Wagner Bettiol

Climate change and plant diseases

As atividades antropicas estao alterando as concentracoes de gases de efeito estufa da atmosfera e causando mudancas no clima do planeta. Certamente, num futuro proximo, devido as mudancas climaticas globais, ocorrerao modificacoes no cenario fitossanitario brasileiro. Os impactos podem ser positivos, negativos ou neutros, pois as mudancas podem diminuir, aumentar ou nao ter efeito sobre as doencas, em cada regiao ou epoca. Esses impactos tambem serao observados sobre as plantas e outros organismos, alem de outros componentes do agroecossistema. Porem, esses impactos nao sao facilmente determinados e, desta forma, os especialistas das diferentes areas precisam ir alem de suas disciplinas e abordar os impactos das mudancas climaticas em um contexto mais amplo. Nessa revisao sao discutidos os aspectos relacionados com os efeitos das mudancas climaticas sobre as doencas de plantas. Na distribuicao geografica e temporal das doencas, um contexto historico e apresentado, incluindo estudos recentes utilizando dados de modelos de previsao do clima futuro associados com modelos de simulacao da doenca a fim de predizer a distribuicao nos cenarios climaticos futuros. Tambem sao apresentados os cenarios futuros de previsao de doencas de algumas culturas no Brasil. Sobre os efeitos do aumento da concentracao de CO2 atmosferico e outros gases sao discutidos importantes aspectos do comportamento das doencas sujeitas as condicoes alteradas de gases atmosfericos no futuro. As consequencias dessas alteracoes sobre o controle quimico e biologico das doencas de plantas tambem sao discutidas.

Antagonistic activity of Bacteria from the chickpea rhizosphere againstFusarium Oxysporum f. sp.Ciceris

The antagonistic activity againstin vitro growth ofFusarium oxysporum f. sp.ciceris was determined for 74 bacterial isolates obtained from the rhizosphere of chickpeas grown in two field soils with different histories of Fusarium wilt, and for seven isolates ofPseudomonas spp. from culture collections. Twenty-four isolates ofBacillus spp. andPseudomonas chlororaphis 30-84 showed a strong antagonism against three races (0, 1 and 5) ofF. o. ciceris tested. Three selectedBacillus isolates andP. chlororaphis 30-84 were further tested against 30 isolates of races 0, 1 and 5 ofF. o. ciceris, races 0, 1 and 2 ofF. o. melonis, F. o. phaseoli and nonpathogenicF. oxysporum. Bacillus isolates differed in their antagonistic activity and were less inhibitory to mycelial growth ofF. o. ciceris than to that of other fungal isolates. Furthermore, the extent of growth inhibition ofF. o. ciceris was influenced both by bacterial isolates and by race of the pathogen. Cell-free culture filtrates of fourBacillus isolates inhibited conidial germination and hyphal growth ofF. o. ciceris and nonpathogenicF. oxysporum. Joint seed+soil treatment with some selected antagonisticBacillus spp. isolates suppressed disease caused by the highly virulentF. o. ciceris race-5 in cv. ICCV 4 and cv. PV 61 chickpeas. However, the degree of protection was influenced by the host genotype and the inoculum concentration of the pathogen.

Bioprospecting endophytic bacteria for biological control of coffee leaf rust

Suppression of plant diseases due to the action of endophytic microorganisms has been demonstrated in several pathosystems. Experiments under controlled conditions involving endophytic bacteria isolated from leaves and branches of Coffea arabica L and Coffea robusta L were conducted with the objective of evaluating the inhibition of germination of Hemileia vastatrix Berk. & Br., race II, urediniospores and the control of coffee leaf rust development in tests with leaf discs, detached leaves, and on potted seedling of cv. Mundo Novo. The endophytic bacterial isolates tested proved to be effective in inhibiting urediniospore germination and/or rust development, with values above 50%, although the results obtained in urediniospore germination tests were inferior to the treatment with fungicide propiconazole. Endophytic isolates TG4-Ia, TF2-IIc, TF9-Ia, TG11-IIa, and TF7-IIa, demonstrated better coffee leaf rust control in leaf discs, detached leaves, and coffee plant tests. The endophytic isolates TG4-Ia and TF9-Ia were identified as Bacillus lentimorbus Dutky and Bacillus cereus Frank. & Frank., respectively. Some endophytic bacterial isolates were effective in controlling the coffee leaf rust, although some increased the severity of the disease. Even though a relatively small number of endophytic bacteria were tested, promising results were obtained regarding the efficiency of coffee leaf rust biocontrol. These selected agents appears to be an alternative for future replacement of chemical fungicide.

Soil organisms in organic and conventional cropping systems

Despite the recent interest in organic agriculture, little research has been carried out in this area. Thus, the objective of this study was to compare, in a dystrophic Ultisol, the effects of organic and conventional agricultures on soil organism populations, for the tomato (Lycopersicum esculentum) and corn (Zea mays) crops. In general, it was found that fungus, bacterium and actinomycet populations counted by the number of colonies in the media, were similar for the two cropping systems. CO2 evolution during the cropping season was higher, up to the double for the organic agriculture system as compared to the conventional. The number of earthworms was about ten times higher in the organic system. There was no difference in the decomposition rate of organic matter of the two systems. In general, the number of microartropods was always higher in the organic plots in relation to the conventional ones, reflectining on the Shannon index diversity. The higher insect population belonged to the Collembola order, and in the case of mites, to the superfamily Oribatuloidea. Individuals of the groups Aranae, Chilopoda, Dyplopoda, Pauropoda, Protura and Symphyla were occasionally collected in similar number in both cropping systems.

Potential of non-pathogenic Fusarium oxysporum isolates for control of Fusarium wilt of tomato

This study was done to evaluate the efficiency of non-pathogeni c Fusarium oxysporum isolates (141/3, 233, 233/1, 245, 245/1, 251, 251/2, 251/5, and 257) in controlling vascular wilt caused by F. oxysporum f. sp. lycopersici, race 2 (isolates C-21A, TO11, and TO245) in tomato (Lycopersicon esculentum) cv. Viradoro seedlings. In order to determine the effect of non-pathogeni c F. oxysporum isolates in tomato plants, the root system of 30-day-old seedlings was immersed in conidial suspensions (10 6 ml -1 ) of each isolate and the seedlings were transplanted to a cultivation substrate. Thirty-five days after transplanting it was observed that the non-pathogenic F. oxysporum isolates were not pathogenic to the cv. Viradoro nor did they affect seedling development. The efficiency of the non-pathogenic F. oxysporum isolates in controlling Fusarium wilt was determined by immersing the tomato seedling roots in the conidial suspension (10 6 ml -1 ) of each isolate and then transplanting them into substrates previously infested with isolates of F. oxysporum f.sp. lycopersici, race 2 (10 5 conidia ml 1 of substrate). Evaluations were performed 35 days after transplanting, for severity in scale with 1=healthy plant to 6=dead plant or plant showing vessel browning and wilted leaves up to the leader shoot and seedling height. The non-pathogenic F. oxysporum isolates were efficient in reducing the severity of the disease and maintaining normal plant development. These results provide evidence of the antagonistic activity of non-pathogeni c F. oxysporum isolates in controlling vascular wilt caused by F. oxysporum f. sp. lycopersici race 2 in tomato. Additional keywords: biological control, Fusarium oxysporum f.sp. lycopersici race 2, nonpathogenic F. oxysporum.

Chemical and physical properties of organic residues

SUMMARY Due to human activity, large amounts of organic residue are generated daily.Therefore, an adequate use in agricultural activities requires the characterizationof the main properties. The chemical and physical characterization is importantwhen planning the use and management of organic residue. In this study, chemicaland physical properties of charcoal, coffee husk, pine-bark, cattle manure, chickenmanure, coconut fiber, sewage sludge, peat, and vermiculite were determined.The following properties were analyzed: N-NH 4+ , N-N0 3 - , and total concentrationsof N, P, S, K, Ca, Mg, Mn, Zn, Cu, and B, as well as pH, Electrical Conductivity (EC)and bulk density. Coffee husk, sewage sludge, chicken manure and cattle manurewere generally richer in nutrients. The EC values of these residues were also thehighest (0.08 - 40.6 dS m -1 ). Peat and sewage sludge had the highest bulky density.Sodium contents varied from 0 to 4.75 g kg -1 , with the highest levels in chickenmanure, cattle manure and sewage sludge. Great care must be taken whenestablishing proportions of organic residues in the production of substrates withcoffee husk, cattle or chicken manure or sewage sludge in the calculation of theapplied fertilizer quantity in crop fertilization programs.Index terms: substrate, organic residue, soil contamination, residue disposal.

Disponibilidade de metais pesados para milho cultivado em Latossolo sucessivamente tratado com lodos de esgoto

Apesar do potencial para o uso agricola de lodos de esgoto, seus conteudos de metais pesados podem se tornar um fator limitante a esse uso. Este estudo teve como objetivo avaliar o efeito de diferentes fontes e doses de lodo de esgoto, oriundos das Estacoes de Tratamento de Esgoto de Barueri (LB), que trata esgoto domestico e industrial, e de Franca (LF), que trata esgoto predominantemente domestico, ambas localizadas no Estado de Sao Paulo, sobre os teores de metais pesados em solo e sobre a fitodisponibilidade desses elementos quimicos para o milho. O experimento foi realizado entre os anos de 1999 e 2001, no Campo Experimental da Embrapa Meio Ambiente, em Jaguariuna (SP), em tres cultivos sucessivos de milho, e estudados os seguintes tratamentos, para os dois lodos: testemunha absoluta; adubacao mineral (NPK) recomendada para a cultura do milho; dose dos lodos de esgoto para fornecer uma, duas, quatro e oito vezes a dose de N do tratamento NPK. Foram determinados os teores totais (solo, folha e grao de milho) e disponiveis (solo) de Cu, Mn, Ni, Pb e Zn. O uso de doses crescentes do LB aumentou os teores disponiveis dos metais avaliados em solo, quando se utilizou a solucao de DTPA. Os incrementos nos teores totais de metais pesados foram maiores nas parcelas adubadas com o LB. As solucoes de Mehlich-1 e DTPA mostraram-se eficientes em predizer a fitodisponibilidade de Zn para o milho, quando as folhas e graos foram analisados.

Impacts of Sewage Sludge in Tropical Soil: A Case Study in Brazil

A long-term assay was conducted to evaluate the environmental impacts of agriculture use of sewage sludge on a tropical soil. This paper describes and discusses the results obtained by applying a interdisciplinary approach and the valuable insights gained. Experimental site was located in Jaguariuna (SP, Brazil). Multiyear comparison was developed with the application of sewage sludge obtained from wastewater treatment plants at Barueri (domestic and industrial sewage) and Franca (domestic sewage), Sao Paulo State. The treatments were control, mineral fertilization, and sewage sludge applied based on the N concentration that provides the same amount of N as in the mineral fertilization recommended for corn crop, two, four, and eight times the N recommended dosage. The results obtained indicated that the amount of sewage sludge used in agricultural areas must be calculated based on the N crop needs, and annual application must be avoided to prevent overapplications.

Controle biológico da podridão radicular (Pythium aphanidermatum) e promoção de crescimento por Pseudomonas chlororaphis 63-28 e Bacillus subtilis GB03 em alface hidropônica

Root rot caused by Pythium species is a major problem in hydroponically-grown crops. Symptoms of canopy stunting are noticed in plants colonized by the pathogen and many times they are not diagnosed by the grower. The aim of this work was to evaluate biological control and plant growth promotion by Pseudomonas chlororaphis 63-28 and Bacillus subtilis GB03, known biocontrol agents of plant diseases. Inoculation of plants with P. aphanidermatum decreased lettuce mass by 20%. The introduction of the biocontrol agents to the nutrient solution was beneficial for plant growth increasing the plant mass (6% to 13%), the number of leaves (4% to 7%) and the chlorophyll content (3%) of the lettuce plants. Further studies are needed, however, to improve the effectiveness of disease control and growth promotion by the biological agents in hydroponic lettuce.

Estoque de carbono e quantificação de substâncias húmicas em Latossolo submetido a aplicação contínua de lodo de esgoto

Este estudo teve como objetivo avaliar o efeito da aplicacao continua de doses de lodo de esgoto oriundo da Estacao de Tratamento de Esgoto de Barueri, SP, sobre os teores e estoques de C e sobre as alteracoes na distribuicao de substâncias humicas em Latossolo Vermelho distroferrico. O experimento foi instalado em 1999, no Campo Experimental da Embrapa Meio Ambiente, em Jaguariuna-SP; os dados foram obtidos apos a sexta aplicacao de lodo e cultivo sucessivo de milho. Foram utilizadas, nas diferentes parcelas experimentais, as seguintes doses acumuladas de lodo de esgoto (base seca): 0, 30, 60, 120 e 240 Mg ha-1, sendo estudados os tratamentos: (L0) testemunha sem adicao de lodo; e aplicacao de lodo de esgoto visando fornecer uma (L1), duas (L2), quatro (L4) e oito (L8) vezes a dose de N requerida pelo milho. Foram avaliados os teores e o estoque de C orgânico nas camadas de solo de 0-10, 10-20, 20-40 e 40-60 cm. Os teores de C associados as substâncias humicas foram avaliados na camada de solo de 0-10 cm. O teor e o estoque de C orgânico aumentaram com o acrescimo nas doses de lodo de esgoto aplicadas, ate a camada de solo de 0-20 cm. A maior parte (50-66 %) do C associado as substâncias humicas esta presente no solo na forma de humina, seguido por C-fracao acidos fulvicos e C-fracao acidos humicos, nesta ordem. A aplicacao de lodo de esgoto implica maior acumulo de substâncias humicas no solo, mas as proporcoes de C-humificado da materia orgânica nao sao alteradas.