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

Strains of Pseudomonas syringae pv. syringae (Pss) are pathogenic in various types of plants, sometimes causing economic damage that requires chemical control. In Chaharmahal va Bakhtiary province, this pathogen damages stone fruit trees, wheat, beans, and greenhouse plants like cucumber. This study investigated the resistance of 62 Pss strains from different hosts to copper ions (copper sulfate) in a culture medium. Results showed that 37.1% and 32.3% of the strains were resistant to 100 and 200 µg/ml copper sulfate concentrations, respectively. Five copper-resistant strains from peach, almond, cherry, wheat, and beans and one sensitive strain from cucumber, were selected for further evaluation. The effect of various formulations containing copper compounds on inhibiting the growth of these strains in the culture medium was assessed. All five isolates showed varying resistance to copper compounds (copper oxychloride, copper oxide, copper carboxylate, and Bordeaux mixture). Doubling the concentration of these compounds did not significantly affect bacterial growth. However, adding mancozeb, zinc sulfate, or iron sulfate to each copper compound significantly inhibited bacterial growth on the culture medium. The copper carboxylate formulation combined with mancozeb was the most effective inhibition. The CopA gene, responsible for copper resistance, was detected in the five resistant strains and other Pss strains, confirming the results of the experiments. In conclusion, there is resistance to copper compounds in various Pss strains. For effective chemical control, compounds with a synergistic effect on bactericidal activity should be added to copper compounds. The most influential formulation identified in this study for reducing the population of copperresistant Pss strains and controlling diseases caused by them is a combination of copper carboxylate or copper oxide with mancozeb and urea.

The ever increasing population and global issue for food security have led us to use multiple approaches to overcome the weed problems that can reduce the crop productivity up to 70%. Chemical herbicides and mechanical and other biological approaches have overcome weed problem on one hand but also destroy the environment and caused some human health impacts on the other hand. Bioherbicides are biological control agents applied in similar ways to chemical herbicides to control weeds. Of the array of bioherbicides currently available, the most successful products appear to be sourced from fungi (mycoherbicides), with at least 16 products being developed for commercial use globally. Over the last few decades, bioherbicides sourced from bacteria and plant extracts (such as allelochemicals and essential oils), together with viruses, have also shown marked success in controlling various weeds. Despite this encouraging trend, ongoing research is still required for these compounds to be economically viable and successful in the long term. This review will explain the importance and impacts of the bioherbicides by elaborating the constraints which this approach is facing in its production and application.

Heliothis (or tomato fruit borer) with the scientific name Helicoverpa armigera (Lep.: Noctuidae) is one of the most important and the oldest pest of crops in the country, especially in Golestan Province, which causes huge management costs for farmers, and also due to the use of various types of chemical pesticides every year it causes environmental damage for the agricultural ecosystem of the country. In order to prevent unnecessary spraying and due to the resistance of this pest to many pesticides, it is necessary to consider the effectiveness of other control methods, including the use of insect pathogenic fungi and biological pesticides containing Bacillus thuringiensis. In this research, the effectiveness of three different formulations of the insect pathogenic fungus Beauveria bassiana and a biological insecticide based on the active ingredient B. thuringiensis subsp. kurstaki (Biolep P) and an organic insecticide based on plants (Rui Agro) were studied in laboratory conditions and also in two tomato field of Golestan Province. The perforation rate of tomato fruits was also investigated. The laboratory bioassay results of different formulations of B. bassiana with a concentration of 1×107 conidia/ml on 3rd instar larvae showed that all three different formulations of the pathogenic fungus caused between 84 and 91% mortality. The laboratory bioassay of different concentrations of Biolep P on the 3rd instar larvae of the H. armigera after eight days showed that when the concentration of Biolep P increased, the mortality rate also increased significantly. The highest mortality rate was observed with 93.33% in the concentration of 1.5 ml/L and the lowest mortality rate was observed with 48.89% in the concentration of 0.5 ml/L. The results in the tomato fields of Qaleh Mahmud village showed that the efficiency of the applied treatments increases with time. The highest percentage of efficiency in all experimental treatments on the 7th and 10th days after foliar spraying was between 50 and 60 percent. In the tomato field of Chalaki Agricultural Research Station, the efficiency (%) of fungal formulations was reduced on the 10th day of foliar application. In relation to the percentage of fruit perforation in both fields studied, the control treatment and the fungal treatment containing distilled water were placed in the same experimental group and showed the highest percentage of fruit perforation. In general, it can be concluded that repeated foliar spraying of biological control agents is necessary for better pest control or the combination of these methods with low–risk or organic pesticides should be considered..

One of the damaging agents for wheat is the cereal cyst nematode (Heterodera avenae). Plant Growth Promoting Bacteria (PGPR) are a group of bacteria that have beneficial properties for plant growth, including iron chelation, siderophore production, phosphate dissolution, nitrogen fixation, as well as the production of protease and chitinase enzymes. These bacteria can also be used as biological control agents. In this study, wheat roots showing suspicious symptoms of cereal cyst nematode were collected from the Dezful county in Khuzestan province during 2022-2023.  After initial investigations, nematode identification and purification was done. According to the morphometric and morphological characteristics of the larvae and cysts, especially its cone top, H. avenae was diagnosed. the effect of seven native growth-stimulating bacterial strains on egg hatching rate and mortality of cereal cyst nematode larvae in the Petri dish was investigated in the laboratory. The effect of four selected bacterial strains with sulfur treatment and Nematex EC nematicide was investigated in the greenhouse against grain cyst nematode. The results showed that in laboratory conditions, the bacterial strains were able to reduce the egg hatching rate by 62% on average. Bacillus pumilus bacteria caused the greatest decrease in egg hatching by 73%. The percentage of mortality of larvae in the laboratory test was also shown to be 63% on average, and the treatment of B. pumilus bacteria showed the highest percentage of mortality with 70%. The results of the greenhouse investigations showed that the treatments involving sulfur-healthy plants, sulfur-nematode, and the B. pumilus and P. fluorescens bacteria were most effective in promoting healthy plant growth and controlling nematode infestation. These treatments resulted in significant improvements in plant height, as well as fresh and dry plant and root weights. Additionally, the greatest reduction in the number of cysts was observed in the B. pumilus treatment, with an average of 49 ± 1 cysts. When examining the number of eggs within the cysts, the most substantial decrease was observed in the Nematex EC and B. pumilus bacteria treatments, with 67 ± 1 and 111 ± 2 eggs, respectively. Furthermore, in the assessment of the number of live larvae in the pot, the greatest decrease in the number of larvae was observed in the Nematex treatment, with 87 ± 1..

Plants resistance against pests is one of the methods of replacing chemical pesticide that can keep the pest population below the economic injury level. Soil symbiotic bacteria can be useful factors in increasing the resistance of plants against herbivorous insects. The two treatments investigated in this research included the bean plant treated with bacteria and the bean plant without bacteria treatment as a control. The Vicia faba L. and black bean aphid were grown in a growth chamber at 25±4 0C, %50±5 RH and a photopriod of 14L: 10D hours. Then, 5 ml of bacterial suspension was added into the soil of sown mugs with a sterile syringe. These experiments on the effect of two treatments on faba bean showed that different treatments have a significant differences effect on the biological properties of black bean aphid. The highest developmental time (19.78±0.20 days) and the lowest fertility rate were occurred on P. polymyxa. There were significant differences between different treatments in terms of inherent rate of population increase (P≤0.5). The highest rate was occurred in control treatment (0.42±0.01 day-1) and the lowest in combination P. polymyxa (0.23±0.001 day-1). The life expectancy of black bean aphids, which was grown on P. polymyxa treated, was significantly lower than control. According to the results, it can be stated that faba bean plant treated can be effective in reducing the population of the aphids of the bean.

Yellow mealworm, Tenebrio molitor, is a wealthy source of proteins and other nutrients. In this study, to improve the breeding of this edible insect, some of its biological parameters were evaluated by feeding on sixteen diets containing different levels of the antibiotic lincomycin (doses of 0, 0.005, 0.01 and 0.02%) and probiotics. Probiotic levels included: 1-probiotic-free (p0), 2- commercial probiotic (pA), 3- probiotic prepared from culture of Lactobacillus bacteria (pB), and 4- probiotic containing commercial yeast (pC). All three probiotics were used at a dose rate of 1% (108 CFU/gr). Treatments were applied to first instar larvae in bran and carrot-based diet. Based on the results, a significant increase was observed in the larval life span in the treatment of pC-dose of 0.01%, with an average of 67.75 ± 1.16 days, compared to the control (64.17 ± 1.04 days). The greatest mean larval weight, 144.17 ± 5.30 mg, was related to the pA-dose of 0.01%, which was significantly different only with pC-dose of 0.01% (117.50 ± 3.05 mg). The pupation percentage at zero dose (84.46 ± 1.77%) was significantly lower than the doses of 0.01 and 0.005% of antibiotics (8 and 9.32%, respectively). Traits of pupal life span, pupal weight, adult weight and adult emergence rate were not affected by diets. Based on the findings, the interaction of antibiotics and probiotics can affect some growth and developmental parameters of the yellow mealworm that can be considered in insect breeding programs.

Wheat is one of the most important agricultural products in Iran, that plays an important role in ensuring food security. Crown and root rot disease by F. pseudograminearum is one of the most important pathogens that cause economic damages every year. In this study, 80 isolates of Bacillus were isolated from wheat rhizosphere. In dual-culture test, UTB 3, UTB 11, UTB 22, UTB 4 and UTB 7 isolates with 60, 55, 37.5, 22.5 and 20% maximum ability, respectively. In effect test of volatile metabolites on inhibination the growth of F. pseudograminearum, UTB 3, UTB 7 and UTB 11 with 54, 52 and 49% showed the highest percentage of inhibition of fungal growth. These isolates were also capable of nitrogen fixation, production of siderophore and extracellular enzymes involved in biological control (protease, lipase and chitinase), but none of the isolates were able to produce phosphatase enzyme. Greenhouse studies by treating wheat seeds with selected isolates showed that UTB 3 was able to control crown and root rot of wheat by 80.33% compared to the control treatment. Also, this isolate could increase the growth indices of wheat (stem length and root dry weight) in the presence and absence of pathogenic fungi. Therefore, this isolate is introduced as the selected isolate to control crown and root rot disease and increase wheat growth indices.

Grapevine is one of the most important agricultural products in Iran. West Azerbaijan province is considered as one of the biggest production centers of grape in Iran, due to its suitable climatic conditions. The aim of this study was to identify grape endophytic bacteria in West Azarbaijan. In this study, 67 endophytic bacteria were isolated from the stems and roots of grapevines. Then, biochemical properties such as hypersensitive reaction, fluorescent and potato soft rot test and the ability to produce proteases, amylase and gelatinase enzymes were tested. Eleven bacterial isolates were selected for molecular identification and it was found that Bacillus and Pseudomonas are the most abundant genera. According to our knowledge, three species of Stenotrophomonas sp., Bosea lathyri and Frigoribacterium faeni are reported for the first time in Iran as grapevine endophytic bacteria. Also, the antifungal effect of endophytic bacteria on three fungal species i.e. Chaetomium globosum, Cytospora chrysosperma and Fusarium sp. was done by dual culture method and three isolates of GI6 (Priestia sp.), GI43 (Pseudomonas kilonensis) and GI45 (Bacillus sp.) showed the most growth inhibitory properties. Due to the importance of endophytic bacteria, their isolation and identification from different parts of the country seems necessary, as the result, these bacteria can be used in biological control of plant diseases and can be replaced by chemical control.

Rice blast disease, which is caused by Pyricularia oryzae, is one of the most important diseases of rice in the world. In this research, out of 150 infected samples collected from rice farms of Guilan province, 20 fungal isolates and 30 bacterial isolates were collected. The isolated bacteria were belonged to Pseudomonas aeruginosa, Enterobacter sp., Enterobacter cloacaeand Bacillus subtilis. Two methods of dual culture and the production of volatile antifungal metabolites were used in the laboratory in order to study biological control. In the greenhouse trial, rice plants (cv Hashemi) were inoculated with the six bacterial isolates as well as P. oryzaepathogen after 12 days. According to the results of this research, in the dual culture method, P. aeruginosa Y–25–3 with 61.11% and in the volatile metabolite method, B. subtilis W with 60.51% were found to be most effective in suppressing mycelial growth of the pathogenic fungus. All isolates significantly alleviated the severity of the P. oryzae–induced disease in greenhouse, but the most effective was P. aeruginosa, which reduced the disease index by 70.53%. Analysis of variance and comparing the characters average in Duncan test and Least Significant Difference (LSD) and based on a completely randomized design revealed significant differences among the bacteria in terms of mycelial inhibition in the dual culture and volatile metabolite methods. Furthermore, in greenhouse trials there were significant differences in the disease index, plant height and fresh weight among the treatments, whereas the treatments did not exhibit any significant differences in dry weight. Based on the results of biocontrol assays in the laboratory and greenhouse, P. aeruginosa Y–25–3 was recognized as the most effective bacterial isolate in the control of rice blast disease.

Pseudomonas syringae pv. syringae (Pss), the causal agent of bacterial canker of stone fruits, is a dangerous pathogen that attacks more than 200 different plant species. Due to the importance of disease, the purpose of this study was to identify the causal agent of the disease in Kohgiluyeh and Boyerahmad province and comparing the resistance of some cherry cultivars to this pathogen. During 2015-2016, 33 bacterial strains were isolated from stone fruit plants with canker, gummosis, and leaf spot symptoms from different regions of Kohgiluyeh and Boyer-Ahmad province. Isolates were rod-shaped, motile, gram-negative, obligate aerobe, oxidase negative, catalase, levan and tobacco hypersensitive reaction positive, arginine dihydrolase and potato rot negative. The genes responsible for syringomycin synthesis (syrB) and syringomycin secretion (syrD) were detected in all isolates. All strains were able to produce necrosis spots on cherry fruit but showed different virulence. Regarding the phenotypic characteristics, pathogenicity test and PCR results of this study, all isolates were identified as Pss. To study the resistance of cherry plants, Takdaneh Mashhad, Ghaheri and Surati cultivars were selected. There was a significant difference between different cultivars, based on the number of the necrotic lesion on the leaf, length of the necrotic region on the branch and bacterial population in leaf tissue. Among the different cherry cultivars studied in this research, Takdaneh Mashhad cultivar was the most susceptible and Surati cultivar showed the least sensitivity to Pss.

Potato soft rot is a common and important disease on potatoes. Fifteen pectolytic bacteria with green metallic colonies on EMB medium were isolated from the tubers showing surface cracking and soft rot symptoms, simultaneously. All the isolates grew at 37 ˚C, no starch digestion, they were not sensitive to erythromycin and negative for phosphatase. They could not use sugars of Xylose, Trehalose, α-methyl D-glycoside and Malonate, while they were able to use Inositol, Rhamnose and Arabitol sugars. Based on These characteristics the isolates recognized as P. carotovorum subsp. carotovorum. The isolates were further identified by PCR amplification with primer G1/L1 which produces two bands similar to those produced in P. carotovorum subsp. carotovorum, but not from P. carotovorum subsp. atrosepticum and Dickeya chrysanthemi. Digestion of the amplified PCR product with restriction enzyme Rsa I resulted in identical 385 bp, 280bp and 180 bp bands formation as described for P. carotovorum subsp. carotovorum. The results of physiological, pathogenicity, biochemical and molecular tests, confirmed that all bacterial isolates induced soft rot symptoms in potato tubers are P. carotovorum subsp. carotovorum.

Wheat is one of the major agricultural crops with respect to human nutrition. It is cultivated over a wide range of environments, because of wide adaptation to diverse environmental conditions. In Iran, 6.2 million hectares are under wheat cultivation, of which 33% is irrigated and 67% is rain-fed, the irrigated wheat growing areas (2 million hectares) are located mostly in southern, central and east of Iran Production of crops is under the influence of plant genetic structure, environmental conditions and their interactions. Biotic and abiotic stresses are considered to lower production. Among the biotic stress, the fungal disease is the main factor limiting production of crop plants in hot and humid regions. Stripe rust was not a serious economic concern to the wheat industry for most of the 1990’s due to the use of resistant varieties. However, by 2003 it had developed into a significant issue, particularly as new path types evolved. Even in the dry years of 2003 and 2004, stripe rust cost growers significant income. Provide country's need for wheat as a strategic product, meanwhile, production is free from chemical fungicide is a high but achievable goal. So in order to achieve fertilizer and fungicide resources that in addition to having no adverse effects on consumers and the environment, has been economically able to provide nutrition need of crop plant, is very important.
With this approach, to survey the effect of Mycorrhiza and Azospirillum in resistance to yellow rust in wheat cultivars, an experiment was conducted at the research station of the Shahid Chamran University of Ahvaz, Iran in 2012-13. The experimental design was factorial based on a randomized complete block design with three replications. The treatments include of Mycorrhiza fungi in three levels (without application of Mycorrhiza strain and using strain Glomus intraradices and Glomus mosseae), Azospirillum lipoferum bacterium in two-levels (non-inoculated seeds and inoculated seed) and wheat cultivars in three levels, Chamran (bread wheat), Dena and Behrang (durum wheat) varieties. In this experiment evaluated, to yellow rust disease, the intensity of infection, the average coefficient of infection, type of infection and area under disease progress curve (AUDPC). Infection type and disease severity were also recorded at flag leaf stage using modified Cobb’s scale. First symptoms of yellow rust were observed in middle January of 2013. Analysis of variance was performed using PROC ANOVA of SAS (version 9.1.3, 2004The comparison of the means was done by Duncan test at a probability level of 5 percent.
Survey on the resistance to yellow rust in wheat cultivars treated with Mycorrhiza and Azospirillum showed that seed inoculation with Azospirillum traits reduced between 10 percent to 13 percent and the use strains of Mycorrhiza fungi intensity of infection 45-51 percent, the average coefficient of infection and AUDPC 74-85 percent respectively for G. intraradices and G. mosseae strains have been reduced compared with control and Chamran cultivar between 40-70 percent showed more Sensitivity to disease from durum varieties. Generally, the lowest of infection intensity (18.33) was obtained from inoculation of C.V Dena seeds with Azospirillum and G. mosseae strain. According to the result, we found yellow rust in all experiment field also the incidence varied between 10-70 percent. Therefore, it is concluded that, given the climatic conditions favorable to the spread of yellow rust, the incidence of yellow rust in the region that have a high degree of pathogenicity. In general the results of this test, mycorrhiza application has a significant role in enhancing wheat resistance to yellow rust. The seed inoculation with Azospirillum although did not have significant role in disease control, but increased at an acceptable level resistance to wheat rust. But the important point was the combined use of fungi and bacteria the synergistic effect of the two substances for all traits were assessed, leading to an increase of more than 20 percent in the wheat varieties resistant to rust.
Generally associated with resistance to yellow rust in wheat cultivars inoculation with A. lipoferum and usage of G. mosseae in Dena cultivar that was durum wheat, showed the highest resistance to yellow rust, probably this has been due to the Dena cultivar which is durum wheat. It seems, use of the biofertilizers can be the perfect solution to eliminate the nutritional requirements of wheat, in addition, it has been an important effect in enhancing resistance to yellow rust.

The quorum sensing is a phenomenon which controls the production of virulence factors in some bacteria. But the correlation between the ice nucleation activities which is one of the most important virulence factor in P.syringae with this system in unknown. In order to investigate that, in spring of 2013, 248 samples (including leaves and flowers) were collected from twigs of stone fruit trees in Khorasan Razavi province. Ice nucleation active bacteria, were identified and among them the P. syringae isolates were distinguished by LOPAT tests. Among virulence factors three of them such as swarming motility, susceptibility to hydrogen peroxide and pyoverdine production were studied. The swarming motility of the isolates with high ice nucleation activity were significantly more than those isolates which indicated low ice nucleation activity. There was no significant different in susceptibility to hydrogen peroxide and pyoverdine production between high and low ice nucleation active isolates. The production of homoserine lactones in six selected P. syringae belonged to the different groups of ice nucleation activity were extracted and detected using Chromobacter violaceum CV026 which was overlaid on Thin-layer chromatography plates. Our results indicated direct correlation between ice nucleation activity and the amount of homoserine lactone production and confirmed that the hypermotile isolates have high ice nucleation activity.

Plant-parasitic nematodes are one of the most important pests worldwide and cause considerable economic loss to many of agricultural products. Some of soil inhabited nematodes are affected by some of antagonistic bacteria, so they can be used in biological control. Nematodes can be affected by bacteria in different ways such as direct suppression, promotion of plant growth, and facilitation of rhizosphere colonization. In overall, regarding to effect of soil inhabits bacteria on nematodes; they can be classified as toxin producing, antibiotic producing and enzyme producing as well as plant growth promoting groups. Based on the recent researches, bacteria are divided to six groups including: parasitic bacteria (nematophagous bacteria), opportunistic parasitic bacteria, rhizobacteria, endophytic bacteria, symbionts of entomopathogenic nematodes and cry protein-forming bacteria. Combination of bacteria with some other antagonistic microorganisms was successful in control of plant parasitic nematodes.

Termites play a major role in reducing and decomposing woody materials within terrestrial ecosystems by degrading lingo-cellulosic materials with the help of the microbial community of their guts. We isolated the lignin-degrading bacteria from Anacanthotermes vagans (Hagen) using liquid and solid media containing wheat straw and lignin hydrochloric acid. Cellulose-degrading bacteria were also isolated using liquid medium containing filter paper، agar-cellulose and Congo red agar-cellulose. By conducting various experiments، 16 bacterial species were isolated and subjected to different biochemical tests for comparing their growth rates. The genera Enterobacter and Klebsiella showed the highest growth rate among the rest species of isolated lignin-degrading bacteria. The species Staphylococcus lentus and Bacillus subtilis were isolated from the media containing cellulose.

Weeds always cause serious problems in pome fruit orchards. These plant species are primary، secondary and epiphytic hosts of some major plant bacteria which upon transmission to fruit trees may result in bacterial infection and crop loss. These weeds include annuals and perennials. The most prevalent perennial and spring annual weeds that serve as secondary hosts were collected during two years of study (2011-2012). Samples were examined for determining incidence of bacteria via conventional bacteriological methods. The more frequent bacteria were identified and checked for pathogenicity and epiphytic phases. Results showed that Xanthomonas spp.، Pseudomonas spp. and Erwinia spp. were found on Avena fatua، Sorghum halepense، Cynodoun dactylon‍‍، Agropyron repense، Hordeum vulgare and Poa sp. as epiphytes. These bacteria could be isolated during spring. Pseudomonas syringae pv. syringae was isolated from some Poaceae species. Erwinia amylovora، the causal agent of fire blight، was isolated from Cynodon dactylon‍‍ and Agropyron repense.