Diversity of filamentous fungi in different systems of land use

Microbial population and activity can be influenced by changes in the physical and chemical conditions of the soil. The objective of this study was to compare fungal diversity under different agricultural management systems and associated differences in soil properties. This research was carried out in three areas, representing the Atlantic Forest, AFS and cassava (Manihot esculenta Crantz) monoculture system. Five composite samples were collected during the rainy and dry seasons from each area. Using the composite soil samples, fungal isolation was carried out using a serial dilution technique. Physical, chemical and DGGE analyses of the filamentous fungi community were performed. The fungal isolation data were used to calculate ecological indices of diversity, species richness, equitability, dominance, similarity and density. In general, Atlantic Forest soil presented the highest ecological indices followed by the AFS. The DGGE technique revealed that the structure of the soil mycobiota of the Atlantic Forest and AFS are more than 50% similar. The data indicate that the similarity of the structure and composition of soil mycobiota between AFS and Atlantic Forest is mainly due to the conservation of above-ground plant diversity, and the conservation of soil characteristics can be attributed to the absence of pesticides and fertilizers.     

Determination of volatile organic compound patterns characteristic of five unifloral honey by solid-phase microextraction-gas chromatography-mass spectrometry coupled to chemometrics

We report the evaluation of the floral origin of honey by analysis of its volatile organic compounds (VOCs) profile, joined with the use of combined pattern recognition techniques. Honey samples, from five floral origins, were analyzed by headspace solid-phase microextraction-gas chromatography-mass spectrometry, selecting 35 VOCs out of the entire profiles, which were analyzed by hierarchical cluster analysis (HCA), stepwise discriminant analysis (SDA), and K-nearest-neighbor (KNN). Both HCA and SDA were used as exploratory tools to select a group of VOCs representing similitude and differences among studied origins. Thus, six out of 35 VOCs were selected, verifying their discriminating power by KNN, which afforded 93% correct classification. Therefore, we drastically reduced the amount of compounds under consideration but kept a good differentiation between floral origins. Selected compounds were identified as octanal, benzeneacetaldehyde, 1-octanol, 2-methoxyphenol, nonanal, and 2-H-1-benzopyran-2-one. The analysis of VOC profiles, coupled to HCA, SDA, and KNN, provides a feasible alternative to evaluate the botanical source of honey.     

Assessing insecticide and fungicide effects on the culturable soil bacterial community by analyses of variance of their DGGE fingerprinting data

To assess the effects of three insecticides (aldicarb, chlorpyrifos, deltamethrin) and two fungicides (tebuconazole and metalaxyl + mancozeb) on the PCR-DGGE fingerprints of culturable soil bacterial communities (CSBC), a greenhouse experiment was carried out with soil samples from an Integrated System for Agroecological Production (ISAP), a Conventional Potato Production Area (CPPA) and a Secondary Forest Area (SFA) close to the CPPA. Samples were obtained at 15 day intervals starting at 32 until 77 days after sowing (DAS) to perform the PCR-DGGE analysis of the CSBC cultured on media amended with soil suspension. Analysis of variance from PCR-DGGE data indicated significant differences among treatments. Regardless the type of pesticide applied, CSBC was disturbed and similarity values varied from 5% to 90% in comparison to the control. Significant shifts on CSBC were only detected among treatments in the first two harvests, while CSBC tended to be more akin to each other at the last two harvest dates. The most significant responses observed were due to different soil sample origins, where values of 5% of similarity to the control were observed on CPPA soil. The use of analysis of variance on PCR-DGGE data was useful to a better understanding of the changes on CSBC induced by pesticides applications.     

Mono- and Multielement Sorption of Trace Metals on Oxidic Industrial By-products

Assessing multielement adsorption of trace metals on materials having potential to be used as soil amendments is an essential stage for the remediation success, as soil contamination rarely occurs with a single element. This study evaluated mono-/multielement adsorption of Zn, Cu, Cd, and Pb on aluminum (AMB) and iron mining by-products (IMB, used for comparison). Prior to adsorption, these products were characterized by X-ray diffraction, isoelectric point, infrared spectroscopy, scanning electron microscopy, and microwave furnace digestion. Sorption experiments comprised: (1) pH adjustment (5.5, 6.5, and natural suspension pH), (2) mono- and multielement adsorption, and (3) desorption. Rising pH from 5.5 to natural suspension values (9.5) increased monoelement adsorption of Zn, Cu, Cd, and Pb on AMB up to 3.8-, 1.4-, 6.2-, and 1.1-fold, whereas multielement adsorption was increased up to 17.3-, 2.0-, 20.3-, and 1.2-fold, respectively. Zinc and Cd were less adsorbed than Cu and Pb and more affected by competition. Multielement adsorption at 5.5 pH in AMB resulted in smaller adsorption of Zn (up to 4.6-fold), Cu (1.4-fold), Cd (3.3-fold), and Pb (1.1-fold) when compared with monoelement adsorption. The lower the pH, the smaller the adsorption and the higher the desorption. The AMB showed higher capacity to maintain the elements adsorbed than the IMB.     

Effects of Recent Human Colonization on the Presence of Mercury in Amazonian Ecosystems

Three Hg sources were characterised and mass balance calculations were used to determine their relative contributions to the contamination of the Amazonian environment. About an order of magnitude more Hg is emitted to the atmosphere by goldmining activity than by the burning of forest biomass. However, anthropogenic atmospheric Hg cannot account for the high Hg burdens found in terrestrial ecosystems: deposition of Hg from goldmining sources is estimated to account for less than 3% of the Hg present in the surface horizons of soils. We propose that erosion of deforested soils following human colonization constitutes a major disturbance of the natural Hg cycle. Deforestation thus increases soil Hg mobilisation by runoff, which may explain the increase of Hg burdens in Amazonian aquatic ecosystems in newly colonized watersheds.     

EARLY DIAGNOSIS OF BORON DEFICIENCY IN CHESTNUT

This study aims to identify an alternative plant tissue to be used in the early diagnosis of boron (B) deficiency in chestnut (Castanea sativa Mill.). A B-deficient orchard was selected, and 16 trees were submitted to two levels of B fertilization. When flowers were in bloom, the following tissues were sampled: leaves, androgynous catkins and flowers. There was a significant increase in B content in plant tissues due to B application. In July, the highest B content was observed in flowers in B0, but leaves had the greatest content in B1. Boron content in the tissues collected in July was positively correlated with B contents in leaves sampled in September. Foliar B concentrations, irrespective of the sampling period, were correlated with chestnut productivity, while the other tissues did not. These results suggest that the leaves, sampled in bloom, were the most efficient tissue for the early diagnosis of B deficiency.