Fungal Communities in Asymptomatic and Symptomatic Needles of Pinus spp. Affected by Pine Needle Diseases

TL;DR

This study explores fungal communities in healthy and diseased pine needles to identify potential pathogens and understand their role in pine needle diseases.

Contribution

The study identifies fungal genera associated with symptomatic and asymptomatic pine needles using high-throughput sequencing.

Findings

Ascomycota dominated all samples, with Lophodermium being the most abundant genus.

Alpha diversity was higher in asymptomatic needles, with significant differences in the Shannon index.

Functional guilds were dominated by pathotroph–saprotroph trophic mode, with 'plant pathogen' being the most abundant.

Abstract

The aim of this study was to determine fungal diversity and composition in an area of high host diversity and identify the organisms involved in the appearance of symptoms in Pinus needles. Asymptomatic and symptomatic live needle samples were obtained from different Pinus spp. in an arboretum with confirmed presence of brown spot needle blight. The samples were analysed using high-throughput sequencing of fungal ITS2rDNA. Ascomycota dominated all samples, with Lophodermium as the most abundant genus, although it showed lower representation in symptomatic needles. Other genera with recognised pathogenic potential, including Lecanosticta, Pestalotiopsis, Cyclaneusma, Rhizosphaera, Neophysalospora, and Cenangium, were also detected, whereas the Dothistroma genus was absent despite its presence in the region. Alpha diversity was higher in asymptomatic needles, with a significant difference only for the Shannon index, while Bray–Curtis dissimilarity revealed significant shifts in community composition between needle types. Functional guilds were dominated by pathotroph–saprotroph trophic mode, and the functional guild ‘plant pathogen’ was the most abundant across samples. These findings identify fungal genera associated with symptomatic and asymptomatic needles and provide guidance for future targeted isolation and detailed morphological and molecular identification using more resolutive techniques, enabling a deeper understanding of pathogenic community presence and their potential synergistic interactions.

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