First Report of Choanephora cucurbitarum Causing Leaf Wilt, Flower Rot, and Stem Necrosis on Crotalaria breviflora.

Crotalaria breviflora (Fabaceae) is used as green manure crop because of its nitrogen fixation and nematode control (Nascimento et al. 2020). In April 2018, leaf wilting, flower rot, and stem necrosis symptoms were observed on C. breviflora with 100% incidence, in Sorriso (12° 33' 31″ S, 55º 42' 51″ W), Santa Carmem (11° 55' 52″ S, 55º 16' 47″ W), and Sapezal (12º 59' 22″ S, 58º 45' 52″ W) counties in the state of Mato Grosso, Brazil. Three monosporic isolates were isolated from symptomatic leaves, cultivated in potato dextrose agar (PDA) medium, and deposited at the Cultures Collection of the University of Brasilia (codes CCUB 1293, CCUB 1667, CCUB 1668). Colonies on PDA were white and cottony with presence of hyaline and coenocytic hyphae. The mycelia later became pale yellow with abundant reproductive structures. Sporangiophores were hyaline, aseptate, unbranched, and apically dilated to form a clavate vesicle, which produced secondary vesicles bearing sporangiola. Secondary vesicles were clavate, light brown, and 37 to 51 µm in diameter. Sporangia were brown to dark brown, globular to ellipsoid, 115 to 140 µm long, and 96 to 122 µm wide. Sporangiospores (n=30) were brown to reddish-brown, ellipsoid to ovoid, with longitudinal striae, 14 to 19 µm long, and 8 to 12 µm wide. Some with hyaline appendages at both ends. Their morphological characteristics were consistent with the descriptions of Choanephora cucurbitarum (Kirk 1984). To confirm the identity, the DNA of the three isolates was extracted and the sequences of Small Subunit (SSU), Large Subunit (LSU), and complete Internal Transcribed Spacer (ITS) of rDNA were amplified using V9G, ITS3, and LR5 primers (GenBank acc. no: MN897836, MN897837 and MN897838). The sequences were aligned with the MAFFT software. The alignment matrix was subjected to Maximum Likelihood (ML) analysis using RAxML v. 8 and Bayesian Inference performed in MrBayes v.3.1.2. The tree was edited in the FigTree software. The sequences showed 100% identity with the sequences from C. cucurbitarum found on the GenBank. To confirm pathogenicity, a suspension at 5.4 ×106 spores/ml was prepared from a 15-day-old culture grown at 25°C and sprayed on asymptomatic plants of C. breviflora. Sterilized water was sprayed as the control. Plants were kept in a humid chamber at 20°C for 48 h. Initial symptoms were visualized 16 days after inoculation. Complete necrosis of leaves and stems with spore mass on infected tissue was observed 19 days after inoculation. To satisfy the Koch's postulates, the fungus was successfully reisolated from the infected tissues. No symptoms were observed on the control plants. In Brazil, this pathogen has been reported on Brassica oleracea var. capitata, Capsicum annuum, Crotalaria spectabilis, Cucurbita sp., and Vigna unguiculata (Alfenas et al. 2018; Mendes and Urben, 2019). C. cucurbitarum has been reported to have a wide range of hosts (Farr and Rossman, 2020). It can infect the crops grown in rotation or in succession, including common bean, corn, cotton, quinoa, soybean, and sunflower. Therefore, this pathogen is of epidemiological importance and poses a threat to the croplands where environmental conditions are conducive to the disease to develop and spread. To our knowledge, this is the first report of C. cucurbitarum causing leaf and flower wilt, and stem rot on C. breviflora in the world. Acknowledgment We thank the Environmental Sciences Graduate Program, Federal University of Mato Grosso, University of Brasilia, PROPeq/PROPG-UFMT, EMBRAPA, CODEX/UFMT, Institute of Agricultural and Environmental Sciences (ICAA)/UFMT and CAPES for providing the Master's scholarship. References Alfenas, R. F., et al. 2018. Plant Dis.102:1456. https://doi.org/10.1094/PDIS-10-17-1610-PDN, Google Scholar. Farr, D. F., and Rossman, A. Y. 2020. Fungal Databases, Syst. Mycol. Microbiol. Lab., ARS, USDA. Retrieved May 26, 2020 from https://nt.ars-grin.gov/fungaldatabases/, Google Scholar. Kirk, P. M. 1984. Mycol Paper. 152:1. Google Scholar. Mendes, M. A. S., and Urben, A. F. 2020. Fungos relatados em plantas no Brasil, Retrived May 26, 2020 from http://pragawall.cenargen.embrapa.br/aiqweb/michtml/fgbanco01.asp, Google Scholar. Nascimento, D. D. et al. 2020. Bioscience Journal. 36:713. https://doi.org/10.14393/BJ-v36n3a2020-42248, Google Scholar.

Induction of phytoalexins and proteins related to pathogenesis in plants treated with extracts of cutaneous secretions of southern Amazonian Bufonidae amphibians.

Cutaneous secretions produced by amphibians of the family Bufonidae are rich sources of bioactive compounds that can be useful as new chemical templates for agrochemicals. In crop protection, the use of elicitors to induce responses offers the prospect of durable, broad-spectrum disease control using the plant's own resistance. Therefore, we evaluated the potential of methanolic extracts of cutaneous secretions of two species of amphibians of the family Bufonidae found in the Amazon biome-Rhaebo guttatus (species 1) and Rhinella marina (species 2)-in the synthesis of phytoalexins in soybean cotyledons, bean hypocotyls, and sorghum mesocotyls. Additionally, changes in the enzyme activity of ß-1,3-glucanase, peroxidase (POX), and polyphenol oxidase (PPO) and in the total protein content of soybean cotyledons were determined. In the soybean cultivar 'TMG 132 RR', our results indicated that the methanolic extract of R. guttatus cutaneous secretions suppressed glyceollin synthesis and ß-1,3-glucanase activity and increased POX and PPO activities at higher concentrations and total protein content at a concentration of 0.2 mg/mL. On the other hand, the methanolic extract of R. marina cutaneous secretions induced glyceollin synthesis in the soybean cultivars 'TMG 132 RR' and 'Monsoy 8372 IPRO' at 0.1-0.2 mg/mL and 0.2 mg/mL, respectively. The methanolic extract of R. marina cutaneous secretions also increased the specific activity of POX and PPO in 'Monsoy 8372 IPRO' and 'TMG 132 RR', respectively, and decreased the activity of ß-1,3-glucanases in 'Monsoy 8372 IPRO'. At 0.3 mg/mL, it stimulated phaseolin synthesis. The extracts did not express bioactivity in the synthesis of deoxyanthocyanidins in sorghum mesocotyls. The study in soybean suggests that the bioactivity in defense responses is influenced by cultivar genotypes. Therefore, these results provide evidence that extracts of cutaneous secretions of these amphibians species may contribute to the bioactivity of defense metabolites in plants.

Atividade antimicrobiana in vitro de extratos metanólicos de secreções cutâneas de anfíbios amazônicos sobre fitopatógenos de interesse agrícola / n vitro antimicrobial activity of methanolic extracts from cutaneous secretions of Amazonian amphibians against phytopathogens of agricultural interest

Os mecanismos de defesa bioquímica dos anfíbios envolvem secreções cutâneas de moléculas bioativas com atividade antimicrobiana. Este estudo avaliou a atividade in vitro de extratos metanólicos da secreção cutânea de duas espécies de anfíbios da família Bufonidae, Rhaebo guttatus e Rhinella marina, no controle dos patógenos Fusarium udum, Fusarium solani, Colletotrichum truncatum, Aspergillus flavus, Rhizoctonia solani, Macrophomina phaseolina e Calonectria pseudometrosideri. O extrato de R. guttatus inibiu o crescimento micelial de F. udum, F. solani, A. flavus e M. phaseolina em algumas concentrações testadas. O extrato de R. marina inibiu o crescimento micelial de C. truncatum na concentração de 0,5 mg mL- ¹, e inibiu o crescimento micelial de A. flavus nas concentrações de 0,1 e 0,5 mg mL- ¹, que foi semelhante à inibição pelo controle positivo. O extrato de R. marina também diminuiu a produção de microescleródios de R. solani nas concentrações de 0,2 e 0,3 mg mL- ¹. Além disso, os extratos inibiram a esporulação e germinação de conídios em graus variados. A inibição da formação de apressórios em C. truncatum pelos extratos de R. guttatus e R. marina foi de 85%­99% e 63%­100%, respectivamente. Nossos resultados demonstraram que o tratamento com extratos da secreção cutânea de R. guttatus e R. marina apresentou atividade antifúngica sobre os fitopatógenos estudados.(AU)

Development, characterization and stability of microemulsionated formulations of bacaba, Oenocarpus bacaba oil

Advances in nanotechnology, combined with the use of natural products, represent a promissing research field. Brazil is a country of a rich biodiversity, especially in the Amazon forest. Fruits commonly used by local communities, such as bacaba (Oenocarpus bacaba), are potentially important for prospection of industrial applications of natural products. In nanotechnology, microemulsions stand out for providing a modified release to conveyed substances. This work aimed to develop microemulsionated formulations of bacaba oil, characterize them and evaluate their stability. We determined the HLB (hydrophile-lipophilic balance) of bacaba oil for formulation development. Six formulations were selected from pseudoternary diagrams, which indicated the proportions of surfactants, aqueous phase and bacaba oil. The viability of these formulations was evaluated through stability tests. We provided the rheological characterization of the formulations, evaluated their potential antioxidant activity through the DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging method, and determined the hydrodynamic diameter of the droplets. The microemulsions were stable throughout the test period. Droplet diameter was below 200 nm, and the microemulsions were characterized as newtonian fluids, presenting an increase in antioxidant activity when compared with the diluted oil. Our results confirm the potential of bacaba oil in microemulsionated formulation as a suitable carrier for active compounds. (AU)

Chemical composition and antifungal activity of propolis on Aspergillus flavus / Composição química e atividade antifúngica de própolis sobre Aspergillus flavus

Research has indicated the antifungal activity of ethanol extracts from propolis (EEP) on fungi of the genera Phakopsora, Colletotrichum, and Cercospora. Here, chemical compositions and antioxidant activity of three EEP (propolis from Scaptotrigona polysticta stingless bee and two types produced by Apis mellifera - red and brown) were evaluated and their action against Aspergillus flavus was investigated. Ash, dry extract, total phenolic and total flavonoid contents were determined. Phenolic composition was evaluated by high performance liquid chromatography, with using the following reference substances: gallic acid, caffeic acid, -coumaric acid, ferulic acid, quercetin, kaempferol, and apigenin. Tests on mycelial growth, sporulation, and germination of spores were performed to assess the biological activity of the EEP on A. flavus. All EEP showed low dry extract content (<11%) with adequate amounts of ash (<5%). The red EEP (Apis mellifera) showed the highest contents of total phenolic and total flavonoid (5.38 and 2.77 g 100 g-1), while the highest recorded antioxidant activity was exhibited by brown EEP (92.9%). The EEP of S. polysticta presented higher levels of -coumaric acid (10.99 mg g-1), while red and brown extracts from A. mellifera stood out with the highest levels of quercetin (27.26 mg g-1) and gallic acid (5.88 mg g-1), respectively. No extract was effective in inhibiting mycelial growth and sporulation of A. flavus, but red EEP inhibited spore germination. On the basis of these results, it is suggested that the inhibitory effect of red EEP on spore germination may be associated with increased levels of flavonoids found in it as compared with the other extracts investigated here.

Outros estudos apontaram a ação antifúngica dos extratos etanólicos de própolis (EEP) sobre fungos do gênero Phakopsora, Colletotrichum e Cercospora. Neste estudo, avaliou-se a composição química e a atividade antioxidante de três EEP (própolis produzido pela abelha sem ferrão Scaptotrigona polysticta e dois tipos de própolis produzida pela Apis melífera: marrom e vermelha) e sua ação contra o Aspergillus flavus. Foram determinados os teores de cinzas, extrato seco, fenólicos e flavonoides totais nos EEP. A composição fenólica foi determinada por cromatografia líquida de alta eficiência, empregando-se as seguintes substâncias de referência: ácido gálico, ácido p-cumárico, ácido ferrúlico, quercitina, kaempferol e apigenina. Para avaliar a atividade biológica dos EEP sobre A. flavus foram realizados os testes de crescimento micelial, esporulação e germinação de esporos. Todos os EEP apresentaram baixos teores de extrato seco (< 11%), porém quantidades de cinzas adequadas (< 5%). O EEP vermelha apresentou os maiores teores de fenólicos e flavonoides totais (5,38 e 2,77 g 100g-1), enquanto que a maior atividade antioxidante registrada foi do EEP marrom (92,9%). O EEP de S. polysticta apresentou maiores teores de ácido p-cumárico (10,99 mg g-1), enquanto que os de A. mellifera, vermelha e marrom, destacaram-se com os maiores níveis de quercetina (27,26 mg g-1) e de ácido gálico (5,88 mg g-1), respectivamente. Nenhum extrato foi eficaz na inibição do crescimento micelial e esporulação de A. flavus, porém observou-se inibição na germinação de esporos pelo EEP vermelha. Sugere-se que o efeito inibitório na germinação de esporos pode estar relacionado com os maiores níveis de flavonoides encontrados na própolis vermelha, quando comparado com os outros extratos investigados.

Influência da concentração, do fotoperíodo e da temperatura de armazenamento na germinação de urediniósporos de Olivea tectonae / Influence of concentration, photoperiod and storage temperature in germination of Olivea tectonae urediniospores

A ferrugem da teca, causada pelo fungo Olivea tectonae, foi constatada no estado do Mato Grosso em 2009, no município de Sinop e nos anos seguintes foi observada em outras regiões do estado. A doença causa manchas necróticas nas folhas da planta, que correspondem aos urediniósporos localizados abaixo da epiderme das folhas e, quando em grande intensidade, levam a desfolha precoce da planta. As plantas desfolhadas ficam debilitadas, o que afeta a produção de madeira. Os objetivos deste trabalho foram: (i) avaliar a influência da concentração e do fotoperíodo na germinação de urediniósporos de O. tectonae; (ii) avaliar a influência da temperatura de armazenamento dos urediniósporos, coletados de folhas caídas e de folhas ainda nas plantas, na germinação destes esporos. Os resultados obtidos mostraram que os maiores níveis de germinação foram na concentração de 6,25 x 104 esporos mL-1 exposto à luz constante por 24 horas (92,75%). Porém quando submetidos ao escuro absoluto, houve germinação de 91,31%, o que significa que esporos de O. tectonae podem germinar na presença e na ausência de luz. Verificou-se que a percentagem de germinação foi maior nos esporos coletados de folhas ainda na planta e armazenados a temperatura de -2°C.

The teak rust, caused by the fungi Olivea tectonae, was found for the first time in Mato Grosso in 2009, in Sinop city and in the next years it was observed in another regions of the state. The pathology cause necrotics spots in plant leaves, that correspond to the urediniospores located below the leaves epidermis and, when they occurs in high intensity, lead to premature defoliation of the plant. The defoliated plants get weakened, what affects the wood production. The objectives of this work were: (i) to evaluate the influence of concentration and photoperiod in the germination of O. tectonae; (ii) to evaluate the influence of the storage temperature of urediniospores, collected from fallen leaves and leaves still on the plants, in the spores germination. The results showed that the higher levels of germination were in the concentration of 6,25 x 104 spores mL-1 exposed to constant light for 24 hours (92,75%). However, when they were submitted to total dark, there was also germination of 91,31%, what means that Olivea tectonae's spores can germinate in both the presence and absence of light. The germination percentual was higher in spores collected from leaves still in the plant and stored at a temperature of -2°C.

Bacillus subtilis: enraizamento e crescimento de miniestacas de eucalipto em Sinop, norte de Mato Grosso / Bacillus subtilis: rooting and growth of eucalyptus mini-cuttings in Sinop, northern Mato Grosso

A crescente demanda pela implantação de florestas plantadas tem exigido diversos estudos para inovações no processo de produção e melhor aproveitamento econômico da floresta. O uso de rizobactérias promotoras de crescimento em plantas vem despontando como uma alternativa viável para otimizar o desenvolvimento e produção dessas florestas. Este trabalho teve como objetivo avaliar o enraizamento e crescimento de miniestacas em cinco clones de eucalipto, H13, 1004, GG100, 1277 e I144, mediado por rizobactérias, através de um inoculante biológico que possui em sua formulação como princípio ativo a rizobactéria Bacillus subtilis. A inoculação foi realizada de três maneiras distintas: diretamente no substrato, por imersão das miniestacas em suspensão de inóculo e pela combinação dos referidos métodos, sendo comparado com o tratamento testemunha que seguiu o padrão do viveiro. Foram avaliados, número de raízes emitidas abaixo do tubete, comprimento de raízes (cm), massa fresca e seca do sistema radicular e da parte aérea (g) e altura (cm) das mudas. Os resultados variaram de acordo com o clone, parâmetros avaliados e método de inoculação. Com base nos resultados houve ganho significativo em todos os parâmetros analisados, com aumento na emissão de raízes de até 53,2%. Na biomassa do sistema radicular e da parte aérea, houve incrementos que variaram entre 45,9 e 45,1%, respectivamente. Para o crescimento das mudas observou-se aumento, variando entre 20,3 a 37,2%. Estes resultados indicam o potencial de uso da rizobactéria Bacillus subtilis para incrementar a produção de mudas de eucalipto em viveiro.

The increasing demand for planted forests has required several studies about innovations in the production process and better economic use of the forest. The use of growth promoting rhizobacteria in plants is emerging as a viable alternative, to optimize the development and production of these forests. This study evaluated rooting and growth of mini-cuttings in five clones of eucalyptus, H13, 1004, GG100, 1277 and I144, mediated by rhizobacteria of the biological inoculant that has in its formulation as the active ingredient Bacillus subtilis rhizobacterium. Inoculation was done in three ways: directly on the substrate, by immersion of mini-cuttings in inoculum suspension and the combination of these methods, in comparison with standard nursery treatment. The parameters evaluated were number of roots below the container, root length (cm), fresh and dry weight of the root system and aboveground part (g) and height (cm) of the seedlings. The results varied according to the clone, the evaluated parameters and method of inoculation. Based on the results, there was significant gain in all parameters analyzed, with an increase in the emission of roots up to 53.2%. Biomass in the root system and aboveground part increased ranging between 45.9 and 45.1%. Seedling height showed an increase ranging from 20.3 to 37.2%. These results indicate the great potential of using Bacillus subtilis to increase the production of eucalyptus seedlings in nurseries.