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In searching for compounds with antioxidant and antifungal activity, our study focused on the subshrub species Empetrum rubrum Vahl ex Willd. (Ericaceae). We measured the antioxidant activity of its methanolic extract (MEE) obtained from the aerial parts (leaves and stems) and of its methanolic extract (MEF) obtained from the lyophilized fruits. The antioxidant activity of the MEE and MEF was evaluated in vitro via a 2,2-Diphenyl-1-picrylhydrazyl (DPPH) free radical and 2,2'-Azino-bis-(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) cationic radical. The results were expressed in gallic acid and Trolox equivalents for the DPPH and ABTS assays, respectively. The antioxidant activities, for the DPPH and ABTS assays, were also evaluated by considering the IC50 values. Concerning the antioxidant activity, the total phenolic content (TPC) in the MEE and MEF was determined using the Folin-Ciocalteu method. Polyphenols contained in the leaves, stems, and fruits of E. rubrum were determined qualitatively by employing high-performance liquid chromatography coupled with mass spectrometry (HPLC-MS) analysis. The antifungal activity of the MEE obtained from the aerial parts of E. rubrum was tested against Rhizoctonia solani. The results of IC50 values measured by the DPPH and ABTS methods with MEE were 0.4145 ± 0.0068 mg mL-1 and 0.1088 ± 0.0023 mg mL-1, respectively, and the IC50 values for MEF were 6.4768 ± 0.0218 mg mL-1 and 0.7666 ± 0.0089 mg mL-1 measured by the DPPH and ABTS methods, respectively. The HPLC-MS analysis revealed the presence of anthocyanins, phenolic acids derivatives, and flavonols. In vitro, mycelial growth of this fungus was reduced from 90% to nearly 100% in the presence of MEE. The observed antifungal effect is related to the presence of the abovementioned phenols, detected in the MEE.

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Pseudomonas fluorescens CFBP2392 has been recognized as a potential biocontrol agent due to its ability to suppress damping-off and root rot disease. This isolate has antibacterial activity in vitro as many other strains from the Pseudomonas fluorescens complex. In this work, the antibacterial and antifungal activity of the strain were explored. Dual culture assays evidenced the antifungal activity of the strain against different phytopathogens: Alternaria sp., Pythium ultimun, Fusarium oxysporum, and Rhizoctonia solani. Purification of an antifungal fraction was performed by preparative HPLC from the chemical extraction of growth media. The fraction showed altered R. solani growth and ultrastructure. Transmission electron microscopy revealed the purified compound induced hypertrophied mitochondria, membranous vesicles, and a higher number of vacuoles in R. salani cytoplasm. In addition, co-cultivation of P. fluorescens CFBP2392 with R. solani resulted in an enlarged and deformed cell wall. To gain genomic insights on this inhibition, the complete genome of P. fluorescens CFBP2392 was obtained with Oxford Nanopore technology. Different biosynthetic gene clusters (BGCs) involved in specialized metabolites production including a lokisin-like and a koreenceine-like cluster were identified. In accordance with the putative BGCs identified, sequence phylogeny analysis of the MacB transporter in the lokisin-like cluster further supports the similarity with other transporters from the amphisin family. Our results give insights into the cellular effects of the purified microbial metabolite in R. solani ultrastructure and provide a genomic background to further explore the specialized metabolite potential.

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Sheath blight (Rhizoctonia solani) causes significant yield losses in rice (Oryza sativa L.). Its sustainable management needs an efficient biocontrol agent. The objective was to screen bacterial isolates as an antagonist to R. solani and identify the most efficient ones as sheath blight suppressors under greenhouse conditions. Two assays (E1 and E2) were performed in a completely randomized design with three replications. E1 tested 21 bacterial isolates antagonists to R. solani in vitro. E2 was conducted under greenhouse conditions, with rice cultivar BRS Pampeira sown in plastic pots (7 kg) containing fertilized soil. Sixty old plants were inoculated with a segment of a toothpick containing fragments of R. solani, followed by spray inoculation of a bacterial suspension (108 CFU/mL). The severity of the disease was determined by calculating the relative lesion size formed on the colm. Isolates BRM32112 (Pseudomonas nitroreducens), BRM65929 (Priestia megaterium), and BRM65919 (Bacillus cereus) reduced R. solani colony radial growth by 92.8, 77.56, and 75.56%, respectively while BRM63523 (Serratia marcescens), BRM65923 and BRM65916 (P. megaterium) and BRM65919 (B. cereus) with 23.45, 23.37, 23.62, and 20.17 cm, respectively were effective at suppressing sheath blight in greenhouse, indicating their potential as a biofungicide for sheath blight suppression.

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Rhizoctonia solani compromises the production of lima bean, an alternative and low-input food source in many tropical regions. Inoculation of bacterial strains has been used, but research on their biocontrol and growth promotion potential on lima bean is scarce. The objective of this study was to evaluate the effects of inoculation with rhizobacterial strains of the genera Bacillus, Brevibacillus, Paenibacillus, Burkholderia, Pseudomonas, and Rhizobium in combination or not with N2-fixing Rhizobium tropici on the control of damping-off disease and growth promotion in lima bean plants. Greenhouse experiments were conducted to evaluate the inoculation with bacterial strains with biocontrol potential in combination or not with R. tropici in substrate infected with R. solani CML 1846. Growth promotion of these strains was also assessed. Strains of Brevibacillus (UFLA 02-286), Pseudomonas (UFLA 02-281 and UFLA 04-885), Rhizobium (UFLA 04-195), and Burkholderia (UFLA 04-227) co-inoculated with the strain CIAT 899 (Rhizobium tropici) were the most effective in controlling R. solani, reducing the disease incidence in 47-60% on lima bean. The promising strains used in the biocontrol assays were also responsive in promoting growth of lima bean under disease and sterile conditions. A positive synergistic effect of co-inoculation of different genera contributed to plant growth, and these outcomes are important first steps to improve lima bean production.

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Biopesticides are recognized as an efficient alternative to synthetic pesticides for pest and disease crop management. However, their commercial production processes use grains, generating large amounts of organic waste, even when agriculture waste or byproducts are the feedstock of choice. Frequently, these organic wastes are rich in nutrients that, after adequate treatment, can be used as nitrogen and carbohydrate sources for secondary metabolite production produced by microorganisms during submerged fermentation. In this sense, this study aimed to prove the concept that biopesticides could be produced under a full biorefinery process, using the entire biomass of an underexplored agroindustrial waste-damaged bean-as the main feedstock. A combination of sequential processes, including solid state fermentation, hydrolysis, and submerged fermentation, were designed for the production of two biopesticides (conventional-fungal conidia and second-generation secondary metabolite-cerulenin) from a high potential biological control agent strain Sarocladium oryzae BRM 59907. The combined processes, using damaged common bean grain as the main feedstock, provided biopesticides and organic fertilizer production that successfully controlled common bean root rot disease. This work proved to be possible the biopesticide production using a full biorefinery concept, inside the same productive chain, contributing to a sustainable environment and economy, together with animal and human health safety.

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Rice cultivation in South America is undergoing several intensification processes for economic reasons that cause more rice to be planted continuously on the same soils. This intensification makes the long-term biological and economic sustainability of systems questionable. Among the most common problems that threaten sustainability in intensified systems is pest and disease pressure. In this context, the primary rice diseases were studied during a 6-year period in a long-term experiment of rice rotations established in 2012 in Uruguay. The experiment consisted of six rice rotations with other crops with different duration and intensification levels. The main disease found was stem rot and, to a lesser extent, aggregate sheath spot and sheath spot of rice. These diseases are of importance in intensified rice systems because they produce sclerotia that accumulate in soils. Disease occurrence was variable among years and rotations. Stem rot incidence increased rapidly in the experiment, reaching values close to 85% in the third year, while the severity varied each year. Sheath spot incidence and severity were low and varied with the year. Continuous rice (CR) reached the highest occurrence values for stem rot, but other systems with short pastures in rotation did not differ. Aggregate sheath spot and sheath spot were of importance only in CR and in some years. When levels of intensification were compared, systems with less time (25 to 60%) occupied with rice showed lower disease severity and higher yields. Comparing CR with rice rotation with pastures of different lengths (1 to 3 years), disease occurrence was higher in 2 of the 4 years analyzed. However, yields were consistently lower, denoting that other factors are influencing productivity. Stem and sheath diseases appear not to be a limiting factor in the medium term in intensified rice systems. Also, there are several alternatives of rice intensification incorporating crops and pastures in the rotation.

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The common bean (Phaseolus vulgaris L.) is the most important grain legume in the human diet, mainly in Africa and Latin America. Argentina is one of the five major producers of the common bean in the world, and the main cultivation areas are concentrated in the northwestern provinces of this country. Crop production of the common bean is often affected by biotic factors like some endemic fungal diseases, which exert a major economic impact on the region. The most important fungal diseases affecting the common bean in Argentina are white mold caused by Sclerotinia sclerotiorum, angular leaf spot caused by Pseudocercospora griseola, web blight and root rot caused by Rhizoctonia solani, which can cause production losses of up to 100% in the region. At the present, the most effective strategy for controlling these diseases is the use of genetic resistance. In this sense, population study and characterization of fungal pathogens are essential for developing cultivars with durable resistance. In this review we report diversity studies carried out on these three fungal pathogens affecting the common bean in northwestern Argentina, analyzing more than 200 isolates by means of molecular, morphological and pathogenic approaches. Also, the screening of physiological resistance in several common bean commercial lines and wild native germplasm is reviewed. This review contributes to the development of sustainable management strategies and cultural practices in bean production aimed to minimize yield losses due to fungal diseases in the common bean.

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In the present study, the effect of biotization of Mentha spicata microplants with Trichoderma asperellum and Bacillus subtilis on growth, Rhizoctonia sp., incidence, and specialized metabolites content was evaluated. Analyses of root tissues of the microplants showed 100% endophytism with both microorganisms. During the acclimatization phase, plants with the endophytes T. asperellum and B. subtilis had a survival rate of 95% and 93%, respectively, compared to 75% for control plants. Then, under greenhouse conditions, a trial was carried out with biotized plants with or without Rhizoctonia sp. inoculation, plants inoculated with Rhizoctonia sp., and endophyte- and pathogen-free control. Biotized plants with the endophytes showed higher dry biomass and the incidence of Rhizoctonia was lower (8% for T. asperellum and 10% for B. subtilis) compared to plants inoculated with the pathogen (82%). In addition, plants with T. asperellum had the highest contents of total polyphenols (280 GAE/100 mg sample) and rosmarinic acid (28 mg RA/100 g sample). Thus, this study shows the potential of the technique of using the endophytes T. asperellum and B. subtilis on M. spicata microplants to improve plant survival and growth, decrease the incidence of Rhizoctonia sp., and improve the contents of specialized metabolites, which can contribute to the sustainable management of this crop.

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RESUMEN Rodriguezia granadensis (Lindl.) Rchb. f. es una orquídea epífita que crece sobre árboles, en zonas poco intervenidas. Para la germinación de sus semillas y en los estadios iniciales de su desarrollo forma relaciones simbióticas con hongos micorrícicos, los cuales, brindan los nutrientes que necesita. En el municipio de Fusagasugá esta especie crece en condiciones naturales y debido a la belleza de sus flores es promisoria para su producción comercial, pero hay poca información sobre los microorganismos asociados a esta planta; por lo tanto, el presente trabajo tuvo como propósito identificar, a nivel de género, los hongos asociados a las raíces de R. granadensis, en el agroecosistema Hacienda Betania. Se tomaron muestras de raíz, anotando el forofito donde se encontraban las plantas. En laboratorio, se dividieron en tres extremos: proximal, medio y distal y se realizaron cortes transversales, para identificar enrollamientos hifales. Adicionalmente, se sembraron explantes en agar papa dextrosa, agar Sabouraud y medio de Ko y Hora. Se identificó al género Rhizoctonia, con una frecuencia del 95 %. Se encontró que el 70 % de las plantas muestreadas crecían sobre árboles de guayabo y el 30 % sobre cítricos. Los resultados indican que R. granadensis pueden tener interacciones con hongos del género Rhizoctonia.

ABSTRACT Rodriguezia granadensis (Lindl.) Rchb. f. is an epiphytic orchid that grows on trees in areas with little intervention. For seed germination and the initial stages of development, it forms symbiotic relationships with mycorrhizal fungi, which provide the necessary nutrients. In the municipality of Fusagasugá, this species grows in natural conditions and, due to the beauty of its flowers is a promissory specie to commercial production, but there is little information about the microorganisms associated with this plant; therefore, the purpose of this work was to identify, at the genus level, the fungi associated with the roots of R. granadensis in Betania farm. Root samples were taken, noting the phorophyte where the plants grew. In the laboratory, they were divided into three sections: proximal, middle, and distal, and made cross-sections to identify hyphal curls. Additionally, explants were put in potato dextrose agar, Sabouraud agar, and Ko and Hora media. The genus Rhizoctonia was identified, with a frequency of 95 %. It was found that 70 % of the sampled plants grew on guava trees and 30 % on citrus. The results indicate that R. granadensis may have interactions with fungi of Rhizoctonia genus.

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Macrophomina phaseolina and Rhizoctonia solani are considered two major soil-borne pathogens of Phaseolus vulgaris in Cuba. Their management is difficult, not only due to their intrinsic biology as soil-borne pathogens, but also because the lack of active ingredients available against these pathogens. Actinobacteria, a heterogeneous bacterial group traditionally known as actinomycetes have been reported as promising biological control agents (BCAs) in crop protection. Thus, the main objective of this study was to evaluate the effectiveness of 60 actinobacterial strains as BCAs against M. phaseolina and R. solani in vitro by dual culture assays. The most effective strains were characterized according to their cellulolytic, chitinolytic and proteolytic extracellular enzymatic activity, as well as by their morphological and biochemical characters in vitro. Forty and 25 out of the 60 actinobacteria strains inhibited the mycelial growth of M. phaseolina and R. solani, respectively, and 18 of them showed a common effect against both pathogens. Significant differences were observed on their enzymatic and biochemical activity. The morphological and biochemical characters allow us to identify all our strains as species belonging to the genus Streptomyces. Streptomyces strains CBQ-EA-2 and CBQ-B-8 showed the highest effectiveness in vitro. Finally, the effect of seed treatments by both strains was also evaluated against M. phaseolina and R. solani infections in P. vulgaris cv. Quivicán seedlings. Treatments combining the two Streptomyces strains (CBQ-EA-2 + CBQ-B-8) were able to reduce significantly the disease severity for both pathogen infections in comparison with the non-treated and inoculated control. Moreover, they showed similar effect than that observed for Trichoderma harzianum A-34 and with Celest® Top 312 FS (Syngenta®; Basilea, Switzerland) treatments, which were included for comparative purposes.

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BACKGROUND: Rice sheath blight (caused by Rhizoctonia solani) and tobacco mosaic virus are very important plant diseases, causing a huge loss in global crop production. Paenibacillus kribbensis PS04 is a broad-spectrum biocontrol agent, used for controlling these diseases. Previously, extracellular polysaccharides (EPS) from P. kribbensis PS04 had been purified and their structure was inferred to be fructosan. This study aimed to evaluate the effects of exogenous EPS treatment on plant­pathogen interactions. RESULTS: Plant defense genes such as phenylalanine ammonia-lyase, catalase, chitinase, allene oxide synthase, and PR1a proteins were significantly induced by exogenous EPS treatment. Moreover, subsequent challenge of EPSpretreated plants with the pathogens (R. solani or tobacco mosaic virus) resulted in higher expression of defenseassociated genes. Increased activities of defense-associated enzymes, total phenols, and flavonoids were also observed in EPS pretreated plants. The contents of malondialdehyde in plants, which act as indicator of lipid peroxidation, were reduced by EPS treatment. CONCLUSIONS: This study comprehensively showed that EPS produced from P. kribbensis PS04 enhances disease resistance in plants by the activation of defense-associated genes as well as through the enhancement of activities of defense-related enzymes.

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Chili pepper (Capsicum annuum L.) production is affected by wilt and root rot, the most devastating disease caused by the pathogen complex of oomycete Phytophthora capsici Leon and the fungi Fusarium oxysporum Schlecht and Rhizoctonia solani Kühn, infecting roots, stems, leaves, and fruits. Fungicides are currently inefficient against this disease and have a high environmental impact. The use of elicitors is a sustainable alternative for inducing resistance to wilting and root rot. DNA fragments of an organism's own origin (conspecific or self-DNA) have shown the ability to inhibit growth and activate defense mechanisms in some plant species. In this investigation, the effect of the fragmented DNA mixture of Phytophthora capsici L., Fusarium oxysporum S., and Rhizoctonia solani K. on the protection against wilt and root rot of Capsicum annuum L. plants was evaluated. Changes in plant performance, phenolics, and flavonoids contents, as well as gene expression involved in the production of defense metabolites after the fragmented and unfragmented DNA mixture in three concentrations (20, 60, and 100 µg mL-1) in chili peppers, were studied. The results obtained showed a decrease in plant height in 60 and 100 µg mL-1 concentrations in absence of pathogens. Moreover, the treatment with fragmented DNA 100 µg mL-1 showed significant increase in the content of phenolic compounds and total flavonoids as well as gene expression associated to plant defense in comparison with control plants. Interestingly, foliar application of DNA fragments of the pathogen complex to a concentration of 100 µg mL-1 caused a 40% decrease in the mortality of infected plants with the pathogens at 30 days post-inoculation compared with control plants inoculated with the pathogen complex but not sprayed with DNA fragments. These results suggested a perspective for application of fragmented DNA of these pathogens at the agricultural level in crop protection strategies to cope with wilt and root rot in Capsicum.

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Zoysia japonica, in Brazil, is commonly infected by Rhizoctonia solani (R. solani) in humid and cool weather conditions. Eight isolates of R. solani, previously identified as belonging to the AG2-2 LP anastomosis group, isolated from samples from large path symptoms, were collected from three counties in São Paulo state (Brazil) and investigated for the presence of mycoviruses. After detection of double-strand RNA (dsRNA) in all samples, RNA_Seq analysis of ribosomal RNA-depleted total RNA from in vitro cultivated mycelia was performed. Forty-seven partial or complete viral unique RNA dependent-RNA polymerase (RdRp) sequences were obtained with a high prevalence of positive sense ssRNA viruses. Sequences were sufficiently different from the first match in BLAST searches suggesting that they all qualify as possible new viral species, except for one sequence showing an almost complete match with Rhizoctonia solani dsRNA virus 2, an alphapartitivirus. Surprisingly four large contigs of putative viral RNA could not be assigned to any existing clade of viruses present in the databases, but no DNA was detected corresponding to these fragments confirming their viral replicative nature. This is the first report on the occurrence of mycoviruses in R. solani AG2-2 LP in South America.

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A fucomannogalactan from Rhizoctonia solani biomass was obtained after hot aqueous extraction and purified by freeze-thaw cycles and gel filtration chromatography on Sepharose CL-6B. The polysaccharide was homogeneous after HPSEC/RID analysis (Mw/Mn~1.1), displaying an average molecular weight of 15.4×103Da. Its chemical structure was determined by methylation analysis (GC/MS) and spectroscopy (FTIR, 1D and 2D NMR). The polysaccharide had a branched α-1,6-linked Galp backbone with 66% linear residues, a number of which were at O-3 methylated. Side chains (34%) were always linked at O-2 positions of the main chain and consisted of single, non-reducing ends of α-d-Manp (6%) and α-l-Fucp (28%). Analysis of its biological activity showed that the highly purified fucomannogalactan from R. solani inhibited the proliferation of colon cancer cells in vitro, but that it did not have the same activity against lung cancer cells.

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OBJECTIVE: The ubiquitous soil pathogen Rhizoctonia solani causes serious diseases in different plant species. Despite the importance of this disease, little is known regarding the molecular basis of susceptibility. SuperSAGE technology and next-generation sequencing were used to generate transcript libraries during the compatible Nicotiana tabacum-R. solani interaction. Also, we used the post-transcriptional silencing to evaluate the function of a group of important genes. RESULTS: A total of 8960 and 8221 unique Tag sequences identified as differentially up- and down-regulated were obtained. Based on gene ontology classification, several annotated UniTags corresponded to defense response, metabolism and signal transduction. Analysis of the N. tabacum transcriptome during infection identified regulatory genes implicated in a number of hormone pathways. Silencing of an mRNA induced by salicylic acid reduced the susceptibility of N. tabacum to R. solani. We provide evidence that the salicylic acid pathway was involved in disease development. This is important for further development of disease management strategies caused by this pathogen.

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Although the productivity of common bean in Tocantins is economically favorable, it has been infected by various pathogens found in soil. Among the major diseases is the web blight and root rot caused by Rhizoctonia solani and collar rot caused by the fungus Sclerotium rolfsii. This study aimed to evaluate the fungitoxic activity of methanol extracts of eight plant species on the inhibition of mycelial growth of S. rolfsii and R. solani. The fungitoxic activities were carried out over the inhibition of mycelial growth by means in vitro assays. The extracts were applied in concentrations of 250, 500, 1000, 2500 e 5000 µg ml-1 in PDA culture medium. In bioassays, it was found the significant effect of plant, concentration and also their interaction on the antifungal activity of the extracts. However, some extracts showed no inhibition of mycelial growth of the pathogens studied. Among those who had higher inhibitions is the extract of Lantana trifolia, which inhibited the mycelial growth of S. rolfsii in all concentrations, being the same as 97% for the highest concentration. When the methanol extract of Piper amplum Kunth, inhibition of the highest concentration was 83% for S. rolfsii and 74% for R. solani. These results show the potential of methanolic extract of Lantana trifolia and Piper amplum Kunth in the control set of plant pathogens studied.

Apesar da produtividade do feijão comum no Tocantins ser economicamente favorável, o mesmo pode ser infectado por vários patógenos habitantes do solo, dentre as principais doenças encontra-se a mela e a podridão radicular causadas pelo fungo Rhizoctonia solani e a podridão do colo causada pelo fungo Sclerotium rolfsii. Este trabalho teve como objetivo avaliar a atividade fungitóxica dos extratos metanólicos de oito espécies vegetais sobre a inibição do crescimento micelial de Sclerotium rolfsii e Rhizoctonia solani. As atividades fungitóxicas foram realizadas perante a inibição do crescimento micelial por meio de ensaios in vitro, sendo os extratos aplicados nas concentrações de 250, 500, 1000, 2500 e 5000 µg ml-1 em meio de cultura BDA. Observou-se o efeito significativo dos fatores planta, concentração e também da interação destes sobre as atividades fungitóxicas. No entanto, alguns extratos não apresentaram inibição do crescimento micelial dos fitopatógenos estudados. Entre os que apresentaram maiores inibições encontra-se o extrato de Lantana trifolia, que inibiu o crescimento micelial do S. rolfsii em todas as concentrações, sendo o mesmo de 97% para a maior concentração. Já a concentração mais elevada do extrato metanólico de Piper amplum apresentou inibição de 83% sobre o crescimento micelial de S. rolfsii e 74% sobre o crescimento micelial de R. solani. Tais resultados evidenciam a potencialidade dos extratos metanólicos das folhas de Lantana trifolia e de Piper amplum no controle dos fitopatógenos estudados.

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A total of one hundred and five isolates of Rhizoctonia belonging to 7 anastomosis groups (AGs) were obtained from the diseased roots and rhizosphere soils of bean, cucumber, eggplant, pepper and tomato plants grown in greenhouses in Samsun province (Black Sea region, Turkey) during the period 2011­2012. The isolates of Rhizoctonia spp. were examined for their cultural characteristics, anastomosis groups and pathogenicity. Of these, 83.8% were multinucleate Rhizoctonia solani (AG-2, AG-4, AG-5 and AG-6) and 16.2% were binucleate Rhizoctonia (AG-A, AG-E and AG-F). Sixty five of the isolates belonged to AG-4 which was the most frequent group (61.9%) in all greenhouses surveyed. Numbers of the isolates belonging to AG-2 (7.6%), AG-5 (6.7%) and AG-6 (7.6%) were 8, 7 and 8, respectively. Seventeen isolates recovered from greenhouses surveyed were identified as binucleate Rhizoctonia AG-A (1.9%), AG-E (6.7%) and AG-F (7.6%). All isolates of Rhizoctonia spp. tested for growth rates grew at temperatures of 10, 15, 20, 25 and 30°C, whereas they were completely inhibited at 5°C. The results of pathogenicity tests showed that the differences in virulence among isolates of Rhizoctonia spp. were statistically significant (P < 0.001). The tests on bean seedlings showed that the highest disease severity was caused by AG-4 isolates. The disease severity index (DSI) of the R. solani AG-4 isolates ranged from 3.2 to 3.8. In addition, the isolates of three AGs belonging to binucleate Rhizoctonia spp. were generally found to be moderately virulent (DSI 2.0­2.4).

Um total de cento e cinco isolados de Rhizoctonia pertencentes a 7 grupos de anastomose (AGs) foram obtidos a partir de raízes doentes e solos rizosféricos de plantas de feijão, pepino, berinjela, pimenta e tomate cultivados em estufas na província de Samsun (região do Mar Negro, Turquia) durante o período 2011-2012. Os isolados de Rhizoctonia spp. foram examinados por suas características culturais, grupos de anastomose e patogenicidade. Destes, 83,8% eram Rhizoctonia solani multinucleadas (AG-2, AG-4, AG-5 and AG-6) e 16,2% era Rhizoctonia binucleadas (AGA, AG-E and AG-F). Sessenta e cinco dos isolados pertenciam ao AG-4, que foi o grupo mais freqüente (61,9%) em todas as estufas pesquisadas. O número de isolados pertencentes a AG-2 (7,6%), AG-5 (6,7%) e AG-6 (7,6%) foi de 8, 7 e 8, respectivamente. Dezessete isolados recuperados de estufas pesquisadas foram identificados como Rhizoctonia binucleada AG-A (1,9%), AG-E (6,7%) e AG-F (7,6%). Todos os isolados de Rhizoctonia spp. testados para taxas de crescimento cresceram a temperaturas de 10, 15, 20, 25 e 30ºC, enquanto que foram completamente inibidos a 5ºC. Os resultados dos testes de patogenicidade mostraram que as diferenças de virulência entre os isolados de Rhizoctonia spp. foram estatisticamente significativas (P <0,001). Os testes em mudas de feijão mostraram que a maior severidade da doença foi causada por isolados AG-4. O índice de gravidade da doença (do inglês, disease severity index - DSI) dos isolados de R. solani AG-4 variou de 3,2 a 3,8. Além disso, os isolados de três AGs pertencentes à Rhizoctonia spp. binucleadas foram geralmente encontrados como moderadamente virulentos (DSI 2,0-2,4).

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Little is known about Orchidaceae plants in Chile and their mycorrhizal associations, a key issue for designing protective actions for endangered species. We investigated root fungi from seven terrestrial orchid species to identify potential mycorrhizal fungi. The main characteristics of Rhizoctonia-like fungi were observed under light microscopy, and isolates were identified through PCR-ITS sequencing. Molecular identification of fungal sequences showed a high diversity of fungi colonizing roots. Fungal ability to germinate seeds of different orchids was determined in symbiotic germination tests; 24 fungal groups were isolated, belonging to the genera Tulasnella, Ceratobasidium, and Thanatephorus. Furthermore, dark septate and other endophytic fungi were identified. The high number of Rhizoctonia-like fungi obtained from adult orchids from the Coastal mountain range suggests that, after germination, these orchids may complement their nutritional demands through mycoheterotrophy. Nonetheless, beneficial associations with other endophytic fungi may also co-exist. In this study, isolated mycorrhizal fungi had the ability to induce seed germination at different efficiencies and with low specificity. Germin ation rates were low, but protocorms continued to develop for 60 days. A Tulasnella sp. isolated from Chloraea gavilu was most effective to induce seed germination of different species. The dark septate endophytic (DSE) fungi did not show any effect on seed development; however, their widespread occurrence in some orchids suggests a putative role in plant establishment.

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Orchidaceae establish symbiotic relationships with fungi in the Rhizoctonia group, resulting in interactions beneficial to both organisms or in cell destruction in one of them (pathogenicity). Previous studies have focused mostly on terrestrial species with a few, preliminary studies, on epiphytes. To further our understanding of the molecular mechanisms involved in these symbioses, we evaluated the interaction between Oncidium sphacelatum Lindl. and the mycorrhizal fungus Thanatephorus sp. strain RG26 (isolated from a different orchid species) in vitro using morphometric and proteomic analyses. Evidence from the morphometric and microscopic analysis showed that the fungus promoted linear growth and differentiation of orchid protocorms during 98 days interaction. On day 63, protocorm development was evident, so we analyzed the physiological response of both organisms at that moment. Proteome results suggest that orchid development stimulated by the fungus apparently involves cell cycle proteins, purine recycling, ribosome biogenesis, energy metabolism, and secretion that were up-regulated in the orchid; whereas in the fungus, a high expression of proteins implicated in stress response, protein-protein interaction, and saccharides and protein biosynthesis were found in the symbiotic interaction. This is the first work reporting proteins differentially expressed in the epiphytic orchid-fungus interaction and will contribute to the search for molecular markers that will facilitate the study of this symbiosis in both wild orchids and those in danger of extinction.

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