Seasonal Variation in the Occurrence of Fungi Associated With Forest Species in a Cerrado-Caatinga Transition Area

Abstract

Although ecotone areas occupy a significant extent in Piauí State, there is little information about these areas, especially regarding the presence of microorganisms. Thus, this study evaluated the effect of seasonality on the occurrence of fungal genera associated with forest species in an ecotone Cerrado-Caatinga in Piauí State, Brazil. The experimental area consisted of one-hectare fragment within a legal reserve, where five plots of 20m x 20m were established and the phytosociological survey was carried out. The collection of the material (healthy leaves and leaves with disease symptoms) was performed in two periods: the dry season (June and August/2017) and the rainy season (December/2017 and February/2018), totaling four collections. In the laboratory, isolation and purification of fungi were performed. The fungal identification was based on morphological characteristics and the use of identification keys. The relative abundance of fungi was calculated, and the data were submitted to multivariate cluster analysis. In total, 225 isolates were found, related to 15 fungal genera, associated with 10 forest species. The occurrence of fungi in the area was influenced by seasonal variation, with more isolates found in the dry period, as examples of important groups, whether beneficial or phytopathogenic microorganisms are: Trichoderma spp. and Lasiodiplodia spp. It was also observed that fungi are more likely to occur in forest species like Bauhinia cheilantha and Pityrocarpa moniliformis, belonging to the Fabaceae family.

Endophytic Trichoderma strains isolated from forest species of the Cerrado-Caatinga ecotone are potential biocontrol agents against crop pathogenic fungi

“…The nineteen Trichoderma spp. isolates (S1 Table ) were obtained from leaves of forest tree species (S2 Table ), located in a Cerrado-Caatinga ecotone in Southwest Piauı ´, Brazil (8˚51 0 7.48@ S and 44˚11 0 39.95@ W) [26], and maintained in potato dextrose agar (PDA) culture medium (Himedia). This area comprised a fragment of one hectare within the legal reserve [26].…”

“…isolates (S1 Table ) were obtained from leaves of forest tree species (S2 Table ), located in a Cerrado-Caatinga ecotone in Southwest Piauı ´, Brazil (8˚51 0 7.48@ S and 44˚11 0 39.95@ W) [26], and maintained in potato dextrose agar (PDA) culture medium (Himedia). This area comprised a fragment of one hectare within the legal reserve [26]. For the identification of the Trichoderma isolates, the gene regions for the translation elongation factor (tef1) and the second largest RNA polymerase subunit (rpb2) were amplified and sequenced, and the construction of phylogenetic trees was performed by comparing the sequences available in GenBank (National Center for Biotechnology Information, NCBI) [27].…”

“…Altogether, the plethora of and the variety of secondary metabolites identified in the present study highlight how Trichoderma strains are capable of producing metabolites with different biological activities, which makes them very promising not only for the biocontrol of plant diseases but also for their application in medical, pharmaceutical and industrial biotechnology. Forest species from the Cerrado-Caatinga ecotone are rich in genetic resources and have diverse fauna and flora, with enormous biotechnological potential, including their diversity of endophytic fungi [26].…”

“…In this study, we investigated the potential role of endophytic Trichoderma strains isolated from forest tree species of the Cerrado-Caatinga ecotone [26,27] as biological control agents of crop pathogenic fungi. First, we evaluated the interaction between endophytes and pathogens by in vitro antagonism bioassays.…”