"Cara inchada" of cattle, an infectious, apparently soil antibiotics-dependant periodontitis in Brazil

The objective of this review on the investigation of "cara inchada" in cattle (CI), pursued over the last 30 years, was to elucidate the pathogenicity of the disease and come to proper conclusions on its etiology. CI has been widely considered to be of nutritional origin, caused primarily by mineral deficiency or imbalance. However, the disease consists of a rapidly progressive periodontitis, affecting the periodontal tissues at the level of the premolars and molars during the period of tooth eruption generally starting in young calves. The disease led to great economic losses for farmers in central-western Brazil, after the occupation of new land for cattle raising in the 1960s and 1970s. The lateral enlargement of the maxillary bones of affected calves gave the disease the popular name of "cara inchada", i.e., swollen or enlarged face. The enlargement was found to be due to a chronic ossifying periostitis resulting from the purulent alveolitis of CI. Black-pigmented non-saccharolytic Bacteroides melaninogenicus, always together with Actinomyces (Corynebacterium) pyogenes, were isolated in large numbers from the periodontal lesions. B. melaninogenicus could be isolated in small numbers also from the marginal gingiva of a few healthy calves maintained on CI-free farms. "In vitro"-assays showed that streptomycin and actinomycin, as well as the supernatants of cultivates of actinomycetes from soils of CI-prone farms, applied in subinhibitory concentrations to the bacteria tested, enhanced significantly (up to 10 times) the adherence of the black-pigmented B.melaninogenicus to epithelial cells of the bovine gingiva. The antibiotics are apparently produced in large quantities by the increased number of soil actinomycetes, including the genus Streptomyces, that develop when soil microflora are modified by cultivating virgin forest or "Cerrado" (tree-savanna) for the first time for cattle grazing. The epidemiology of CI now provides strong evidence that the ingestion with the forage of such antibiotics could possibly be an important determinant factor for the onset and development of this infectious periodontitis. The antibiotic enhanced adherence of B.melaninogenicus to the sulcus-epithelium of the marginal gingiva, is thought to allow it to colonize, form a plaque and become pathogenic. There is experimental evidence that this determinant factor for the development of the periodontitis is present also in the milk of the mothers of CI-diseased calves. It has been shown that the bacteria isolated from the periodontal CI-lesions produce enzymes and endotoxins capable of destroying the periodontal tissues. The epidemiology of CI, with its decline in incidence and its disappearance after several years, could be explained by the fact that the former equilibrium of the microflora of the once undisturbed virgin soil has been reached again and that the number of antibiotic producing actinomycetes has been anew reduced. By this reasoning and all the data available, CI should be considered as a multifactorial infectious disease, caused primarily by the anaerobic black-pigmented non-saccharolytic Bacteroides melaninogenicus, always together with the micro-anaerobic Actinomyces pyogenes. Accordingly, the onset and development of the infectious periodontitis is apparently determined by ingestion with the forage of subinhibitory concentrations of antibiotics produced in recently cultivated virgin soils. This hypothesis is supported by the recent observation of renewed outbreaks of CI-periodontitis in former CI-prone areas, following fresh cultivation after many years. The infectious nature of CI is confirmed by trials in which virginiamycin was used efficiently for the oral treatment of CI-diseased cattle. Previously it has been shown, that spiramycin and virginiamycin, used as additives in mineral supplements, prevented CI-periodontitis.

Root exudation of imazapyr by eucalypt, cultivated in soil

Imazapyr has been used to control stump sprouting in stand of Eucalyptus plantations, where herbicide is applied to the tree trunk before cutting. The herbicide is applied exclusively on the stump to be killed, but little is known about the final fate of the molecule. Imazapyr exudation via roots of eucalypt grown in soil as the substrate was evaluated under greenhouse conditions. Different herbicide doses (0.000, 0.375, 0.750, 1.125, 1.500, and 3.000 kg ha-1 a.i.) were applied on the aerial parts of 8-month-old Eucalyptus grandis clonal seedlings, cultivated in pots with 18.0 dm³ of soil. Forty days after this treatment, the eucalypt plants were cut and a lateral opening in the containers was made and the plants inclined 90º, with plants sensitive to herbicide presence (sorghum and cucumber) sown into the openings along the exposed soil surface. After 15-day sowing, toxicity symptoms on the shoots as well as the shoot and root system dry biomass of the bio-indicators were evaluated. The results suggest that eucalypt roots do exude imazapyr, and/or its metabolites, at concentrations high enough to cause toxicity to the bio-indicators. Toxicity effects were observed in all plants sown along the exposed soil profile of the container, with higher intensity at higher doses.

Seed longevity of red rice ecotypes buried in soil

Red rice is a troublesome weed in irrigated rice production and is spread through contaminated commercial rice seed and machinery. Seed dormancy is a major trait for red rice. Studies were carried out at two locations to determine red rice seed longevity in the soil of several ecotypes from four US states. Five months after burial near Beaumont, Texas only three ecotypes had viable seed (<1%) when buried at 5 cm, but 9 ecotypes had viable seed after two years when buried at 25 cm. At the thirty-sixth month after burial, ecotypes Arkansas 2, Louisiana 2 and 4, Mississippi 4 and Texas 1 had viable seeds, but at less than 1%. Freshly harvested red rice seeds buried at 12 cm near College Station, TX, survived longer than seeds placed on the soil surface. The percentage of maximum viable seeds was 2% for blackhull type Texas 4, after 17 months. In both studies, commercial rice cultivar seeds were not viable after 5 months, regardless of their position in the soil. Under farming conditions with no fallow land preparations or deep tillage, most red rice seed germinated or was dead after 2 to 3 years, with only minor variation among ecotypes.

Development of bean plants in soil contaminated with trifloxysulfuron-sodium after Stizolobium aterrimum and Canavalia ensiformis cultivation

Phytoremediation, the use of plants to decontaminate soils and water resources from organic pollutants such as herbicides, is economically and environmentally a promising technique applied in many areas, including agriculture. The objective of this work was to evaluate the development of bean plants cultivated in the field, in soil with different levels of trifloxysulfuron-sodium contamination, following cultivation of two green manure species, as well as to evaluate the possibility of recontamination of the area by such herbicide with the straw permanence on the soil. The experiment was carried out in Coimbra, MG, Brazil, on a sandy clayey Red - Yellow Argisol from March to November 2003. Four levels of soil contamination with trifloxysulfuron-sodium (0.00; 3.75; 7.50; and 15.00 g ha-1) were used as well as the following five types of cultivation prior to bean sowing in the area after herbicide application: black velvet beans (Stizolobium aterrimum) followed by removal of straw; S. aterrimum, followed by permanence of straw; jack bean (Canavalia ensiformis), followed by removal of straw; C. ensiformis followed by permanence of straw; and without prior cultivation, weed-free (weeded control). The leguminous plants were kept in the area for 65 days, cut close to the soil, and with its aerial part left or not on the surface of the experimental plot, depending on the treatment. Fifteen days after the species were cut, bean was sown in the area. At 45 days after emergence (DAE) of the bean plants, plant height and dry mass of the aerial part were evaluated. Grain productivity was determined during harvest. Height, dry matter of the aerial part and grain productivity of the bean plants, cultivated in an area previously contaminated with trifloxysulfuron-sodium at any of the levels tested, were higher with prior cultivation of S. aterrimum or C. ensiformis. At the lowest level of herbicide contamination, prior cultivation of C. ensiformis was found to be more efficient than that of S. aterrimum in mitigating the harmful effects of trifloxysulfuron-sodium on bean grain production. The permanence of the straw of the green manure species during the bean cycle did not harm the development of the plants or caused culture productivity losses, indicating that straw permanence in the area does not promote recontamination of the area.

Seed bank from soil of coffee plantations associated with grevillea trees

This study aimed to study the composition and dynamics of seed bank from soil of coffee plantations associated with grevilea trees in the experimental fields of the Southwest Bahia State University, on Vitória da Conquista campus. The experiments were carried out from September 2006 to May 2007. The coffee trees (Coffea arabica) were sown at three x one m spacing, associated with grevillea trees (Grevillea robusta) and maintained at densities of 277, 139, 123, 69, 62 and 31 plants ha-1, under direct sunlight. One hundred grams of soil were taken from each treatment with four repetitions and later identified and counted with a 10x magnifying glass. To determine seedling emergence, four soil samples of 1000 g were collected from each experimental field and transported to the greenhouse. Seedling emergence was observed by counts after 15, 30 and 45 days. The experimental design was randomized blocks of seven treatments (soil from different tree densities) and four replicates; the experimental unit consisted of a plastic tray (0, 30 x 0.22 x 0.06 m) containing 1.000 g of soil. The variables utilized to characterize the bank and its dynamics were: relative frequency, relative density, relative abundance, importance index and species diversity (Shannon-Weaver index).Increased number of monocotyledon seeds and sprouts were verified in the treatments maintained under full sunlight.

Effects of glyphosate and endosulfan on soil microorganisms in soybean crop

Transgenic soybean, resistant to glyphosate, is the most dominant transgenic crop grown commercially in the world. Research works on herbicide and insecticide mixtures and their effects on microorganisms are rarely reported. This work aimed to study the impact of glyphosate, endosulfan and their mixtures on the microbial soil activity in soybean crop. The experiment was carried out in a complete randomized block design with four treatments and five replications. The treatments were glyphosate 480 SL [540 g of active ingredient (a.i.) ha-1], endosulfan 350 EC (525 g a.i. ha-1), the glyphosate 480 SL [540 g of active ingredient (a.i.) ha-1] mixed with endosulfan 350 EC (525 g a.i. ha-1) and the control. Microbial activity was evaluated five days after treatment application. Glyphosate application was not an impacting factor for soil CO2 production. Endosulfan application (alone or mixed with glyphosate) suppressed CO2 production by microorganisms in the soil. Microbial biomass and microbial quotient were lower in the treatments using endosulfan alone and in those using endosulfan mixed with glyphosate than in the treatments using glyphosate alone and control.