Pathogen Interactions and Defense Mechanisms in Fruit Systems

Fruit tissues present a dynamic battleground in which pathogenic microbes deploy specialised strategies to invade, colonise and exploit host resources, while plants activate layered defence mechanisms to limit or prevent disease. Unripe or immature fruit often resist infection through physical barriers, restricted nutrient availability and basal immune responses that produce antimicrobial compounds and reinforce cell walls. As fruit ripen, physiological changes such as cell wall softening, sugar accumulation and shifts in phytohormone balance can render tissues more susceptible. Necrotrophic fungi in particular capitalise on ripening‐associated senescence processes, secreting enzymes that degrade pectin and other wall components and generating toxins to kill host cells. To counter these threats, fruit employ inducible defences including the rapid accumulation of reactive oxygen species, pathogenesis‐related proteins and secondary metabolites such as flavonoids and phenolics. Phytohormones—especially jasmonic acid, salicylic acid and abscisic acid—coordinate the timing and intensity of these responses, while receptor‐like kinases and nucleotide‐binding leucine‐rich repeat proteins sense pathogen‐associated molecular patterns and effector molecules. Postharvest treatments that elicit induced resistance can prolong shelf life by maintaining a heightened defensive state. Advances in transcriptomic, proteomic and metabolomic profiling have clarified the molecular dialogue at different ripening stages, revealing targets for breeding or biotechnological enhancement of resistance and for the development of early‐warning diagnostic tools.

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Pathogen Interactions and Defense Mechanisms in Fruit Systems publication trend

The graph below shows the total number of articles in pathogen interactions and defense mechanisms in fruit systems across all publications each year (not limited to Nature Index journals).

Technical terms

Induced resistance: A defence state triggered by elicitors that primes fruit tissues to mount stronger and faster responses upon pathogen challenge.

Necrotrophic pathogen: A microbe that kills host cells and feeds on dead tissue, often by secreting cell‐wall‐degrading enzymes and toxins.

Reactive oxygen species (ROS): Highly reactive molecules produced in host tissues to damage invading pathogens and reinforce cell walls.

Phytohormone signalling: Hormone‐mediated networks (e.g. jasmonic acid, salicylic acid, abscisic acid) that regulate defence gene expression.

Quiescent infection: A latent stage in which a pathogen remains inactive in unripe fruit, becoming aggressive only after host ripening triggers.

References

1. Induced Resistance in Fruit and Vegetables: A Host Physiological Response Limiting Postharvest Disease Development. Annual Review of Phytopathology (2023).
2. Grapevine gray mold disease: infection, defense and management. Horticulture Research (2024).
3. Bioassays and proteomics as early detection tools in postharvest management of table grapes (Vitis vinifera L.) diseases – A Review. Food Bioscience (2023).
4. Infection Strategies Deployed by Botrytis cinerea, Fusarium acuminatum, and Rhizopus stolonifer as a Function of Tomato Fruit Ripening Stage. Frontiers in Plant Science (2019).
5. Insights into molecular and metabolic events associated with fruit response to post-harvest fungal pathogens. Frontiers in Plant Science (2015).