Campinas, Brazil
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Nematodes are important pests of sugarcane crop in Brazil. However, no studies have been reported on the spatial and temporal variability of nematodes population in sugarcane fields and such studies are indispensable for the development of sampling plans, aimed at their application in integrated management programs. This work was carried out in two commercial fields of approximately 1 ha, both of them infested by Meloidogyne javanica and Pratylenchus zeae. In each area, samples represented by about 50 g of roots, were collected every two months, within a grid measuring 10.5 × 10 m (experiment 1) and 9.8 × 10 m (experiment 2). The highest nematodes populations were obtained during the rainy season, when high temperatures and moistures were favorable to root development. For this reason the rainy season was considered the best time to collect samples to identify areas with nematodes problem. Among the 52 calculated semivariograms (28 for M. javanica or P. zeae populations in area 1 and 24 for M. javanica or P. zeae populations in area 2), 22 could not be fitted to any model and presented a pure nugget effect. The spherical model showed the best fit to the semivariograms of data observed in the other 30 conditions. In those cases, values of range in semivariogram varied from 22 to 77 m, with 47 m on average and suggesting that, to obtain a reliable estimate for the population of these plant parasites in a given area, samples should be collected 47 m apart, which is equivalent to 1.5 sampling points per hectare.

de Assis A.C.C.,Instituto Agronomico | Coelho R.M.,Instituto Agronomico | da Pinheiro E.S.,Federal University of Amazonas | Durigan G.,Instituto Florestal
Plant Ecology | Year: 2011

Soil is one of the environmental elements to influence Cerrado vegetation. Aluminum toxicity of Cerrado soils is well known, but the importance of water availability is still to be understood, especially in Cerrado under wetter climates. We studied the association between Cerrado physiognomies (cerradosensu stricto and cerradão) and morphological, chemical, physical, and physical-hydrical soil attributes at southwestern São Paulo State, Brazil. Characterization of soil morphology, classification and sample collection for particle-size distribution, and chemical and water-retention analyses were carried out in 15 permanent plots, where vegetation was characterized floristically and structurally. Simple correlation and canonical correspondence analyses were performed with soil data. Classification of soils (U. S. Soil Taxonomy) with very low clay contents was not able to separate soils under cerradão-forestry physiognomy-from those under cerradosensu stricto-savannic physiognomy, even though it tends to distinguish soils under greater biomass from those under lower biomass physiognomies. High soil acidity of all studied soils and increased at the sites with greater contents of organic matter, mainly with the cerradão physiognomy, precluded Al toxicity as a cause of the physiognomic gradient within Cerrado. Clay content, microporosity, and residual and saturation moisture were the most significant soil attributes to correlate directly with the cerradão physiognomy, indicating that water availability is the main factor explaining the physiognomic gradient of Cerrado vegetation in a local scale, where climate and soil fertility do not vary spatially. © 2011 Springer Science+Business Media B.V.

Esper R.H.,Instituto Biologico | Goncalez E.,Instituto Biologico | Marques M.O.,Instituto Agronomico | Felicio R.C.,University Estadual Of Santa Cruz | Felicio J.D.,Instituto Biologico
Frontiers in Microbiology | Year: 2014

Aflatoxin B1 (AFB1) is a highly toxic and carcinogenic metabolite produced by Aspergillus species on food and agricultural commodities. Inhibitory effects of essential oils of Ageratum conyzoides (mentrasto) and Origanum vulgare (oregano) on the mycelial growth and aflatoxin B1 production by Aspergillus flavus have been studied previously in culture medium. The aim of this study was to evaluate aflatoxin B1 production by Aspergillus flavus in real food systems (corn and soybean) treated with Ageratum conyzoides (mentrasto) and Origanum vulgare (oregano) essential oils. Samples with 60 g of the grains were treated with different volumes of essential oils, 200, 100, 50, and 10 μL for oregano and 50, 30, 15, and 10 μL for mentrasto. Fungal growth was evaluated by disk diffusion method. Aflatoxin B production was evaluated inoculating suspensions of A. flavus containing 1.3 × 10 spores/mL in 60 g of grains (corn and soybeans) after adjusting the water activity at 0.94. Aflatoxin was quantified by photodensitometry. Fungal growth and aflatoxin production were inhibited by essential oils, but the mentrasto oil was more effective in soybeans than that of oregano. On the other hand, in corn samples, the oregano essential oil was more effective than that of mentrasto. Chemical compositions of the essential oils were also investigated. The GC/MS oils analysis showed that the main component of mentrasto essential oil is precocene I and of the main component of oregano essential oil is 4-terpineol. The results indicate that both essential oils can become an alternative for the control of aflatoxins in corn and soybeans. © 2014 Esper, Gonçalez, Marques, Felicio and Felicio.

The objective of this work was to evaluate nitrate movement on soil columns considering mainly, total amount recovered, fit among experimental and model-predicted transposition curves, and model-obtained retardation factors. Samples of A and B horizons of Udox and Udult soils were used. A leaching experiment was carried out considering the miscible displacement theory, using 100 mL of a 10-mmol L-1 KNO3 solution as pulse. The amounts of nitrate leached and recovered in the columns for Udox and Udult soils in horizons A and B varied from 0.405 to 1.432 mmol L-1. There was significant (p<0.05) correlation between experimental and model-predicted curves for columns Udult-A, Udult-B and Udox-B. The mathematical model used is suitable for predicting nitrate lixiviation in B-horizon columns in Udox and Udult soils. The retardation factor was greater than 1.0 in the soil columns with good fit among experimental and predicted data, which indicates that the nitrate movement is delayed in comparison to the advance of the soil wetting front.

There are still doubts with regard to the efficiency of P fertilization in the sugarcane ratoon and the interaction between P and other nutrients that could affect the responses to P reapplication. An experiment was set up to evaluate the effects of P rates (45 and 90 kg ha-1 of P2O5) applied either in the absence or presence of Mg fertilizer (50 kg ha-1 of Mg) on the stalk yield, of sugarcane ratoon. P fertilization increased stalk yield in 17% compared to the control treatment (no P fertilizer). However, such response did not depend on Mg fertilization, suggesting that Mg was not critical to the occurrence of P response. The P nutritional status of sugarcane was not also affected by Mg application, being altered exclusively by P fertilization. P content in the leaves varied significantly (p<0.05) from 1.4 g kg-1 in the control to 1.7 g kg-1 and 1.9 g kg-1 in the treatments with application of 45 and 90 kg ha-1 of P2O5, respectively. P fertilization increased in 21% and 16%, the efficiency in the use of N and K fertilizers, respectively, compared to the control. The results suggest that increases in the yield of sugarcane ratoon cultivated in a low-P soil can be obtained with P reapplication, what might be related to the improvements on the P nutritional status of the plants.

Andrade S.A.L.,University of Campinas | Silveira A.P.D.,Instituto Agronomico | Mazzafera P.,University of Campinas
Science of the Total Environment | Year: 2010

Studies on mycorrhizal symbiosis effects on metal accumulation and plant tolerance are not common in perennial crops under metal stress. The objective of this study was to evaluate the influence of mycorrhization on coffee seedlings under Cu and Zn stress. Copper (Cu) and zinc (Zn) uptake and some biochemical and physiological traits were studied in thirty-week old Coffea arabica seedlings, in response to the inoculation with arbuscular mycorrhizal fungi (AMF) and to increasing concentrations of Cu or Zn in soil. The experiments were conducted under greenhouse conditions in a 2×4 factorial design (inoculation or not with AMF and 0, 50, 150 and 450mgkg-1 Cu or 0, 100, 300 and 900mgkg-1 Zn). Non-mycorrhizal plants maintained a hampered and slow growth even in a soil with appropriate phosphorus (P) levels for this crop. As metal levels increased in soil, a greater proportion of the total absorbed metals were retained by roots. Foliar Cu concentrations increased only in non-mycorrhizal plants, reaching a maximum concentration of 30mgkg-1 at the highest Cu in soil. Mycorrhization prevented the accumulation of Cu in leaves, and mycorrhizal plants showed higher Cu contents in stems, which indicated a differential Cu distribution in AMF-associated or non-associated plants. Zn distribution and concentrations in different plant organs followed a similar pattern independently of mycorrhization. In mycorrhizal plants, only the highest metal concentrations caused a reduction in biomass, leading to significant changes in some biochemical indicators, such as malondialdehyde, proline and amino acid contents in leaves and also in foliar free amino acid composition. Marked differences in these physiological traits were also found due to mycorrhization. In conclusion, AMF protected coffee seedlings against metal toxicity. © 2010 Elsevier B.V.

Berenschot A.S.,Instituto Agronomico | Quecini V.,Embrapa Uva e Vinho
Physiology and Molecular Biology of Plants | Year: 2014

Flower color and plant architecture are important commercially valuable features for ornamental petunias (Petunia x hybrida Vilm.). Photoperception and light signaling are the major environmental factors controlling anthocyanin and chlorophyll biosynthesis and shade-avoidance responses in higher plants. The genetic regulators of these processes were investigated in petunia by in silico analyses and the sequence information was used to devise a reverse genetics approach to probe mutant populations. Petunia orthologs of photoreceptor, light-signaling components and anthocyanin metabolism genes were identified and investigated for functional conservation by phylogenetic and protein motif analyses. The expression profiles of photoreceptor gene families and of transcription factors regulating anthocyanin biosynthesis were obtained by bioinformatic tools. Two mutant populations, generated by an alkalyting agent and by gamma irradiation, were screened using a phenotype-independent, sequence-based method by high-throughput PCR-based assay. The strategy allowed the identification of novel mutant alleles for anthocyanin biosynthesis (CHALCONE SYNTHASE) and regulation (PH4), and for light signaling (CONSTANS) genes. © 2013 Prof. H.S. Srivastava Foundation for Science and Society.

Bernini C.S.,Instituto Agronomico | Paterniani M.E.A.G.Z.,Instituto Agronomico
Pesquisa Agropecuaria Tropical | Year: 2012

Hybrids developed with the efficient use of heterosis contribute significantly for increasing maize yield. This study aimed to evaluate F 2 hybrid populations, concernings agronomic traits, and estimate genetic parameters of F 2 populations, as well as heterosis, by using the Gardner & Eberhart method. Higher estimates of F 2 populations effect, for grain mass, were noticed in the Pop.9, Pop.11, Pop.14, and Pop.15, being considered suitable for intrapopulational recurrent selection programs and for obtaining superior lines. The Pop.10 and Pop.16 distinguished themselves by presenting the higher effects of parental heterosis, for grain mass. The Pop.12 x Pop.10 and Pop.13 x Pop.10 hybrids showed high yield and specific heterosis effects, revealing the existence of dominant locus in the genetic control of grain mass.

de Abreu C.A.,Instituto AgronOmico | Coscione A.R.,Instituto AgronOmico | Pires A.M.,Embrapa Meio Ambiente | Paz-Ferreiro J.,Technical University of Madrid
Journal of Geochemical Exploration | Year: 2012

Phytoremediation is a sound alternative to soil decontamination, as it has lower costs and is more environmentally friendly than other practices. The need to handle contaminated biomass after harvesting and the search for new renewable energy sources have shifted research interests from typical edible or scenic plant species to those that can be used to produce biofuels. The castor oil plant (Ricinus communis L.) is a fast growing plant with high biomass production and is a potential phytoaccumulator of several metals. In recent years, the federal government of Brazil has encouraged castor oil plant cultivation for biodiesel and bioethanol production. The aim of the present work was to evaluate the phytoextraction potential of R. communis L. and the effect of organic matter addition (peat vs. filter cake) to a soil contaminated with scrap metal residue containing heavy metals and boron. The experiment consisted of a completely randomized block design with two organic matter sources and four rates of amendment (0, 20, 40 and 80Mgha-1 organic carbon). Treatments were replicated three times. The castor oil plants were harvested 74days after sowing. No accumulation of Cr, Ni, Cd, Cu, Pb or Zn was observed in the plants, but the concentration of B increased to 626mgkg-1 upon filter cake addition in castor oil shoots. Peat addition reduced by 2.7years the time needed for removal of 50% of soil B content compared to the treatment with no organic matter addition. The transfer factor and transference index values obtained for B with castor oil plants in the present study were comparable to those obtained for hyperaccumulator species. Although our results are promising, further studies should be conducted to prove the usefulness of plants grown in contaminated areas for remediation purposes and for biofuel production. © 2012 Elsevier B.V.

Dinardo-Miranda L.L.,Instituto Agronomico | dos Anjos I.A.,Instituto Agronomico | da Costa V.P.,Instituto Agronomico | Fracasso J.V.,Instituto Agronomico
Pesquisa Agropecuaria Brasileira | Year: 2012

The objective of this work was to evaluate the oviposition preference of Diatraea saccharalis and the effect of ten sugarcane cultivars on larval development. Oviposition preference was assessed under greenhouse conditions by three releases of couples of moths, with subsequent counting of egg masses and eggs per plant. In order to evaluate the effect of the cultivars on larval development, each plant was infected with about 150 eggs, and, 29 days later, the total number of internodes, number of bored internodes, number of life forms found, larval and pupal weight and length, and the width of larval head capsule were evaluated. The cultivars IACSP94-2101 and IACSP96-2042, the least preferred by D. saccharalis for oviposition, and IACSP94-2094, the most unfavorable for larvae entrance and development, show resistance to the pest.

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