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1
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A comparison between Pseudomonas aureofaciens (chlororaphis) and P. fluorescens in biological control of cotton seedling damping-off disease

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Samavat S., Heydari A., Zamanizadeh H. R., Rezaee S., Aliabadi A. A.
Journal of Plant Protection Research
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2014
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tom 54
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nr 2
Due to the importance of the biological control of plant diseases, testing and introducing new biocontrol-active microorganisms is a major concern among plant pathologists. The causal agent of cotton seedling damping-off disease is Rhizoctonia solani. In this regard, we tried to investigate the antagonistic activities of Pseudomonas aureofaciens (chlororaphis) 30–84 (phenazine producing wild type and non-phenazine producing mutant) strains on R. solani, in comparison with some isolates of P. fluorescent under both in vitro (laboratory) and in vivo (greenhouse) conditions. In the laboratory experiment, the inhibitory effects of all the bacteria, on the growth of R. solani, were evaluated using the dual culture procedure. Results showed that five isolates of P. fluorescent along with both strains of P. aureofaciens significantly inhibited the growth of R. solani. Effective bacterial antagonists were then evaluated in a greenhouse experiment where cotton seeds were coated with their suspensions and were sown in pasteurised field-soil. The soil had been pre-inoculated with a virulent isolate of R. solani. The efficacy of the bacterial antagonists was evaluated by counting the number of surviving seedlings in different treatments, at 15 and 60 days after sowing, for determining pre- and post-emergence damping-off incidence. According to the results of the greenhouse experiment, at both intervals, two isolates of P. fluorescens along with both strains of P. aureofaciens caused significant increases in the number of healthy seedlings, in comparison with the untreated control, and a commonly used fungicide (carboxin-thiram). The efficacy of phenazine producing a wild type strain of P. aureofaciens was higher than its non-phenazine producing mutant, indicating that phenazine plays an important role in the antagonistic activity of P. aureofaciens. Effective bacterial antagonists were then studied for their antagonistic mechanisms. The results showed that all four bacteria employed different mechanisms. The bacteria produced siderophore, and volatile metabolites and non-volatile metabolites, in their antagonistic activities. The results of this study suggest that P. auerofaciens may be a new biocontrol agent for controlling cotton seedling mortality disease.
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Application of new bioformulations of Pseudomonas aureofaciens for biocontrol of cotton seedling damping-off

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Samavat S., Heydari A., Zamanizadeh H. R., Rezaee S., Aliabadi A. A.
Journal of Plant Protection Research
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2014
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tom 54
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nr 4
Pseudomonas aureofaciens (30-84) is a phenazine producing bacterium and reported as asuccessful biocontrol agent of some plant fungal pathogens. In the present study, the possibility of biological control of cotton damping-off caused by Rhizoctonia solani (AG-4) through phenazine production by the 30-84 strain, was investigated. In the search for the development of bioformulations of Pa (m) (PhzR–) and Pa (w) (PhzR+) strains of 30-84, four new carriers including soybean meal (SM), cottonseed meal (CM), rice bran (RB), and talc powder (TAL) were selected. The efficacy of bacterial formulations in reducing disease incidence was evaluated in four intervals (15, 30, 45, and 60 days after sowing), and compared with each bacterial suspension efficacy under green-house conditions. The results revealed that organic carriers were more effective than talc powder. It was also found that all the bioformulations were more efficient than each bacterial suspension. The most effective in reducing disease incidence was Pa (w) + RB. In contrast, Pa (m), Pa (m) + TAL, and Pa (m) + RB did not significantly suppress the disease in comparison with the infested control. Thus, phenazine production as a main biocontrol mechanism of P. aureofaciens (30-84) may be affected by the kind of carriers used for the bioformulation development.
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Biological control of garlic (Allium) white rot disease using antagonistic fungi-based bioformulations

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Mahdizadehnaraghi R., Heydari A., Zamanizadeh H. R., Rezaee S., Nikan J.
Journal of Plant Protection Research
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2015
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tom 55
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nr 2
White rot disease caused by Sclerotium cepivorum is a major yield reducing fungal disease of garlic found throughout the world, including Iran. The use of chemical fungicides is the most common control method for the disease at the present time. This control measure is costly, contaminates the environment, and harms non-target organisms. Moreover, since the pathogen is soil-borne, chemical control strategy is not quite effective against the disease. In this study, we tried to develop and prepare some new bioformulations based on three antagonistic fungal species: Trichoderma harzianum, T. asperellum, and Talaromyces flavus. Six isolates of the abovementioned fungi were used along with the organic and inorganic carriers, rice bran and talc, to develop twelve new bioformulations. The effectiveness of the bioformulations were then evaluated in the control of garlic white rot disease in the greenhouse conditions in comparison with the healthy control, infected control, and the commonly used fungicide Carbendazim. The design of the experiment was completely randomised. There were 15 treatments each, with four replicates. The results of the greenhouse experiments indicated that almost all the developed bioformulations resulted in significant reductions (34.50 to 64.50%) in the incidence of white rot disease. In general, bioformulations which contained the organic carrier (rice bran) performed more effectively than those that contained the inorganic carrier (talc). Bioformulations which contained an organic carrier (rice bran) were as effective as the fungicide Carbendazim.
4
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Controlling sugar beet mortality disease by application of new bioformulations

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Jorjani M., Heydari A., Zamanizadeh H. R., Rezaee S., Naraghi L., Zamzami P.
Journal of Plant Protection Research
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2012
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tom 52
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nr 3
There is growing interests in the use of biological approaches to replace or reduce the application of chemical pesticides in modern agriculture. In this regard, antagonistic fungi and particularly bacteria have proved to be potential candidates. In the search for efficient alternative biofungicides, eight new Bioformulations were developed and prepared using two strains of Pseudomonas fluorescens (B1) and Bacillus coagulans (B2) isolated from different rhizospheric soils and plant roots of Iranian sugar beet fields. Bioformulations were developed using procedures described in the literature. Bioformulations included a talc-based powder and bentonite-based powder as inorganic carriers, and peat and rice bran as organic carriers. The results of our greenhouse experiment, where these bioformulations were applied to sugar beet seeds to control seedling mortality disease, showed that most of the treatments at different intervals (15, 30, 45 and 60 days after sowing) were effective in reducing the disease (compared to the untreated control). According to the results, six out of eight of the developed bioformulations, including Peat-B1, Peat-B2, R.B.-B2, Bent.-B1, Talc-B1 and Talc-B2, were more effective than commonly used fungicides (Carboxin-thiram) in controlling sugar beet mortality disease. Yet, two bioformulations (R.B.-B1 and Bent.-B2) were less effective than carboxin-thiram in the reduction of the disease incidence.
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