D. F. Parreira

Incidência de Colletotrichum graminicola em colmos de genótipos de milho

Stalk rot (Colletotrichum graminicola) is one of the most serious disease affecting maize crop in Brazil, especially after the flowering phase, when yield losses can reach significant levels. The use of genetically resistant cultivars is the most efficient strategy to control the disease. The aim of this work was to evaluate the incidence of stalk rot in maize commercial hybrids sinde there is scarce information to allow the use of genetic resistance as a strategy to control this disease. Eighteen maize commercial hybrids were evaluated in 2005, 2006, and 2007 in the experimental area of EMBRAPA Maize and Sorghum Research Center Sete Lagoas, Minas Gerais State, Brazil, under conditions of natural infection. From each plot, three stalk segments of three plants were sampled: the second internode above the soil line, the internode of ear insertion, and the internode right bellow the tassel. Four tissue fragments of each stalk segment were surface sterilized and transferred to oatmeal agar plates, which were incubated under continuous fluorescent light at 25oC. Pathogen identification and quantification were performed after three to four days of incubation. The hybrids BR201 and BR206 showed the lowest infection level (below 30%) whereas the highest incidence (above 60%) was observed for the hybrid BRS1010. The pathogen was observed in all analyzed stalk segments, but was most frequently isolated from the internode right below the tassel. No evaluated hybrid could be considered to have high resistance to the pathogen.

First report of pathogenicity of Pantoea ananatis in sorghum (Sorghum bicolor) in Brazil

Bacterial isolates from sorghum plants showing leaf spot symptoms were identified through molecular and phenotypic traits, showing that the isolates belong to Pantoea ananatis. Sorghum plants inoculated with those isolates showed a pathogenic reaction. The causal agent was reisolated and Koch’s postulates were fulfilled. This is the first report of P. ananatis causing leaf spots on sorghum plants in Brazil.

Cercosporoid hyphomycetes associated with Tibouchina herbacea (Melastomataceae) in Brazil

A survey of fungal pathogens associated with cane tibouchina, Tibouchina herbacea (Melastomataceae), was conducted in the neotropics, concentrated in south and southeastern Brazil and aimed at finding potential biological control agents for this herbaceous invasive weed for introduction into Hawaii. Numerous fungal species were found, including five cercosporoid fungi. Four new taxa are described and illustrated here: Passalora tibouchinae, Pseudocercospora subsynnematosa, Pseudocercospora tibouchina-herbaceae and Pseudocercospora tibouchinicola. A phylogenetic analysis of the ITS and TEF-1α regions of the three new species of Pseudocercospora was conducted and confirmed their separation as distinct taxa as indicated by morphological and cultural features. Additionally, Cercospora apii is reported for the first time on T. herbacea. Among the species of fungi described in this study, two appear particularly promising for use in a biological control program because they were found to cause severe disease on T. herbacea: Passalora tibouchinae and Pseudocercospora subsynnematosa. Additional tests, including host-specificity screening, will be required in order to confirm this potential.

First report of Pseudocercospora muntingiae on Muntingia calabura in Brazil

Pseudocercospora muntingiae is recorded as the cause of leaf spots on Muntingia calabura (Tiliaceae), for the first time from Brazil and also in South America.

Primeiro relato de Oidiopsis haplophylli (Erysiphales) em Vernonia scorpioides (Asteraceae)

ed., Nova Odessa: Inst. Plantarum, 2000. 608p.). Emoutubro de 2004, plantas doentes dessa especie foram encon-tradas as margens da rodovia MG-265 em trecho proximo a Acai-aca. Estas apresentavam manchas cloroticas na face superiordas folhas culminando com a queima e encarquilhamento dolimbo foliar. Correspondendo ao tecido lesionado, observou-sena face inferior das folhas a presenca de uma pulverulencia bran-ca correspondente as estruturas do patogeno (Fig. 1). O materialcoletado foi conduzido ao Laboratorio de Micologia do Depar-tamento de Fitopatologia da Universidade Federal de Vicosaonde foi examinado. Para o exame ao microscopio optico forampreparadas lâminas contendo estruturas do patogeno, utilizan-do-se lactofucsina como meio de montagem. Uma amostra domaterial foi devidamente herborizada e depositada no herbariolocal (VIC 27837).O fungo apresentava as seguintes caracteristicas: