The aim of this work was to assess the sporulation and diversity of arbuscular mycorrhizal fungi (AMF) at different forest sites with Araucaria angustifolia (Bert.) O. Ktze. (Brazil Pine). In addition, a greenhouse experiment was carried out to test the use of traditional trap plants (maize + peanut) or A. angustifolia to estimate the diversity of AMF at each site. Soil samples were taken in two State Parks at southwestern Brazil: Campos do Jordão (Parque Estadual de Campos do Jordão [PECJ]) and Apiaí (Parque Estadual Turístico do Alto Ribeira [PETAR]), São Paulo State, in sites of either native or replanted forest. In PECJ, an extra site of replanted forest that was impacted by accidental fire and is now in a state of recuperation was also sampled. The spore densities and their morphological identification were compiled at each site. In the greenhouse, soil samples from each site were used as inoculum to promote spore multiplication on maize + peanut or A. angustifolia grown on a sandy, low-fertility substrate. Plants were harvested, respectively, after 4 months or 1 year of growth and assessed for mycorrhizal root colonization. Spore counts and identification were also performed in the substrate, after the harvest of plants. Twenty-five taxa were identified considering all sites. Species richness and diversity were greater in native forest areas, being Acaulospora, the genus with the most species. Differences in number of spores, diversity, and richness were found at the different sites of each State Park. Differences were also found when maize + peanut or A. angustifolia were used as trap plants. The traditional methodology using trap plants seems to underestimate the diversity of the AMF. The use of A. angustifolia as trap plant showed similar species richness to the field in PECJ, but the identified species were not necessarily the same. Nevertheless, for PETAR, both A. angustifolia and maize + peanut underestimated the species richness. Because the AMF sporulation can be affected by many conditions, it is impossible to draw detailed conclusions from this kind of survey. More precise experiments have to be set up to isolate the different factors that modulate the ecophysiological interactions between host plant and endophyte.
Araucaria angustifolia (Bert.) O. Ktze. is an endangered Brazilian coniferous tree that has been almost exterminated in the native areas because of uncontrolled wood exploitation. This tree has been shown to be highly dependent on arbuscular mycorrhizal fungi (AMF) and, therefore, AMF may be essential for forest sustainability and biological diversity. Root colonization, density and diversity of AMF spores were assessed in two Araucaria forest stands at the State Park of Alto Ribeira (PETAR), at two sampling dates: May and October. A comparison was made between a mature native stand composed of Araucaria trees mixed into a variety of tropical trees and shrubs, without any sign of anthropogenic interference (FN) and an Araucaria stand planted in 1987 (R), which has been used as a pasture. Assessments included percent root colonization, AMF spore numbers and species richness, Simpson's dominance index (Is), and Shannon's diversity index (H). Mycorrhizal root colonization did not differ between ecosystems in May. In October, however, the native stand (FN) presented a higher colonization than the planted forest (R), and the root colonization was more intense than in May. When considering both sampling periods and forests, 27 species of AM fungi, with higher numbers of spores in FN than in R were found. Canonical discriminant analysis (CDA) indicated Shannon's diversity index as the ecological attribute that contributed the most to distinguish between forest ecosystems, with higher value of H in FN in relation to R. CDA showed to be a useful tool for the study of ecological attributes. Key words: Brazilian Pine, diversity, spore density, root colonization, multivariate analysis BIODIVERSIDADE E DISTRIBUIÇÃO DE FUNGOS MICORRÍZICOS ARBUSCULARES EM FLORESTA DE Araucaria angustifoliaRESUMO: O pinheiro brasileiro, Araucaria angustifolia (Bert.) O. Ktze é uma espécie arbórea ameaçada de extinção, quase exterminada pela exploração descontrolada de madeira. Essa espécie demonstra alta dependência de fungos micorrízicos arbusculares (FMA), de grande importância para a estabilidade do ecossistema e manutenção da biodiversidade. Avaliou-se a colonização radicular, a densidade e a diversidade de esporos de FMA em duas florestas com araucária, distintas no processo sucessional, em duas épocas de amostragem: maio e outubro. As florestas, localizadas no Parque Estadual Turístico do Alto do Ribeira (PETAR), correspondem a 1) Floresta Ombrófila Mista nativa (FN), em estágio clímax, sem sinais de interferência antrópica, e a 2) floresta de araucária plantada em 1987 (R), submetida a pastoreio. Foram avaliados: colonização radicular, número de esporos e riqueza de espécies de FMA e calculados os índices de dominância de Simpson (Is) e de diversidade de Shannon (H). A colonização radicular não diferiu entre as duas comunidades na primeira amostragem (maio). Na segunda amostragem (outubro), houve maior colonização radicular na floresta nativa do que na floresta plantada e a colonização radicular foi mais intensa em comparação c...
Araucaria angustifolia (Bert.) O. Ktze., a native forest tree from Brazil, is under extinction risk. This tree depends on arbuscular mycorrhizal fungi for growth and development, especially in tropical low-P soils but, despite being a conifer, Araucaria does not form ectomycorrhiza, but only the arbuscular endomycorrhiza. This study aimed at surveying data on the spore density and root colonization (CR) by arbuscular mycorrhizal fungi (AMF) in Araucaria angustifolia forest ecosystems, in order to discriminate natural, implemented, and anthropic action-impacted ecosystems, by means of Canonical Discriminant Analysis (CDA). Three ecosystems representative of the Campos do Jordão (SP, Brazil) region were selected: 1. a native forest (FN); 2. a replanted Araucaria forest (R); and 3. a replanted Araucaria forest, submitted to accidental fire (RF). Rhizosphere soil and roots were sampled in May and October, 2002, for root colonization, AMF identification, and spores counts. Root percent colonization rates at first collection date were relatively low and did not differ amongst ecosystems. At the second period, FN presented higher colonization than the other two areas, with much higher figures than during the first period, for all areas. Spore density was lower in FN than in the other areas. A total of 26 AMF species were identified. The percent root colonization and spore numbers were inversely related to each other in all ecosystems. CDA indicated that there is spatial distinction among the three ecosystems in regard to the evaluated parameters. Key words: Brazil pine, biodiversity, species richness, reforestation DENSIDADE DE ESPOROS E COLONIZAÇÃO RADICULAR POR FUNGOS MICORRÍZICOS ARBUSCULARES EM ECOSSISTEMAS DE Araucaria angustifolia (Bert.) O. Ktze. PRESERVADOS E IMPACTADOSRESUMO: A Araucaria angustifolia (Bert.) O. Ktze. é uma espécie florestal nativa do Brasil e encontrase ameaçada de extinção. É altamente dependente de fungos micorrízicos arbusculares para seu desenvolvimento, principalmente em solos com baixos teores de fósforo. Embora sendo uma conífera, esta árvore não forma ectomicorriza, mas sim a endomicorriza arbuscular. O presente estudo teve como objetivo levantar dados sobre a densidade de esporos e a colonização radicular de fungos micorrízicos arbusculares (FMAs) em ecossistemas florestais de Araucaria angustifolia, visando discriminar os ecossistemas natural, implantado e impactado pela ação antrópica, através da Análise Canônica Discriminante (ACD). Foram selecionados três ecossistemas representativos da região de Campos do Jordão (SP): 1. floresta nativa (FN); 2. floresta replantada de araucária (R); e 3. floresta replantada de araucária, submetida a uma queima acidental (RF
Araucaria angustifolia is an important Brazilian conifer, but it is endangered of extinction due to excessive logging. The objective of the present case study was to survey data on the diversity of AMF in Araucaria angustifolia forests, and to learn whether it is possible to discriminate between the AMF communities associated with natural, introduced, and impacted-byanthropogenic-action ecosystems. Three ecosystems representative of the Campos do Jordão (São Paulo State, Brazil) region were selected, as follows: (i) a native climax forest, with predominance of Araucaria trees, without anthropogenic interference (NF), (ii) Araucaria forest introduced in 1959 (RE), and (iii) Araucaria forest introduced in 1958, submitted to accidental fire in July 2001 (RF). Sampling of rhizosphere soil was performed at a 0-20 cm depth around each Araucaria tree, and 2 m from the trunk, in the months of May and October, 2002. AMF spores were separated from the soil, counted, and taxonomically identified, while the roots were evaluated for mycorrhizal colonization. The ecological indices R (Richness), Is (Simpson's dominance index) and H (Shannon's diversity index) were calculated. All the data were submitted to univariate (two-way ANOVA) and correspondence analysis (CA). Considering both samplings and the three areas, twenty-six AMF species were found, distributed among five genera, Acaulospora and Glomus being the most frequent ones. There were no differences among the three areas for R, Is, and H. CA demonstrated that there is a spatial separation among the three areas, and the AMF that preferentially associated with each area.
Resumo -Objetivou-se avaliar a interação entre fungos micorrízicos arbusculares nativos (FMA) com plantas de amendoim (Arachis hypogea) cultivar RUNNER IAC 886, em diferentes doses de fósforo (P). O experimento foi conduzido em casa de vegetação em delineamento inteiramente casualizado, em esquema fatorial (2 x 5), sendo com e sem a inoculação dos endófitos e cinco doses de P (0; 20; 40; 60 e 180 mg kg -1 na forma de KH 2 PO 4 ), com quatro repetições. Avaliaram-se massa seca de: raiz, parte aérea, total, taxa de colonização radicular (CR), dependência micorrízica (DM) e eficiência micorrízica (EM). Concluiuse que as doses crescentes de adubação fosfatada promoveram aumento no desenvolvimento das plantas de amendoim. Os FMA promoveram a produção máxima de massa seca total do amendoim na dose estimada de 114,0 mg kg -1 de P. A maior colonização radicular e eficiência micorrízica foram verificadas na dose 60 mg kg -1 de P. Palavras-chave -Amendoim. Adubação. Fertilizantes fosfatados. Fungos micorrízicos arbusculares.Abstract -The objective was to evaluate the interaction between native arbuscular mycorrhizal fungi (AMF) with peanut plants (Arachis hypogea) RUNNER cultivar IAC 886, at different levels of phosphorus (P). The experiment was conducted in a greenhouse in a randomized design in factorial (2 x 5), with and without inoculation of AMF and five P levels (0; 20; 40; 60 and 180 mg kg -1 in the form of KH 2 PO 4 ) in four replications. Shoot, root and total dry mass, root colonization, mycorrhizal dependency and mycorrhizal efficiency were evaluated. It was concluded that increasing levels of phosphorus caused an increase in the development of peanut plants. The AMF promoted maximum production of total dry mass of the peanut in estimated dose of 114.0 mg kg -1 of P. The highest root colonization and mycorrhizal efficiency were observed at 60 mg kg -1 of P.
RESUMOCom o objetivo de avaliar o efeito de doses crescentes de fósforo sobre a diversidade, esporulação e colonização de fungos micorrízicos arbusculares (FMA) nativos de florestas de Araucaria angustifolia, foi conduzido um experimento em casa de vegetação, utilizando a araucária como planta-isca. O experimento foi montado em delineamento inteiramente casualizado, com cinco repetições, compreendendo quatro doses de fósforo (0, 20, 50 e 150 mg kg -1 ) de substrato na forma de KH 2 PO 4 . As plântulas de araucária, inoculadas com 100 g de solo rizosférico, proveniente de mata nativa, foram cultivadas em vasos contendo 10 kg de solo, pelo período de um ano. Após a colheita, determinou-se a densidade de esporos, a taxa de colonização micorrízica e a diversidade de FMA, através da identificação morfológica dos esporos. Os dados foram submetidos à análise univariada e análise de correspondência (AC). Considerando as quatro doses de P, foram identificadas 11 espécies de FMA (Acaulospora bireticulata, Acaulospora morrowiae, Acaulospora sp., Entrophospora colombiana, Gigaspora margarita, Glomus diaphanum, Glomus etunicatum, Glomus macrocarpum, Scutellospora calospora, Scutellospora gilmorei e Scutellospora pellucida). Não houve efeito significativo da dose de P sobre o número de esporos e a colonização radicular. A AC demonstrou que houve efeito da dose de P sobre a abundância de esporulação de cada espécie, sendo que alguns FMA se associaram mais com determinada dose de P, e outros com outra. Palavras-chave: FMA; diversidade; densidade de esporos; pinheiro brasileiro. ABSTRACTA greenhouse experiment was installed with bait cultures to extract the AMF species present in a rhizosphere soil sample of a native Araucaria angustifolia forest in Campos do Jordão, Brazil. The experimental design was completely randomized, with four increasing phosphorus doses (0, 20, 50, and 150 mg kg -1 , as triple superphosphate), with five replicates, the bait plant was araucaria, and all pots were inoculated with 100 g of rhizospheric soil collected in an araucaria forest. After twelve months the spores were extracted, counted and identified, and the percent root colonization was also determined. When taking all four P doses into account, eleven AMF species could be identified: Acaulospora bireticulata, Acaulospora morrowiae, Acaulospora sp., Entrophospora colombiana, Gigaspora margarita, Glomus diaphanum, Glomus etunicatum, Glomus macrocarpum, Scutellospora calospora, Scutellospora gilmorei, and Scutellospora pellucida. There was no effect of the P dose on the total amount of spores neither on the percent root colonization. However, the correspondence analysis showed that the different AMF species were selectively associated mostly to either one or another P dose.
The occurrence of rhizobial communities at four sites under natural vegetation and one site under pasture were examined. Isolates of rhizobia originating from crotalaria (C. junceae), common bean (Phaseolus vulgaris) and pigeon pea (Cajanus cajan) were studied in relation to population density, host specificity and the interaction between rhizobial occurrence, climatic conditions and soil properties. pH values and potential acidity were the soil properties that most affected rhizobial occurrence. Rhizobia from crotalaria and common bean were evaluated at four sites, and from pigeon pea, at five sites. Common bean was the most specific legume, followed by peanuts, crotalaria and pigeon pea. Key words: Rhizobium, Bradyrhizobium, crotalaria, pigeon pea, common bean OCORRÊNCIA DE RIZÓBIOS NATIVOS EM PLANTAS HOSPEDEIRAS DE SOLOS DO ESTADO DE SÃO PAULO, BRASILRESUMO: Foi examinada a ocorrência de comunidades de rizóbios em quatro locais de vegetação natural e um local de pastagem. Isolados de rizóbio originados de crotalária (C. junceae), feijão (Phaseolus vulgaris) e guandu (Cajanus cajan) foram estudados em relação à densidade populacional, planta hospedeira e interação entre ocorrência de rizóbio, condições climáticas e propriedades do solo. Os valores de pH e potencial de acidez foram as propriedades do solo que mais contribuíram para a ocorrência de rizóbio. A ocorrência de rizóbio em crotalária e feijão foi estudada em quatro locais, e em guandu em cinco locais. O feijão foi mais específico, seguido por crotalária e guandu. Palavras-chave: Rhizobium, Bradyrhizobium, crotalária, guandu e feijão
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