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-The incorporation of organic matter has been used to manage of diseases caused by soilborne pathogen, but there is a gap in the use of coffee residues on disease supressiveness. The objective of this study was to evaluate the effect of organic matter sources against cassava root rot caused by F. solani CFF109. Fertilization with coffee residue (CR), cattle manure (CM), earthworm excrements (EE) and goat manure (GM) resulted in suppression of cassava root rot. The treatments of CR and CM presented higher reduction in the cassava disease severity. There were changes in the soil microbial community structure by organic matter incorporation, mainly in total fungi and Gram-negative bacteria populations. The total organic carbon and magnesium are negatively associated with disease severity. The microbial quotient, alkaline and acid phosphatase activities were positively and the biomarker a-15:0 was negatively associated with disease severity. This study indicated that agro-industrial residues can be recycled for providing organic matter and nutrients with effect for management of plant diseases by suppressing soilborne pathogens. This is the first evidence that the industrial residue of coffee can be use in the management of cassava root rot, caused by F. solani.Keywords: Manihot esculenta. Fusarium solani. Coffee residue. Extracellular soil enzyme. Microbial community structure. FAMES E ATIVIDADES MICROBIANAS ENVOLVIDAS

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Yeasts have been used to manage a large number of plant diseases, but little is known about the mechanisms used by these biocontrol agents. The objectives of the present study were to evaluate the antagonistic effect of yeasts against Rhizoctonia solani and possible mechanisms of action in cowpea plants. Seventy yeast isolates were obtained from leaf, root and stem tissues of cowpea and common bean plants. Screening experiments were conducted in a greenhouse at temperatures ranging from 15 to 26°C in the first and from 22 to 31°C in the second experiment. Candida saopaulonensis C6A, Cryptococcus laurentii FVC10 and Bullera sinensis FVF10 (R1) reduced disease severity by 57.4%, 48.5% and 66.3%, respectively. Cowpea plants treated with FVF10 (R1) showed the highest peroxidase and catalase activities. The mechanisms of action were based on competition and induction of enzymes such as peroxidase, catalase and ascorbate peroxidase in cowpea. Candida saopaulonensis C6A, C. laurentii FVC10 and B. sinensis FVF10 (R1) are potential biocontrol agents of damping-off and stem rot caused by R. solani on cowpea plants.

Sandy soils of 19 arable fields were analyzed for disease suppressiveness against root rot disease of cassava, caused by Fusarium solani CFF109. Analysis of chemical, physical, biochemical, microbial population and activity, and soil characteristics were assessed. Soils with different management histories and covers most commonly found in the region were collected to build a greenhouse experiment, to evaluate the natural suppressiveness of soils against cassava root rot. The severity was submitted with all data across correlation and multivariate analyses to find correlation between disease suppressiveness and abiotic or biotic soils attributes. Differences in disease suppressiveness were found between the treatments for cassava root rot. Significant disease suppression was found in 37% of the soils. The sandy soil covered with consortium of Zea mays + Vigna unguiculata was the most efficient in suppressiveness against disease caused by F. solani. The data indicated significant correlation between soil characteristics and suppressiveness cassava root rot. The soil supressiveness against cassava root rot was favored by increase by total bacteria, fluorescent group bacteria populations and activity of acid and alkaline phosphatase and β-glucosidase.

The objective of the present study was to evaluate the natural suppressive capacity of soils from forest, and monocropping and intercropping systems, against root rot, caused by Scytalidium lignicola, in a greenhouse experiment. We used soils from a tropical dry forest (FOR) and two intercropping and two monoculture systems. The first intercrop was maize and beans (CORNCOWP), and the second intercrop was cassava, pigeon peas and beans (CASPIGPCOWP). The first monoculture was beans, and the second was passion fruit. The intercropping soils showed a higher capacity to suppress black root rot in cassava than the monoculture because such soils were able to reduce disease severity by about 50%. Bean soil in the monoculture showed less microbial biomass carbon than in the intercrop, with means of 10.05 and 38.2 mg/kg, respectively. The higher density of bacteria and fungal populations, microbial biomass, urease and arylsulphatase activities correlated with a decrease in disease severity. Soils from the intercrops produced changes in soil quality, primarily in the population and density of microorganisms, enzymatic activities, total organic carbon and nutrients, reducing disease severity in cassava plants. These effects were validated by multivariate principal component analysis and showed three distinct groups: one FOR, one intercropping and one monocropping. The majority of vectors were in the direction of FOR and intercropping soils. We have provided some of the first data related to the beneficial effects of intercropping on the suppression of black root rot in cassava, which is validated through different attributes.

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