Fabio Fernando de Araujo

Uso de Bacillus subtilis no controle da meloidoginose e na promoção do crescimento do tomateiro

The objective of this research was to evaluate the Bacillus subtilis (PRBS-1) effect as growth promoter and suppressor agent of root-knot nematode (Meloidogyne spp.) in tomato cultivation. The treatments consisted in the application of B. subtilis formulation and of the nematicide carbofuran. The plants were maintained in greenhouse during 85 days, when the plants were colleted. Roots were separated from aerial part of the plants to evaluate the treatments effect. The fresh matter production by the aerial part increased either by the chemical or by the biological treatments. The fresh matter of the roots was reduced with application B. subtilis. The effect of the biological treatment on the nematode reproduction was more evident by the reduction of egg masses in the root. The present study indicates that the strain PRBS-1 of B. subtilis promotes tomato plant growth and reduces knoot-root nematode reproduction in tomato roots under greenhouse conditions.

INFLUÊNCIA DE BACILLUS SUBTILIS NA ECLOSÃO, ORIENTAÇÃO E INFECÇÃO DE HETERODERA GLYCINES EM SOJA

The utilization of microorganisms for biological control of plant diseases has been studied in the world. In soybean cyst nematode (Heterodera glycines), an important diseases in soybeans, biological control strategies are important tools mostly because the lack of an efficient chemical control. The effect of Bacillus subtilis on H. glycines was studied on greenhouse and laboratory experiments. The presence of B. subtilis reduced the number of appeared H. glycines eggs when under stimulus of soybean exudes. Also, treatment of soybean roots with B. subtilis inhibited the juvenile larvae of H. glycines migration towards the soybean roots. In greenhouse experiments using soil infested with eggs of H. glycines, a reduction in the number of females was observed in the soybean root when both soil and seeds were previously treated with either wettable powder or solution containing B. subtilis. Considering the results of this research, and that H. glycines depends on plant exude for show up and orientation of larvae, it can be assumed that B. subtilis might interfere in the nematode life cicle.

Coinoculação rizóbio e Bacillus subtilis em feijão-caupi e leucena: efeito sobre a nodulação, a fixação de N2 e o crescimento das plantas

This research aimed to evaluate co-inoculation of Bradyrhizobium and Bacillus subtilis on nodulation, N2 fixation and growth of cowpea (Vigna unguiculata) and leucaena (Leucaena leucocephala) grown in a red Oxisol. Treatments consisted by: a) control; b) NPK; c) inoculation with Bradyrhizobium + PK; d) co-inoculation Bradyrhizobium + Bacillus subtilis + PK. There was an increase in nodulation of cowpea with co-inoculation. The shoot dry weight, N accumulation and chlorophyll were higher in both co-inoculated and fertilized (NPK) treatments. For leucaena, there were not differences between NPK, inoculated and co-inoculated treatments. The dry weight roots of cowpea and leucaena increased with co-inoculation. The co-inoculation Bradyrhizobium and Bacillus subtilis favored the increase in nodulation of cowpea and it has potential to increase biological N2 fixation and plant growth.

Supressividade dos nematóides Meloydogine javanica e Heterodera glycines em soja por adição de lodo de esgoto ao solo

Sewage sludge has shown great potential for use in agriculture, where it has been widely used. There are some modifications on chemical, physical and biological properties of the soil due to its composition of macro and micronutrients and organic substances. These alterations can provide benefits as an increase to the availability of nutrients to the plants, suppressiveness induction of soilborne plant pathogens and resistance to foliar diseases. However, it may influence negatively the biological and chemical balance in the soil, due to the presence of considerable amounts of available N, soluble salts and heavy metals. The aim of this work was to evaluate the effect of sewage sludge incorporation to the soil and the suppressiveness induction of nematodes (Meloydogine javanica (Treub) Chitwood and Heterodera glycines Ichinoe) in soybean (Glycine max L.). Experiments were performed in laboratory and in a greenhouse using collected soil in an experimental area of the Embrapa Meio Ambiente, Jaguariuna, SP. This area received successive applications of sewage sludge, originary from the sewage treatment of Barueri and Franca, in Sao Paulo State, Brazil, during five years (1998-2002). In relation to the suppressiveness induction of nematodes, the sludge did not affect significantly the development of H. glycines in the soil, but reduced the M. javanica reproduction, in the soybean root.

Azospirillum sp. as a Challenge for Agriculture

Several processes mediated by soil microorganisms play an important role in nutrient cycling. One such process is biological nitrogen fixation (BNF) by representatives of various bacterial phylogenetic groups, which are called diazotrophs. Most studies of the Azospirillum-plant association have been conducted on cereals and grasses. Currently, 17 species of Azospirillum have been described. However, a great diversity of these bacteria continues to be revealed, and little is known of the potential applications of the many species that have been described. The Azospirillum-plant association begins with the adsorption and adherence process of these bacteria in roots. Involved in these processes is the recognition of bacterial polysaccharides by the host plant, a step that is necessary in successfully forming a positive relationship between roots and Azospirillum. The presence of Azospirillum in the rhizosphere can minimize the susceptibility to diseases caused by plant pathogens. Furthermore, the ability to produce phytohormones, mainly auxins (indole-3-acetic acid) and other molecules from secondary metabolism has been suggested to underlie the growth response to inoculation by Azospirillum species. These positive aspects of Azospirillum colonization in the roots are also responsible for the alleviation of plant stress. For all of the above-mentioned reasons, Azospirillum are also widely used as commercial inoculants, resulting in a significant economic impact in crop yields in many countries. In fact, solid and liquid formulations containing Azospirillum are marketed in various countries, such as Brazil, Argentina, Mexico, Italy, France, Belgium, Africa, Germany, Pakistan, Uruguay, India and the USA. In addition, new formulations containing Azospirillum, such as polymeric inoculants (alginate, agar, chitosan and gum), are already used for the improvement of many crops. This chapter summarizes the positive effects of Azospirillum-plant interactions and their biological importance for the improvement of agriculture worldwide.

Efeito de lodo de esgoto sobre patógenos habitantes do solo e severidade de oídio da soja

Sewage sludge, complying with environmental demands, has potential for use in agriculture. The incorporation of sewage sludge may changes the chemical, physical and biological soil properties, for being rich in macro and micronutrients and organic matter. These changes can provide benefits such as the increase in the availability of nutrients for plants, and the induction of suppressiveness to soilborne plant pathogens and resistance to foliar diseases. However, it may influence negatively the biological and chemical balance of the soil, due to the presence of contaminants. The objective of this work was to evaluate the effect of sewage sludge on the severity soybean (Glycine max) powdery mildew (Erysiphe diffusa) and on suppressiveness to Rhizoctonia solani and Macrophomina phaseolina The experiments used soil which received four successive applications of sewage sludge (from 1999 to 2001), originally from the wastewater treatment station of Barueri and Franca counties, Sao Paulo State, Brazil, in concentrations of 0, 1, 2, 4 and 8 times (0N to 8N) the dose of N recommended for corn. Two experiments were conducted to investigate the effects of sewage sludge on soybean powdery mildew (E. diffusa) in a naturally infested greenhouse. In another experiments, the soybean emergency and powdery mildew severity were evaluated in plants growing in container media mixed with 0; 2.5; 5; 10; 15 and 20% of sewage sludge from Franca Sewage Treatment Station. A similar experiment was conducted twice to evaluate the effects of sewage sludge on seedling emergence, damping-off incidence, and severity of R. solani and M. phaseolina. In this case, the soil was artificially infested with the pathogens. Sewage sludge incremented elicitation of phytoalexins in soybean and the severity of powdery mildew was reduced with an increase in the concentration of sludge in the soil and substrate. Seedling emergence, in the three cropping periods, was inversely proportional to the Franca sewage sludge concentrations, at 20% totally inhibited the soybean seedling emergence. Franca sewage sludge not affects damping-off and severity caused by R. solani. For Barueri sludge, in the first cropping, there was a quadratic response for damping-off, with increased of 1N and 2N, and reduction at 4N. In the second cropping, increased damping-off, but a quadratic response with an inflection point at 1N. On the other land, the damping-off was the same for control and 8N. For severity, in two soybean cropping, Barueri sludge presents a quadratic response with an inflection point at 4N. The incidence of M. phaseolina was inversely proportional to Franca sewage sludge concentration. In the present study, there were no treatment affects the suppressiveness of R. solani and M. phaseolina.

Less abundant bacterial groups are more affected than the most abundant groups in composted tannery sludge-treated soil

The application of composted tannery sludge (CTS) has promoted shifts in soil chemical properties and, therefore, can affect the soil bacterial community. This study assessed the effect of the CTS on the soil bacterial community over time. The CTS was applied at five rates (0, 2.5, 5, 10 and 20 t/ha), and the bacterial community was evaluated for 180 days. The principal curve response (PRC) analysis showed that the most abundant phyla were not influenced by the CTS rates over time, while the analysis of the bacterial community showed that some of the less abundant phyla were influenced by the CTS rates. Similarly, the PRC analysis for the bacterial classes showed the significant effect of the CTS rates. The redundancy analyses for the bacterial phyla and classes showed the relationship between the significant chemical properties and the bacterial community of the soil after the CTS amendment over time. Therefore, there was a shift in the bacterial community over time with the application of the composted tannery sludge. Our study has shown that the less abundant bacterial groups were more influenced by the CTS than the most abundant bacterial groups and that these bacterial groups were driven by soil chemical properties, primarily chromium (Cr) and the soil pH.

Soil Microbial Biomass Across a Gradient of Preserved Native Cerrado

The different physiognomies and soil conditions across the Cerrado gradient may influence soil microbial biomass. The present study evaluated the soil microbial biomass and enzyme activity across a preserved Cerrado gradient and correlated these with environmental conditions. The site, sampling period and their interaction influenced soil microbial biomass and activity. Soil conditions, i.e., chemical and microclimatic properties, varied across the Cerrado gradient and influenced soil microbial biomass and activity. The highest and lowest values for microbial biomass and enzyme activity were found in Cerradao and Campo graminoide, respectively, during both seasons. Multivariate analysis showed that the sites were clearly separated into different groups, indicating that distinct physiognomies and environmental conditions influenced soil microbial biomass and enzyme activities.

Responses of microbial biomass, available phosphorus, and sugarcane yield after filter cake amendment in a tropical soil,

A field experiment was conducted from 2012 to 2015 aiming to evaluate two different P sources (TSP - triple superphosphate and NP - natural phosphate) associated with filter cake (FC) on soil microbial biomass, available P and sugarcane yield...