RESUMO Fungos fitopatogênicos durante o processo de penetração e colonização são capazes de secretar uma variedade de enzimas, as quais os tornam capazes de infectar o tecido vivo do hospedeiro, atuando na degradação de ceras, cutícula e das paredes celulares. A capacidade de um agente patogênico em produzir ou não enzimas pode determinar o grau de severidade da doença. Foram avaliados 33 isolados de Colletotrichum gloeosporioides relacionados à antracnose e mancha manteigosa do cafeeiro, quanto a sua capacidade de produção de enzimas hidrolíticas (amilase, lipase, protease, lacase, pectinase e celulase) e enzimas específicas degradadoras da parede celular “EDPC” (poligalacturonase, polimetilgalacturonase e pectinaliase), e sua relação com a patogenicidade/agressividade dos isolados. Para todos os isolados de C. gloeosporioides foi possível a detecção de enzimas extracelulares, com exceção de celulases. Os isolados I-9 e I-24 apresentaram os maiores índices de produção de enzimas extracelulares, e assim como de EDPCs. Os mesmos obtiveram os maiores índices de intensidade de doença, sugerindo a relação entre estas e a agressividade dos isolados.

ABSTRACT Phytopathogenic fungi during the penetration and colonization process are capable of secreting several enzymes, which enable infection of the host live tissue, acting on the degradation of wax, cuticle and cell walls. The ability of a pathogenic agent to produce enzymes or not can determine the severity degree of a disease. In this study, 33 isolates of Colletotrichum gloeosporioides related to anthracnose and blister spot on coffee trees were evaluated for their ability to produce hydrolytic enzymes (amylase, lipase, protease, laccase, pectinase and cellulase) and specific cell wall degrading enzymes “CWDEs” (polygalacturonase, polymethylgalacturonase and pectin-lyase), as well as their relationship with the pathogenicity/aggressiveness of isolates. For all isolates of C. gloeosporioides, extracellular enzymes could be detected, except cellulases. Isolates I-9 and I-24 produced the highest levels of extracellular enzymes, as well as CWDEs. They also had the highest disease intensity indexes, suggesting a relationship between enzymes and aggressiveness of the isolates.

ABSTRACT This study was conducted as a first step in exploiting endophytic bacteria to improve yam production. Little information is available on population densities and genetic diversity of endophytic bacteria in yam cultivated in tropical regions. This study demonstrated that higher densities of total endophytic bacteria and Bacillus occur in the interior of roots and decrease as the sampled plant organ departs from soil. Bacillus represents approximately 1% of the total bacterial endophytic population. Random Amplified Polymorphic DNA (RAPD) analyses performed with 88 randomly-selected Bacillus isolates resulted in 28 groups, and sequence analyses of the 16S region of the ribosomal DNA of 24 isolates representing all major RAPD groups revealed that they could be clustered in 2 clades: Bacillus cereus and B. pumilus. While B. cereus was able to colonize the entire plant, B. pumilus remained confined to the rhizophores. Further research should concentrate on the application of these isolates in biotechnological processes, such as biocontrol and yam growth promotion.

Colletotrichum gloeosporioides no Brasil está associado a um complexo de sintomas na cultura do café. Apesar da observação e da identificação da patogenicidade deste, o patógeno ainda tem sua importância questionada, devido às várias formas endofíticas do mesmo, levantando dúvidas sobre a real importância do patossistema. O presente trabalho teve como objetivo demonstrar por meio da utilização de um isolado transformado com o gene gfp a capacidade de infecção e colonização de C. gloeosporioides em plântulas de café. Pode-se observar após o quarto dia da inoculação a exteriorização de sintomas como necrose pontuais as quais progrediram durante o período de avaliação, culminando na morte das plântulas. Por meio de microscopia de epifluorescencia pode-se confirmar a presença do patógeno nas plântulas, assim como visualizar a colonização interna do tecido, a formação de acérvulos e produção de conídios, confirmando que o mesmo foi o responsável pelos sintomas observados.

In Brazil, Colletotrichum gloeosporioides is associated with a complex of symptoms in coffee culture. Although this pathogen had its pathogenesis observed and identified, its importance has still been questioned due to its several endophytic forms, raising doubts as to the real importance of the pathosystem. The aim of this study was to demonstrate, by using an isolate transformed with the gene gfp, the infection and colonization capability of C. gloeosporioides in coffee seedlings. After the fourth day of inoculation, manifestation of symptoms as punctual necrosis could be observed, which progressed during the evaluation period, culminating in the death of seedlings. Epifluorescence microscopy confirmed the presence of the pathogen in the seedlings, as well as the visualization of internal colonization of tissues, acervulus formation and conidium production, confirming that it was responsible for the observed symptoms.

Blister spot (Colletotrichum gloeosporioides) is now widespread in most coffee producing states of Brazil, becoming a limiting factor for production. The lack of data relating to the reproduction of typical symptoms (light green, oily patches) leaves a gap within the pathosystem, forcing the search for new methodologies for monitoring the disease. Monitoring of genetically modified organisms has proven to be an effective tool in understanding the host x pathogen interactions. Thus, the present study was carried out to evaluate the effectiveness of two systems of genetic transformation in obtaining mutants using the gfp reporter gene. Using the two transformation systems (PEG and electroporation) revealed the efficiency of both, confirmed by fluorescence microscopy and resistance to the antibiotic hygromycin-B, when incorporated into the culture medium. The fungus maintained its cultural and morphological characteristics when compared to wild strains. When inoculated on coffee seedlings, it was found that the pathogenicity of the processed isolates had not changed.

O uso do consórcio entre plantas de cobertura e culturas anuais, no Cerrado, tem sido prática cada vez mais difundida, pela possibilidade de implantação das forrageiras durante o desenvolvimento das culturas anuais, através da diferença de profundidade e sistema de semeadura. Objetivou-se, neste trabalho avaliar a emergência e algumas características agronômicas de quatro espécies de plantas de cobertura, em diferentes profundidades, visando ao seu emprego na consorciação e sobressemeadura em culturas anuais. O experimento foi conduzido em casa-de-vegetação, no delineamento experimental de blocos ao acaso, em arranjo fatorial 4 x 7, composto pelas plantas de cobertura Brachiaria brizantha, B. decumbens, B. ruziziensis e Panicum maximum cv. Tanzânia, e por seis profundidades de semeadura e um sistema de cobertura de sementes (0 sem cobertura, 0 com cobertura, 1, 4, 8, 10 e 15 cm). As sementes foram semeadas em vasos e as plantas cultivadas por 40 dias. Avaliou-se o índice e o tempo de emergência, a altura de plantas, a fitomassa verde e seca da parte aérea, a área foliar, a fitomassa seca radicular e a densidade de comprimento radicular. O maior desenvolvimento das plantas estudadas foi detectado nas semeaduras até 1 cm de profundidade. O P. maximum não apresentou aptidão para uso em consórcio com culturas anuais.Não se recomenda a semeadura das plantas de cobertura a partir de 10 cm.

The use of the consortium between cover crops and annual crops in the Cerrado, is an increasingly widespread practice, because of the possibility of deployment of cover crops during the development of annual crops by the difference in depth and seeding system. The objective was to evaluate the emergency and some agronomic characteristics of four species of cover crops at different seeding depths, to use them in consortium and oversown in annual crops. The experiment was conducted in a greenhouse, and the experimental design of randomized blocks in factorial arranged 4 x 7, where it was four cover crops: Brachiaria brizantha, B. decumbens, B. ruziziensis and Panicum maximum cv. Tanzania, and six depths of sowing and a cover of seed system (0 cm without any mulch, 0 cm with a mulch of soybean leaves, 1, 4, 8, 10 and 15 cm). The cover crops were cropped in vase for 40 days. We evaluated emergence index, emergence time, plant height, green biomass and dry biomass of the above-ground part, leaf area, root dry biomass and root length density. The largest development of the cover crops was detected in the sowing up to 1 cm of depth. The P. maximum showed no ability to use in consortium with annual crops. The sowing of the cover crops from 10 cm is not recommended.

O objetivo deste trabalho foi avaliar a capacidade de estabelecimento de plantas de cobertura em sobressemeadura na cultura soja. A soja foi semeada em diferentes épocas para que, no estádio R7 (maturação fisiológica), ocorressem diferentes condições climáticas para implantação das plantas de cobertura. O experimento foi realizado em Rio Verde, GO, na safra de verão 2005/2006, em Latossolo Vermelho distroférrico. Foram avaliadas seis plantas de cobertura: Brachiaria brizantha, B. ruziziensis, B. decumbens, Eleusine coracana, Pennisetum glaucum e o híbrido Cober Crop [Sorghum bicolor (L.) Moench x Sorghum sudanense Piper Stapf], e uma testemunha mantida em pousio. A soja foi semeada em quatro épocas: 27/10/2005, 10/11/2005, 24/11/2005 e 14/12/2005. A sobressemeadura das plantas de cobertura foi realizada manualmente, a lanço, quando a soja atingiu o estádio R7. Com exceção da segunda época de semeadura da soja, que apresentou a menor média de estande em todas as plantas de cobertura, em razão da maior matocompetição, todas as demais possibilitaram crescimento inicial satisfatório das plantas de cobertura sobressemeadas em R7, com base na emergência, altura de plantas, cobertura do solo e produção de palhada. B. ruziziensis, B. brizantha, B. decumbens e o híbrido Cober Crop apresentam maior potencial para a produção de palhada durante a entressafra no Cerrado, com uso da sobressemeadura.

The objective of this work was to evaluate the establishing capacity of cover crops, oversown onto soybean. The soybean was planted at different seasons, so that in the R7 stage (physiologic maturation) different climatic conditions would be present for cover crop implantation and growth. The experiment was carried out in Rio Verde, GO, Brazil, in the summer crop season 2005/2006, on a Rhodic Ferralsol. Six cover crops were evaluated: Brachiaria brizantha, B. ruziziensis, B. decumbens, Eleusine coracana, Pennisetum glaucum, and the hybrid Cober Crop [Sorghum bicolor (L.) Moench x Sorghum sudanense Piper Stapf]. Fallow treatment was used as control. Soybean was planted at four sowing seasons: 10/27/2005, 11/10/2005, 11/24/2005 and 12/14/2005. Oversowing was carried out manually, by broadcasting at the R7 stage of soybean. Except for the second sowing season, in which weed competition reduced the mean stand of cover crops, all the remaining sowing seasons of soybean resulted in satisfactory initial cover crop growth, as given by: emergence, crop height, soil cover, and biomass accumulation. Oversowing with B. ruziziensis, B. brizantha, B. decumbens and the hybrid Cober Crop show higher potential to produce mulch, during the off-season in Cerrado.