Rosilaine Carrenho

Root colonization and spore abundance of arbuscular mycorrhizal fungi in distinct successional stages from an Atlantic rainforest biome in southern Brazil

The influence of plant functional groups and moderate seasonality on arbuscular mycorrhizal (AM) fungal status (root colonization and spore density) was investigated during 13 consecutive months in a chronosequence of succession in southern Brazil, consisting of grassland field, scrub vegetation, secondary forest and mature forest, in a region of transition from tropical to subtropical zones. AM root colonization and spore density decreased with advancing succession and were highest in early successional sites with grassland and scrub vegetation, intermediary in the secondary forest and lowest in the mature forest. They were little influenced by soil properties, but were sufficiently influenced by the fine root nutrient status and fine root traits among different functional plant groups. AM root colonization and spore density were higher during the favourable plant growth season (spring and summer) than during the less favourable plant growth season (autumn and winter). Spore density displayed significant seasonal variation at all sites, whilst root colonization displayed significant seasonal variation in grassland, scrub and secondary forest, but not in mature forest. The data suggest that (1) different plant functional groups display different relationships with AM fungi, influencing their abundance differentially; (2) plant species from early successional phases are more susceptible to AM root colonization and maintain higher AM sporulation than late successional species; (3) fine root traits and nutrient status influence these AM fungal attributes; and (4) higher AM spore production and root colonization is associated with the season of higher light incidence and temperature, abundant water in soil and higher plant metabolic activity.

The effect of different soil properties on arbuscular mycorrhizal colonization of peanuts, sorghum and maize

ABSTRACT – (The effect of different soil properties on arbuscular mycorrhizal colonization of peanuts, sorghum and maize).Arbuscular mycorrhizal fungi (AMF) are important for plant growth since they increase mineral influx. However, symbiosis efficiencyis affected by many environmental factors. This study evaluated the effects of different treatments (+/- phosphorus; +/- liming; +/-organic matter; field, sandy or clayey soil textures) on root colonization (RC) of peanuts, sorghum and maize. The combination of theseresulted in seventy-two treatments. The 2×2×2×3×3 factorial experiment was laid out in a randomized design. All data were subjectedto variance analysis and the means were compared (Tukey at P≤0.05). Three months after seed germination, roots were collected toevaluate the percentage of RC. Results showed that soil texture and liming were the most important factors influencing colonizationpercentage in maize, sor ghum and peanuts by AMF. Significant dif ferences were also observed between the phytobionts. Or ganic matter(OM) had very little influence and phosphorus addition had no effect on RC.

Aspects of arbuscular mycorrhizal fungi in an atlantic forest chronosequence parque estadual turístico do Alto Ribeira (petar), SP

Foi levantada a ocorrencia de colonizacao por micorriza nas raizes das especies arboreas que dirigem a sucessao secundaria sobre solo calcario em uma area localizada no Parque Estadual Turistico do Alto Ribeira (PETAR), sudeste do Estado de Sao Paulo, Brasil. O levantamento fitossociologico foi realizado em tres areas justapostas correspondentes a diferentes idades de abandono apos cultivo de subsistencia sobre um solo calcario: Fase Inicial com 15 anos; Fase Intermediaria com 25 anos e Fase Tardia com mais de 36 anos sem corte raso. O inventario indicou a predominância de especies da familia das leguminosas, especialmente Piptadenia gonoacantha (Mimosoideae) nos estagios iniciais de sucessao. A ocorrencia de colonizacao por micorriza nas raizes das especies arboreas decresceu ao longo da sucessao durante a estacao com menos chuva (inverno). Durante o periodo de verao, estacao mais umida, a colonizacao nao apresentou diferencas significativas entre as fases de sucessao. A colonizacao por micorriza nas raizes apresentou correlacao com a ocorrencia de diferentes estrategias de regeneracao entre as especies arboreas: positivamente com o aumento de ocorrencia de especies pioneiras e negativamente com especies secundarias tardias. A colonizacao apresentou tambem correlacao negativa com o conteudo de materia orgânica e saturacao de bases no solo. Foram identificadas 25 especies de fungos micorrizicos arbusculares pertencentes a quatro generos, e seis especies apenas foram identificadas ao nivel de genero. A especie Glomus etunicatum Becker & Gerd. representou 10 % dos esporos encontrados na rizosfera das amostras analisadas, tendo ocorrido em todas as fases sucessionais e estacoes. O genero Glomus representou 57% do total de esporos. Os indices de diversidade para a comunidade de fungos micorrizicos indicaram os seguintes valores: H’ = 2.3, J’ = 0.97 e R = 4.12. Estes resultados sao importantes contribuicoes para um melhor conhecimento da biodiversidade da Mata Atlântica e podem ser decisivos no sucesso de acoes para a reabilitacao de areas degradadas neste que e um dos biomas mais ameacados do planeta.

Fungos micorrízicos arbusculares em rizosferas de três espécies de fitobiontes instaladas em área de mata ciliar revegetada

To evaluate the specific composition of arbuscular mycorrhizal fungi (AMF) established in recomposed areas of gallery forest, samples of rhizospheric soil were collected from Croton urucurana Baill., Inga striata Willd. and Genipa americana L. These plants are indigenous in gallery forests, being the first considered as pioneer, the second as early secondary and G. americana as climax, according to the successional stages. Twenty-two species of AMF were identified. The highest richness was observed in rhizospheres of C. urucurana and I. striata (15 species), while the highest number of spores occurred in G. americana rhizospheres (511 spores/100g dry soil). Glomus showed the highest number of species (10), followed by Acaulospora (6), Scutellospora (4), Gigaspora and Entrophospora (each with one species). The most frequent species in Croton was G. macrocarpum Tul. & Tul.; in Inga, E. kentinensis Wu & Liu, G. etunicatum Becker & Gerd. and G. macrocarpum; and in Genipa, G. claroideum Schenck & Smith, G. etunicatum, G. macrocarpum and G. occultum Walker. We concluded that the number of spores increases with the successional stages; conversely, the indices of diversity, richness and equability diminish in the rhizosphere of climax plants.

Effects of using different host plants on the detected biodiversity of arbuscular mycorrhizal fungi from an agroecosystem

The influence of peanut (Arachis hypogaea L.), sorghum (Sorghum bicolor (L.) Moench) and maize (Zea mays L.) on the development and diversity of arbuscular mycorrhizal fungi (AMF) from an agrosystem was investigated. Soil collected from an agricultural field where maize had been grown was inserted into sowing holes, under the seeds of peanut, sorghum and maize those were subsequently grown in sterilised quartz sand separately in plastic boxes for five months. After this period, collections of roots and rhizospheric soil were made to evaluate the percentages of root colonization (RC), number of spores (NS) and species of AMF. Peanut showed the highest average values for RC and NS: 24.5% and 547.8/100 g of soil, respectively. Maize had an average RC of 19.7% and 415.2 spores/100g soil. Sorghum showed the lowest values: 15.9% for average RC and 349.8 spores/100 g soil. A total of fourteen species of AMF were identified. Seven species were identified from peanut rhizospheres, Entrophospora colombiana being the most abundant and frequent. In sorghum rhizospheres, twelve species were found, Glomus geosporum was the dominant taxon in terms of number of spores and frequency. Ten species were detected in maize with Acaulospora longula being the most abundant and the most frequent. It was observed that peanut was the best plant for promoting the sporulation of AMF, while sorghum favoured the establishment of most AMF species, followed by maize.

Successive cultivation of maize and agricultural practices on root colonization, number of spores and species of arbuscular mycorrhizal fungi

A large number of propagules and a broad spectrum of species are two important components of ecosystem (including agroecosystem) sustainability. Previous studies carried out in temperate areas showed that repeated monoculture leads to a decrease in the species abundance of arbuscular mycorrhizal fungi (AMF). This study evaluated the influence of maize monoculture and its agricultural practices on AMF during three consecutive cropping years in a Brazilian field. At the end of each cycle, soil and root samples were evaluated for species composition, spore populations and root colonization by AMF. The AMF community present during this period was scored according to the Spearman rank correlation and Principal Components Analysis. The mean percent root colonization values for the three cultivation periods were: 66.9, 60.7 and 70.5, respectively. Seven species were detected in the first year, Scutellospora persica being the most abundant (24.1% of spores) and Glomus macrocarpum the most observed (100% of samples). In the second year, Glomus etunicatum was the species with the greatest number of spores (24.7%) and, like G. macrocarpum, the most frequently observed (90%) in a community of thirteen. In the third year, twenty-three AMF species were identified, Scutellospora sp. 1 being the most abundant (17.4%), and Gigaspora decipiens and Glomus claroideum the most frequent (both with a relative frequency of 70%). The main soil factors influencing root colonization and sporulation by AMF were pH (and related properties), phosphorus and organic matter contents.

Comparação entre as técnicas de amostragem direta em campo e cultura-armadilha para mensuração da diversidade de espécies de fungos micorrízicos arbusculares

O conhecimento das comunidades de fungos micorrizicos arbusculares (FMA) depende dos esporos, que podem ou nao ser recolhidos na coleta. Este trabalho teve como objetivo determinar a diversidade de especies de FMA a partir do exame de amostras do campo e de culturas-armadilha. Foram coletadas cinco amostras de solo em tres areas, a fim de isolar os esporos e realizar a multiplicacao dos FMA em vasos. Os esporos foram extraidos do solo via peneiramento umido e centrifugacao em sacarose, montados em lâminas e identificados. As comunidades de FMA foram avaliadas por meio de indices descritores de alfa e beta diversidade. Nas areas I, II e III verificaram-se respectivamente 12, 17 e 15 especies. Nos vasos foram isoladas seis especies na area I, 12 na area II e 10 na area III. Constatou-se que o levantamento da diversidade de FMA e mais eficiente quando as duas tecnicas sao associadas.

Fungos micorrízicos arbusculares em cultivos de citros sob manejo convencional e orgânico

Os fungos micorrizicos arbusculares (FMA) apresentam um grande potencial biotecnologico, mas, para que seu emprego seja bem-sucedido, e necessario conhecer como esses organismos respondem as praticas agricolas. O objetivo deste trabalho foi avaliar o efeito de duas formas de manejo, convencional e orgânica, em pomares e viveiros de citros, nas comunidades de FMA, comparadas com solo de mata nativa. Um total de 36 amostras de solo foram coletadas, e suas caracteristicas quimicas e a ocorrencia de especies de FMA foram avaliadas. Os sistemas de manejo nao alteraram as comunidades de FMA, apesar das modificacoes quimicas no solo causadas pelas aplicacoes de fertilizantes orgânicos, que elevaram os valores de pH, materia orgânica, Ca e magnesio. No entanto, as comunidades foram afetadas pelo tempo de implantacao e pelas regioes onde se localizam os pomares e viveiros. Estas diferencas se devem provavelmente a estabilidade dos pomares mais antigos e as caracteristicas evolutivas de cada local.

Diversidade de fungos micorrízicos arbusculares em remanescente florestal impactado (Parque Cinqüentenário - Maringá, Paraná, Brasil)

As micorrizas sao consideradas importante componente na recuperacao e restabelecimento da vegetacao em areas frageis ou degradadas, bem como na manutencao da biodiversidade de plantas e das funcoes dos ecossistemas. O conhecimento da diversidade e dinâmica dos fungos micorrizicos arbusculares (FMA) em areas impactadas pela acao humana e importante para seu manejo e como indicador de sua qualidade. O Parque Cinquentenario, localizado no municipio de Maringa, PR, pertence a formacao original do conjunto Mata Atlântica, do dominio da floresta Estacional semi-decidual, e um dos poucos remanescentes florestais existentes na cidade de Maringa, PR, e encontra-se em estadio acelerado de degradacao. O objetivo deste trabalho foi avaliar a diversidade de FMA nativos no solo e o grau de micorrizacao das plantas neste ecossistema. Amostras de solo e raizes foram coletadas em 65 pontos diferentes, na profundidade de 0-20 cm. A determinacao da porcentagem de colonizacao micorrizica arbuscular foi feita sob microscopio estereoscopico, pelo metodo da intersecao de quadrantes. A identificacao das especies de FMA foi realizada de acordo com a analise morfologica dos esporos. Foram estimados indices de diversidade, calculados com base no numero de esporos em cada amostra. Foi verificada a ocorrencia de 50 especies de FMA, distribuidas em cinco generos: Glomus (31 especies), Acaulospora (10 especies), Scutellospora (6 especies), Gigaspora (duas especies) e Paraglomus (uma especie). Glomus foi o genero mais abundante, com varias especies esporocarpicas.

Arbuscular mycorrhizal fungi in Citrus sinensis/C. limon treated with fosetyl-Al and metalaxyl

The influence of Fosetyl-Al and Metalaxyl on the diversity of arbuscular mycorrhizal fungi (AMF) was evaluated on naturally established citrus plants. Thirteen AMF species were recovered from rhizospheres of Citrus sinensis/C. limon treated or not with Fosetyl-Al and/or Metalaxyl. Spores of AMF were obtained from 100 g of rhizospheric soil at two sites in Sao Paulo state, Brazil. The soil samples were treated by the wet-sieving technique and the spores were quantified and identified. The number of Spores was low at both sites. Fosetyl-Al reduced the number of spores and the diversity of AMF in one site but not in the other. Metalaxyl at low concentration increased the diversity of species in some experiments, but at higher concentration it tended to reduce the number of spores of AMF. Scutellospora was the genus that presented the largest number of species (7) followed by Acaulospora (3), Glomus (2) and Gigaspora (1). Gigaspora ramisporophora was the dominant species in one site, Glomus macrocarpum and Scutellospora gilmorei were dominant at the other.