Morphological characterization and genetic analysis of Drechslera teres isolates

Net blotch, caused by the phytopathogen Drechslera teres, is a common disease of barley (Hordeum vulgare L) and is responsible for large economic losses in some barley growing areas. In this study the morphology and genetic variability of eight D. teres isolates from different regions of the Brazilian state of Rio Grande do Sul were investigated. Colony morphology was studied on potato-dextrose-agar (PDA) and genetic variability investigated using the random amplified polymorphic-DNA (RAPD) technique. 27 commercially available primers were tested of which 16 were selected for use in polymorphic analysis due to their good resolution and reproducibility. Similarity coefficients were used to construct dendrograms based on colony morphology and RAPD data showing the relationship between the eight isolates studied. Colony morphology showed variability between the isolates while RAPD assays showed high similarity coefficients, but grouping of the isolates according to the geographic origins of the seeds from which they were isolated was not possible

Controle de larvas de Boophilus microplus por Metarhizium anisopliae em pastagens infestadas artificialmente Control of Boophilus microplus larvae by Metarhizium anisopliae in artificially infested pastures

O objetivo deste trabalho foi avaliar a eficiência do controle exercido por Metarhizium anisopliae na população de Boophilus microplus, em pastagens de Brachiaria brizantha, e do híbrido Tifton 85 (Cynodon spp.), artificialmente infestadas com fêmeas ingurgitadas do carrapato. Trinta canteiros com 1 m² de área cada foram distribuídos aleatoriamente. Quinze foram pulverizados com esporos do fungo e quinze controles em cada forrageira, constituindo cinco repetições de cada tratamento, foram infestados com número e peso padronizados de fêmeas ingurgitadas do ácaro. Aplicou-se o fungo, na concentração de 1,8x10(8) conídios mL-1, em três situações: pulverização antes da infestação com o carrapato, após a infestação e posterioriormente à emergência das primeiras larvas nos capins. A ação do fungo foi avaliada no 35º, 38º, 41º, 48º, 55º e 61º dia pós-infestação, por meio da contagem de larvas recuperadas. Obteve-se controle de larvas do ácaro, que, nas avaliações realizadas entre o 35º e o 48º dia pós-infestação, variou entre 87% e 94%. As médias das contagens de estágios larvares do carrapato foram menores em todas as amostragens realizadas no capim-Tifton 85, indicando que houve efeito da pastagem na ação do fungo. A situação de aplicação influencia a atividade do fungo, com melhor resultado nas coletas realizadas entre o 41º e 55º dia após infestação em B. brizantha, e aplicação dos conídios logo após a emergência das primeiras larvas.<br>The objective of this work was to evaluate the efficiency of Metarhizium anisopliae fungus against Boophilus microplus population in Brachiaria brizantha and Tifton 85 (Cynodon) pastures, artificially infested with tick engorged females. Thirty plots of 1 m² each were randomly distributed in fifteen treated and fifteen control groups per type of grass, establishing five repetitions for each treatment. Pastures were infested with engorged tick females standardized by number and weight. Metarhizium anisopliae suspension with 1.8x10(8) conidia mL-1 concentration was sprayed on the plot in three different assays, prior infested with tick females, immediately after tick inoculation and at first larvae emergency. The fungus action was evaluated at 35th, 38th, 41st, 48th, 55th and 61st day post infestation by counting recovered larvae. A significative reduction of larvae counts occurred in fungus treated groups during 35th to 48th day post infestation, ranging between 87% and 94% of efficacy on tick larvae control. The mean values for larvae counting in Tifton 85 pasture were lower than in B. brizantha plot in all analysis, suggesting the pasture effect on fungus action. Treatment strategy influenced on M. anisopliae activity, which demonstrated better results at 41st and 55th day post infestation in B. brizantha, submitted to conidia challenge after larvae emergency