BIO CONTROL IN PLANT PROTECTION
Year:2016 | Volume:4 | Issue:1 (7) |Papers Count:9

The charcoal rot disease caused by Macrophomina phaseolina is the most common disease of soybean in many parts of the world. Because of the soil-born and high saprophytic nature of the fungus in the soil, lack of effective control of the disease and environmental contamination due to the application of chemical pesticides, beneficial microorganisms such as Trichoderma species can be used for biocontrol of plant diseases. In this study, two isolates of Trichoderma harzianum and T. atroviride were studied in biocontrol of M. phaseolina and in the induction of plant resistance to pathogen under greenhouse conditions. The results showed that in treatments of soil inoculated with pathogen, T. harzianum isolate reduced the disease by 62 and 65 percent in sterile and non-sterile soil, respectively. The T. atroviride isolate reduced the disease by 59 and 62 percent in the sterile and non-sterile soil, respectively. The combination of two Trichoderma isolates reduced the disease by 67 and 70 percent, respectively. According to the results, in the treatment of soybeans inoculated with pathogen, T. harzianum isolate reduced the disease by 56 and 58 percent in sterilized and non-sterilized soil, respectively. The Trichoderma atroviride isolate reduced the disease by 52 and 53 percent in sterile and non-sterile soil, respectively. The combination of two Trichoderma isolates reduced the disease by 60 and 63 percent, respectively. Trichoderma isolates in the non-sterile soil were more effective in reducing disease. Trichoderma isolates in treatments of inoculated soil with the pathogen were more effective in reducing disease. T. harzianum isolate decreased the disease more than T. atroviride isolate in both methods that pathogen was used. The combining of two Trichoderma isolates also had a greater impact on the reduction of disease and resistance induction.

The rice brown spot disease caused by Bipolaris spp., is one of the most important diseases of rice in Iran and world. Eighty fungal isolates were isolated from 220 collected samples in Guilan province fields using PDA and WA. Morphological characteristics were used for identification of these fungi. Identified fungal species belonged to Bipolaris victoriae (24 isolates), Bipolaris oryzae (12 isolates), Alternaria tenuissima (11 isolates), Preussia sp. (8 isolates), Fusarium verticillioides (6 isolates), Alternaria infectoria (7 isolates), Alternaria citri (9 isolates), Trichoderma harzianum (one isolate) and Trichoderma virens (two isolates). Pathogenicity of all isolates of Bipolaris spp. was proved and among fungal isolates belonged to other fungal genera, 20 isolates which did not cause disease on rice or their pathogenicity was low were selected for biocontrol studies. In the laboratory, various methods were used such as inhibition of B. victoriae using culture filtrate, dual culture of the studied antagonistic fungi and B. victoriae by slide culture and effect of volatile metabolites on the inhibition of growth of this fungus. T. harzianum had been recognized as the most effective isolate in mycelial growth inhibition of the causal agent in vitro. In the greenhouse experiment, all isolates, except A. tenussima and F. verticilliodes, reduced disease rating of brown spot. The Preussia sp. isolate with 33. 4% reduction in disease rating was the most effective antagonist followed by T. harzianum, A. citri, A. infectoria and T. virens which had the highest effect in control of disease, respectively. Analyze of variance and comparing the average characters in LSD method showed significant difference in terms of efficiency in disease control among studied fungi.

The root-knot nematode, Meloidogyne javanica, is one of the major tomato pathogens in Iran. In the current study, Pseudomonas fluorescens UTPF101 and UTPF68 strains were evaluated for biological control of the pathogen. The strains were studied in terms of having phlD gene through polymerase chain reaction (PCR). The ability of bacteria to produce antimicrobial metabolites and their effect on hatching eggs and larvicidal activity were then studied in vitro. Finally, the ability of bacteria to control nematode on four varieties of tomatoes was studied via a factorial experiment in a randomized complete block design with four replications under greenhouse conditions. PCR procedure results showed that both strains contained phlD gene and 629 bp DNA fragment was reproduced in both of them. Bacterial strains were capable of producing DAPG antibiotic, hydrogen cyanide and protease in in vitro conditions. UTPF68 strain showed a greater impact on the egg hatching compared to strain UTPF101, while in terms of the impact on larvae mortality; both strains performed the same. The greenhouse results indicated that both bacterial strains increased the growth factors and reduced nematode pathogenicity in the infected plants. The rate of growth or controlling nematode was different depending on tomato cultivar or bacterial strain.

Fungal antagonist, Talaromyces flavus, is one of the most important biocontrol agents of soil borne plant diseases including seedling damping-off. In this research, to increase the effectiveness of T. flavus isolates obtained from cucumber greenhouses and tomato fields, five chemical stabilizers were tested. Based on the results of the previous studies, the most effective substrate for the growth, sporulation and stability of T. flavus isolates related to the above-mentioned plants was a mixture of rice bran and peat-moss. For each plant, the greenhouse experiment was performed as randomized complete blocks with seven treatments and three replications. Experimental treatments included five different stabilizers (aminophenol, D-cycloserine, magnesium sulfate, carboxymethyl cellulose, and sodium nitrate), infected control and healthy control. The final evaluation of different treatments was based on the number of healthy plants. The overall results of this study, indicted that T. flavus inocula containing sodium nitrate, D-cycloserine, and carboxymethyl cellulose were more effective than aminophenol and magnesium sulfate in controlling seedling damping-off disease.

In this study, the growth inhibiion potential of methanol, ethanol, acetone, and chloroform extracts of rind, gel, latex and whole leaf of Aloe vera was evaluated using agar diffusion disc method. The bacteriostatic and bactericidal activity were also tested by minimal inhibitive and bactericidal concentration methods. Results showed that all leaf parts of A. vera had antibacterial potential. Methanol could release more growth inhibitory substances than other solvents studied in disc diffusion method. Results also showed that chloroform released the lowest amount of bacteriostatic and bactericidal substances. Leaf gel showed more bacteriostatic and bactericidal activities than other leaf parts of the plant. In total, 31 chemicals were identified using gas chromatography, of which 25 were found in latex. Some antibacterial substances such as cinnamic acid, tetradecanoid acid, 2-hydroxy propionate, sitosterol, carvone, lupeol, 1-heptanol, 2-propyle, 1, 2-banzan di-carboxylic acid were found in different parts of A. vera leaf. Based on the overall results, the antibacterial activity of A. vera against the pathogenic bacteria can be considered as a biocontrol potential in the future.

In this research, the interaction between two biocontrol strains of Pseudomonas fluorescens (PF153mcherry and CHA0gfp2) and three wheat cultivars (Boulani, Roushan, Forno) were studied to control wheat leaf rust disease (Puccinia triticina) under greenhouse conditions. Bacteria were appliedusing the seed treatment method. Results showed a reduction in disease severity on the leaves in certain combinations of bacterial strains and wheat cultivars. This was particularly evident for the interaction between CHA0gfp2 and Forno with 69. 74% decrease in the number of pustules on leaves. The Bolani and Forno cultivars that were not treated by bacteria exhibited the highest infection of leaf rust. Study of bacteria– wheat-pathogen interactions showed that the interaction between PF153mcherry with infected and non-infected Forno showed the highest bacterial colonization (7801. 1 and 8154. 4 cfu per mg dry root, respectively). Interaction between CHA0gfp2 with infected and non-infected Roushan cultivar induced the lowest colonization on the rhizosphere by 938. 2 and 887. 3 cfu per mg dry root, respectively. However, interaction between pathogen and cultivars resulted in the increase of peroxidase and phenylalanine ammonia lyase (PAL) activity in the leaves. In summary, we observed negative correlations between the bacterial colonization (cfu per mg dry root) and the number of rust pustules on the leaves. There was significant correlation between PAL activity and disease severity. Overall results of this study indicate that there is a promising beneficial interaction between the bacterial isolates and wheat cultivars which induce systemic resistance and suppress the leaf diseases in the sustainable agricultural system.

Fungal and bacterial infections are main problems in the micropropagation of bulbous plants which can affect the efficiency of these propagation methods. To investigate the effect of different concentrations of herbal compounds on the growth and regeneration of crown imperial, an experiment was conducted based on the completely randomized design in factorial arrangement with five replications. Treatments included various concentrations of S-carvon, thymol and carvacrol. The concentrations of thymol and carvacrol significantly (P<0. 05) inhibited the fungal and bacterial growth. Thymol at 150 ppm and carvacrol at 100 ppm completely inhibited the growth of Alternaria sp. (100%). Investigation on the effects of plant extract compounds on bacterial pathogens removal revealed that 200 ppm of thymol and carvacrol completely inhibited the growth of Pectobacterium carotovora subsp. carotovorum with 0. 1-0. 2 OD (Optical density). Moreover, maximum growth inhibition of P. carotovorum subsp. carotovorum with OD=2 by thymol and carvacrol was observed at the rate of 300 and 400 ppm, respectively. Various concentrations of S-carvon did not significantly affect fungal and bacterial pathogens comparing to the control. In general, carvacrol and thymol could effectively prevent the fungal and bacterial growth and could be used as a potential candidate for the prevention of fungal and bacterial infection of culture medium in the micropropagation of plants such as crown imperial.

The predation rate and prey preference is essential in the selection and efficiency of appropriate combinations of beneficial species for biological control. Amblyseius swirskii is a phytoseiid mite that feeds on many species of small arthropods as well as pollen grains. In the present study, predation capacity of this mite in control of Tetranychus urticae and Phyllocoptes adalius as two serious pests in greenhouse were studied under laboratory conditions. The experiments, were conducted at 25± 0. 5° C, 70-75% RH and photoperiod of 16: 8 (L: D) and adults were introduced in Manger cages. For quantification of the daily predation rate, 10 and 20 individuals of the tetranychus and eriophid were supplied to the adult of A. swirskii, respectively. The average predation rate (C0) on eriophid and tetranychus mites was 183 and 420 mite, respectively that shows a high rate of predation on the pest population. The maximum consumption was recorded for the adult female during the oviposition period. Results suggest that A. swirskii is able to feed on both prey mites and could be used for biological control of these pests.

In this study the effects of natural grain-based media on the sporulation and germination of conidia and blastospores of Metarhizium anisopliae were investigated. Experiments were conducted with factorial arrangement in a completely randomized design with nine treatments and three replications. The obtained results showed that there was significant difference in the yield of conidia among different treatnents, two weeks after inoculation, (F= 4. 66, df= 7, 16, p<0. 01). Highest average yields were obtained as 3. 1×108 and 3×108 conidia/g in rice flour and Sabouraud’ s Dextrose Agar with 1% yeast extract, respectively. The lowest level of conidia yield was 4×106 conidia/g which obtained in the wheat bran medium. There was significant difference between blastospores yields four days after inoculation of the media, (F=2. 57, df= 8, 18, p<0. 05). The highest and lowest average yield of blastospores were 6. 1×108 and 4. 5×108 blastospores/ml and were obtained in the wheat bran+rice bran+yeast extract and rice bran+yeast extract media, respectively. Analysis of variance of nutritional and chemical amendments which were added to blastospores media showed significant differences in the yield among different treatments (F=5. 02, df=13, 29, p<0. 01). The highest average yield of blastospores were 6. 6×108, 6. 1×108 and 5. 7 ×108 blastospores/ml which were obtained in the rice bran+wheat bran+yeast extract+whey powder, rice bran+wheat bran+yeast extract, and wheat bran+rice bran+magnesium sulfate media, respectively. The lowest average yield of the blastospores was obtained in the media containing grape juice. Results also showed significant difference between the means of germination rate of conidia one, two and three month storage at 4 ° C and 25 ° C. The highest germination rate belonged to treatments stored in the refrigerator.