Fungos micorrízicos arbusculares em ambientes dunares da ilha de Upaon Açu: diversidade e atividade

Abstract

The dunes are a very peculiar ecosystem with numerous environmental functions, however, anthropogenic action has caused a lot of degradation and leading to loss of biological diversity and in turn affecting microbial activity, which reduces the beneficial effects these organisms can offer such as Arbuscular mycorrhizal fungi (AMF) that act in plant nutrition, but are also recognized to assist in establishing the plant community in degraded environments and in the initial process of colonization. Several studies indicate the occurrence and diversity of AMF in dunes worldwide and in Brazil, however, the dunes of Maranhão state do not have reports of studies with this group of fungi. In this context this work aimed to estimate the diversity of arbuscular mycorrhizal fungi and characterize their community in dunes of the beaches of São Marcos and Carimã-MA. Soon, four dunes of São Marcos beach (PDM) and Carimã beach (PC) were randomly selected. The samples were collected during the dry season (Nov / 2017) and during the rainy season (May / 2018). Five composite soil samples were collected (three single samples), at depth 0-20 cm, in each beach, totaling 40 samples. by season. These samples were separated and sent for further analysis. The experimental design was characterized as completely randomized, with 2x2 factorial arrangement and 20 replications.All variables were submitted to Tukey's test (p <0.05). Glomerospore density ranged from 0.04 to 4.76 glomerospores per g of soil in the dry period, and from 91 to 11.54 glomerospores per g of soil in the dry period. We identified 45 AMF species distributed in seven families and 12 genera. The highest species richness was observed in the rainy season when compared to the dry period. The area with the highest AMF diversity during the rainy season was the PSM, with 28 species identified, while during the dry season the highest diversity was observed in the PC area, with 22 species. Of the identified species only four (Racocetra gregaria, Cetraspora gilmorei, Funneliformis halonatum and Acaulospora scrobiculata) occurred in both areas and times of the year. The highest Shannon index (H ') was detected in PSM in the rainy season and PCM in both seasons, while the highest Pielou index (J') was observed in PCM in both the rainy season. Both areas presented a higher rate of mycorrhizal colonization during the dry season, while in the rainy season the tendency of increased mycorrhizal infection potential (MIP) was higher in the PSM area. The contents of BRSP, EE-BRSP and COT presented sensitivity to seasonal variation, with increase in the rainy season. The highest correlations were observed for (EE-BRSP x BRSP, EE-BRSP x COT and BRSP x COT) indicating that these protein fractions influence the increase of soil carbon concentration in dunes