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Bacterial Disease Induced Changes in Fungal Communities of Olive Tree Twigs Depend on Host Genotype

Summary

This research investigated how a bacterial disease affects the natural fungal communities living on and inside olive tree branches. The study reveals that disease-causing bacteria can dramatically change which fungi are present, with different effects depending on the olive tree variety. Understanding these complex interactions could help develop better disease control strategies for olive growers. Impacts on everyday life: • Helps farmers choose olive tree varieties that better resist disease • Could lead to more effective and natural disease control methods • Improves understanding of how to maintain healthy olive orchards • May reduce crop losses and improve olive oil production • Contributes to more sustainable agricultural practices

Background

Plant pathogens rarely act alone in nature, as their disease potential is mediated by different microbe interactions occurring within the pathobiome. While bacterial-fungal interactions have been shown important for human health, their relevance for plant health remains poorly understood. The olive knot disease caused by Pseudomonas savastanoi pv. savastanoi (Psv) provides a model system for studying these complex interactions in field conditions.

Objective

This study aimed to investigate how olive knot (OK) disease impacts the epiphytic and endophytic fungal communities of olive tree twigs from three different cultivars with varying disease susceptibility. The research sought to determine the effect of olive knot disease and tree genotype on fungal communities, whether these effects differ between epi- and endophytic fungi, and if specific fungal consortia are associated with disease presence/absence and host susceptibility.

Results

The study identified 179 fungal OTUs belonging to two phyla, with Ascomycota being dominant (97.2%). OK disease primarily affected epiphytic fungi, reducing their abundance, richness and diversity. Endophytic fungal abundance increased in symptomatic tissues, particularly potential pathogens. The most OK-tolerant cultivar (Cobrançosa) showed the greatest loss of fungal diversity when infected. Disease was the primary driver of fungal community composition, while host cultivar shaped these communities in symptomatic tissues. Specific fungal signatures were identified for both healthy and diseased tissues.

Conclusion

Olive knot disease significantly alters the resident fungal communities of olive twigs, with stronger effects on epiphytes than endophytes. The bacterial pathogen appears to suppress fungal colonization on knot surfaces while promoting certain endophytic fungi inside infected tissues. Host plant genotype influences fungal community assembly, particularly after disease establishment. The identification of specific fungal signatures associated with healthy and diseased states suggests an important role for the fungal community in disease development.
  • Published in:Scientific Reports,
  • Study Type:Field Study,
  • Source: 10.1038/s41598-019-42391-8
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