Arbuscular mycorrhizal fungi activity in the rhizosphere of tree seedlings subjected to residual herbicides / Atividade de fungos micorrízicos arbusculares na rizosfera de mudas de árvores submetidas a herbicidas residuais

Abstract Trees occurring on the margins of agricultural areas can mitigate damage from residual herbicides. Rhizospheric microbial activity associated with trees is one of the main remedial capacity indicators. The objective of this study was to evaluate the rhizospheric microbiological activity in tree species subjected to the herbicides atrazine and sulfentrazone via the rhizosphere. The experiment was designed in four blocks and a 6 × 3 factorial scheme. The first factor consisted of six tree species from Brazil and the second of atrazine, sulfentrazone, and water solutions. Four herbicide applications were performed via irrigation. The total dry mass of the plants, mycorrhizal colonization, number of spores, basal respiration of the rhizospheric soil, and survival rate of bioindicator plants after phytoremediation were determined. Trichilia hirta had higher biomass when treated with atrazine and sulfentrazone. Herbicides decreased the microbial activity in Triplaris americana and did not affect the microbiological indicators of Myrsine gardneriana, Schizolobium parahyba, and Toona ciliata. Fewer bioindicator plants survived in soil with Triplaris americana and sulfentrazone. Microbiological indicators were influenced in different ways between species by the presence of herbicides in the rhizosphere.

Resumo As árvores que ocorrem nas margens das áreas agrícolas podem mitigar os danos dos herbicidas residuais. A atividade microbiana rizosférica associada às árvores é um dos principais indicadores de capacidade corretiva. O objetivo deste trabalho foi avaliar a atividade microbiológica rizosférica em espécies arbóreas submetidas aos herbicidas atrazina e sulfentrazone via rizosfera. O experimento foi estruturado em quatro blocos e esquema fatorial 6 × 3. O primeiro fator consistiu em seis espécies de árvores do Brasil e o segundo em soluções de atrazine, sulfentrazone e água. Quatro aplicações de herbicidas foram realizadas via irrigação. Foram determinados a massa seca total das plantas, colonização micorrízica, número de esporos, respiração basal do solo rizosférico e taxa de sobrevivência de plantas bioindicadoras após fitorremediação. Trichilia hirta apresentou maior biomassa quando tratada com atrazina e sulfentrazone. Os herbicidas diminuíram a atividade microbiana em Triplaris americana e não afetaram os indicadores microbiológicos de Myrsine gardneriana, Schizolobium parahyba e Toona ciliata. Menos plantas bioindicadoras sobreviveram no solo com Triplaris americana e sulfentrazone. Os indicadores microbiológicos foram influenciados de formas distintas entre as espécies pela presença dos herbicidas na rizosfera.

Arbuscular mycorrhizal fungi in wheat grown in copper contaminated soil / Fungos micorrízicos arbusculares no cultivo de trigo em solo contaminado com cobre

At high soil concentrations, copper (Cu) is toxic to plant development. Symbiosis carried out between microorganisms and plant species are alternatives to minimize plant toxicity in copper contaminated soil. The present study aimed to select species of arbuscular mycorrhizal fungi for the development of wheat plants in copper contaminated soil. The experimental design was completely randomized in a 4 × 6 factorial arrangement, with four sources of inocula: three species of arbuscular mycorrhizae (Acaulospora colombiana, Gigaspora Margarita and Rhizophagus clarus) and one without inoculum (control), and six doses of copper in the soil (0, 80, 160, 240, 320, and 400 mg kg-1), with seven replications. Plant height, root length, root volume, root dry mass, specific surface area, average root diameter, root, shoot and grain Cu content and mycorrhizal colonization rate were evaluated. Root dry mass and mycorrhizal colonization were negatively affected by high Cu doses in the soil. The mycorrhizal isolates Acaulospora Colombiana and Gigaspora Margarita provide greater wheat height, root length and specific surface area and lower Cu content. Mycorrhizal colonization with the fungi Acaulospora Colombiana, Gigaspora Margarita and Rhizophagus clarus results in lower copper content in wheat shoots and grains.(AU)

Em elevadas concentrações no solo, o cobre (Cu) é tóxico para o desenvolvimento dos vegetais. Simbioses realizadas entre microrganismos e espécies vegetais são alternativas para minimizar a toxidez das plantas em solo contaminado com cobre. O trabalho teve como objetivo selecionar espécies de fungos micorrízicos arbusculares para o desenvolvimento de plantas de trigo em solo contaminado com cobre. O delineamento experimental foi inteiramente casualizado em arranjo fatorial 4 × 6, sendo quatro fontes de inóculos: três espécies de micorrizas arbusculares (Acaulospora colombiana, Gigaspora margarita e Rhizophagus clarus) e sem inóculo (testemunha) e seis doses de cobre no solo (0, 80, 160, 240, 320 e 400 mg kg-1), com sete repetições. Avaliou-se a altura de plantas, comprimento de raiz, volume de raízes, massa seca de raiz, área superficial específica, diâmetro médio de raiz, teor de cobre na raiz, na parte aérea e no grão e porcentagem de colonização micorrízica. A massa seca de raiz e a colonização micorrízica foram afetadas negativamente com altas doses de Cu no solo. Os isolados micorrízicos Acaulospora Colombiana e Gigaspora Margarita proporcionam maior altura, comprimento de raiz e área superficial específica e menor teor de Cu no grão na cultura do trigo. A colonização micorrízica com os fungos Acaulospora Colombiana, Gigaspora Margarita e Rhizophagus clarus resulta em menor teor de cobre na parte aérea e nos grãos do trigo.(AU)

Response of Rhizobacterial strains and organic amendments on chickpea growth / Resposta de cepas de rizobactérias e alterações orgânicas no crescimento do grão-de-bico

Plant Growth Promoting Rhizobacteria (PGPR) are beneficial bacteria that colonize plant roots and promote plant growth through a variety of mechanisms such as phosphate solubilization, phytohormones production, antifungal activity and also improve plant growth and yield. Field experiment was carried out to investigate the residual effect of organic amendments plus soil microbes along with integrated nutrient management. (PGPR) are important soil organism that promotes plant growth and yield root colonization is an example of a direct and indirect mechanism. The treatments included control, (inorganic fertilizer and no organic fertilization).Five bacterial strains were identified morphologically and biochemically screened from the rhizospheres of chickpea, lentil, barseem, mungbean, and sesame. The experiment was conducted at the Arid Zone Research Center in D.I.Khan (Pakistan). The majority of isolates resulted in significant increase in shoot length, root length, and dry matter production of Cicer arietinum seedlings' shoot and root. The experiment represented that isolates treated plots with rhizobium strain inoculation resulted in greater plant height (35.000 cm) and nodule count (38.00) No of pods per plant-1 (44.66) when compared to the control treatment, While (Mesorhizobium cicero) along with organic amendments showed significant response the greater root length (50 cm) was observed in T4 treatment. The Performance of rhizobial strains on chickpea germination in an arid environment was found to significantly increase crop germination percentage. This combination thus increases nitrogen and phosphorus uptake in inoculation treated plots. The study found that plots with inoculation treatments yielded significantly higher than non-treated plots Treatment with Mesorhizobium Cicero and compost resulted in a higher grain yield (8%) as compared to the control. The greater grain yield was observed in Treatment T4 (183.67).The result showed that use of PGPR have the potential to increase nutrient absorption from soil while improved growth of chickpea.(AU)

As rizobactérias promotoras de crescimento de plantas (PGPR) são bactérias benéficas que colonizam as raízes das plantas e promovem o crescimento das plantas através de uma variedade de mecanismos, como solubilização de fosfato, produção de fito-hormônios, atividade antifúngica e também melhoram o crescimento e o rendimento das plantas. O experimento de campo foi realizado para investigar o efeito residual de corretivos orgânicos mais micróbios do solo, juntamente com o manejo integrado de nutrientes. PGPR são importantes organismos do solo que promovem o crescimento das plantas e produzem a colonização de raízes, que é um exemplo de mecanismo direto e indireto. Os tratamentos incluíram controle (fertilizante inorgânico e sem adubação orgânica). Cinco cepas bacterianas foram identificadas morfologicamente e bioquimicamente selecionadas das rizosferas de grão-de-bico, lentilha, barseem, feijão-mungo e gergelim. O experimento foi conduzido no Arid Zone Research Center em D.I.Khan (Paquistão). A maioria dos isolados resultou em aumento significativo no comprimento da parte aérea, comprimento da raiz e produção de matéria seca da parte aérea e raiz das plântulas de Cicer arietinum. O experimento demonstrou que isolados de parcelas tratadas com inoculação de cepa de rizóbio resultaram em maior altura de planta (35.000 cm) e contagem de nódulos (38,00) n.º de vagens por planta-1 (44,66), quando comparado ao tratamento controle, enquanto (Mesorhizobium cicero), juntamente com as alterações orgânicas, apresentaram resposta significativa quanto maior o comprimento da raiz (50 cm) observado no Tratamento T4. O desempenho de linhagens de rizóbios na germinação do grão-de-bico em ambiente árido aumentou significativamente a porcentagem de germinação da cultura. Esta combinação aumenta assim a absorção de nitrogênio e fósforo nas parcelas tratadas com inoculação. O estudo constatou que as parcelas com tratamentos de inoculação produziram significativamente mais do que as parcelas não tratadas. O tratamento com Mesorhizobium cicero e composto resultou em maior produtividade de grãos (8%) em comparação com o controle. A maior produtividade de grãos foi observada no Tratamento T4 (183,67). O resultado mostrou que o uso de PGPR tem potencial para aumentar a absorção de nutrientes do solo enquanto melhora o crescimento do grão-de-bico.(AU)

Evaluation of the incidence of endophytic fungi in leaves, stems and roots of bean plants in the State of Paraná / Avaliação da incidência de fungos endofíticos em folhas, caules e raízes de plantas de feijão no Estado do Paraná

The present study aimed to isolate endophilic fungi from plant tissues (leaves, stems and roots) of beans, in addition to identifying them at the genus level. The experiment was conducted at IDR-Londrina. Bean samples were collected at the Londrina Research Station and at UENP-Bandeirantes. The leaves, stems and roots were separated; fragments of 5 mm diameter were cut and disinfested. They were later transferred to BDA culture medium. The plates were incubated at room temperature for seven days for growth of the microorganisms present. The presence and absence, colonization rate (TC) for each tissue and gender identification of fungi were evaluated. The experiment was conducted in a completely randomized design, with five replications. Forty-eight endophilic isolates were found, 13 in root, 17 in stem and 18 in leaf. CT ranged from 17-100% (leaf), 17-83% (stem) and 16-100% (root). The genus Alternaria sp. and Cladosporium sp. have greater specificity with the leaf and stem, Penicillium sp. root and stem. The genera Fusarium sp. and Aspergillus sp. are found in all organs, Curvularia sp., Nigrospora sp. and Thichoderma sp. demonstrated leaf specificity, Macrophomina sp. the root, and Colletotrichum sp. to the stem. Thus, the identified fungi present potential for future studies in their application in the biocontrol of various plant diseases.

O presente estudo teve como objetivo realizar o isolamento de fungos endofíticos dos tecidos vegetais (folhas, caules e raízes) de feijão, além de identifica-los a nível de gênero. O experimento foi conduzido no IDR-Londrina. Amostras de feijão foram coletadas na Estação de Pesquisa de Londrina e na UENP-Bandeirantes. Foram separadas as folhas, caules e raízes, cortados fragmentos de 5 mm diâmetro e desinfestados. Posteriormente foram transferidos para meio de cultura BDA. As placas foram incubadas à temperatura ambiente por sete dias, para crescimento dos microrganismos presentes. Foram avaliados a presença e ausência, taxa de colonização (TC) para cada tecido e identificação a nível de gênero dos fungos. O experimento foi conduzido em delineamento inteiramente casualizado, com cinco repetições. Encontrou-se 48 isolados endofíticos, sendo 13 em raiz, 17 em caule e 18 em folha. A TC variou de 17-100% (folha), de 17-83% (caule) e 16-100% (raiz). O gênero Alternaria sp. e Cladosporium sp. apresentam especificidade maior com a folha e caule, o Penicillium sp. com raiz e caule. Os gêneros Fusarium sp. e Aspergillus sp. são encontrados em todos os órgãos, Curvularia sp., Nigrospora sp. e Thichoderma sp. demonstraram especificidade em folha, Macrophomina sp. a raiz, e Colletotrichum sp. ao caule. Dessa forma, os fungos identificados apresentam-se com potencial para futuros estudos em sua aplicação no biocontrole de diversas doenças de plantas.

Growth, leaf gas exchange and mycorrhizal colonization of three medicinal species submitted to different irradiance levels / Crescimento, trocas gasosas foliares e colonização micorrizica de três espécies de plantas medicinais submetidas a diferentes níveis de irradiância

This study o evaluated growth, leaf gas exchange and arbuscular mycorrhizal fungi root colonization in three medicinal plant species under different irradiance intensities. Fridericia chica (Bonpl.) L.G.Lohmann, Mikania laevigata Sch.Bip. ex Baker and Varronia curassavica Jacq. were propagated by cutting and cultivated for 120 days in artificially shaded environments using black shade-type screens, obtaining four irradiance levels: 100%, 70%, 50% and 30%. The experimental design was completely randomized in a 3 x 4 factorial scheme (three plant species and four irradiation levels) with seven replicates. The three medicinal species showed higher liquid assimilation, mass growth and arbuscular mycorrhizal fungi root colonization rates when exposed to environments with 70% light availability. In relation to physiological responses, V. curassavica presented higher photosynthetic rate, stomatal conductance and transpiration when submitted to 70% irradiance, being able to be cultivated in more open environments with higher irradiation levels. Conversely F. chica and M. laevigata presented shade tolerance characteristics. At the initial growth phase, the results obtained can be used as indicators to recommend the ideal cultivation environment for these species in agroforestry systems.

O objetivo deste trabalho foi avaliar o crescimento, as trocas gasosas foliares e a colonização por fungos micorrízicos arbusculares em três espécies de plantas medicinais, sob diferentes intensidades de irradiância. Fridericia chica (Bonpl.) L.G. Ohmmann, Mikania laevigata Sch.Bip. ex Baker e Varronia curassavica Jacq. foram propagadas por estaquia e cultivadas por 120 dias em ambientes artificialmente sombreados, utilizando telas do tipo sombrite, em quatro níveis de irradiância, 100%, 70%, 50% e 30%. O delineamento experimental foi inteiramente casualizado, em esquema fatorial 3 x 4 (três espécies de plantas e quatro níveis de irradiação) com sete repetições. As três espécies medicinais avaliadas apresentaram maiores taxas de assimilação líquida, crescimento em massa e colonização radicular por fungos micorrízicos arbusculares quando expostas a ambientes com 70% de disponibilidade de luz. Em relação às respostas fisiológicas, V. curassavica apresentou maior taxa fotossintética, condutância estomática e transpiração quando submetidas a 70% de irradiância, podendo ser cultivada em ambientes mais abertos e com maiores níveis de radiação. Por outro lado, F. chica e M. laevigata apresentaram características de plantas tolerantes à sombra. Os resultados obtidos na fase inicial de crescimento podem ser utilizados como um indicador para recomendar o ambiente de plantio dessas três espécies medicinais em sistemas agroflorestais.

Inoculation of arbuscular mycorrhizal fungi as a strategy to improve annatto (Bixa orellana L. ) growth

This study aimed to assess the occurrence of arbuscular mycorrhizal fungi (AMF) in annatto (Bixa orellana L.) cultivars and their response to AMF inoculation using biometric parameters. The occurrence surveys were conducted in annatto fields in three municipalities from Pernambuco Forest Zone: Lagoa de Itaenga, Gloria de Goitá, and Vitoria de Santo Antão, and in four cultivars (Red Piave, Green Piave, Red Peruvian Paulista, and Green Peruvian Paulista). In a greenhouse, biometric parameters of annatto seedlings of Red Piave, Red Peruvian Paulista, Embrapa-36, and Embrapa-37 cultivars inoculated with AMF isolated from annatto fields. The Red Piave cultivar exhibited greater root colonization than the Green Peruvian Paulista in the Lagoa de Itaenga and Vitoria de Santo Antão municipalities. The cultivar Red Piave showed a more beneficial association with AMF in plants and soil than cultivar Green Peruvian Paulista did, in both Lagoa de Itaenga and Vitoria de Santo Antão. AMF inoculation was effective in promoting the growth of annatto plants, particularly those inoculants with S. heterogama and C. etunicatum.

Inoculation of arbuscular mycorrhizal fungi as a strategy to improve annatto (Bixa orellana L. ) growth

This study aimed to assess the occurrence of arbuscular mycorrhizal fungi (AMF) in annatto (Bixa orellana L.) cultivars and their response to AMF inoculation using biometric parameters. The occurrence surveys were conducted in annatto fields in three municipalities from Pernambuco Forest Zone: Lagoa de Itaenga, Gloria de Goitá, and Vitoria de Santo Antão, and in four cultivars (Red Piave, Green Piave, Red Peruvian Paulista, and Green Peruvian Paulista). In a greenhouse, biometric parameters of annatto seedlings of Red Piave, Red Peruvian Paulista, Embrapa-36, and Embrapa-37 cultivars inoculated with AMF isolated from annatto fields. The Red Piave cultivar exhibited greater root colonization than the Green Peruvian Paulista in the Lagoa de Itaenga and Vitoria de Santo Antão municipalities. The cultivar Red Piave showed a more beneficial association with AMF in plants and soil than cultivar Green Peruvian Paulista did, in both Lagoa de Itaenga and Vitoria de Santo Antão. AMF inoculation was effective in promoting the growth of annatto plants, particularly those inoculants with S. heterogama and C. etunicatum.(AU)

Soil phosphorus availability and uptake by mycorrhizal and non-mycorrhizal plants in an onion no-tillage system / Disponibilidade e absorção de fósforo no solo por plantas micorrízicas e não micorrízicas em sistema de plantio direto de cebola

ABSTRACT: Onion is an important vegetable crop, predominantly grown under conventional tillage system management. Alternatively, the vegetable no-tillage system uses cover crops to form a residue layer, which improves soil physical, chemical, and biological attributes. Aiming to understand the interaction of mycorrhizal and non-mycorrhizal cover crops, phosphatase activity, and soil phosphorus availability and uptake by plants, a no-tillage vegetable production system experiment with onion was carried out in Ituporanga, Southern Brazil. The treatments were black oats (Avena strigosa); rye (Secale cereale); oilseed radish (Raphanus sativus); rye + oilseed radish; black oats + oilseed radish, and a control with spontaneous plants. Additionally, two plots, a conventional tillage system area and a forest, both adjacent to the experiment, were evaluated. We measured cover crop biomass, onion yield, acid phosphatase activity, and resin-extracted phosphorus in the soil, shoot and root phosphorus content, and root colonization in cover crops, spontaneous plants, and onions. The treatments with cover crops had the highest plant biomass in winter and onion yield. Available soil phosphorus and acid phosphatase activity were higher in no-tillage plots than in the conventional tillage system area. The presence of non-mycorrhizal oilseed radish was associated with decreased colonization of rye and onion roots by arbuscular mycorrhizal fungi. No-tillage areas with cover crops or spontaneous plants in winter accumulated more phosphorus than conventional tillage system areas. The conventional tillage system showed adverse effects on most soil attributes, as shown by a Principal Component Analysis.

RESUMO: A cebola é uma importante cultura vegetal, cultivada predominantemente sob sistema de preparo convencional. Como alternativa, o sistema de plantio direto de hortaliças utiliza culturas de cobertura para formar uma camada de biomassa, o que melhora os atributos físicos, químicos e biológicos do solo. Com o objetivo de entender a interação de culturas de cobertura micorrízicas e não-micorrízicas, atividade da fosfatase ácida e disponibilidade e absorção de fósforo do solo pelas plantas, foi realizado um experimento em sistema de plantio direto de hortaliças com a cultura da cebola em Ituporanga, sul do Brasil. Os tratamentos foram: aveia preta (Avena strigosa); centeio (Secale cereale); nabo forrageiro (Raphanus sativus); centeio + nabo forrageiro; aveia preta + nabo forrageiro e um controle com vegetação espontânea. Além disso, duas outras parcelas, uma área em sistema de preparo convencional e uma floresta, ambas adjacentes ao experimento, foram avaliadas. Medimos a biomassa da cultura de cobertura, o rendimento de cebola, a atividade de fosfatase ácida e o fósforo extraído por resina no solo, bem como o conteúdo de fósforo da parte aérea e da raiz e a colonização das raízes em plantas de cobertura, plantas espontâneas e cebolas. Os tratamentos com plantas de cobertura apresentaram a maior biomassa de culturas de cobertura e rendimento de cebola. A atividade de fosfatase ácida e fósforo disponível no solo foram maiores nas parcelas de plantio direto do que na área convencional. A presença de nabo forrageiro, uma planta não micorrízica, foi associada a reduções na colonização de raízes de centeio e cebola por fungos micorrízicos arbusculares. As áreas de plantio direto com plantas de cobertura ou plantas espontâneas no inverno acumularam mais fósforo do que as áreas com preparo convencional. O sistema convencional de lavoura mostrou efeitos adversos para a maioria dos atributos do solo, como mostra a Análise de Componentes Principais.

Soil phosphorus availability and uptake by mycorrhizal and non-mycorrhizal plants in an onion no-tillage system / Disponibilidade e absorção de fósforo no solo por plantas micorrízicas e não micorrízicas em sistema de plantio direto de cebola

Onion is an important vegetable crop, predominantly grown under conventional tillage system management. Alternatively, the vegetable no-tillage system uses cover crops to form a residue layer, which improves soil physical, chemical, and biological attributes. Aiming to understand the interaction of mycorrhizal and non-mycorrhizal cover crops, phosphatase activity, and soil phosphorus availability and uptake by plants, a no-tillage vegetable production system experiment with onion was carried out in Ituporanga, Southern Brazil. The treatments were black oats (Avena strigosa); rye (Secale cereale); oilseed radish (Raphanus sativus); rye + oilseed radish; black oats + oilseed radish, and a control with spontaneous plants. Additionally, two plots, a conventional tillage system area and a forest, both adjacent to the experiment, were evaluated. We measured cover crop biomass, onion yield, acid phosphatase activity, and resin-extracted phosphorus in the soil, shoot and root phosphorus content, and root colonization in cover crops, spontaneous plants, and onions. The treatments with cover crops had the highest plant biomass in winter and onion yield. Available soil phosphorus and acid phosphatase activity were higher in no-tillage plots than in the conventional tillage system area. The presence of non-mycorrhizal oilseed radish was associated with decreased colonization of rye and onion roots by arbuscular mycorrhizal fungi. No-tillage areas with cover crops or spontaneous plants in winter accumulated more phosphorus than conventional tillage system areas. The conventional tillage system showed adverse effects on most soil attributes, as shown by a Principal Component Analysis.

A cebola é uma importante cultura vegetal, cultivada predominantemente sob sistema de preparo convencional. Como alternativa, o sistema de plantio direto de hortaliças utiliza culturas de cobertura para formar uma camada de biomassa, o que melhora os atributos físicos, químicos e biológicos do solo. Com o objetivo de entender a interação de culturas de cobertura micorrízicas e não-micorrízicas, atividade da fosfatase ácida e disponibilidade e absorção de fósforo do solo pelas plantas, foi realizado um experimento em sistema de plantio direto de hortaliças com a cultura da cebola em Ituporanga, sul do Brasil. Os tratamentos foram: aveia preta (Avena strigosa); centeio (Secale cereale); nabo forrageiro (Raphanus sativus); centeio + nabo forrageiro; aveia preta + nabo forrageiro e um controle com vegetação espontânea. Além disso, duas outras parcelas, uma área em sistema de preparo convencional e uma floresta, ambas adjacentes ao experimento, foram avaliadas. Medimos a biomassa da cultura de cobertura, o rendimento de cebola, a atividade de fosfatase ácida e o fósforo extraído por resina no solo, bem como o conteúdo de fósforo da parte aérea e da raiz e a colonização das raízes em plantas de cobertura, plantas espontâneas e cebolas. Os tratamentos com plantas de cobertura apresentaram a maior biomassa de culturas de cobertura e rendimento de cebola. A atividade de fosfatase ácida e fósforo disponível no solo foram maiores nas parcelas de plantio direto do que na área convencional. A presença de nabo forrageiro, uma planta não micorrízica, foi associada a reduções na colonização de raízes de centeio e cebola por fungos micorrízicos arbusculares. As áreas de plantio direto com plantas de cobertura ou plantas espontâneas no inverno acumularam mais fósforo do que as áreas com preparo convencional. O sistema convencional de lavoura mostrou efeitos adversos para a maioria dos atributos do solo, como mostra a Análise de Componentes Principais.

Soil phosphorus availability and uptake by mycorrhizal and non-mycorrhizal plants in an onion no-tillage system / Disponibilidade e absorção de fósforo no solo por plantas micorrízicas e não micorrízicas em sistema de plantio direto de cebola

Onion is an important vegetable crop, predominantly grown under conventional tillage system management. Alternatively, the vegetable no-tillage system uses cover crops to form a residue layer, which improves soil physical, chemical, and biological attributes. Aiming to understand the interaction of mycorrhizal and non-mycorrhizal cover crops, phosphatase activity, and soil phosphorus availability and uptake by plants, a no-tillage vegetable production system experiment with onion was carried out in Ituporanga, Southern Brazil. The treatments were black oats (Avena strigosa); rye (Secale cereale); oilseed radish (Raphanus sativus); rye + oilseed radish; black oats + oilseed radish, and a control with spontaneous plants. Additionally, two plots, a conventional tillage system area and a forest, both adjacent to the experiment, were evaluated. We measured cover crop biomass, onion yield, acid phosphatase activity, and resin-extracted phosphorus in the soil, shoot and root phosphorus content, and root colonization in cover crops, spontaneous plants, and onions. The treatments with cover crops had the highest plant biomass in winter and onion yield. Available soil phosphorus and acid phosphatase activity were higher in no-tillage plots than in the conventional tillage system area. The presence of non-mycorrhizal oilseed radish was associated with decreased colonization of rye and onion roots by arbuscular mycorrhizal fungi. No-tillage areas with cover crops or spontaneous plants in winter accumulated more phosphorus than conventional tillage system areas. The conventional tillage system showed adverse effects on most soil attributes, as shown by a Principal Component Analysis.(AU)

A cebola é uma importante cultura vegetal, cultivada predominantemente sob sistema de preparo convencional. Como alternativa, o sistema de plantio direto de hortaliças utiliza culturas de cobertura para formar uma camada de biomassa, o que melhora os atributos físicos, químicos e biológicos do solo. Com o objetivo de entender a interação de culturas de cobertura micorrízicas e não-micorrízicas, atividade da fosfatase ácida e disponibilidade e absorção de fósforo do solo pelas plantas, foi realizado um experimento em sistema de plantio direto de hortaliças com a cultura da cebola em Ituporanga, sul do Brasil. Os tratamentos foram: aveia preta (Avena strigosa); centeio (Secale cereale); nabo forrageiro (Raphanus sativus); centeio + nabo forrageiro; aveia preta + nabo forrageiro e um controle com vegetação espontânea. Além disso, duas outras parcelas, uma área em sistema de preparo convencional e uma floresta, ambas adjacentes ao experimento, foram avaliadas. Medimos a biomassa da cultura de cobertura, o rendimento de cebola, a atividade de fosfatase ácida e o fósforo extraído por resina no solo, bem como o conteúdo de fósforo da parte aérea e da raiz e a colonização das raízes em plantas de cobertura, plantas espontâneas e cebolas. Os tratamentos com plantas de cobertura apresentaram a maior biomassa de culturas de cobertura e rendimento de cebola. A atividade de fosfatase ácida e fósforo disponível no solo foram maiores nas parcelas de plantio direto do que na área convencional. A presença de nabo forrageiro, uma planta não micorrízica, foi associada a reduções na colonização de raízes de centeio e cebola por fungos micorrízicos arbusculares. As áreas de plantio direto com plantas de cobertura ou plantas espontâneas no inverno acumularam mais fósforo do que as áreas com preparo convencional. O sistema convencional de lavoura mostrou efeitos adversos para a maioria dos atributos do solo, como mostra a Análise de Componentes Principais.(AU)

Development of mycorrhizal soybean grown in coppercontaminated soil / Desenvolvimento da soja micorrízada cultivada em solo contaminado com cobre

High concentrations of copper in the soil are toxic to the development of plants and microorganisms. The aim of this study was to select arbuscular mycorrhizal fungi efficient for the development and yield of soybeangrown in copper-contaminated soil. The experiment was laid out in a completely randomized design with a 7 × 4 factorial arrangement corresponding to seven rates of copper (0, 80, 160, 240, 320, 400, and 480 mg kg-1 of soil) and four inocula (uninoculated control and three mycorrhizal fungi, namely, Acaulospora colombiana, Dentiscutata heterogama and Rhizophagus clarus), in seven replicates. Shoot height; collar diameter; number of grains per plant; shoot and root-system dry mass; leaf area; specific root surface; copper content and accumulation in the shoots, roots, and grain; chlorophyll parameters; and mycorrhizal colonization percentage were evaluated. Inoculation with the arbuscular mycorrhizal fungi Acaulospora colombiana, Dentiscutata heterogama and Rhizophagus clarus increases the phenological and physiological parameters of soybean and its yield when grown in soil contaminated with up to 480 mg kg-1 of copper applied to the soil. The Rhizophagus clarus isolate provides greater development and yield in soybean grown in soil contaminated with up to 480 mg kg-1 of copper applied to the soil, as compared with the other isolates.(AU)

O cobre em elevada concentração no solo torna-se tóxico ao desenvolvimento das plantas e microrganismo. O trabalho objetivou selecionar fungos micorrízicos arbusculares eficientes para o desenvolvimento e produtividade da soja cultivada em solo contaminado com cobre. O delineamento experimental foi em Inteiramente casualizado em arranjo fatorial 7 × 4, sendo, sete doses de cobre (0, 80, 160, 240, 320, 400 e 480 mg de cobre kg-1 de solo), quatro inóculos (testemunha sem inoculação e três fungos micorrízicos: Acaulospora colombiana, Dentiscutata heterogama e Rhizophagus clarus), com 7 repetições. Avaliou-se a altura da parte aérea, diâmetro do colo, número de grão por planta, massa seca da parte aérea e sistema radicular, área foliar, área superficial específica de raízes, teores e acúmulo de cobre na parte aérea, radicular e no grão, parâmetros da clorofila, e porcentagem de colonização micorrízica. A inoculação com fungos micorrízicos arbusculares Acaulospora colombiana, Dentiscutata heterogama, Rhizophagus clarus aumenta os parâmetros fenológicos e fisiológicos da soja e a sua produtividade soja em solo contaminado com até 480 mg kg-1 de cobre aplicado no solo. O isolado Rhizophagus clarus promove maior desenvolvimento da soja e aumenta sua produtividade em solo contaminado com até 480 mg kg-1 de cobre aplicado no solo em relação aos demais isolados.(AU)

Diversity of bacterial strains in biochar-enhanced Amazon soil and their potential for growth promotion and biological disease control in tomato / Diversidade de isolados bacterianos em solo amazônico enriquecido com biocarvão e seu potencial para a promoção de crescimento e controle biológico de doenças em tomate

The use of bacteria in growth promotion and biological control of plant diseases can minimize environmental contamination caused by the indiscriminate use of pesticides and chemical fertilizers. We aimed to evaluate growth promotion and biological control of Corynespora cassiicola in tomato seedlings mediated by beneficial bacteria isolated from a non-rhizospheric Amazon soil containing different amounts of biochar, and to identify to which groups of bacteria the strains belong. We obtained 200 strains of bacteria from experimental plots containing biochar doses of 0, 40, 80 and 120 t ha-1. Of these, 53 strains were selected by root colonization tests. Based on growth promotion parameters, 25 strains were screened, identified by molecular characterization and evaluated for indoleacetic acid (IAA) production, phosphate solubilization and biological control. The best dose of biochar for colony formation was 40 t ha-1, and a regression model indicated 34 t ha-1 as the optimal dose. The production of IAA was observed in 18 (75%) strains, and two (8%) strains were able to solubilize phosphate. The efficiency in root growth promotion was up to 125%, and the percentage of plant protection ranged from 50 to 59%. Molecular characterization showed that the bacteria used in this study belong to the genera Bacillus and Lysinibacillus.(AU)

O uso de bactérias na promoção do crescimento e no controle biológico de doenças em plantas pode minimizar a contaminação ambiental causada pela aplicação indiscriminada de pesticidas e fertilizantes químicos. Objetivamos avaliar a promoção do crescimento e o controle biológico de Corynespora cassiicola em mudas de tomate mediadas por bactérias benéficas isoladas de solo amazônico não-rizosférico contendo diferentes dosagens de biocarvão, e identificar a quais grupos de bactérias os isolados pertencem. Obtivemos 200 isolados de parcelas experimentais contendo doses de biocarvão de 0, 40, 80 e 120 t ha-1. Destes, 53 foram selecionados por testes de colonização radicular. Com base nos parâmetros de promoção do crescimento, 25 isolados foram selecionados, identificados através de análise molecular e avaliados para produção de ácido indolacético (AIA), solubilização de fosfato e controle biológico. A melhor dose de biocarvão para a formação de colônias foi 40 t ha-1, e um modelo de regressão indicou 34 t ha-1como dose ótima. A produção de AIA foi observada em 18 (75%) isolados e dois (8%) isolados foram capazes de solubilizar fosfato. A eficiência na promoção do crescimento das raízes foi de até 125%, e a porcentagem de proteção das plantas variou de 50,3 a 59,0%. A caracterização molecular indicou que as bactérias utilizadas nesse estudo pertencem aos gêneros Bacillus e Lysinibacillus.(AU)

Bioprospection and molecular phylogeny of culturable endophytic fungi associated with yellow passion fruit

Endophytic microorganisms live inside the plants without causing any damage to their hosts. In the agricultural field, these endophytes might be a strategy of biological control for phytopathogens. We aimed to isolate endophytic fungifrom yellowpassion fruit (Passiflora edulis) leaves, evaluating its biocontrol capacity by in vitroantagonism against phytopathogen Colletotrichum sp. CNPU378. We also carried out greenhouse experiments in bean seedlings. A high colonization frequency was obtained (89%), and the molecular identification based on DNA sequencing attested Colletotrichumas the most frequent genus and minor occurrence of Curvulariaendophytes. The endophytes tested showed different types of competitive interactions in in vitro antagonism inhibition rate ranging from 28.8 to 48.8%. There were 10 promising antagonists tested for their antagonist activity of crude extracts of secondary metabolites, in which strain PE-36 (20.8%) stood out among the other strains evaluated. In the greenhouse assay, plants inoculated only with endophyte Colletotrichumsp. PE-36 was symptomless and suggest that the endophyte strengthened the growth promotion in common bean plants, especially in the root length and number of leaves when compared to control plantsand other treatments. Despite many fungiof Colletotrichumgenus being described as causative agents of anthracnose, in this study, the plant sampled was colonized predominantly by Colletotrichumendophytes living in asymptomatic relationship. By the way,we come across a Colletotrichumsp. endophyte able to antagonize a Colletotrichumsp. pathogen

Intercropping Acacia mangium stimulates AMF colonization and soil phosphatase activity in Eucalyptus grandis

Arbuscular mycorrhizal fungi (AMF) are very important to plant nutrition, mostly in terms of acquisition of P and micronutrients. While Acacia mangium is closely associated with AMF throughout the whole cycle, Eucalyptus grandis presents this symbiosis primarily at the seedling stage. The aim of this study was to evaluate the dynamics of AMF in these two tree species in both pure and mixed plantations during the first 20 months after planting. We evaluated the abundance, richness and diversity of AMF spores, the rate of AMF mycorrhizal root colonization, enzymatic activity and soil and litter C, N and P. There was an increase in AMF root colonization of E. grandis when intercropped with A. mangium as well as an increase in the activity of acid and alkaline phosphatase in the presence of leguminous trees. AMF colonization and phosphatase activities were both involved in improvements in P cycling and P nutrition in soil. In addition, P cycling was favored in the intercropped plantation, which showed negative correlation with litter C/N and C/P ratios and positive correlation with soil acid phosphatase activity and soil N and P concentrations. Intercropping A. mangium and E. grandis maximized AMF root colonization of E. grandis and phosphatase activity in the soil, both of which accelerate P cycling and forest performance.

Intercropping Acacia mangium stimulates AMF colonization and soil phosphatase activity in Eucalyptus grandis

Arbuscular mycorrhizal fungi (AMF) are very important to plant nutrition, mostly in terms of acquisition of P and micronutrients. While Acacia mangium is closely associated with AMF throughout the whole cycle, Eucalyptus grandis presents this symbiosis primarily at the seedling stage. The aim of this study was to evaluate the dynamics of AMF in these two tree species in both pure and mixed plantations during the first 20 months after planting. We evaluated the abundance, richness and diversity of AMF spores, the rate of AMF mycorrhizal root colonization, enzymatic activity and soil and litter C, N and P. There was an increase in AMF root colonization of E. grandis when intercropped with A. mangium as well as an increase in the activity of acid and alkaline phosphatase in the presence of leguminous trees. AMF colonization and phosphatase activities were both involved in improvements in P cycling and P nutrition in soil. In addition, P cycling was favored in the intercropped plantation, which showed negative correlation with litter C/N and C/P ratios and positive correlation with soil acid phosphatase activity and soil N and P concentrations. Intercropping A. mangium and E. grandis maximized AMF root colonization of E. grandis and phosphatase activity in the soil, both of which accelerate P cycling and forest performance.(AU)

Contribution of dark septate fungi to the nutrient uptake and growth of rice plants

The use of dark septate fungi (DSE) to promote plant growth can be beneficial to agriculture, and these organisms are important allies in the search for sustainable agriculture practices. This study investigates the contribution of dark septate fungi to the absorption of nutrients by rice plants and their ensuing growth. Four dark septate fungi isolates that were identified by Internal transcribed spacer phylogeny were inoculated in rice seeds (Cv. Piauí). The resulting root colonization was estimated and the kinetic parameters Vmax and Km were calculated from the nitrate contents of the nutrient solution. The macronutrient levels in the shoots, and the NO3--N, NH4+-N, free amino-N and soluble sugars in the roots, sheathes and leaves were measured. The rice roots were significantly colonized by all of the fungi, but in particular, isolate A103 increased the fresh and dry biomass of the shoots and the number of tillers per plant, amino-N, and soluble sugars as well as the N, P, K, Mg and S contents in comparison with the control treatment. When inoculated with isolates A103 and A101, the plants presented lower Km values, indicating affinity increases for NO3--N absorption. Therefore, the A103 Pleosporales fungus presented the highest potential for the promotion of rice plant growth, increasing the tillering and nutrients uptake, especially N (due to an enhanced affinity for N uptake) and P.(AU)

Morphological pattern of colonization by mycorrhizal fungi and the microbial activity observed in Barbados cherry crops / Padrão morfológico de colonização por fungos micorrízicos arbusculares e atividade microbiana em cultivos de acerola

Our objective was to evaluate the morphological pattern of colonization by arbuscular mycorrhizal fungi (AMF) as well as to study the microbiological activity of the soil on family farms where Barbados cherry was cultivated. Soil and root samples were selected from four areas in the municipality of Maranguape-CE where Barbados cherry was grown, which were named according to the age of plants in the following manner: A1-3, A2-3, and A3-3 (3 years), and A4-2 (2 years). After sampling, the arbuscular mycorrhizal colonization, morphological colonization pattern, basal soil respiration (SBR), and density of mycorrhizal spores (DS) were analyzed. The Paris-type morphological pattern was predominant in the root system of Barbados cherry; the affinity of this pattern in the culture was clear. Time of installation and management of Barbados cherry orchards in family farming areas promoted reduction in SBR. P levels in the soil may have negatively influenced root colonization and density of mycorrhizal spores.

Objetivou-se avaliar o padrão morfológico de colonização por Fungos Micorrízicos Arbusculares (FMA), bem como a atividade microbiológica do solo sob cultivo da aceroleira em áreas de agricultores familiares. Para as coletas de solos e raízes foram selecionadas quatro áreas com aceroleira no município de Maranguape-CE, essas foram denominadas de acordo com a idade das plantas A1-3, A2-3 e A3-3 (3 anos) e A4-2 (2 anos). Após as coletas foi analisado a colonização micorrízica arbuscular, o padrão morfológico de colonização, a respiração basal do solo (RBS) e a densidade de esporos micorrízicos (DE). O padrão morfológico do tipo Paris foi predominante no sistema radicular da aceroleira, ficado claro a afinidade desse padrão na cultura. O tempo de instalação e o manejo do pomar da aceroleira nas áreas de agricultura familiar promoveu uma redução na RBS. Os teores de P no solo podem ter influenciado negativamente a colonização radicular e a densidade de esporos de fungos micorrízicos arbusculares.

Morphological pattern of colonization by mycorrhizal fungi and the microbial activity observed in Barbados cherry crops / Padrão morfológico de colonização por fungos micorrízicos arbusculares e atividade microbiana em cultivos de acerola

Our objective was to evaluate the morphological pattern of colonization by arbuscular mycorrhizal fungi (AMF) as well as to study the microbiological activity of the soil on family farms where Barbados cherry was cultivated. Soil and root samples were selected from four areas in the municipality of Maranguape-CE where Barbados cherry was grown, which were named according to the age of plants in the following manner: A1-3, A2-3, and A3-3 (3 years), and A4-2 (2 years). After sampling, the arbuscular mycorrhizal colonization, morphological colonization pattern, basal soil respiration (SBR), and density of mycorrhizal spores (DS) were analyzed. The Paris-type morphological pattern was predominant in the root system of Barbados cherry; the affinity of this pattern in the culture was clear. Time of installation and management of Barbados cherry orchards in family farming areas promoted reduction in SBR. P levels in the soil may have negatively influenced root colonization and density of mycorrhizal spores.(AU)

Objetivou-se avaliar o padrão morfológico de colonização por Fungos Micorrízicos Arbusculares (FMA), bem como a atividade microbiológica do solo sob cultivo da aceroleira em áreas de agricultores familiares. Para as coletas de solos e raízes foram selecionadas quatro áreas com aceroleira no município de Maranguape-CE, essas foram denominadas de acordo com a idade das plantas A1-3, A2-3 e A3-3 (3 anos) e A4-2 (2 anos). Após as coletas foi analisado a colonização micorrízica arbuscular, o padrão morfológico de colonização, a respiração basal do solo (RBS) e a densidade de esporos micorrízicos (DE). O padrão morfológico do tipo Paris foi predominante no sistema radicular da aceroleira, ficado claro a afinidade desse padrão na cultura. O tempo de instalação e o manejo do pomar da aceroleira nas áreas de agricultura familiar promoveu uma redução na RBS. Os teores de P no solo podem ter influenciado negativamente a colonização radicular e a densidade de esporos de fungos micorrízicos arbusculares.(AU)

Tripartite symbiosis of Sophora tomentosa, rhizobia and arbuscular mycorhizal fungi

ABSTRACT Sophora tomentosa is a pantropical legume species with potential for recovery of areas degraded by salinization, and for stabilization of sand dunes. However, few studies on this species have been carried out, and none regarding its symbiotic relationship with beneficial soil microorganisms. Therefore, this study aimed to evaluate the diversity of nitrogen-fixing bacteria isolated from nodules of Sophora tomentosa, and to analyze the occurrence of colonization of arbuscular mycorrhizal fungi on the roots of this legume in seafront soil. Thus, seeds, root nodules, and soil from the rhizosphere of Sophora tomentosa were collected. From the soil samples, trap cultures with this species were established to extract spores and to evaluate arbuscular mycorhizal fungi colonization in legume roots, as well as to capture rhizobia. Rhizobia strains were isolated from nodules collected in the field or from the trap cultures. Representative isolates of the groups obtained in the similarity dendrogram, based on phenotypic characteristics, had their 16S rRNA genes sequenced. The legume species showed nodules with indeterminate growth, and reddish color, distributed throughout the root. Fifty-one strains of these nodules were isolated, of which 21 were classified in the genus Bacillus, Brevibacillus, Paenibacillus, Rhizobium and especially Sinorhizobium. Strains closely related to Sinorhizobium adhaerens were the predominant bacteria in nodules. The other genera found, with the exception of Rhizobium, are probably endophytic bacteria in the nodules. Arbuscular mycorrhizal fungi was observed colonizing the roots, but arbuscular mycorhizal fungi spores were not found in the trap cultures. Therefore Sophora tomentosa is associated with both arbuscular mycorhizal fungi and nodulating nitrogen-fixing bacteria.(AU)

Production of native arbuscular mycorrhizal fungi inoculum under different environmental conditions

In order to obtain an arbuscular mycorrhizal fungi (AMF) native inoculum from Sierra de Moa and determine the most appropriate conditions for its big scale production, four light and temperature combinations were tested in three plant species (Calophyllum antillanum, Talipariti elatum and Paspalum notatum). Growth and development parameters, as well as the mycorrhizal functioning of the seedlings were evaluated. The natural light treatment under high temperatures (L-H) was the most suitable for the growth and development of the three plant species, showing the highest total biomass values, mainly of root, and a positive root-shoot ratio balance. This treatment also promoted higher values of root mycorrhizal colonization, external mycelium and AMF spore density. A total of 38 AMF species were identified among the plants and environmental conditions tested. Archaeospora sp.1, Glomus sp.5, Glomus brohultii and G. glomerulatum were observed in all the treatments. The L-H condition can be recommended for native inoculum production, as it promotes a better expression of the AM symbiosis and an elevated production of mycorrhizal propagules.(AU)