Evelynne Urzêdo Leão

Manejo da adubação potássica e da irrigação no progresso de doenças fúngicas e produtividade da melancia

Entre as principais doencas da melancia, o crestamento gomoso do caule (Didymella bryoniae) e o mildio (Pseudoperonospora cubensis) se destacam devido as grandes perdas que causam na produtividade e qualidade de frutos. Para investigar a influencia da adubacao potassica no progresso do crestamento gomoso e na produtividade da melancia e a influencia da lâmina de agua e do intervalo de irrigacao no progresso do mildio, foram conduzidos dois ensaios em condicoes de campo em Gurupi-TO, nos anos de 2009 e 2010. O ensaio I foi conduzido em blocos ao acaso e os tratamentos se constituiram em tres doses de potassio aplicadas em cobertura (0, 50 e 100 kg ha-1 de KCl) e 12 repeticoes, sendo avaliada a severidade do crestamento gomoso, por meio de uma escala de notas e os dados de producao e qualidade dos frutos. No ensaio II, utilizou-se o delineamento em blocos ao acaso com quatro repeticoes, em esquema fatorial de 3 x 3, tres lâminas de irrigacao (100, 300 e 500 mm de agua durante o ciclo da cultura) e tres intervalos de irrigacao. Avaliou-se alem da severidade do mildio, tambem a producao e a qualidade dos frutos. Constatou-se que as doses de potassio nao influenciaram no progresso do crestamento gomoso e no numero, peso medio e qualidade dos frutos. As lâminas de irrigacao aplicadas influenciaram no progresso do mildio. Maiores niveis de severidade do mildio foram observados nas plantas mantidas sob irrigacao com lâmina de 500 mm de agua. As lâminas de agua aplicadas tambem influenciaram significativamente na producao e qualidade dos frutos. Observou-se a presenca de maior numero de frutos deformados ou tortos nas plantas mantidas sob deficit hidrico, na lâmina de 100 mm. As maiores produtividades comerciais e totais foram obtidas nas plantas irrigadas com a lâmina de 500 mm de agua.

Severidade de doenças foliares e produtividade de genótipos de milho em resposta à adubação nitrogenada

As doencas foliares, principalmente, helmintosporiose (Bipolaris spp.), antracnose (Colletotrichum graminicola) e ferrugem (Puccinia spp.), podem ocasionar reducao do rendimento da cultura do milho. Este estudo teve como objetivo avaliar a ocorrencia e severidade de helmintosporiose, antracnose e ferrugem, bem como a produtividade de genotipos de milho, em resposta a doses crescentes de nitrogenio. Avaliou-se a severidade das doencas, utilizando-se escala de notas, em nove genotipos de milho (AG9040, AG7088, 30F35, 3F624, 1F583, 1F632, 1F557, 1F640 e ID219), submetidos a quatro doses de nitrogenio (67; 112; 157; e 202 kg ha-1), em duas safras (2009/2010 e 2010/2011). Para determinar a produtividade, utilizou-se a massa dos graos coletados. Os graus de severidade da helmintosporiose, da antracnose e da ferrugem variaram em resposta as doses de nitrogenio e, entre os genotipos de milho avaliados durante as duas safras, entretanto, nao houve relacao clara entre as doses de nitrogenio aplicadas e a ocorrencia das doencas nas duas safras. A ferrugem foi detectada apenas durante a safra I. Apesar da severidade das doencas foliares, elas, de modo geral, nao afetaram significativamente a produtividade dos genotipos de milho avaliados. Desses, o genotipo de milho AG7088 pode ser considerado o mais produtivo e o mais resistente as doencas avaliadas.

Essential Oils for Alternative Teak Rust Control

The objectives of this study were to evaluate the effect of lemon grass, citronella grass, Mexican-tea and noni essential oils on urediniospore germination of Olivea neotectonae, the agent responsible for rust in Teak (Tectona grandis L.f.); to evaluate the phytotoxic effect of these essential oils on teak seedlings; and to evaluate the use of essential oils to control rust in teak plants when preventively and curatively applied. We found that the noni and lemon grass essential oils inhibited 100% of urediniospore germination. On the other hand, the essential oils from noni and lemon grass caused phytotoxicity when applied to seedlings at concentrations of 2000 and 1500 μL L-1, respectively. The major constituents found in lemon grass essential oil were Geranial and Neral, while Octanoic Acid was found in noni oil. Lower values in the area below the rust progress curve were observed with the preventive application of lemon grass and noni essential oils.

PATOGENICIDADE E TRANSMISSÃO DE FUNGOS ASSOCIADOS ÀS SEMENTES DE Tectona grandis L.f.

The production of teak seedlings is mainly carried out by seeds, which is an important vehicle for the transmission of various pathogens. The purpose of this study was to identify and quantify the fungi associated with teak seeds, the pathogenicity of these microrganisms to the seedlings and the seed-seedling transmission. There were used seeds collected in Tocantins and others acquired in the states of Goias (GO) and in Sao Paulo (SP) for the sanity test. The treatments used were seeds disinfested and not disinfested, and seeds with and without mesocarp. The analysis was conducted using the paper filter method (Blotter test). To pathogenicity test in seedlings, were utilized the isolates of Fusarium sp., Botryodiplodia sp., Alternaria sp. and Plenodomus sp. To evaluate the fungal seedling-transmission were used seeds of each location.The following genera of fungi were identified in the seeds: Fusarium, Trichoderma, Botryodiplodia, Aspergillus, Penicillium, Rhizopus, Cladosporium, Alternaria and Plenodomus . A higher occurrence of fungi was observed in the seeds from the states of GO and SP. Fusarium was the fungal genera with the highest incidence in the seeds of the three states. Only the Fusarium and Botryodiplodia genera were pathogenic to teak seedlings. There was low seed-seedling transmission, with only the phytopathogenic genus Fusarium being transmitted.

Morphological and molecular characterization of Curvularia lunata pathogenic to andropogon grass

The fungal genus Curvularia is associated with a number of diseases in plants, commonly producing foliar spots in forage grasses. The objective of this study was to characterize the morphological and molecular diversity of the isolates of Curvularia sp. associated with Andropogon seeds, and to assess both their capacity to transmit disease and the pathogenicity of this fungus to crop. Ten isolates of Curvularia sp. were sourced from Andropogon seeds from agricultural producing regions in the Brazilian states Tocantins and Pará. Morphological characterization was achieved by observing fungus colonies and conidia and molecular characterization by DNA extraction and amplification with sequence-specific primers. PLANT PROTECTION Note Morphological and molecular characterization of Curvularia lunata pathogenic to Andropogon grass Patrícia Resplandes Rocha dos Santos, Evelynne Urzêdo Leão, Raimundo Wagner de Souza Aguiar, Maruzanete Pereira de Melo, Gil Rodrigues dos Santos* Universidade Federal do Tocantins Agronomia Departamento de Produção Vegetal Gurupi (TO), Brazil. *Corresponding author: gilrsan@uft.edu.br Received: Aug. 4, 2017 – Accepted: Sept. 18, 2017 The disease transmission was evaluated from seed sowing, in which after 40 days typical symptoms of Curvularia sp. were observed. Pathogenicity was evaluated by inoculating conidial suspension into the leaves of healthy plants, and after ten days, inspecting for pathogenic symptoms. Based on morphological and molecular features, the pathogen associated with Andropogon seeds was identified as Curvularia lunata, which, as such, is transmitted through the Andropogon plants via its seeds and is pathogenic to this species of forage grass.

Seleção de genótipos de arroz para integrar uma mistura varietal visando o controle da brusone

A brusone, causada por Magnaporthe oryzae (Herbert) Barr é uma das doenças mais importantes na cultura do arroz. Várias estratégias de manejo da doença, como o uso de genótipos resistentes têm sido utilizadas, entretanto, o grande número de raças do patógeno dificulta a obtenção de cultivares com resistência durável. Neste contexto, o uso da mistura varietal pode constituir uma estratégia viável e promissora no controle da doença. Assim, objetivou-se com este estudo avaliar a reação de cultivares de arroz às raças de M. oryzae e a eficiência da mistura varietal na redução da severidade da brusone em condições Santos, G.R.; Chagas, J.F.R.; Castro Neto, M.D.; Fidelis, R.; Leão, E.U. Seleção de genótipos de arroz para integrar uma mistura varietal visando o controle da brusone. Summa Phytopathologica, v.43, n.4, p.290-296, 2017.

Essential Oil of Cymbopogon citratus on the Control of the Curvularia Leaf Spot Disease on Maize

The Curvularia Leaf Spot is becoming more common due to the culture expansion and the low resistance of the cultivated genotypes in tropical regions. Thus, the objective was to evaluate the fungitoxicity of the essential oil of Cymbopogon citratus upon the phytopathogen Curvularia lunata, causative agent of the Curvularia Leaf Spot. There was realized pathogenicity tests of C. lunata in maize plants, phytotoxicity of the essential oil of C. citratus and gas chromatography attached, germination tests of the conidia, and of in vitro inhibition of C. lunata. Also, there were realized tests aiming at verifying the phytopathogen control in vivo. In the pathogenicity tests, there were verified symptoms of the disease in all of the suspensions tested on plants. It was observed that the essential oil concentrations of 7.5 µL mL−1 to 50 µL mL−1 were phytotoxic. The majoritarian chemical components of the essential oil of C. citratus were Geranial (41.46%) and Neral (32.43%). The concentrations of 5 and 7.5 µL mL−1 inhibited 100% of conidia germination. None of the concentrations evaluated effectively inhibited C. lunata mycelial growth in in vitro tests. In the preventive control, the concentration of 7.5 µL mL−1 was sufficient for the reduction of the progress of the disease, however the curative control was not efficient on the tested dosages.

Temporal progress of teak rust in a tropical area of Tocantins State, Brazil

Rust, caused by Olivea neotectonae, stands out as the main teak disease, causing premature defoliation regardless of the tree’s growth stage. In this study, we aimed to assess the temporal progress of rust in adult teak plants in southern Tocantins State (Brazil). Both rust incidence and severity were evaluated and the disease progress curves were obtained, adjusting to monomolecular, logistic and Gompertz mathematical models. Data from incidence and severity were correlated with climate variables collected by the agrometeorological station located in the study area. Rust incidence reached 100% at 98 days after beginning of the evaluations (DBE). The highest severity (equal or above 75%) was observed at 147 DBE. There was a significant and negative correlation between severity and minimum temperature. The adjustment of the Gompertz model suggests that control measures should be aimed primarily to reduce the rate of disease progress.

Reação de genótipos experimentais de melancia ao crestamento gomoso do caule

O crestamento gomoso do caule, causado pelo fungo Didymella bryoniae e uma das principais doencas que ocorrem na melancia, provocando tombamento das plântulas e formacao de cancros no caule e nas hastes, reduzindo a produtividade e a qualidade dos frutos. Apesar de existirem fontes de resistencia a essa doenca, no Brasil ainda sao poucos os trabalhos realizados para incorporacao de resistencia em cultivares comerciais e os resultados obtidos nao sao satisfatorios para a adocao em condicoes de campo. O objetivo desse trabalho foi, a partir da selecao de isolados de D. bryoniae, avaliar a reacao de genotipos experimentais de melancia ao crestamento gomoso do caule, em condicoes de casa de vegetacao e em campo. No experimento em casa de vegetacao observaram-se variacoes quanto a resistencia dos genotipos testados. Alguns dos materiais foram resistentes em condicao de casa de vegetacao e tambem apresentaram reacao de resistencia em campo. Os genotipos WMX-001E-PL#13-01, WMX-001E-PL#04-01 e WMX-001E-PL#02-02 foram resistentes a infeccao por D. bryoniae no caule (casa de vegetacao) e nas folhas (campo).