جستجوی مقالات مرتبط با کلیدواژه « Antagonist » در نشریات گروه « گیاهپزشکی »

One of the effective methods to reduce pest damage is to induce resistance in plants. This study investigated the impact of inducing resistance using indigenous isolates of Trichoderma spp. and a commercial product (Trichorun), as well as indigenous isolates of Bacillus subtilis (Ehrenberg) and a commercial product (Serenade), along with chemical compounds like Salicylic acid and Humic acid on the host preference and oviposition of the greenhouse whitefly Trialeurodes vaporariorum (Westwood), as well as on plant growth factors. Four tests were conducted to assess the effects of these treatments on the growth factors of tomato (Vadaro 1012), total phenol levels, host preference and oviposition of whitefly in the greenhouse conditions (25 ± 2°C, 60-70% RH, 16:8 h light: dark). The results indicated that the root treatment of the plants with the native strain of Trichoderma harzianum (Rifai) and the treatment of the combination of Trichorun with Serenade have the best performance in plant growth with a significant increase in the root volume, fresh and dry weight of the root and aerial parts of tomato compared to the control. Compared to control, Serenade treatment showed the best results in measuring total phenol, host preference and oviposition of whitefly in the greenhouse with a significant decrease in the average number of insects attracted to the leaf underside, and egg laying rate in the selective test and emerged adult insects in F1generation in the non-selective test.  The findings of this research showed that root inoculation with native isolates of T. harzianum fungus and B. subtilis bacteria increased tomato growth factors, induced resistance to greenhouse whitefly and reduction of host preference and oviposition of whitefly.

Curtobacterium flaccumfaciens pv. flaccumfaciens is the cause of bean bacterial wilt (CFF) and a dangerous pathogen for bean fields. To date, no definitive control has been found for this pathogen. In sustainable agriculture, it is used to control plant pathogens by applying management methods related to preserving the environment and producing organic products. The use of biological agents such as Trichoderma fungi and Pseudomonas bacteria is among these management methods. Minimal research has been done worldwide on biological agents' effects on CFF. Therefore, the present research will investigate the effect of inhibiting the growth and activity of two biological agents , including Pseudomonas fluorescens and Trichoderma harzianum, against CFF in laboratory and greenhouse conditions.

First, the pathogenicity test of CFF was carried out on the greenhouse's Sadri variety pinto bean plant. Then, the effect of fungal and bacterial biological agents against the pathogenic agent was investigated by two methods of mutual culture and their secreted substances in laboratory conditions. By measuring the diameter of the transparent halo formed around the extract and spot culture of biological agents, the growth inhibition power of these biological agents against CFF was evaluated. In order to investigate the effect of these biological agents against bacterial wilt disease in greenhouse conditions, these biological agents and pathogens were propagated and expanded, and a standard suspension was first prepared from them. These suspensions were inoculated on the host plant using the spraying method. During 21 days, disease symptoms and bean plant indicators have been recorded. Then, the disease severity of progress under the influence of these biological factors was checked using the 0 to 4 scoring system. Also, the plant resistance type to the pathogen was evaluated using the 1-5 scoring system. The data obtained from the laboratory (inhibition percentage) and greenhouse (treatment changes, plant resistance, and plant indices) studies were analyzed in a completely randomized design using SPSS 21 software.

In laboratory conditions, P. fluorescens and T. harzianum treatment prevented the growth of pathogenic bacteria CFF by 18.67 and 27.33%, with a diameter of the inhibitory halo of 14 and 20.5 mm, respectively. It was also found that a significant part of the inhibitory effect of P. fluorescens bacteria (about 85.70%) is related to the secreted substances of the bacterial cells. In contrast, in the biological fungus T. harzianum, the effect of the secreted substances was about 50.02%. The effect of biological factors on CFF in greenhouse conditions showed that these biological factors strengthen the defense reaction of bean plants against CFF. So, the sensitive reaction of the plant against CFF bacteria (with a disease severity of 83.13%) was transformed into a semi-resistant reaction by inoculating P. fluorescens and T. harzianum with the diseased plant. Also, the inoculation of the combination of these two biological factors made the plant resistant to pathogenic bacteria. Treatment of P. fluorescens+T. harzianum, by affecting CFF bacteria, was the best treatment in reducing the severity of the disease during 7, 14, and 21 days; the severity of the disease on these days was 21.87, 33.12, and 36.25%, respectively, which showed a significant difference with the disease severity index in infected treatment during these few days at the statistical level of 1%. Treatment of P. fluorescens+T. harzianum, with a disease severity index of 36.25% and a 57.04% reduction in disease severity, showed the most significant effect on the reduction of bean bacterial wilt disease.

In the present study, the use of two biological agents, P. fluorescens and T. harzianum, showed significant controlling effects on CFF in laboratory and greenhouse conditions, and 57.04% reduced the severity of this disease in the bean plant. These two biological factors prevent the growth and spread of plant pathogens by using mechanisms such as the production of secondary metabolites, acidifying the environment, competing for food and space, colonizing and stimulating the plant to produce phytoalexin, proteins related to pathogens, salicylic acid, etc. Therefore, using these two biological agents as safe, effective, and durable biological control agents in sustainable agriculture against bean bacterial wilt disease is recommended.

The aim of this study is to investigate the interaction effects of two Trichoderma spices (T.koningii and T. virens) mutants and endophyte Piriformospora indica on infected cucumber plants by Fusarium oxysporum f. sp. radicis-cucumerinum (Forc) and evaluating their mutual influence on growth indexes in cucumber plants.The efficient wild-type Trichoderma isolates were selected by dual-culture test (T.koningii NAS-108 with 50% and T.virens NAS-115 with 33% inhibition of pathogenic growth) and their spore suspension with a concentration of 106 (spore/ml) in a dose range of 250 Gy was irradiated with gamma rays. NARS-TKM101 and NARS-TviM112 mutants showed highest antagonistic activity by 20% and 100% increase compared to their wild-type strains and they with their wild-type strains, were used for greenhouse evaluations. The combined treatments of Trichoderama sp. (total wild types and total mutants) with P. indica showed the most positive effects on seedlings growth indices length and dry weight (stem and root). No significant difference was observed between un-irradiated and mutant strains of Trichoderma in reducing disease index, (p<5%), but the combined treatments of two Trichoderma fungi (total mixed Trichoderama wild types and total mutants) with P. indica led to significant reduction of disease index (p<5%) and were more successful than the carbendazim fungicide in the plants infected with Forc.

Macrophomina phaseolina causal agent of charcoal rot, stem, and seedling rot, causes economic losses on over 500 plant species including tomato and melon around the world every year. One of the most important and effective alternative methods for chemicals and reducing their risks is biocontrol using different agents such as endophytic fungi. In the present study, the effect of some endophytic fungi on charcoal rot disease and the growth indices of tomato and melon plants were assessed. In the dual culture test, among the 12 endophyte species, five isolates including Chaetomium globosum 2S1, Ch. globosum 3L2, Fusarium fujikuroi 37F6, F. acuminatum GO2L1, and F. incarnatum 25S3 which had the highest inhibition of pathogen mycelia growth, were selected for further tests. In the volatile compounds test, all endophytic isolates showed more than 90% inhibition of pathogen mycelia growth. In biocontrol assay under greenhouse conditions, all endophytic isolates except F. fujikori 37F6, completely prevented disease on both tomato and melon plants. In the evaluation of the growth indices and by comparing the treated plants with the infected and healthy controls, no positive effect of the selected endophytic isolates was observed on the growth indices of both plants. However, they reduced the harmful effects of the pathogen and thus reduced the charcoal rot disease severity. Recovery of endophyte isolates from both inoculated melon and tomato plants showed that the surveyed isolates can become endophytes in plant tissue.

One of the aggravating factors in the amount of frost damage, is the presence of epiphytic ice nucleation bacteria on plant philosopher. Biological control of ice nucleation bacteria seems to be a promising option to reduce this type of frost damage. In this study, the antimicrobial capacity of epiphytic bacteria and actinomycetes was evaluated through growth inhibition of ice nucleation active bacteria (Pseudomonas fragi raf3) on pistachio in Rafsanjan. For this purpose, samples were collected from healthy pistachio leaves in Rafsanjan. Among the isolated bacteria and actinomycetes, two isolates (A4 and B52) with the highest inhibitory zone were subject to different biochemical and physiological tests. Results showed that the zone of inhibition growth of ice nucleation bacterium on Petri dish, was 20 mm and 14 mm for isolates A4 and B52 respectively. Analysis of morphological and biochemical characteristics showed that isolate A4 was noted to be Gram-positive and to form white, dry colonies similar to actinomycetes. It was able to degrade glucose and sucrose as a carbon source and able to produce lipase, protease and catalase enzymes. This isolate was able to grow in conditions with pH 5 and 7, as well as, showed 2, 5,7 and 10% (w/v) salt-salt (sodium chloride) tolerance. It was tetracycline-sensitive and penicillin-resistance. The other antagonist isolate, B52, had yellow colonies on nutrient agar media Gram-negative bacterium, catalase positive, oxidase negative, facultative anaerobic and lactose fermenting.

Gray mold, caused by Botrytis cinerea is one of the most important diseases in strawberry, causing pre– and postharvest fruit rot. One of the safe and healthy ways to reduce this disease is biocontrol and the use of biological control agents. In this study, using culture–based methods, 268 bacterial strains, and 136 fungal isolates, were isolated and purified from the phyllosphere of strawberry plants in the greenhouse and field in Jiroft city. The antagonistic effect of the isolates against the pathogen B. cinerea was investigated using dual culture and investigation of the inhibition zone, and the effect of volatile compounds under in vitro conditions, as well as the antifungal properties of the antagonistic bacteria on strawberry fruit. Identification of the selected bacterial and fungal strains was made by polymerase chain reaction, respectively, by determining the nucleotide sequence of a part of the 16S–rDNA gene and its region. The results showed that among the examined isolates, bacterial isolates UJB1, UJB3, UJB4, UJB10, UJB5, UJB6, UJB7, UJB11, UJB2, UJB8 and UJB9 and fungal isolates UJF1300, UJF1301, UJF1302, UJF1303, UJF1304, UJF1305 had an effective inhibitory effect against B. cinerea and their volatile compounds reduced pathogenic mycelium growth. In evaluating the antifungal impact of bacterial isolates on strawberry fruit, bacterial isolates UJB8, UJB2, UJB11, UJB6, UJB5, UJB10, UJB4, and UJB1 significantly increased the disease index caused by B. cinerea compared to They reduced the witness. According to morphological and molecular data, bacterial isolates belonging to the genera Delftia (isolates UJB1, UJB3, UJB4, UJB10), Bacillus (isolates UJB5, UJB6, UJB7, UJB11, and UJB2) and Stenotrophomonas (isolates UJB8 and UJB9) and fungal isolates belonging to Albifimbria verrucaria, Aspergillus terreus, Leptosphaerulina australis, Pilidium lythri, Pseudozyma flocculosa, and Seimatosporium pistaciae species.

To evaluate the effects of Streptomyces bacteria on biocontrol of Tylenchulus semipenetrans in Citrus aurantifolia and Meloidogyne incognita in Actinidia deliciosa, samples were collected from the rhizosphere of citrus and kiwifruit trees in Mazandaran, Guilan, and Golestan provinces. In vitro, 9 Streptomyces isolates showed good antagonistic potential and reduced the rate of egg hatching and larval mortality of citrus nematode and root-knot nematode. Isolates of Streptomyces sp. (C, D, E, G, and H) which had high control ability in vitro were examined in the greenhouse. Among the isolates studied, isolates D and G in greenhouse conditions showed the greatest effect on the control of citrus nematodes by reducing the number of female nematodes by 86.81% and 77.65% compared with the fenamiphos 64.47% Also, these two isolates decreased galls by 67.78% and 71.15% compared with the fenamiphos 50.93% and reduced the number of egg masses by 86.54% ccompared with the phenamiphus 68.90%, had good performance in root-knot nematode control.

The greenhouse whiteflies, Trialeurodes vaporariorum (Westwood), are one of the major pests of vegetable and ornamental crops in greenhouses in the world. They damage crops through direct feeding, inserting their stylet into leaf veins, and extracting nourishment from the phloem sap. As a by-product of feeding, honeydew is excreted, which is an indirect but yet another substantial source of damage. The third most harmful characteristic is the ability of adults to transmit various plant viruses. Induced resistance is a non-chemical control method that has no negative impact on the environment and human health and can be a desirable approach in plant protection and pest control. Trichoderma spp. has spread in many ecosystems and its various species such as Trichoderma harzianum Rifai have been successful as non-pathogenic symbionts in controlling plant pathogens via different mechanisms. Some of these mechanisms include enzymatic degradation, secretion of antibiotics, and increasing root absorption capacity. Recent findings suggest that T. harzianum is also a potent inducer of Induced Systemic Resistance (ISR) and can stimulate the immune system in plants against plant diseases and pests. In this study, the efficacy of T. harzianum Tr6 was investigated on host preference and egg production of T. vaporariorum.

To evaluate the effect of T. harzianum Tr6, four tests were carried out: 1) Total phenol assay using Folin–Ciocalteu reagent, 2) The effect of time on induced resistance, 3) Free choice, and 4) Non choice. These tests were conducted on tomato plants (Falat cultivar) at 25±2°C, relative humidity of 60-70%, and a photoperiod of 8 h/16 h (day/night). Also, these experiments were performed on one-day-old adults in plots with four or six leaves in shelves equipped with organza mesh.

According to the phenol assay, the highest amount of total plant phenol was observed three and four days after inoculation by Tr6 strain respectively 0.3503±0.001 and 0.3323±0.001mg/g. Therefore, for the next three tests, plants that were inoculated after three days were used as treated samples, and plants watered with distilled water were used as control ones. In these experiments, the lowest number of adults on the back of the leaves after 24 hours was observed two and four days upon inoculation respectively 2.2±  0.86 and 2.0±  0.63. On the other hand, plants inoculated by Tr6 displayed a significant decrease in adults on the back of the leaves (3.4± 0.66), egg-laying (7.4± 1.51), and honeydew droplets (1± 0.28) compared to control plants.

The most important factor in controlling the whitefly population is reducing the reproduction rate. Induced resistance can repel insects from plants and limit their nutrition, and thus, reduce their reproduction. This study implied that the inoculation of tomato by T. harzianum Tr6 strain could induce resistance to whitefly and reduce host preference and egg production, as well as honeydew secretion. Therefore, this strain can be a promising option in preventing the outbreak of this multi-generational pest.

Take-all disease of wheat caused by Gaeumannomyces graminis var. tritici is one of the important diseases of wheat worldwide. In this study, application of two Trichoderma species on the control of this disease was evaluated under laboratory and greenhouse conditions. The causal agent of disease was isolated from suspected diseased plants in wheat fields of Khorrramabad district, identified according to scientific mycological literatures and its pathogenicity was proven in greenhouse. The mycelial inhibition potential of Trichoderma harzianum and T.viride in dual culture and volatile metabolite effects against the pathogen were tested in vitro. Then, single and combined greenhouse application of the two Trichoderma isolates and triadimenole fungicide for control of take-all disease were investigated using a completely randomized design with 16 treatments and four replications and disease severity and growth indices were recorded and analyzed statistically. In vitro experiments showed that both of the Trichoderma species disintegrated the hypha and inhibited the mycelia growth of G. graminis. Combined application of triadimenole fungicide with the two antagonists, triadimenole, and single application of T. harzianum and T. viride reduced take-all severity by 70.6, 58, 47.06 and 47.06 percent, respectively in greenhouse after 30 days of sowing. Trichoderma biocontrol agent and integration of chemical compounds with antagonists would provide promising strategy for management of wheat talke-all disease.

Colonization and population of antagonistic bacteria on rhizosphere have a definite role on their antagonistic effect. In this study in order to determine optimal population density of antagonistic bacteria, in a way that they would be able to induce maximal defensive power in plant, and also in order to investigate effect of initial inoculated population and amount of plant defense enzymes, microelements uptake, chlorophyll and carotenoids; level of peroxidase, polyphenol oxidase, phenylalanine ammonia lyase, total phenolic compounds, total protein, Zn, Fe, Mn, chlorophyll a, chlorophyll b, total chlorophyll and carotenoids in population of 104, 106 and 108 of four antagonistic bacteria Pseudomonas fluorescens VUPF5, P. fluorescens T-17, Bacillus subtilis V1 and B. subtilis 96 in Sarakhs cultivar of pistachio was measured. Experiments were done in randomized complete block design with three replications per each treatment. Studies showed in the measured factors despite of diverse results in bacterial populational treatments, all populational treatments follow a constant pattern in a way that along with increasing in bacterial population, amount of measured enzymes, total phenol content, microelements, chlorophyll and carotenoids increases.

In this study, the effect of some plant probiotic bacteria were isolated from salty and dry areas were investigated in control the fungus agent pistachio gummosis disease and growth stimulating properties. 200 bacteria isolates were isolated from rhizosphere and non rhizosphere areas of pistachio trees and weeds in the margins of gardens in Kerman province. Thirty isolates were able to endure the used salt tolerant. The bacteria isolates were investigated at the hypersensitivity reaction (HR) test. Three of them were eliminated due to positive result of HR and the other were studied more as antagonist agents. In the early stage the biocontrol ability of these isolates against the fungus causing pistachio gummosis diseases such as Phytophthora drechsleri were surveied. For this purpose, inhibition zone test (antibiosis) was performed that antagonist isolates showed significant effect on P. drechsleri growth. In the secondary stage, The ability of isolates to produce some biocontrol metabolites including protease, antifungal volatile compounds and hydrogen cyanide were evaluated. Growth stimulating characteristics of these isolates incloding amount of siderophore and IAA production were measured. soluble ability of insoluble mineral phosphate was surveied, too. The results showed from 27 studied isolates for growth stimulating properties, %80 at least had one of the PGPR properties. %64 of the isolates were productive of siderophore, %80 productive of IAA, %45 having solving ability of insoluble mineral phosphate. The isolates C16, F47 and G11 as superior isolates of this study in vitro were successful in controlling the disease.

Induced resistance is one of the ways by which plants cope with the biotic stress. Phenylalanine ammonia-lyase (PAL) and lipoxygenase (LOX) as inducible defense enzymes, are synthesized by plant in response to biotic stress. This research was carried out with the aim of investigating the effect of Pseudomonas sp. isolates (antagonistic and inducer bacteria) and potassium silicate treatment on expression changes and production of enzymes at 0, 6, 12, 24, 48 and 72 hours after rice seedling contamination of Fajr cultivar to R. solani, the causal agent of rice sheath blight disease. Analysis of gene expression showed that the maximum expression was observed in 72 hours after plant inoculation, and the combination of antagonistic bacteria and potassium silicate as an inducer had the highest expression during the first 6 hours of infection. Analysis of enzyme content showed that the use of treatment compounds in the initial time interval of zero to 6 hours were caused a significant increase in protein content, which was more than the phenylalanine ammonia-lyase in the combination of the antagonistic bacteria and the potassium silicate as an inducing agent for the lipoxygenase enzyme. In general, by attacking the pathogens, the plant increases the amount of these enzymes due to the important role of these genes in defense against the pathogen. Increasing the expression level of these genes directly increases the activity of the enzymes which indicate direct role of these gens in plant defense system, that, it is possible to increase their expression by applying potassium silicate and antagonistic and inducer bacteria on the plant.

Leaf stripe disease (LSD) of grapevine, which was previously known as esca complex disease, is one of the most important and destructive trunk diseases of grapevines.Phaeoacremonium minimum is the principle hyphomycete associated with disease. Chemical control of LSD has proven difficult, meanwhile, application of biological control agents for disease management have been promising. The aim of present study was to evaluate inhibitory potentiol of three Trichoderma species sincluding one commercial product (Trichoderma harzianum T22) and two endophytic isolates, T. longibrachiatum and T. brevicompactum, against four isolates of Pm. minimum with opposite mating type (two MAT1-1 and two MAT1-2 isolates) using dual culture, volatile and non-volatile metabolite assays. The results of this study showed that all three species of the antagonist had significant inhibitory effect on the growth of Pm. minimum, in comparison to the control. In dual culture assay, T. harzianum T22 showed the highest potential in the inhibition of the Pm. minimum growth, with 76.53 percent growth inhibition, in comparison to the two other antagonists. In volatile metabolites assay, significant differences were observed among the antagonists in growth inhibition of the Pm. minimum. In non-volatile compounds assay, T. brevicompactum with 75.46 percent growth inhibition of pathogen, showed the highest control potential in comparison with the other two species. Non-volatile compounds of T. longibrachiatum and T. harzianum T22 showed 46.93 and 17.67 percent inhibition on colony growth, respectively. Evaluation of the inhibitory effects of these antagonists on the opposite mating types of Pm. minimum showed that volatile compounds of T. longibrachiatum were more effective on MAT1-1 (48.74% growth inhibition) compared to MAT1-2 (35.10 growth inhibition). Overall, the results of this study reveal T. brevicompactum as an effective antagonist against Pm. minimum; hence, further evaluation of its biocontrol properties and efficacy in disease control under greenhouse and field condition remain to be studied.

The present paper tends to assess the inhibitory impacts of the three isolates of Trichoderma harzianum obtained from the commercial products of Trianum-P, Trichomix-HV and TricofungS and the two native isolates of T. harzianum, Th1 and Th2, applied to control melon Fusarium wilt using seed coating method under both laboratory and greenhouse conditions. Melon seeds were infected with pathogen and treated by T. harzianum isolates were assessed for germination in vitro. Research results showed that Trianum and Th1 were the most effective treatments for germination (with 95 and 92.5%, respectively), in comparison with the control sample 25% and they indicated significant difference. In greenhouse, disinfected seed by tested treatments were planted in pots containing soil infected by pathogen. Treatments included the three mentioned commercial products and two propagated isolates in bran at three concentrations of 0.5, 1.5 and%0 2.5 and two fungicides of Rovral TS and Thiabendazole in concentrations of 1.5,2 and %02.5. plant growth parameters and disease severity were measured. Trianum, Tricofung, Trichomix and Rovral in concentrations of 2.5, 1.5, 2.5 and %2 reduced disease severity by 80% and 67.5%, 67.5%, 67.5% respectively. In control samples, the percentage of plants with no wilt symptoms was 7.5%. For growth parameters, the plants treated by Rovral %ₒ2, Th1, Th2 and Trianum %ₒ2.5 were the most effective seed coatings. Research results indicated that commercial and native isolates of T. harzianum had the potential of controlling Fusarium wilt in melon using seed coating method as well as tested chemical fungicides. However, different isolates of T. harzianum had different biological effects.

In order to identify and biological control of the causal agents of leaf spot on tomato in Sistan area, sampling from different fields and greenhouses have been done during the years of 2013_2014. Isolation and identification of species was achieved by using standard methods in laboratory. Finally, 102 fungi isolates were obtained and placed in 6 species of Alternaria alternate, A. dumosa, A. tenuissima, A. mimicula, A. tomaticola and Cladosporium cladosporiodes based on morphological characteristics. All of the isolated fungi were pathogenic on tomato. In this study, C. cladosporiodes is reported as the factor of disease on tomato for first time in Iran. For the sake of biological control of pathogens, from all 220 isolate of bacteria and fungi isolated from tomato rhizospheres, 10 isolates showed high antagonistic effects against pathogenic fungi using dual- culture tests. These isolates were Trichoderma harzianum, T. virens and Bacillus subtilis. In laboratorial studies, it had been revealed that T. harzianum, T. virens, BS1 and BS2 had higher antagonistic effects. The highest inhibitory effect on A. alternata was 55.67, 52.83, 58.71 and 58.57 percent, respectively. Because of this reason, these isolates were selected for biocontrol experiments in greenhouse conditions. Based on the results of greenhouse experiments, antagonistic isolates caused a decrease in the intensity of pathogenicity and improved the performance of crop characteristics. Among the antagonistic fungi, T. harzianum, and among the bacterial isolates, BS1 had shown a better result antifungal activity.