Araucaria angustifolia Aboveground Roots Presented High Arbuscular Mycorrhizal Fungal Colonization and Diversity in the Brazilian Atlantic Forest

摘要

Almost 30 different arbuscular mycorrhizal fungi(AMF) species, distributed in different genera such as Glomus, Acaulospora,Scutellospora, Entrophospora, Ambispora, Kuklospora, Gigaspora, and Archeospora, have been identified in the root zone of Araucaria angustifolia, known as Brazil Pine. During our AMF survey in this ecosystem, our attention was called to the presence of many superficially growing Araucaria roots. Our hypothesis was that these roots were colonized with AMF because of the presence of AMF spores in organic material aboveground. Samples of these superficial roots and the organic substrate they were growing on were evaluated for their mycorrhizal status. DNA was extracted from the AMF-colonized superficial roots and submitted to polymerase chain reaction(PCR) amplification using the NS31-AM1 primer pair, followed by cloning and sequencing. We found that the root colonization percentages were between 31% and 52%, and the number of AMF spores in the substrate ranged from 27 to 164 spores per 50 g dry substrate. The phylogenetic analyses and tree construction using maximum parsimony(MP) and neighbor-joining(NJ)methods identified 13 different species of the phylum Glomeromycota belonging to the genera Glomus, Funneliformis, Rhizophagus,Gigaspora, Acaulospora, and Archaeospora, and five isolates were identified only at the genus level. To our knowledge, this is the first report on Araucaria angustifolia with roots growing aboveground, producing runner roots that develop on dead tree trunks and organic material. The higher colonization of the aboveground roots than those commonly found in belowground Araucaria roots suggests that they may present active metabolic uptake of nutrients.