Célia Maria Maganhotto de Souza Silva

Paclobutrazol effects on soil microorganisms

The side effects of paclobutrazol, a plant growth regulator, on soil microbial community and activity were assessed in soil samples from Petrolina (PE), Pernambuco State and from Lins (SP), Sao Paulo State, in Brazil. The first experiment was carried out with soils from mango orchards of Petrolina, subjected to frequent field applications of paclobutrazol. A second experiment was conducted with soils from Petrolina and Lins with application of paclobutrazol under greenhouse conditions. For orchard soils, plate counting of soil microorganisms was carried out, while for the greenhouse experiment the parameters evaluated were: microbial biomass C, living hyphal length, dehydrogenase activity, and paclobutrazol dissipation. The paclobutrazol addition to soils of mango orchards in Petrolina, affected negatively the soil microbial community. The average values for total number of bacteria, fungi and actinomycetes were reduced by 58, 28, and 28%, respectively, compared to the paclobutrazol unamended soil. For the greenhouse experiment, the paclobutrazol application in the soils from Petrolina influenced negatively the dehydrogenase activity and the living hyphal length, but not the microbial biomass C. The addition of this substance to the Lins soils had no effect on the microbial parameters evaluated.

Effect of Salinity on Soil Microorganisms

Whilst the majority of countries have criteria to evaluate the quality of the air and water, the same does not occur for the quality of the soil. Traditionally soil quality is associated with productivity, but recently it has been defined in terms of sustainability, that is, the capacity of the soil to absorb, store and recycle water, minerals and energy such that the production of the crops can be maximized and environmental degradation minimized. Thus preservation of soil quality is a critical factor for environmental sustainability. A significant decline in soil quality has occurred throughout the entire world as a result of adverse changes in its physical, chemical and biological properties. According to Steer (1998), in the last decades of the last century, about 2 billion of the 8.7 billion agricultural lands, permanent pastures, forests and wild native lands were degraded. The global grain production growth rate fell from 3% in the seventies to 1.3% in the period from 1983-1993, and one of the main reasons for this decline was inadequate soil and water management. Inventories carried out on the soil productive capacity in the last decade indicated that 40% of the degradations of arable land were induced by man as a result of soil erosion, atmospheric pollution, intensive cultivation, over-grazing, deforestation, salinization and desertification (Oldeman, 1994). Soil degradation processes constitute a serious problem on a worldwide basis, with significant environmental, social and economic consequences. As the world population increases, so does the need to protect the soil as a vital resource, particularly for food production, . The soil is a dynamic medium, constituting the habitat of abundant biodiversity, with unique genetic patterns where one can find the greatest amount and variety of living organisms, which serve as a nutrient reservoir. One gram of soil in good conditions can contain 600 million bacteria belonging to 15,000 or 20,000 different species. These values decrease to 1 million bacteria encompassing from 5000 to 8000 species in desert soils (Informativo Capebe, 2010). Depending on the amount of organic matter present in the soil, the biological activity eliminates pathogenic agents, decomposes organic matter and other pollutants into simpler components (frequently less noxious), and contributes to maintaining the physical and biochemical properties required for soil fertility and structure. However, soil is not an inexhaustible resource and consciousness of this, allied to knowledge of the need to maintain or increase the capacity of this agro-ecosystem, directing its multiple functions in an adequate way, is increasing, as also changes in the overall perception of its importance as an environmental component.

Requisitos nutricionais para o fungo Alternaria alternata

A strain of Alternaria alternata (ALT A) was tested using different sources of C, N and vitamins in order to find a medium for its growth and sporulation. The mycelial growth was evaluated for seven days after sowing and the sporulation on the tenth day of incubation. Among various C, N and vitamins compounds tested, highest mycelial growth was achieved with maltose and glucose (C), NH4Cl (N) and biotin, with an average ratio of 0.75 cm/day. Sporulation reached highest values with galactose and arabinose (5.0 x 103 and 4.1 x 103 conidia mL-1, respectively). Others vitamins and N compounds did not influence the growth and sporulation.

Soil amendment with sewage sludge and its impact on soil microflora

O objetivo deste trabalho foi verificar o efeito de frequentes aplicacoes de lodo ao solo na atividade e no C da biomassa microbiana. Os resultados demonstraram que a utilizacao de doses excessivas de lodo pode prejudicar a microflora do solo.

An appraisal of five methods for the measurement of the fungal population in soil treated with chlorothalonil.

An experiment was carried out in a greenhouse with the aim of determining an acceptable method to quantify the fungal population in a soil treated with the fungicide chlorothalonil. Doses of the fungicide ranging from 12 to 96 μg AIg -1 soil were applied and microbial biomass carbon (C), soil ergosterol content, living hyphal length, as well as counts of total and cellulolytic fungi colonies, were measured 1,2,3,4 and 5 weeks after application. At the end of 16 weeks a new evaluation was done using the three first methods. The microbial biomass C was the least sensitive parameter and, on balance, the living hyphal length was the most sensitive parameter for demonstrating effects of chlorothalonil on the fungal population. Some problems related to the efficiency of the ergosterol content and living hyphal length measurements in the evaluation of the effect of the fungicide on the fungal microflora are discussed, as is the need to compare short-term (0-5 weeks after treatment) with longer-term (16 weeks) results.

Production of phenol-oxidases and peroxidases by fungi isolated from irrigated rice

A proposta deste trabalho foi estudar o potencial das linhagens fungicas, consideradas potenciais degradadoras dos herbicidas quinclorac e propanil, para producao de enzimas ligninoliticas. Oito linhagens fungicas foram cultivadas em meio de cultura liquido Kings B suplementado com 0,05% de Remazol Brilliant Blue R (RBBR) e em meio de cultura liquido contendo farelo de trigo como substrato. Os sistemas enzimaticos avaliados foram: lignina peroxidase, manganes peroxidase e lacases. Os resultados demonstraram padroes diferenciados quanto a producao de enzimas ligninoliticas entre as linhagens, sendo que as maiores atividades enzimaticas estiveram relacionadas a producao de lignina peroxidase. Das oito linhagens, duas (P3SA1F e P11SA2F) apresentaram descoloracao do RBBR, sugerindo a possibilidade de sua aplicabilicacao em estudos de biorremediacao

Isolamento de fungos degradadores de carbendazim

The systemic fungicides belonging to the benzimidazoles group are widely used in agricultural practice and its indiscriminate use has been cause of environmental contamination. The dissipation and the loss of the pesticide biological activity depends, most of the time, on the microor- ganisms action. The present research was carried out with the objective to select fungi with potential to degrades benomyl and its hydrolysis product, carbendazim, and to quantify its degradation potential. The fungi were isolated from three different kinds of soils collected in the region of the irrigated agriculture of Guaira, SP, Brazil, with intensive use of fungicides. Among the analyzed fungi, Alternaria alternata had the growth rate less affected by increasing the benomyl concentration. Under the maximum concentration, the inhibition for A. alternata was 22%; for the other ones it was superior to 45%. In a liquid culture medium, enriched with carbendazim, the biomass growth rate for A. alternata was 43% superior to growth rate observed in the culture media without carbendazim. A. alternata soon degraded the fungicide, reaching 66.21% of the disappearance of the product in two days. The half-life of carbendazim in this study was of 1.16 days.

Assessing the safety of Pseudomonas putida introduction in the environment: An overview of ecotoxicological tests

Risk assessment guidelines for the environmental release of microbial agents are performed in a tiered sequence which includes evaluation of exposure effects on non-target organisms. However, it becomes important to verify whether environmental risk assessment from temperate studies is applicable to tropical countries, as Brazil. Pseudomonas putida is a bacteria showing potential to be used for environmental applications as bioremediation and plant disease control. This study investigates the effects of this bacteria exposure on rodents and aquatic organisms (Daphnia similis) that are recommended to be used as non-target organism in environmental risk assessments. Also, the microbial activity in three different soils under P. putida exposure was evaluated. Rats did not show clinical alterations, although the agent was recovered 16h after the exposure in lung homogenates. The bacteria did not reduce significantly the reproduction and survival of D. similis. The soil enzymatic activities presented fluctuating values after inoculation with bacteria. The measurement of perturbations in soil biochemical characteristics is presented as an alternative way of monitoring the overall effects of the microbial agent to be introduced even in first stage (Tier I) of the risk assessment in tropical ecosystems.