Doses de fósforo determinam a prevalência de fungos micorrízicos arbusculares em <i>Araucaria angustifolia</i>

Abstract

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.

Colonization and Spore Richness of Arbuscular Mycorrhizal Fungi in Araucaria Nursery Seedlings in Curitiba, Brazil

“…The least abundant genus in this experiment belonged to the genus Gigaspora (Table 2). Gigaspora has been associated with moderate acidy soils and high levels of phosphate availability [13,14]. In our experiment, however, Gigaspora was not related to phosphate but it was slightly associated with potential soil acidity (Al + and H + Al + ; Figure 2).…”

“…To date, araucaria AMF spore richness varied from 8 [23] to 13 [11] in forests of the State of Rio Grande do Sul and from 26 [24] to 58 [25] in forests of Sao Paulo. The variation in spore AMF richness has been frequently attributed to heterogeneity in soil habitat and to the variable capacity of AMF species to adapt to climate and soil in different regions [10,13]. Therefore, although the AMF richness is great under field conditions, only few species are probably well adapted to nursery conditions.…”

“…Pioneer studies already reported AMF in fine araucaria roots [9]; however, it was only recently that the AMF has been considered as a strategy to increase araucaria growth under nursery conditions [10,11]. In fact, the studies performed so far show two important facts: first, that araucaria is colonized by a large and diverse number of AMF species [10,12]; and second that the araucaria positively respond to inoculation of some AMF species, both in high and low P supply [13]. However, we do not know precisely the most efficient and competitive AMF species under nursery seedling production [14].…”

Arbuscular Mycorrhizal Fungi and Dark Septate Endophytic Fungi on the Biomass Development of Vetiver Grass

“…The cultivation of tillers colonized by native mycorrhizal fungi, cultivated with 800 mg.dm -3 of the P 2 O 5, reduced mycorrhizal colonization from 56.6%, observed in the tillers collected from the field, to 10.2%. In this context, Moreira, Barretta and Cardoso (2012) observed that increasing phosphorus content up to 150 mg kg -1 a decrease of Scutellospora gilmorei and Glomus etunicatum sporulation was observed, and high phosphorus stimulated sporulation of Acaulospora. Similarly, in our study, the application of phosphorus fertilizers in high dosages may have influenced colonization of tillers with high phosphorus dosage, in the control, and in the treatments with the UFLAs isolates.…”