Abstract
Fungal endophytes are ubiquitous in nature. They are known as potential sources of natural products, and possible agents for biocontrol attributing to their ability to produce a repertoire of bioactive compounds. In this study, we isolated fungal endophytes from three different tissues (needle, stem and root) of four Pinus species (Pinus densiflora, Pinus koraiensis, Pnus rigida, and Pinus thunbergii) across 18 sampling sites in Korea. A total number of 5872 culturable fungal endophytes were isolated using standard culturing techniques. Molecular identification based on the sequence analyses of the internal transcribed spacer (ITS) or 28S ribosomal DNA revealed a total of 234 different fungal species. The isolated fungal endophytes belonged to Ascomycota (91.06%), Basidiomycota (5.95%) and Mucoromycota (2.97%), with 144 operational taxonomic units (OTUs) and 88 different genera. In all sampling sites, the highest species richness (S) was observed in site 1T (51 OTUs) while the lowest was observed in site 4T (27 OTUs). In terms of diversity, as measured by Shannon diversity index (H’), the sampling site 2D (H′ = 3.216) showed the highest while the lowest H’ was observed in site 2K (H’ = 2.232). Species richness (S) in three different tissues revealed that root and needle tissues are highly colonized with fungal endophytes compared to stem tissue. No significant difference was observed in the diversity of endophytes in three different tissues. Among the four Pinus species, P. thunbergii exhibited the highest species richness and diversity of fungal endophytes. Our findings also revealed that the environmental factors have no significant impact in shaping the composition of the fungal endophytes. Furthermore, FUNGuild analysis revealed three major classifications of fungal endophytes based on trophic modes namely saprotrophs, symbiotrophs, and pathotrophs in four Pinus species, with high proportions of saprotrophs and pathothrops.
Highlights
Microbial endophytes are microbes that live in plant tissues without eliciting any disease symptoms and represent symbiotic interactions between microbes and host plants [1,2,3]
The total number of isolated culturable fungal endophytes varied depending on Pinus species: P. thunbergii (n = 1791), P. densiflora (n = 1469), P. rigida (n = 1379), and P. koraiensis (n = 1233)
Further identification of the morpho-species based on rDNA internal transcribed spacer (ITS) or LSU rDNA revealed 88 genera with a total of 144 operational taxonomic units (OTUs)
Summary
Microbial endophytes (fungi and bacteria) are microbes that live in plant tissues without eliciting any disease symptoms and represent symbiotic interactions between microbes and host plants [1,2,3]. Fungal endophytes can influence plant ecology, the evolution of plant community structure, and the diversity of interacting organisms including nematodes and insects [8,9,10]. For these reasons, many researchers have studied the importance of fungal endophytes’ geographical distributions, as well as their ecological associations in the plant populations and community biodiversity [11,12,13]. Pine trees are widely distributed in the world, and they grow well on acid and drainage soils [14] They are able to tolerate poorly drained wet soils. According to the number of vascular bundles in the needle, the genus can be classified into two subgenera: Pinus subgenus Pinus, and Pinus subgenus Strobus
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