RESUMO
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
The fungal species Curvularia senegalensis was isolated from a soil sample collected at a Brazilian region of cerrado transition. This microorganism was grown in vitro and the extract of the culture medium was fractionated by chromatographic methods yielding an oil rich in phthalates, from which seven derivatives were identified by infrared, 1H and 13C NMR and mass spectrometry as 1-hexyl-2-propylphthalate, 1-ethyl-2-heptylphthalate, 1-hexyl-2-butylphthalate, 1-heptyl-2-proylphthalate, 1-propyl-2-nonylphthalate and two positional isomers of 1-decyl-2-butane phthalate. This is the first report on the phthalates production by Curvularia senegalensis revealing a scientific basis for the use of this species on biodegradation experiments. Since C. senegalensis is a very common pathogen in some commercial crops, presence of highly toxic phthalates on the final feed products should be investigated.