Bradyrhizobium and Pseudomonas strains obtained from coal-mining areas nodulate and promote the growth of Calopogonium muconoides plants used in the reclamation of degraded areas.

AIMS: The objective of this work was to isolate and characterize indigenous rhizobia from coal-mining areas able to efficiently nodulate and fix nitrogen in association with Calopogonium mucunoides (calopo). METHODS AND RESULTS: Isolation, authentication and morphological, biochemical and molecular characterization of the autochthonous rhizobia were performed and their symbiotic efficiency (SE) evaluated. Efficient rhizobial isolates suitable for the inoculation of calopo in coal-mining regions were obtained. A total of 30 isolates were obtained after nodulation authentication, of which five presented high SE with plant-growth promoting traits such as indole-3-acetic acid production, phosphate solubilization and biofilm formation. These isolates were identified as belonging to Bradyrhizobium, Pseudomonas and Rhizobium. CONCLUSIONS: Bradyrhizobium sp. A2-10 and Pseudomonas sp. A6-05 were able to promote calopo plant growth using soil obtained from coal-mining degraded areas, thus indicating their potential as inoculants aiming at land reclamation. SIGNIFICANCE AND IMPACT OF THE STUDY: To our knowledge, this is the first report of Pseudomonas nodule formation in calopo. Furthermore, the results demonstrated that autochthonous rhizobia obtained from degraded soils presented high SE in calopo and possess a wide range of plant-growth promoting traits. Ultimately, they may all contribute to an increased leguminous plant growth under stress conditions. The selected rhizobia strains may be used as inoculants and present a valuable role in the development of strategies aiming to recover coal-mining degraded areas. Bacterial inoculants would greatly reduce the use of often harmful nitrogen fertilizers vastly employed in revegetation programmes of degraded areas.

Microbiological and faunal soil attributes of coffee cultivation under different management systems in Brazil.

Brazil is the biggest coffee producer in the world and different plantation management systems have been applied to improve sustainability and soil quality. Little is known about the environmental effects of these different management systems, therefore, the goal of this study was to use soil biological parameters as indicators of changes. Soils from plantations in Southeastern Brazil with conventional (CC), organic (OC) and integrated management systems containing intercropping of Brachiaria decumbens (IB) or Arachis pintoi (IA) were sampled. Total organic carbon (TOC), microbial biomass carbon (MBC) and nitrogen (MBN), microbial activity (C-CO2), metabolic quotient (qCO2), the enzymes dehydrogenase, urease, acid phosphatase and arylsulphatase, arbuscular mycorrhizal fungi (AMF) colonization and number of spores and soil fauna were evaluated. The greatest difference between the management systems was seen in soil organic matter content. The largest quantity of TOC was found in the OC, and the smallest was found in IA. TOC content influenced soil biological parameters. The use of all combined attributes was necessary to distinguish the four systems. Each management presented distinct faunal structure, and the data obtained with the trap method was more reliable than the TSBF (Tropical Soils) method. A canonic correlation analysis showed that Isopoda was correlated with TOC and the most abundant order with OC. Isoptera was the most abundant faunal order in IA and correlated with MBC. Overall, OC had higher values for most of the biological measurements and higher populations of Oligochaeta and Isopoda, corroborating with the concept that the OC is a more sustainable system.

Microbiological and faunal soil attributes of coffee cultivation under different management systems in Brazil / Atributos microbiológicos e da fauna do solo com diferentes sistemas de cultivo de cafeeiro no Brasil

Abstract Brazil is the biggest coffee producer in the world and different plantation management systems have been applied to improve sustainability and soil quality. Little is known about the environmental effects of these different management systems, therefore, the goal of this study was to use soil biological parameters as indicators of changes. Soils from plantations in Southeastern Brazil with conventional (CC), organic (OC) and integrated management systems containing intercropping of Brachiaria decumbens (IB) or Arachis pintoi (IA) were sampled. Total organic carbon (TOC), microbial biomass carbon (MBC) and nitrogen (MBN), microbial activity (C-CO2), metabolic quotient (qCO2), the enzymes dehydrogenase, urease, acid phosphatase and arylsulphatase, arbuscular mycorrhizal fungi (AMF) colonization and number of spores and soil fauna were evaluated. The greatest difference between the management systems was seen in soil organic matter content. The largest quantity of TOC was found in the OC, and the smallest was found in IA. TOC content influenced soil biological parameters. The use of all combined attributes was necessary to distinguish the four systems. Each management presented distinct faunal structure, and the data obtained with the trap method was more reliable than the TSBF (Tropical Soils) method. A canonic correlation analysis showed that Isopoda was correlated with TOC and the most abundant order with OC. Isoptera was the most abundant faunal order in IA and correlated with MBC. Overall, OC had higher values for most of the biological measurements and higher populations of Oligochaeta and Isopoda, corroborating with the concept that the OC is a more sustainable system.

Resumo O Brasil é o maior produtor mundial de café e diferentes sistemas de manejo têm sido aplicados para melhorar a sustentabilidade e a qualidade do solo. Pouco se conhece sobre os efeitos ambientais desses sistemas de manejo, assim, o objetivo desse estudo foi utilizar parâmetros biológicos do solo como indicadores de mudanças nos sistemas. Foram amostrados, na região sudeste do Brasil, solos com cultivo convencional (CC), orgânico (OC) e sistema integrado de cultivo consorciado com Brachiaria decumbens (IB) ou com Arachis pintoi (IA) na entrelinha. Foram avaliados o carbono orgânico total (TOC), carbono e nitrogênio da biomassa microbiana (MBC e MBN), atividade microbiana (C-CO2), quociente metabólico (qCO2), as enzimas desidrogenase, urease, fosfatase ácida e arilsulfatase, a colonização e número de esporos de fungos micorrízicos arbusculares (AMF) e a fauna do solo. A maior diferença entre os sistemas de manejo foram verificadas no teor de matéria orgânica do solo. O maior teor de TOC foi encontrado no OC, e o menor teor encontrado no sistema IA. O teor de TOC influenciou os parâmetros biológicos e a diferenciação da fauna do solo. O uso combinado de todos os atributos foi necessário para diferenciar os quatro sistemas de cultivo. Cada manejo apresentou estruturas diferentes de fauna, e dados obtidos com o método de armadilhas tipo pitfall foi mais confiável do que o método TSBF (Solos Tropicais). A análise de correlação canônica mostrou que Isopoda foi correlacionado com TOC e a ordem mais abundante em OC. Isoptera foi a ordem da fauna mais abundante em IA e foi correlacionada com MBC. Em geral, OC apresentou os maiores valores para a maioria dos atributos biológicos, inclusive para abundância de indivíduos de Oligochaeta e Isopoda, corroborando com o conceito de que OC é um sistema mais sustentável.

Genetic diversity of polysporic isolates of Moniliophthora perniciosa (Tricholomataceae).

The causal agent of witches' broom disease, Moniliophthora perniciosa is a hemibiotrophic and endemic fungus of the Amazon basin and the most important cocoa disease in Brazil. The purpose of this study was to analyze the genetic diversity of polysporic isolates of M. perniciosa to evaluate the adaptation of the pathogen from different Brazilian regions and its association with different hosts. Polysporic isolates obtained previously in potato dextrose agar cultures of M. perniciosa from different Brazilian states and different hosts (Theobroma cacao, Solanum cernuum, S. paniculatum, S. lycocarpum, Solanum sp, and others) were analyzed by somatic compatibility grouping where the mycelium interactions were distinguished after 4-8 weeks of confrontation between the different isolates of M. perniciosa based on the precipitation line in the transition zone and by protein electrophoresis through SDS-PAGE. The diversity of polysporic isolates of M. perniciosa was grouped according to geographic proximity and respective hosts. The great genetic diversity of M. perniciosa strains from different Brazilian states and hosts favored adaptation in unusual environments and dissemination at long distances generating new biotypes.