4.5
Sitejabber
4.4

Related Tags