Implementation of plant-derived antimicrobial peptides for enhanced apple conservation

Postharvest losses in the apple industry are primarily driven by fungal pathogens that compromise fruit quality during storage. Among these, grey mould caused by Botrytis cinerea is a persistent global threat. The widespread use of synthetic fungicides has raised significant alarms regarding environmental toxicity and pathogen resistance, sparking an urgent search for sustainable biotechnological alternatives that ensure food safety.

This research explored the potential of antimicrobial peptides (AMPs) from the South American native species Peltophorum dubium as natural biocontrol agents. Using transcriptome mining of germinated seeds, four candidate defensins were identified and produced via recombinant technology in Escherichia coli to precisely evaluate their antifungal potency.

Purified peptides PdDf11 and PdDf13 achieved complete inhibition of B. cinerea growth in vitro at a concentration of 6 µM. Most notably, in trials with cold-stored apples, purified PdDf11 reduced disease severity by 97% and incidence by 86%. These findings validate plant defensins as powerful, natural tools for eco-friendly fruit protection in the postharvest stage.

Phytosanitary Challenges in the Apple Value Chain

Apples are a cornerstone of global fruit production. However, postharvest decay significantly limits marketability. While industrial cooling and controlled atmospheres are standard for slowing fruit respiration, they are often insufficient to prevent infections from pathogens such as Botrytis cinerea, Penicillium expansum, and Alternaria spp. These infections lead to substantial economic losses and reduced shelf life across all major production regions.

Shifting Towards Sustainable Postharvest Protection

The historical reliance on chemical fungicides is facing increasing pressure due to regulatory changes and consumer demand for residue-free produce. Antimicrobial peptides (AMPs) are emerging as a promising solution. These small biomolecules (2–7 kDa) are key components of innate immunity. Their ability to target essential cellular processes makes them highly effective while significantly lowering the risk of pathogens developing resistance compared to traditional chemical treatments.

Among AMPs, plant defensins are a key superfamily involved in phytopathogen defense. They are characterized by high stability due to a conserved cysteine-stabilized alpha-beta (CSαβ) motif. This structural "scaffold" allows them to remain functional despite fluctuations in pH and temperature, a crucial trait for ensuring efficacy within the demanding environment of commercial cold storage.

Exploring South American native flora has proven to be an effective strategy for discovering new bio-control agents. Transcriptome mining of Peltophorum dubium identified 14 defensin sequences, including both canonical and atypical variants. Atypical defensins, with their elongated terminal regions, suggest unexplored biological functions and enhanced structural stability, representing a new frontier in sustainable agricultural biotechnology.

Objectives and Validation of Novel Antifungal Tools

The aim of this study was to experimentally characterize these recombinant defensins and understand the relationship between their structure and antifungal activity.

By purifying the most active peptides, PdDf11 and PdDf13, the research validated their performance both in vitro and in real cold-storage conditions. Ultimately, the study establishes these peptides as viable, sustainable alternatives to conventional fungicides, aligning with the industry's move toward green technologies.

Source

Roberto Castro Rosas , Rodrigo Becco , María Fernanda Ramos Arangüena , Eloísa Arrartre , Gianna Cecchetto , Mariana Barraco-Vega
Plant-Derived Antimicrobial Peptides as Natural Alternatives to Chemical Fungicides for Postharvest Control of Botrytis cinerea in Apples https://www.preprints.org/frontend/manuscript/e87bbbb0034e04b2df42a07d2e9ae259/download_pub
doi:10.20944/preprints202603.2035.v1