No abstract

Fungi of Rhizoctonia complex are mycorrhizal of orchids and may to germinate yours seeds and development the seedlings. In this context, our objective was to select a fungal isolate to promote seed germination and seedling development of Cyrtopodium saintlegerianum. Pelotons were found in the roots and three mycorrhizal fungi were isolated. We tested mycorrhizal isolates obtained from C. saintlegerianum roots and six mycorrhizal fungi from other orchids as well three pathogenic isolates (of rice and bean) to germinate the seeds in oatmeal-agar medium. Seeds not inoculated were used as control. The isolates En07 (Waitea circinata), Cs10 (Tulasnella sp.) and Ro88 (Rhizoctonia oryzae) were efficient to promote seed germination, but only En07 differing statistically of the control. The non-specific isolate En07 promoted germination in 81% of seeds and the specific isolate (Cs10) promoted 60%, evidencing the non-specificity mycorrhizal association in this orchid during germination. Axenic seedlings were inoculated with four mycorrhizal fungi (non-inoculated seedlings - control). After six months, the isolates En07 and Cs10 were efficient in the interaction with the seedlings, but did not differ to the control. Therefore, our results suggested that fungi of the Rhizoctonia complex can be used in the germination and seedling development of C. saintlegerianum.

ResumoAs orquídeas podem ser propagadas in vitro em meios de cultivo assépticos ou em simbiose com fungos micorrízicos. Epidendrum nocturnum ocorre em áreas de Cerrado e neste estudo objetivou-se a visualização de fungos micorrízicos em suas raízes bem como o cultivo assimbiótico de suas plântulas em diferentes meios e a micorrização in vitro. No desenvolvimento assimbiótico testou-se três meios de cultura em um ensaio e, em outro ensaio, foram testadas formulações alternativas do meio Knudson C modificado, com a adição de polpa de frutas. Fungos micorrízicos de orquídeas foram usados na micorrização in vitro. Pelotons foram visualizados nas raízes de E. nocturnum. O meio Knudson C modificado diferiu estatisticamente dos demais, nas duas intensidades luminosas, no primeiro ensaio. No segundo ensaio, após sete meses, os meios com formulação alternativa não diferiram estatisticamente entre si. Na micorrização in vitro as plântulas com o isolado fúngico En07 (Waitea circinata) apresentaram maior vigor visual em relação aos demais tratamentos, mas não houve diferença estatística com o controle. Os meios com formulação alternativa e o Knudson C modificado podem ser utilizados no desenvolvimento in vitro de E. nocturnum e o isolado En07 pode ser usado na micorrização visando estratégias de conservação desta orquídea. Palavras-chave: orquídea, desenvolvimento assimbiótico, micorrização, fungo. AbstractOrchids can be propagated in vitro in aseptic culture media or in symbiosis with mycorrhizal fungi. Epidendrum nocturnum occurs in areas of Cerrado and this study aimed to mycorrhizal fungi visualization in their roots and its asymbiotic growing their seedlings in different media and in vitro mycorrhization. In asymbiotic development was tested three culture in a test and, another test, alternative formulations of medium Knudson C modified with addition of fruit pulp. Mycorrhizal fungi orchids were used in in vitro mycorrhization. Pelotons were visualized in the roots of E. nocturnum. The medium Knudson C modified statistically different from the others, the two light intensities, in the first test. In the second test, after seven months, with the alternative formulation means were not statistically different from each other. In vitro mycorrhization plantlets with isolated fungal En07 (Waitea circinata) showed greater visual effect compared to other treatments, but there was no statistical difference with control. The media with alternative formulation and Knudson C modified can be used in vitro development of E. nocturnum, and the isolated fungal En07 can be used in order mycorrhization of this orchid conservation strategies.

Rice production is affected by important pathogens such as Magnaporthe oryzae, Cochliobolus miyabeanus, Monographella albescens and Sarocladium oryzae, and orchid mycorrhizal fungi can contribute to the biocontrol of these diseases. The aim of this study was to characterize the antagonism mechanisms of W. circinata against rice pathogens. The indoleacetic acid (IAA) and lytic enzymes of W. circinata were quantified. The effectiveness of the bioagent and its metabolites was assessed in vitro. Antagonism in vivo against rice blast was also investigated. Waitea circinata produced IAA (2.3 µg ml-1), cellulase and polyphenol oxidase in a qualitative test. Glucanase, chitinase and protease were also produced in culture with cell walls and in co-culture with pathogens to explain antibiosis. W. circinata acts on direct antagonism by antibiosis and volatile metabolites. Mycelial suspension reduced M. oryzae conidial germination, appressorium formation, and rice blast by 61, 82 and 84%, respectively. W. circinata, a unique bioagent, controls four rice pathogens from mechanisms of parasitism and antibiosis. The results could contribute to new formulations containing this fungus, enzymes as well as its volatile metabolites.

The BRS Tropical rice cultivar was developed for tropical foodplains, but is susceptible to sheath blight, making the Waitea circinata bioagent an important tool in managing the disease. This study aimed to assess the W. circinata mechanisms involved in the parasitism and resistance induction to sheath blight. The in vitro antagonism was assessed by optical microscopy and scanning electron microscopy, followed by quantification of the lytic enzymes involved in parasitism, such as chitinase, glucanase and protease. An effect of the W. circinata mycoparasite against Rhizoctonia solani was observed. The W. circinata application suppressed the sheath blight by up to 65 % and increased the chitinase, glucanase and lipoxygenase activity 72 h after the inoculation and that of the peroxidase 96 h after the inoculation. Thus, W. circinata showed to be efficient in suppressing sheath blight by parasitism and induced resistance via the activation of biochemical mechanisms.

Purple ipe (Handroanthus impetiginosus) is an important tree species in Cerrado biome conservation and very popular at the landscaping and urban afforestation. However, its micropropagation is affected by pathogens, such as Oidium sp. The aim this study was evaluate the efficiency of seed treatments in the control of powdery mildew of purple ipe obtained by micropropagation. The symptoms were observed during in vitro germination, a Koch’s postulates were performed for confirm the pathogenicity, colonization of the pathogen on the leaves was analyzed in optical and scanning microscopes and a scale to evaluate severity was proposed. Two experiments were realized to powdery mildew control using a completely randomized design, with 30 replicates. First experiment: Seeds were treated with ethanol (Et), chlorothalonil + thiophanate-methyl (C+TM), and sodium hypochlorite (NaOCl); second experiment: Seeds were treated with Et, NaOCl, C+TM, and neem oil. Disease severity and area under the disease progress curve (AUDPC) were assessed in both experiments. Disease symptoms and typical pathogen structures were observed, and the pathogenicity was confirmed. The disease severity was reduced by 30.78% in 1.5% neem oil for 10 min when compared with C+TM for 15 min. We conclude that neem oil can be a strategy sustainable for the control of powdery mildew in purple ipe in tissue culture.

RESUMOOrquídeas são plantas muito procuradas em função da beleza e diversidade, de cores e formatos, de suas flores. Visando obter uniformidade, vigor e sanidade das mudas bem como produzir grandes quantidades para a comercialização usa-se a propagação in vitro. O objetivo deste trabalho foi avaliar a geminação e o desenvolvimento in vitro de Cyrtopodium saintlegerianum para aclimatação. Os meios MS, MS½, Knudson C modificado e Simplificado foram testados na germinação das sementes. No desenvolvimento das plântulas foram avaliados os meios Knudson C modificado, MS e MS modificado (adição de auxina e citocinina). Os meios MS, MS½ e Knudson C modificado promoveram germinação acima de 80% após sete dias. Contudo, no meio Simplificado as sementes germinaram após trinta dias. Nas duas avaliações, trinta e sessenta dias após o início do experimento, o meio Knudson C modificado foi eficiente para as variáveis observadas demonstrando seu potencial uso na germinação e desenvolvimento dessa espécie. Palavras-chave: Cyrtopodium saintlegerianum Rchb. f., Orchidaceae, meios de cultivo, reguladores de crescimento. ABSTRACT In vitro germination and development of the Cerrado epiphytic orchidOrchids are very popular plants due to the beauty and diversity, of colors and shapes, of their flowers. In order to obtain uniformity, vigor and sanity of the seedlings as well as to produce large quantities for the commercialization is used the in vitro propagation. The objective of this study was to evaluate the germination and in vitro development of Cyrtopodium saintlegerianum for acclimatization. The MS, MS½, Knudson C modified and Simplified media were tested on seed germination. In the development of the seedlings were evaluated Knudson C modified, MS and MS modified (addition of auxin and cytokinin). The MS, MS½ and Knudson C modified media promoted germination above 80% after seven days. However, in the Simplified medium the seeds germinate after thirty days. In the two evaluations, thirty and sixty days after the beginning of the experiment, the Knudson C modified medium was efficient for the observed variables demonstrating their potential use in germination and development of this species.

Waitea circinata (Warcup & Talbot) is an orchid antagonist mycorrhizal fungus with biocontrol potential against rice pathogens. This study aimed to optimize the extraction method, obtain a new extract and evaluate its efficiency against rice pathogens in vitro and in vivo, as well as to compare it with other extraction methods and W. circinata. The extracts were obtained and screened for in vitro growth inhibition against the pathogens Cochliobolus miyabeanus, Monographella albescens and Sarocladium oryzae, using the following extracts: mycelial, crude, lyophilized and mycelial mass. An additional in vitro assay was performed with the principal rice pathogen (Magnaporthe oryzae), in order to evaluate the conidial germination and appressorium formation. Based on this evaluation, the lyophilized and mycelial mass extracts were tested in vivo against rice blast (M. oryzae) and compared to the W. circinata mycelial suspension, in different application forms (simultaneous and previous). The mycelial mass extract inhibited all the pathogens, and the crude and lyophilized extracts inhibited C. miyabeanus and M. albescens, respectively. The mycelial mass extract inhibited the M. oryzae conidial germination and appressorium formation by 80 %, and the simultaneous and previous applications suppressed the rice blast by 94 %. These results indicate that the new extract can be used to control rice pathogens.