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Sheath blight, caused by Rhizoctonia solani AG1-IA, is one of the most destructive disease. Conventional methods of disease control using fungicides may develop new problems. Therefore, understanding molecular mechanisms of plant–pathogen interaction is necessary to adopt effective approaches for managing the disease. Here for the first time, by using bioinformatics tools and RT-PCR analysis and sequencing confirmed the presence of a Magnaporthe oryzae Avr-pita gene orthologous sequence designated as Rhiz-pita1 gene in three different geographic isolates of R. solani AG1- IA( A2,R1 and T2) genome. SignalP program predicted a secretion signal upstream of Rhiz-pita1 gene. Nucleotide sequences of 5' region of Rhiz-pita1 gene from geographical isolates showed 99% identity in exons and 100% in introns which are characteristics of fast evolving effector proteins. Also, 98% homology between Rhiz-pita and M.oryza-pita1gene suggests that Rhiz-pita encodes an effector protein. Howevere, more researchs are necessary to confirm of this suggestion. Keywords: Rhizoctonia solani, signal peptide Rice blast , Effector

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In vitro antifungal activity of silver nanoparticles, at concentrations of 6, 8, 10, 12, 14 and 16 ppm, was studied on five phytopathogenic fungi, and a biocontrol agent. Then effect of silver nanoparticle at 6 ppm (optimum concentration) was evaluated on Macrophomina phaseolina in greenhouse. For in vitro experiment, the fungal isolates were grown on potato dextrose agar medium amended with silver nanoparticles. Radial fungal growth was recorded after 1, 2, 3, 5 and 10 days and mycelial growth inhibition rates were calculated. The most sensitive fungus to nanoparticles was Pythium aphanidermatum, since all tested concentrations showed 100% inhibition during the 10 days of observation.The second most sensitive fungus was Sclerotinia sclerotiorum, since it was able to grow only at concentration of 6 ppm and M. phaseolina was the third in sensitivity since its growth was inhibited in all concentrations after three days. In greenhouse experiments, five treatments including no nanosilver-no pathogen (Negative control), no nanosilver +pathogen (Positive control), 6 ppm nanosilver– no pathogen, 6 ppm nanosilver +pathogen, Carboxin-Thiram (0.15%) +pathogen were compared. Four characters viz shoot and root fresh and dry weights were measured. Based on the greenhouse experimental results, treatments with nanosilver and fungicide gave higher yields than the positive control. The chemical control treatment had the highest measured parameters, while 6 ppm nanosilver +pathogen treatment had the same parameters as negative control. It may therefore be suggested to use nanosilver as a safer alternative to chemical fungicides for control of M. phaseolina.

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Rhizoctonia solani is the most serious problem on sugar beet Beta vulgaris L. grown in North Dakota and Minnesota. Picoxystrobin, a quinone outside inhibitor, and penthiopyrad, a succinate dehydrogenase inhibitor, were used alone and in combinations for controlling R. solani AG 2-2 IIIB on sugar beet under greenhouse conditions of 22 ± 2 °C and a 12-h photoperiod. Fungicides were applied in-furrow at planting, followed by inoculation with R. solani grown on barley seeds. The experimental design was a randomized complete block with four replicates and the experiment was repeated three times. Stand counts were taken and roots were evaluated for symptoms using a 0 to 7 scale 21 days after inoculation. Analysis of variance was conducted by the SAS general linear model, and Fisher’s protected least significant difference at α = 0.05 was used to compare treatment means. Fungicides used alone and in mixtures provided effective control of R. solani, which had significantly greater percent survivors than the inoculated check. This research demonstrated that picoxystrobin and penthiopyrad have the potential to be used for providing control of R. solani on sugar beet.  

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In recent years, biological control has become a promising and ecologically friendly alternative to chemical control in the management of soil-borne plant diseases and several biological control agents have been introduced as potential bio-fungicides. The aim of this study was to investigate different biological control agent consortia against Rhizoctonia solani root rot disease of common bean. Bacillus pumilus INR7, Trichoderma harzianum and Rhizophagus intraradices were used individually or in combination. There were two application methods: simultaneous application of biocontrol agents with the plant pathogen, and pre-inoculation of biocontrol agents one month before the pathogen. Treatments containing B.pumilus INR7 were the best treatments for suppression of the disease in the simultaneous application method, where B. pumilus INR7 + T. harzianumreduced the disease up to 54%. However, in pre-inoculation method T. harzianum alone was the only treatment that reduced disease severity up to 49% compared to the infected control; other treatments did not haveany significant effect on disease severity. In current study, combination of T. harzianum and R. intraradices was unable to decrease disease severity and improve plant growth. This phenomenon was common in both simultaneous and pre-inoculation experiments. However, results showed that B. pumilus INR7 and R. intraradices were compatible with each other. Their combination not only decreased the disease, but also improved the dry weight of common bean in both application methods. Our results revealed that B. pumilus INR7 had positive interaction with T. harzianum. This combination increased their ability to suppress root rot disease and improve plant health, significantly. Overall, combinations of biocontrol agents have good potential to be applied in modern agriculture, but such combinations need to be checkedin advance for their compatibility in greenhouse and field experiments.

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Damping-off disease, caused by the fungus Rhizoctonia solani, is one of the most important diseases of cucumber plant and causes significant yield losses. R. solani possess some characters, such as wide host range and unlimited survival in soil, that make it as pathogen one of the most difficult agents to control. Therefore, the research for finding a biocontrol agent against this disease will be valuable. Two species of mycorrhizal fungi Glomus mosseae and Glomus clarum were evaluated against R. solani on cucumber plants. Mycorrhiza inoculated plants with both species showed a significant reduction in disease severity (DS), 21% and 25%, respectively, whereas the disease severity was 65% for non-inoculated plants. Furthermore, the effects of mycorrhizal fungi were evaluated on growth parameters of cucumber plants. Plants inoculated with both species of mycorrhizal fungi showed a significant increase in both shoot dry weight and root dry weight compared with noninoculated plants. It is concluded that both mycorrhiza species could be an important tool to control some soil-borne pathogens, increase plant nutrients absorption and increase resistance to abiotic stresses.

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Rhizoctonia root rot caused by Rhizoctonia solani is one of the critical factors influencing bean plants' yield. This study investigates the effects of some biofertilizers for controlling R. solani and their impact on the growth parameters of bean plants in the greenhouse. Biofertilizers, Funneliformis mosseae (F. mos), vermicompost (Verm), and mealworm frass (Meal), were used in a completely randomized design with five replications. Compared with diseased control, biofertilizers applied separately or in combination, reduced disease severity (except Meal) and disease incidence (except Verm). The combination of Meal + Verm had the best effect on both indices. All biofertilizer treatments increased the dry root weight (except Verm and F. mos + Meal + Verm), fresh root, and foliage weight. Also, root length, and dry foliage weight was increased only in combination treatments, and stem length in Meal + Verm and F. mos + Verm. The highest growth of foliage parameters, root length, and fresh and dry root weight was observed in Meal + Verm, F. mos + Verm, and F.mos + Meal, respectively. The highest mycorrhizal colonization was in F. mos and F. mos + Verm. Therefore, combinations of biofertilizers had better effects on the plant growth and inhibition of Rhizoctonia root rot. The tested biofertilizers and their combinations could be considered as promising tools for reducing the use of chemicals and enhancing sustainable agriculture and disease management. The appropriate timing and application rates for these biofertilizers must be determined accurately during field experiments.

 

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In vitro and greenhouse studies were conducted to investigate the possibility of an interaction between two systemic insecticides of: Thiodicarb (Larvin DF 80) and Imidacloprid (Guacho SW 70), and seedling disease organisms of: Rhizoctonia solani, Fusarium moniliforme and Pythium ultimum. When in vitro concentrations of Imidacloprid and Thiodicarb were applied, a fungistatic activity occurred. These insecticides inhibited mycelial growth of R. solani and F. moniliforme by 6.6-14.1 % and 15.2-70.8 %, respectively. F. moniliforme was more seriously affected by the insecticides while no significant effect was observed on P. ultimum. The pot experiments confirmed in vitro results so that, Thiodicarb provided excellent protection against pre- and post-emergence damping-off of the plant by 54.2% and 90.6 %, respectively.

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Biotic as well as abiotic factors may influence the biocontrol activity and population density of Pseudomonas fluorescens. However, limited studies have been carried out on the effects of extracellular metabolites of other competitor bacteria, especially on the biocontrol efficiency of P. fluorescens. A greenhouse experiment was conducted to evaluate the potential of the two P. fluorescens isolates UTPF68 & UTPF109 in the biocontrol of bean damping-off caused by Rhizoctonia solani (AG-4), when applied individually or in combination with the culture filtrates of five rhizobia isolates (RH3 to RH7). Although all treatments reduced bean damping-off severity in comparison with the untreated control, RH4 + UTPF109 gave the lowest severity of damping-off (0.56 ,<1%). Beside the effect on disease control, seeds treatment with both P. fluorescens isolates individually or in combined treatments especially RH4+UTPF109 and RH6+UTPF68 significantly improved bean growth factors such as shoot and root fresh/dry weights. On the other hand, all tested rhizobia and P. fluorescens isolates especially, RH4, proved to be siderophore, HCN, IAA, and exopolysaccharide producers. Also, all tested bacteria except RH5 and RH7 produced chitinase. Furthermore, our in vitro studies demonstrated that the filtrates of tested rhizobia isolates can effectively increase the population density of both P. fluorescens isolates as a biotic factor. Thus, certain rhizobia seem to have a capacity to interact synergistically with P. fluorescens isolates having potential biocontrol activity.

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The use of essential oils and new drug delivery systems have been considered two approaches for controlling plant pathogenic fungi. This study aimed to synthesize, characterize, and evaluate the antifungal activity of Solid Lipid Nanoparticles (SLNs) incorporating Mentha×Piperita L. Essential oil (MPE) compared to the free MPE. In the present study, the formulations of SLNs incorporating MPE (MPE-SLNs) were synthesized by high-shear homogenization and ultrasound method, and they were assessed by Z-average diameter, particle size distribution, Zeta potential, leakage stability during 6 months of storage, encapsulation efficacy, and morphological properties of the SLN formulations. The results indicated that the particle size of MPE-SLN formulations was 155.5±4.7 nm with a PDI of 0.156±0.012, a Zeta potential of -15.93±0.87 mV, and encapsulation efficacy of about 88±0.88%. They were physically stable for 6 months of storage. The results also showed that the in vitro minimum inhibition concentration for MPE on the fungal microorganisms, Rhizoctonia solani and Rhizopus stolonifer, were 2,000 and 1,000 ppm, respectively, and for MPE-SLNs it was 1,000 and 750 ppm, respectively. Therefore, the antifungal activity of MPE-SLNs was more significant than MPE, and none of the fungi were susceptible to essential oil-free SLNs. Based on the results, MPE-SLNs can be used for the safe preservation of a wide array of foods and agricultural products.