RESUMOOs fungos micorrízicos arbusculares (FMAs) são importantes componentes dos ecossistemas terrestres onde acreditase desempenharem papel fundamental para a sustentabilidade destes. Estes fungos sofrem influência de diversos fatores antrópicos como o uso da terra, que modificam a estrutura e diversidade das comunidades podendo comprometer suas funções ecológicas. No presente estudo avaliou-se o comportamento de FMAs isolados de solos sob diferentes sistemas de uso (SUT). Effectiveness of arbuscular mycorrhiza fungal isolated from soils under different land use systems in the Alto Solimões river region in the AmazonABSTRACT Arbuscular mycorrhizal fungi (AMF) are important components of terrestrial ecosystems where they are believed to play a fundamental role for their sustainability. These fungi are influenced by a number of anthropic factors such as, land use which modifies the structure and diversity of fungal communities and this may compromise their ecological functions. In the present study it was evaluated the behavior of AMF isolated from soils under different land use systems in (LUS). Fifty-one AMF were isolated in trap cultures from soil samples from different SUT tested on cowpea [Vigna unguiculata (L.) Walp] under controlled conditions. It was found that all AMF colonize the cowpea, but in a highly variable intensity. Similar results were found for phosphorus uptake and plant growth. Colonization ranged from 1 to 68%. Growth positive effects ranged from 33 to 148%, being more common in isolates from pasture and crops ecosystems. The enhancement in phosphorus uptake was generalized (95% all fungi), but their growth promoting effects did not followed the same trend. Only 39% of fungal isolated tested were efficient. These more isolated from almost all LUS. Fungal treatments with high efficiency had the following species: A. foveata, Glomus sp.1, Acaulospora sp.1 and a mixture the first two species with A. bireticulata and E. infrequens. The results indicate a wide efficiency diversity of AMF in the Alto Solimões region. Although this characteristic has no direct relationship with the LUS, the proportion of effective isolates varied with their origin.
Arbuscular mycorrhizal fungi provide several ecosystem services, including increase in plant growth and nutrition. The occurrence, richness, and structure of arbuscular mycorrhizal fungi communities are influenced by human activities, which may affect the functional benefits of these components of the soil biota. In this study, 13 arbuscular mycorrhizal fungi isolates originating from soils with different land uses in the Alto Solimões-Amazon region were evaluated regarding their effect on growth, nutrition, and cowpea yield in controlled conditions using two soils. Comparisons with reference isolates and a mixture of isolates were also performed. Fungal isolates exhibited a wide variability associated with colonization, sporulation, production of aboveground biomass, nitrogen and phosphorus uptake, and grain yield, indicating high functional diversity within and among fungal species. A generalized effect of isolates in promoting phosphorus uptake, increase in biomass, and cowpea yield was observed in both soils. The isolates of Glomus were the most efficient and are promising isolates for practical inoculation programs. No relationship was found between the origin of fungal isolate (i.e. land use) and their symbiotic performance in cowpea.
A Salmonella é uma bactéria patogênica responsável por gastroenterites, sendo o principal agente de doenças de origem alimentar em várias partes do mundo, inclusive no Brasil. Visando inibir seu crescimento, pode-se utilizar conservantes como metabissulfito, bissulfito e benzoato de sódio, e o sorbato de potássio, que são amplamente empregados na preservação de alimentos. Estudos utilizando esses aditivos para inibição da Salmonella Typhimurium são escassos e, devido à sua importância para a segurança alimentar, objetivou-se determinar a Concentração Inibitória Mínima (CIM) dos conservantes, a fim de fornecer mais informações sobre a resistência da bactéria. Nas condições do experimento, os conservantes metabissulfito e bissulfito de sódio apresentaram maior atividade antimicrobiana contra a S. Typhimurium, ambos com CIM de 1.250 μg.mL-1. Já os conservantes benzoato de sódio e sorbato de potássio necessitaram do dobro da quantidade para inibi-la, apresentando CIM de 2.500 μg.mL-1 e 2.300 μg.mL-1, respectivamente. Concentrações tão elevadas de conservantes se devem às condições do experimento, principalmente em relação ao pH do meio de cultura (pH ~ 7,3), já que estes conservantes são mais efetivos em condições ácidas.
-This paper evaluates the possible use of liquid preservation methods for rhizobia long term conservation under ambient temperature conditions. Saline solution (sterile distilled water + NaCl), glycerol and carboxymethycellulose (CMC) were evaluated for preservation of Rhizobium tropici and Bradyrhizobium japonicum cultures up to 180 days and regarding their capacity to promote common bean (Phaseolus vulgaris [L.]) and soybean (Glycine max [L.]) nodulation. The total population was determined after 0; 1; 7; 15; 21; 30; 60; 90; 120; 150 and 180 days of conservation and conserved bacteria were evaluated for symbiotic characteristics after 15, 60 and 120 days of conservation. Although there were significant species x conservation method interactions, both saline solution and CMC may be used for short storage terms, allowing the production of inoculant for field experiments, and its test for purity and concentration before field establishment. The utilized techniques have low cost and easier usage as inoculants, compared to the traditional turf-based products, and if determined feasible by further research it could be a low cost addition to the standard microbiological techniques, particularly as working culture preservation media.Key words: Bradyrhizobium. Carboxymethycellulose. Glycerol. Preservation of bacterial cultures.RESUMO -Neste trabalho foi avaliado o possível uso de métodos de preservação líquida para conservação de rizóbio ao longo do tempo, sob condições de temperatura ambiente. Solução salina (água destilada esterilizada + NaCl), glicerol e carboximetilcelulose (CMC) foram avaliados visando à preservação de culturas de Rhizobium tropici e Bradyrhizobium japonicum por 180 dias e em relação a sua capacidade para promover a nodulação do feijão comum (Phaseolus vulgaris [L.]) e da soja (Glycine max [L.]). A população total foi determinada após 0; 1; 7; 15; 21; 30; 60; 90; 120; 150 e 180 dias de conservação e, as bactérias conservadas foram avaliadas quanto as suas características simbióticas após 15, 60 e 120 dias de conservação. Embora tenham ocorrido interações significativas entre os métodos de conservação x espécies, a solução salina e o CMC podem ser usados por períodos curtos de armazenamento, permitindo a produção de inoculante para experimentos de campo e teste de pureza e concentração antes do seu estabelecimento em campo. As técnicas utilizadas têm custo baixo e uso mais prático do que as tradicionais formulações em base turfosa, e se determinada a viabilidade por meio de novas pesquisas, poderia ser uma adição de baixo custo para a padronização de técnicas microbiológicas, particularmente como meio de trabalho para preservação de culturas.Palavras-chave: Bradyrhizobium. Carboximetilcelulose. Glicerol. Preservação de culturas bacterianas. *Autor para correspondência 1 Recebido para publicação em 21/03/2012; aprovado em 28/03/2013
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