Endophytic fungal hitch-hikers have been difficult to detect in the past, and have potentially spread these latent pathogens via the global plant trade. The African genera
Protea
,
Leucospermum
and
...Leucadendron
, commercially referred to as proteas, form the basis of a global flower production industry. The largest producers of proteas are Australia and South Africa, followed by Portugal and Spain. In the 1990s propagation material from South Africa was used to establish protea orchards in Portugal. We utilized metabarcoding to determine if this plant trade has carried host-specific fungal pathogens to a new environment. Wood samples collected from asymtomatic twigs from Portuguese farms, where propagation material had been imported from South Africa, was compared to material from South African farms that originally produced and supplied rooted and unrooted cuttings. DNA metabarcoding, using fungal-specific primers for the ITS2 gene region, produced 1237 OTUs. Focusing only on known pathogens of protea, we found that the Portuguese orchards contained fungal disease agents associated with Proteaceae or other plant families from the Southern Hemisphere. Our sampling technique could be used by agencies and applied to other plant material and pathogens to reduce the spread of pathogens.
Fungal communities in above-ground tree tissues are hyperdiverse and are influenced by biotic interactions with other organisms living in or on these tissues. These biotic interactions are, however, ...still poorly understood. In this study, we aimed to understand how insect-associated gall formation on
foliage correlates with the diversity of foliar fungal communities in surrounding healthy leaf tissue, as well as the co-occurrence patterns among the members of the fungal community. We used ITS metabarcoding to characterise the foliar fungal communities of 179 individual
trees. These trees were assigned to infestation levels of the wasp
(Eulophidae: Hymenoptera), which causes gall formation on shoot tips and leaves of its host. Fungal community networks were calculated using a Pearson correlation coefficient. The composition and diversity of fungal communities were influenced by the severity of
infestations. We identified potential
pathogens with high sequence abundance at all disease severity levels, but network analysis indicated that the co-occurrence of potential pathogens between no to mild and medium to heavy infestation differed significantly. A better understanding of microbial interactions, especially the role of pathogens, can be useful for controlling disease- and beneficial host-associated microbial communities.
Fungi represent a common and diverse part of the microbial communities that associate with plants. They also commonly colonise various plant parts asymptomatically. The molecular mechanisms of these ...interactions are, however, poorly understood. In this study we use transcriptomic data from Eucalyptus grandis, to demonstrate that RNA-seq data are a neglected source of information to study fungal–host interactions, by exploring the fungal transcripts they inevitably contain. We identified fungal transcripts from E. grandis data based on their sequence dissimilarity to the E. grandis genome and predicted biological functions. Taxonomic classifications identified, amongst other fungi, many well-known pathogenic fungal taxa in the asymptomatic tissue of E. grandis. The comparison of a clone of E. grandis resistant to Chrysoporthe austroafricana with a susceptible clone revealed a significant difference in the number of fungal transcripts, while the number of fungal taxa was not substantially affected. Classifications of transcripts based on their respective biological functions showed that the fungal communities of the two E. grandis clones associate with fundamental biological processes, with some notable differences. To shield the greater host defence machinery in the resistant E. grandis clone, fungi produce more secondary metabolites, whereas the environment for fungi associated with the susceptible E. grandis clone is more conducive for building fungal cellular structures and biomass growth. Secreted proteins included carbohydrate active enzymes that potentially are involved in fungal–plant and fungal–microbe interactions. While plant transcriptome datasets cannot replace the need for designed experiments to probe plant–microbe interactions at a molecular level, they clearly hold potential to add to the understanding of the diversity of plant–microbe interactions.
•The effect of Rotstop on H. parviporum biomass was quantified in Norway spruce stumps.•The interaction between fungal community in the stump and Rotstop was also studied.•Incomplete stump treatment ...allowed H. parviporum colonies to survive in stumps.•20% less biocontrol cover translated in 2-fold biomass increase of surviving colonies.•Fungi of the genus Debaryomyces associated with P. gigantea colonisation.
Protection against the root rot fungus Heterobasidion annosum s. l. is achieved by mechanically spraying stumps with spores of the antagonistic fungus Phlebiopsis gigantea, commercialized as Rotstop®. An extensive colonisation of the stump by P. gigantea is required for protection. Colonisation may depend on how the biocontrol agent interacts with the fungal community that is endophytically inhabiting the stump, as well as with other fungi establishing after the treatment is applied. In this research, we studied how the distribution and abundance of Heterobasidion and P. gigantea is modulated by the fungal community inhabiting Norway spruce (Picea abies) stumps. First thinning stumps were treated with Rotstop and/or artificially inoculated with H. parviporum under field conditions. After two months, P. gigantea or Heterobasidion distribution was measured by qPCR, and both pathogen and biocontrol abundance gradients were correlated with members of the fungal community determined by high throughput sequencing. Rotstop application decreased Heterobasidion biomass by almost 200 times, though the strongest biomass reductions were only achieved when stumps were well covered by P. gigantea. Poor Rotstop applications resulting in, for instance, a drop of 20% in terms of stump covered area by the biocontrol, were associated with a 2-fold biomass increase of the surviving Heterobasidion colonies. Unlike Heterobasidion, some fungi such as Peniophora sp. and F. pinicola did not change their relative abundance following the Rotstop treatment and were associated with areas of low P. gigantea presence. Yeast-like fungi of the genus Debaryomyces increased its relative abundance following Rotstop treatment, and were the only taxa associated with both a higher abundance of the biocontrol, and a lower abundance of the pathogen. Ours is the first study quantifying at microscale the interaction between H. parviporum and P. gigantea in stumps subjected to Rotstop treatment, showing how incomplete stump cover may result in large shifts in terms of biomass for either the pathogen or the biocontrol. Our results stress the importance of achieving a complete cover of the stump surface in practice. Debaryomyces sp. might facilitate P. gigantea colonisation of the stump and could be added as enhancers of Rotstop treatment, though the mechanism of interaction with the pathogen and the biocontrol should be further studied.
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