A highly diverse fungal community associated with leaves of the mangrove plant Acanthus ilicifolius var. xiamenensis revealed by isolation and metabarcoding analyses.

Wei-Chiung Chi,Hyo-Jung Cha,Tsz Wai Ho,Weiling Chen,Chih-Chiao He,Sheng-Yu Guo,Ling Ming Tsang,Ka-Lai Pang

doi:10.7717/peerj.7293

Abstract

A high diversity of culturable foliar endophytic fungi is known from various mangrove plants, and the core taxa include species from Colletotrichum, Pestalotiopsis, Phoma, Phomopsis, Sporomiella, among others. Since a small fraction of fungi is able to grow in culture, this study investigated the diversity of fungi associated with leaves of Acanthus ilicifolius var. xiamenensis using both isolation and metabarcoding approaches. A total of 203 isolates were cultured from surface-sterilized leaves, representing 47 different fungal species: 30 species from the winter samples (104 isolates), and 26 species from the summer samples (99 isolates). Ascomycota was dominant in both types of leaf samples, while Basidiomycota was isolated only from the summer samples. Drechslera dematioidea (10.58%, percentage of occurrence), Colletotrichum sp. 3 (7.69%) and Alternaria sp. (7.69%) were dominant in the winter samples; Fusarium oxysporum (13.13%), Diaporthe endophytica (10.10%) and Colletotrichum sp. 1 (9.09%) in the summer samples. Overall, Corynespora cassiicola (6.90%), F. oxysporum (6.40%) and Guignardia sp. (6.40%) had the highest overall percentage of occurrence. In the metabarcoding analysis, a total of 111 operational taxonomic units (OTUs) were identified from 17 leaf samples: 96 OTUs from the winter and 70 OTUs from the summer samples. Sequences belonging to Ascomycota and Basidiomycota were detected in both samples but the former phylum was dominant over the latter. Based on read abundance, taxa having the highest percentage of occurrence included Alternaria sp. (3.46%), Cladosporium delicatulum (2.56%) and Pyrenochaetopsis leptospora (1.41%) in the winter leaves, and Aureobasidium sp. (10.72%), Cladosporium sp. (7.90%), C. delicatulum (3.45%) and Hortaea werneckii (3.21%) in the summer leaves. These latter four species also had the highest overall percentage of occurrence. Combining the results from both methods, a high diversity of fungi (at least 110 species) was found associated with leaves of A. ilicifolius var. xiamenensis. Many of the fungi identified were plant pathogens and may eventually cause diseases in the host.

Highlights

Mangroves are tropical intertidal forest communities, situated at coastal areas from low to high salinities (Tomlinson, 1986)
A total of 203 isolates were cultured from leaves of Acanthus ilicifolius var. xiamenensis collected in January and July 2014 at Kinmen Township, Taiwan and including the 5.8S rDNA (ITS) of the representative isolate for each morphotype was sequenced (Tables 1–2)
Nine species were common between the two sampling times, 47 different fungal species were isolated from leaves of A. ilicifolius var. xiamenensis

Summary

Introduction

Mangroves are tropical intertidal forest communities, situated at coastal areas from low to high salinities (Tomlinson, 1986) These communities host both terrestrial and marine fungi: terrestrial fungi, such as endophytic fungi, occur on the aerial parts of the plants, while marine fungi usually grow on the submerged/intertidal dead branches of the trees. Abundance and richness of endophytic fungi of mangrove plants are dependent on mangrove plant species and their tissue types, i.e., stem, leaf or root (Xing et al, 2011; Zhou et al, 2018). De Souza Sebastianes et al (2013) studied endophytic fungi in branches and leaves of Rhizophora mangle, Avicennia schaueriana and Laguncularia racemosa and found that branches had a higher frequency of colonization and diversity than leaves. Diversity of endophytic fungi increased with leaf age and some fungi may switch from an endophytic lifestyle to a saprobic one after leaf fall (Kumaresan & Suryanarayanan, 2002)

Methods

Results

Conclusion