RESUMO
This study explored the composition of the mycobiome in the rhizosphere of Inga seedlings in two different but neighboring forest ecosystems in the undisturbed tropical Amazon rainforest at the Tiputini Biodiversity Station in Ecuador. In terra firme plots, which were situated higher up and therefore typically outside of the influence of river floods, and in várzea plots, the lower part of the forest located near the riverbanks and therefore seasonally flooded, tree seedlings of the genus Inga were randomly collected and measured, and the rhizosphere soils surrounding the root systems was collected. Members of the Fabaceae family and the genus Inga were highly abundant in both forest ecosystems. Inga sp. seedlings collected in terra firme showed a lower shoot to root ratio compared to seedlings that were collected in várzea, suggesting that Inga seedlings which germinated in várzea soils could invest more resources in vegetative growth with shorter roots. Results of the physical-chemical properties of soil samples indicated higher proportions of N, Mo, and V in terra firme soils, whereas várzea soils present higher concentrations of all other macro- and micronutrients, which confirmed the nutrient deposition effect of seasonal flooding by the nearby river. ITS metabarcoding was used to explore the mycobiome associated with roots of the genus Inga. Bioinformatic analysis was performed using Qiime 2 to calculate the alpha and beta diversity, species taxonomy and the differential abundance of fungi and arbuscular mycorrhizal fungi. The fungal community represented 75% of the total ITS ASVs, and although present in all samples, the subphylum Glomeromycotina represented 1.42% of all ITS ASVs with annotations to 13 distinct families, including Glomeraceae (72,23%), Gigasporaceae (0,57%), Acaulosporaceae (0,49%). AMF spores of these three AMF families were morphologically identified by microscopy. Results of this study indicate that AMF surround the rhizosphere of Inga seedlings in relatively low proportions compared to other fungal groups but present in both terra firme and várzea Neotropical ecosystems.
RESUMO
The biogeographic region of Argentinean Puna mainly extends at elevations higher than 3,000 m within the Andean Plateau and hosts diverse ecological communities highly adapted to extreme aridity and low temperatures. Soils of Puna are typically poorly evolved and geomorphology is shaped by drainage networks, resulting in highly vegetated endorheic basins and hypersaline basins known as salar or salt flats. Local communities rely on soil fertility for agricultural practices and on pastures for livestock rearing. From this perspective, investigating the scarcely explored microbiological diversity of these soils as indicators of ecosystems functioning might help to predict the fragility of these harsh environments. In this study we collected soil samples from 28 points, following a nested design within three different macro-habitats, i.e., Puna grassland, hypersaline salar and family-run crop fields. Total fungi and arbuscular mycorrhizal fungi (AMF) occurrence were analyzed using eDNA sequencing. In addition, the significance of soil salinity and organic matter content as significant predictors of AMF occurrence, was assessed through Generalized Linear Mixed Modeling. We also investigated whether intensive grazing by cattle and lama in Puna grasslands may reduce the presence of AMF in these highly disturbed soils, driving or not major ecological changes, but no consistent results were found, suggesting that more specific experiments and further investigations may address the question more specifically. Finally, to predict the suitability for AMF in the different macro-habitats, Species Distribution Modeling (SDM) was performed within an environmental coherent area comprising both the phytogeographic regions of Puna and Altoandino. We modeled AMF distribution with a maximum entropy approach, including bioclimatic and edaphic predictors and obtaining maps of environmental suitability for AMF within the predicted areas. To assess the impact of farming on AMF occurrence, we set a new series of models excluding the cultivated Chaupi Rodeo samples. Overall, SDM predicted a lower suitability for AMF in hypersaline salar areas, while grassland habitats and a wider temperature seasonality range appear to be factors significantly related to AMF enrichment, suggesting a main role of seasonal dynamics in shaping AMF communities. The highest abundance of AMF was observed in Vicia faba crop fields, while potato fields yielded a very low AMF occurrence. The models excluding the cultivated Chaupi Rodeo samples highlighted that if these cultivated areas had theoretically remained unmanaged habitats of Puna and Altoandino, then large-scale soil features and local bioclimatic constraints would likely support a lower suitability for AMF. Using SDM we evidenced the influence of bioclimatic, edaphic and anthropic predictors in shaping AMF occurrence and highlighted the relevance of considering human activities to accurately predict AMF distribution.
Assuntos
Micorrizas , Humanos , Animais , Bovinos , Micorrizas/genética , Solo , Ecossistema , Entropia , Agricultura/métodosRESUMO
Many plant species simultaneously interact with multiple symbionts, which can, but do not always, generate synergistic benefits for their host. We ask if plant life history (i.e. annual vs perennial) can play an important role in the outcomes of the tripartite symbiosis of legumes, arbuscular mycorrhizal fungi (AMF), and rhizobia. We performed a meta-analysis of 88 studies examining outcomes of legume-AMF-rhizobia interactions on plant and microbial growth. Perennial legumes associating with AMF and rhizobia grew larger than expected based on their response to either symbiont alone (i.e. their response to co-inoculation was synergistic). By contrast, annual legume growth with co-inoculation did not differ from additive expectations. AMF and rhizobia differentially increased phosphorus (P) and nitrogen (N) tissue concentration. Rhizobium nodulation increased with mycorrhizal fungi inoculation, but mycorrhizal fungi colonization did not increase with rhizobium inoculation. Microbial responses to co-infection were significantly correlated with synergisms in plant growth. Our work supports a balanced plant stoichiometry mechanism for synergistic benefits. We find that synergisms are in part driven by reinvestment in complementary symbionts, and that time-lags in realizing benefits of reinvestment may limit synergisms in annuals. Optimization of microbiome composition to maximize synergisms may be critical to productivity, particularly for perennial legumes.
Assuntos
Fabaceae , Micorrizas , Rhizobium , Fósforo , Raízes de Plantas , SimbioseRESUMO
Breeding selection of germplasm under fertilized conditions may reduce the frequency of genes that promote mycorrhizal associations. This study was developed to compare variability in mycorrhizal colonization and its effect on mycorrhizal dependency (MD) in improved soybean genotypes (I-1 and I-2) with differential tolerance to drought stress, and in unimproved soybean genotypes (UI-3 and UI-4). As inoculum, a mixed native arbuscular mycorrhizal fungi (AMF) was isolated from soybean roots, showing spores mostly of the species Funneliformis mosseae. At 20 days, unimproved genotypes followed by I-2, showed an increase in arbuscule formation, but not in I-1. At 40 days, mycorrhizal plants showed an increase in nodulation, this effect being more evident in unimproved genotypes. Mycorrhizal dependency, evaluated as growth and biochemical parameters from oxidative stress was increased in unimproved and I-2 since 20 days, whereas in I-1, MD increased at 40 days. We cannot distinguish significant differences in AMF colonization and MD between unimproved and I-2. However, variability among improved genotypes was observed. Our results suggest that selection for improved soybean genotypes with good and rapid AMF colonization, particularly high arbuscule/hyphae ratio could be a useful strategy for the development of genotypes that optimize AMF contribution to cropping systems.
Assuntos
Glomeromycota/fisiologia , Glycine max/microbiologia , Micorrizas/fisiologia , Simbiose , Secas , Genótipo , Glomeromycota/crescimento & desenvolvimento , Micorrizas/crescimento & desenvolvimento , Estresse Oxidativo , Nodulação , Raízes de Plantas/microbiologia , Raízes de Plantas/fisiologia , Seleção Genética , Glycine max/genética , Glycine max/fisiologia , Estresse FisiológicoRESUMO
Aluminum (Al) toxicity is one of the greatest limitations to agriculture in acid soils, particularly in tropical regions. Arbuscular mycorrhizal fungi (AMF) can supply plants with nutrients and give protection against Al toxicity. The aim of this work was to evaluate the effects of soil liming (i.e., reducing Al saturation) on the AMF community composition and structure in the roots of maize lines contrasting for Al tolerance. To this end, we constructed four 18S rDNA cloning libraries from L3 (Al tolerant) and L22 (Al sensitive) maize lines grown in limed and non-limed soils. A total of 790 clones were sequenced, 69% belonging to the Glomeromycota phylum. The remaining sequences were from Ascomycota, which were more prominent in the limed soil, mainly in the L3 line. The most abundant AM fungal clones were related to the family Glomeraceae represented by the genera uncultured Glomus followed by Rhizophagus and Funneliformis. However, the most abundant operational taxonomic units with 27% of the Glomeromycota clones was affiliated to genus Racocetra. This genus was present in all the four libraries, but it was predominant in the non-limed soils, suggesting that Racocetra is tolerant to Al toxicity. Similarly, Acaulospora and Rhizophagus were also present mostly in both lines in non-limed soils. The community richness of AMF in the non-limed soils was higher than the limed soil for both lines. The results suggest that the soil Al saturation was the parameter that mostly influences the AMF species composition in the soils in this study.
Assuntos
Alumínio/metabolismo , Biota , Micorrizas/classificação , Micorrizas/isolamento & purificação , Raízes de Plantas/microbiologia , Poluentes do Solo/metabolismo , Zea mays/microbiologia , Alumínio/toxicidade , Ascomicetos/classificação , Ascomicetos/genética , Ascomicetos/isolamento & purificação , Brasil , Análise por Conglomerados , DNA Fúngico/química , DNA Fúngico/genética , DNA Ribossômico/química , DNA Ribossômico/genética , Glomeromycota/classificação , Glomeromycota/genética , Glomeromycota/isolamento & purificação , Dados de Sequência Molecular , Micorrizas/genética , Filogenia , RNA Ribossômico 18S/genética , Análise de Sequência de DNA , Poluentes do Solo/toxicidadeRESUMO
Objetivo. Obtener un sistema de micorrización in vitro en sistemas de cultivo autotrófico para plantas de mora de castilla (Rubusglaucus, Benth). Materiales y métodos. Se utilizaron esporas y fragmentos de raíces con vesículas del Hongo Formador de MicorrizaArbuscular (HFMA) Glomus sp. (GEV02). Se estableció un sistema de cultivo autotrófico para plántulas de mora, comparando dosmétodos de inoculación directa con el HFMA. Se cuantificó el número de esporas producidas, la longitud del micelio extraradical; asícomo el porcentaje de colonización del HFMA. Adicionalmente se midió la longitud aérea y radical, el peso fresco y seco de la partefoliar y radical para determinar el desarrollo de las plantas. Resultados. El sistema de cultivo autotrófico fue exitoso para plantas demora de castilla (Rubus glaucus, Benth); observándose un óptimo crecimiento de la parte aérea y radical de la planta. Adicionalmenteen este estudio se pudo obtener un sistema que permitió el desarrollo de Glomus sp (GEV02) bajo condiciones in vitro, con formaciónde estructuras típicas de la simbiosis como una buena colonización intraradical, con producción de arbúsculos y vesículas, así comoel desarrollo de micelio extraradical con hifas ramificadas y la formación de nuevas esporas. Conclusión. Las plantas de moramicropropagadas se asociaron con éxito, por primera vez, con un hongo formador de micorriza arbuscular bajo condiciones in vitro,permitiendo el desarrollo del sistema simbiótico HFMA Glomus sp., asociado a las raíces de plántulas de mora castilla micropropagadas...
Objective. Obtain an in vitromycorrhization system in autotrophic culture systems of blackberry plants (Rubus glaucus, Benth). Materials and methods. We usedspores and root fragments with vesicles of Arbuscular Mycorrhizal Fungus (AMF) Glomus sp (GEV02). We established an autotrophicculture system of blackberry plantlets comparing two methods of direct inoculation of the AMF. We measured the number of sporesproduced, the length of the extraradical mycelium as well as the percentage of colonization of the AMF. Additionally, we measuredthe shoot and root length, and the fresh and dry weight of the leaf and root parts to determine the plant development. Results. Theautotrophic culture system was successful for blackberry plants (Rubus glaucus, Benth; an optimal shoot and root growth was observed.Additionally, we obtained a system that allowed the development of Glomus sp. in in vitro conditions, with the formation of structurestypical of the symbiosis as well as a good intraradical colonization, with the production of arbuscules and vesicles, development ofextraradical mycelium with branched hyphae, and formation of new spores. Conclusion. For the first time, micropropagated blackberryplants associated successfully with an AMF under in vitro conditions, enabling the development of the symbiotic system AMF Glomussp. associated to roots of micropropagated blackberry plantlets...
Objetivo. Obter umsistema de micorrização in vitro em sistemas de cultura autotróficos para plantas de amora-preta (Rubus glaucus, Benth). Materiais emétodos. Foram usados esporos e fragmentos de raízes com vesículas do Fungo Formador Micorrízico Arbuscular (FFMA) Glomus sp.(GEV02). Foi estabelecido um sistema de cultivo autotrófico para mudas de amora-preta, comparando dois métodos de inoculação diretacom o FFMA. Foi quantificado o número de esporos produzidos, o comprimento do micélio extra radicular; bem como a porcentagemde colonização do FFMA. Além disso, foi medido o comprimento e o peso fresco e seco da parte folhar e radicular para determinar odesenvolvimento das plantas. Resultados. O sistema de cultivo autotrófico foi bem-sucedido para as plantas de amora-preta (Rubusglaucus, Benth), onde foi observado um crescimento ótimo da parte aérea e da raidicular da planta. Além disso, neste estudo foi obtido umsistema que permitiu o desenvolvimento de Glomus sp (GEV02) sob condições in vitro, com formação de estruturas típicas da simbiosecomo uma boa colonização intra radicular, com produção de arbúsculos e vesículas, assim como o desenvolvimento de micélio extraradicular com hifas ramificada e a formação de novos esporos. Conclusão. As plantas de amora-preta micropropagadas associaram-secom sucesso, pela primeira vez, com um fungo formador micorrízico arbuscular em condições in vitro, permitindo o desenvolvimentodo sistema simbiótico FFMA Glomus sp., associado às raízes das plântulas de amora-preta micropropagadas...
Assuntos
Fungos/crescimento & desenvolvimento , Micorrizas/crescimento & desenvolvimento , Micorrizas/genéticaRESUMO
El establecimiento de la simbiosis planta-hongos formadores de micorrizas Arbusculares (HFMA) requiere procesos armónicos a nivel espacio-temporal, que dependen de señales para el reconocimiento, colonización e intercambio bidireccional de nutrientes. Las plantas presentan respuestas de defensa frente a posibles organismos invasores; sin embargo, frente a HFMA estas son débiles, localizadas y no impiden la colonización del hongo. Los beneficios de la simbiosis generalmente se asocian a nutrición vegetal, aunque, también está relacionada con el incremento de la tolerancia-resistencia de plantas a los estreses bióticos. La resistencia inducida HFMA (MIR) es importante en el control de patógenos foliares, comedores de hojas y necrótrofos, encontrándose protección de plantas micorrizadas tanto a nivel local como sistémico, relacionada con los niveles de ácido jasmónico en tejidos. Un mecanismo en la MIR está asociado con el priming, que permite una rápida y eficiente respuesta de defensa de plantas micorrizadas. Se han planteado posibles mecanismos de atenuación de las respuestas de defensa, considerando: activación de supresores de defensa; plantas que producen respuestas de defensa frente a HFMA y otras que no las producen, y plantas que suprimen las respuestas de defensa en la simbiosis. Aunque el control de la simbiosisestá regulado básicamente por la planta, aún se desconoce el papel de los HFMA en el debilitamiento de las respuestas de defensa. Recientemente, se ha dado un avance importante en entender los mecanismos mediante los cuales se establece y mantiene la biotrofía del hongo, al describirse la proteína SP7 que interactúa con el factor de transcripción PR, ERF19 en el núcleo de la célula vegetal. Se ha sugerido que SP7 es un efector que actúa oponiéndose al programa de inmunidad de la planta.
Harmonic processes between plant and arbuscular mycorrhyzal fungi (AMF) are required for the symbiosis formation between the two organisms. These processes depend on specific signalling for the plant-fungus recognition, colonisation and bidirectional nutrient exchange. Plants show defence responses against invasive organisms, however they react weakly and localised when challenged by AMF. The benefits derived from the mycorrization are described for the nutritional aspect; however, it is known that mycorrhized plants are more tolerant to biotic stresses. Mycorrhizal induced resistance (MIR) is especially important for the control of foliar pathogens, leaf cutters and necrotrophs. There has also been found that mycorrhizal plants are protected both locally and systemically and their protection is related with jasmonic acid levels at their tissues. One of the most important mechanisms for MIR is the so called priming that allows plants to exert a fast and efficient defence response. Possible mechanisms to unravel mycorrhizal plants lower defence systems include: defence suppressor activation, differential plants response towards AMF from inexistent to low, and plant defence response suppression during the AMF symbiosis. The symbiosis control is known to be regulated by the plant, however, no role has been assigned to the AMF for the weakening of the plant defence system. Recently, a big step towards understanding of the fungal role has been made. A protein SP7 that interacts with a PR transcription factor ERF19, in the plant nucleus, has been described. This discovery indicates a possible mechanism to establish and maintain the biotrophic status of the AMF counteracting the immune plant system.
Assuntos
Fungos , Micorrizas , Simbiose , Plantas , Fatores de ProteçãoRESUMO
A green house study was conducted to investigate the ability of an isolate of Trichoderma harzianum (P52) and arbuscular mycorrhizal fungi (AMF) in enhancing growth and control of a wilt pathogen caused by Fusarium oxysporum f. sp. lycopersici in tomato seedlings. The plants were grown in plastic pots filled with sterilized soils. There were four treatments applied as follows; P52, AMF, AMF + P52 and a control. A completely randomized design was used and growth measurements and disease assessment taken after 3, 6 and 9 weeks. Treatments that significantly (P < 0.05) enhanced heights and root dry weights were P52, AMF and a treatment with a combination of both P52 and AMF when compared the control. The treatment with both P52 and AMF significantly (P < 0.05) enhanced all growth parameters (heights; shoot and root dry weight) investigated compared to the control. Disease severity was generally lower in tomato plants grown with isolate P52 and AMF fungi either individually or when combined together, though the effect was not statistically significant (P0.05). A treatment combination of P52 + AMF had less trend of severity as compared to each individual fungus. T. harzianum and AMF can be used to enhance growth in tomato seedlings.
RESUMO
A green house study was conducted to investigate the ability of an isolate of Trichoderma harzianum (P52) and arbuscular mycorrhizal fungi (AMF) in enhancing growth and control of a wilt pathogen caused by Fusarium oxysporum f. sp. lycopersici in tomato seedlings. The plants were grown in plastic pots filled with sterilized soils. There were four treatments applied as follows; P52, AMF, AMF + P52 and a control. A completely randomized design was used and growth measurements and disease assessment taken after 3, 6 and 9 weeks. Treatments that significantly (P < 0.05) enhanced heights and root dry weights were P52, AMF and a treatment with a combination of both P52 and AMF when compared the control. The treatment with both P52 and AMF significantly (P < 0.05) enhanced all growth parameters (heights; shoot and root dry weight) investigated compared to the control. Disease severity was generally lower in tomato plants grown with isolate P52 and AMF fungi either individually or when combined together, though the effect was not statistically significant (P≥ 0.05). A treatment combination of P52 + AMF had less trend of severity as compared to each individual fungus. T. harzianum and AMF can be used to enhance growth in tomato seedlings.
RESUMO
A green house study was conducted to investigate the ability of an isolate of Trichoderma harzianum (P52) and arbuscular mycorrhizal fungi (AMF) in enhancing growth and control of a wilt pathogen caused by Fusarium oxysporum f. sp. lycopersici in tomato seedlings. The plants were grown in plastic pots filled with sterilized soils. There were four treatments applied as follows; P52, AMF, AMF + P52 and a control. A completely randomized design was used and growth measurements and disease assessment taken after 3, 6 and 9 weeks. Treatments that significantly (P 0.05) enhanced heights and root dry weights were P52, AMF and a treatment with a combination of both P52 and AMF when compared the control. The treatment with both P52 and AMF significantly (P 0.05) enhanced all growth parameters (heights; shoot and root dry weight) investigated compared to the control. Disease severity was generally lower in tomato plants grown with isolate P52 and AMF fungi either individually or when combined together, though the effect was not statistically significant (P0.05). A treatment combination of P52 + AMF had less trend of severity as compared to each individual fungus. T. harzianum and AMF can be used to enhance growth in tomato seedlings.
RESUMO
Plant cover loss due to changes in land use promotes a decrease in spore diversity of arbuscular mycorrhizal fungi (AMF), viable mycelium and, therefore, in AMF colonization, this has an influence in community diversity and, as a consequence, in its recovery. To evaluate different AMF propagules, nine plots in a tropical dry forest with secondary vegetation were selected: 0, 1, 7, 10, 14, 18, 22, 25, and 27 years after abandonment in Nizanda, Oaxaca, Mexico. The secondary vegetation with different stages of development is a consequence of slash and burn agriculture, and posterior abandonment. Soil samples (six per plot) were collected and percentage of AMF field colonization, extrarradical mycelium, viable spore density, infectivity and most probable number (MPN) ofAMF propagules were quantified through a bioassay. Means for field colonization ranged between 40% and 70%, mean of total mycelium length was 15.7 +/- 1.88 mg(-1) dry soil, with significant differences between plots; however, more than 40% of extracted mycelium was not viable, between 60 and 456 spores in 100 g of dry soil were recorded, but more than 64% showed some kind of damage. Infectivity values fluctuated between 20% and 50%, while MPN showed a mean value of 85.42 +/- 44.17 propagules (100 g dry soil). We conclude that secondary communities generated by elimination of vegetation with agricultural purposes in a dry forest in Nizanda do not show elimination of propagules, probably as a consequence of the low input agriculture practices in this area, which may encourage natural regeneration.
La vegetación secundaria con diferentes grados de desarrollo es consecuencia de prácticas agrícolas de rozatumba- quema y su posterior abandono. La remoción de la vegetación por cambios de uso de suelo promueve una disminución en la diversidad de esporas, micelio viable y por lo tanto de la colonización de los hongos micorrizógenos arbusculares (HMA), lo cual repercute en la diversidad de la comunidad y como consecuencia en su regeneración. Para evaluar los propágulos de HMA se seleccionaron nueve parcelas con vegetación secundaria con diferentes edades de abandono: 0, 1, 7, 10, 14, 18, 22, 25, 27 años, en la región de Nizanda, Oaxaca, México. Se recolectaron muestras de suelo (seis por parcela) y se cuantificó la colonización de campo, el micelio extrarradical, la densidad de esporas viables, así como la infectividad y el número más probable de propágulos infectivos (NMP). Los promedios de la colonización de campo fueron de 40 a 70 %, el promedio de la longitud de micelio total alcanzó 15.7 ± 1.88 mg-1 suelo seco con diferencias significativas entre parcelas, pero más del 40 % del micelio extraído no fue viable. Se encontraron entre 60 y 456 esporas en 100 g de suelo pero más del 64 % presentaron algún tipo de daño. Los valores de infectividad se encontraron entre 20 % y 50 %, mientras que el NMP presentó un promedio de 85.42 ±44.17 (100 g de suelo seco). Concluimos que las comunidades secundarias generadas por la eliminación de la vegetación con fines agrícolas en la selva baja caducifolia en Nizanda o presentan eliminación de propágulos, probablemente por el bajo impacto de la agricultura, lo cual indica que la regeneración natural es posible.
Assuntos
Esporos Fúngicos/crescimento & desenvolvimento , Microbiologia do Solo , Micélio/crescimento & desenvolvimento , Micorrizas/crescimento & desenvolvimento , Árvores/microbiologia , Clima Tropical , Contagem de Colônia Microbiana , Fatores de Tempo , MéxicoRESUMO
Mycorrhizal colonization was assessed in roots of trees within an Atlantic Forest chronosequence, located in the southeastern of São Paulo State, Brazil, inside Tourist State Park of the High Ribeira Valley (PETAR). The phytosociological survey was carried out in three adjacent areas, all on calcareous soil, which correspond to different time intervals during which they have been left abandoned following a slash-and-burn agricultural perturbation. Early Phase (EP) with 15 years; Mid Phase (MP) with 25 years; and Late Phase (LP) with more than 36 years without clear-cut. The inventory indicated a continuum of tree species substitution, which is dominated by species of Leguminosae, especially Piptadenia gonoacantha (Mart.) J.F. Macbr. (Mimosoideae) in the earlier successional phases. Mycorrhizal colonization, estimated by the occurrence of the mycorrhizal structures in the tree species roots, diminished during the season with less rain (winter), and showed no significant differences between successional phases in the wet season (summer). Rather, the mycorrhizal colonization was correlated with occurrence of the trees successional status: being positively correlated with occurrence of pioneer species, and negatively correlated with late secondary species. Mycorrhizal colonization was also correlated negatively with soil organic matter and base saturation. Twenty five species of arbuscular mycorrhizal fungi belonging to four genera were identified. Six species were only identified to generic level. The species Glomus etunicatum Becker & Gerd. represented 10% of the total number of spores and occurred in all phases and seasons, while the genus Glomus represented 57% of the total of spores found in the rhizosphere. The diversity indices evaluated for the mycohrriza community were: H = 2.3, J = 0.97 and R = 4.12. These results are a contribution to the knowledge of The Atlantic Forest biodiversity and may have implications to support programs regarding rehabilitation of degraded vegetation in one of the Worlds most threatened Biomes.
Foi levantada a ocorrência de colonização por micorriza nas raízes das espécies arbóreas que dirigem a sucessão secundária sobre solo calcário em uma área localizada no Parque Estadual Turístico do Alto Ribeira (PETAR), sudeste do Estado de São Paulo, Brasil. O levantamento fitossociológico foi realizado em três áreas justapostas correspondentes a diferentes idades de abandono após cultivo de subsistência sobre um solo calcário: Fase Inicial com 15 anos; Fase Intermediaria com 25 anos e Fase Tardia com mais de 36 anos sem corte raso. O inventário indicou a predominância de espécies da família das leguminosas, especialmente Piptadenia gonoacantha (Mimosoideae) nos estágios iniciais de sucessão. A ocorrência de colonização por micorriza nas raízes das espécies arbóreas decresceu ao longo da sucessão durante a estação com menos chuva (inverno). Durante o período de verão, estação mais úmida, a colonização não apresentou diferenças significativas entre as fases de sucessão. A colonização por micorriza nas raízes apresentou correlação com a ocorrência de diferentes estratégias de regeneração entre as espécies arbóreas: positivamente com o aumento de ocorrência de espécies pioneiras e negativamente com espécies secundárias tardias. A colonização apresentou também correlação negativa com o conteúdo de matéria orgânica e saturação de bases no solo. Foram identificadas 25 espécies de fungos micorrizicos arbusculares pertencentes a quatro gêneros, e seis espécies apenas foram identificadas ao nível de gênero. A espécie Glomus etunicatum Becker & Gerd. representou 10 % dos esporos encontrados na rizosfera das amostras analisadas, tendo ocorrido em todas as fases sucessionais e estações. O gênero Glomus representou 57% do total de esporos. Os índices de diversidade para a comunidade de fungos micorrizicos indicaram os seguintes valores: H = 2.3, J = 0.97 e R = 4.12. Estes resultados são importantes contribuições para um melhor conhecimento da biodiversidade da Mata Atlântica e podem ser decisivos no sucesso de ações para a reabilitação de áreas degradadas neste que é um dos biomas mais ameaçados do planeta.