Trang Minh Tran

Agriculture faces increasing pressure from climate change, which drives extreme weather events and promotes the spread and virulence of fungal and oomycete pathogens. Concurrently, European legislation is accelerating the transition from conventional crop protection products to biocontrol strategies. One promising approach is defence priming, whereby plants are placed in a heightened state of readiness. Although green leaf volatiles (GLV) are well-established priming agents, their downstream effects have been studied almost exclusively in monocots. This study investigates the mode of action of the GLV cis-3-hexenyl acetate (Z3HAC) as a priming agent against Phytophthora infestans in potato (Solanum tuberosum L.). Integration of multispectral imaging, messenger and small non-coding RNA transcriptomics and volatilomics revealed the molecular mechanisms underlying Z3HAC-mediated defence priming. Transcriptome analysis showed that early Z3HAC perception activates mitogen-activated protein kinase-, abscisic acid- and reactive oxygen species-associated signalling, followed by defence activation through calcium- and salicylic acid-mediated pathways. This signalling network differs from the jasmonic acid-centred priming models described in monocots, while microRNA provides an additional finetuning layer of defence regulation. Simultaneously, Z3HAC exposure reprogrammes volatile metabolism towards defence-related signalling. GLV-induced priming in potato involves a complex hormonal and terpenoid signalling network. This study provides the first mechanistic framework for GLV-mediated priming in a dicot crop, revealing a signalling topology distinct from monocot systems. This research provides a foundation for developing green leaf volatile-based biocontrol strategies in agriculture to enhance potato resistance against Phytophthora infestans.

With increased mycotoxin contamination, the search for eco-friendly biocontrol strategies has become increasingly important. This study aimed to evaluate the efficiency of stilbenoid-enriched Merlot (Me) and Tannat (Ta) vine root extracts, and their major active molecule, vitisin B (VIT), against Aspergillus carbonarius growth and its ochratoxin A (OTA) production using in vitro liquid and solid, and ex vivo grape-berry assays. In liquid assay, Me and Ta (125 mg/L) and VIT (36 mg/L) significantly inhibited extracellular OTA. Additionally, VIT temporarily reduced both fungal growth and total OTA. Transcriptomics showed that VIT and Me slightly induced OTA biosynthesis genes. In solid and ex vivo assays, doses above 1 g/L decreased OTA production by up to 48% without impacting fungal growth. This lack of correlation suggested a distinct regulatory response to extract-induced stress. Importantly, the fungicide tebuconazole showed method-dependent effects. On in vitro solid medium, it significantly inhibited the fungal growth without affecting OTA yield, whereas in ex vivo berry assays, it significantly inhibited both. Our findings emphasize the potential of stilbenoid-enriched extracts as biocontrol agents targeting OTA production, highlighting the value of multi-assay evaluations. Future studies should elucidate their modes of action and optimize their efficacy.

Boosting plant immunity by priming agents can lower agrochemical dependency in plant production. Levan and levan‐derived oligosaccharides (LOS) act as priming agents against biotic stress in several crops. Additionally, beneficial microbes can promote plant growth and protect against fungal diseases. This study assessed possible synergistic effects caused by levan, LOS and five levan‐ and LOS‐metabolizing Bacillaceae (Bacillus and Priestia) strains in tomato and wheat. Leaf and seed defense priming assays were conducted in non‐soil (semi‐sterile substrate) and soil‐based systems, focusing on tomato‐Botrytis cinerea and wheat‐Magnaporthe oryzae Triticum (MoT) pathosystems. In the non‐soil system, seed defense priming with levan, the strains (especially Bacillus velezensis GA1), or their combination significantly promoted tomato growth and protection against B. cinerea. While no growth stimulatory effects were observed for wheat, disease protective effects were also observed in the wheat‐MoT pathosystem. When grown in soil and subjected to leaf defense priming, tomato plants co‐applied with levan and the bacterial strains showed increased resistance to B. cinerea compared with plants treated with levan or single strains, and these effects were synergistic in some cases. For seed defense priming in soil, more synergistic effects on disease tolerance were observed in a non‐fertilized soil as compared to a fertilized soil, suggesting that potential prebiotic effects of levan are more prominent in poor soils. The potential of using combinations of Bacilliaceae and levan in sustainable agriculture is discussed.

Cereal crops are frequently affected by Fusarium species that are responsible for the devastating fungal disease Fusarium Head Blight (FHB). These Fusarium species are also capable of producing mycotoxins that accumulate in grains. Reducing the use of synthetic fungicides in agriculture while guaranteeing low levels of mycotoxin contamination in crops requires the development of innovative and environment-friendly solutions. TickCore3 (TC3) is an antimicrobial peptide derived from a defensin DefMT3 of the tick Ixodes ricinus. This peptide was previously reported as a potent antifungal and anti-mycotoxin agent but was only tested against one strain of Fusarium graminearum, which is only one of the species causing FHB. In this study, we demonstrated that TC3 is active against major Fusarium species infecting wheat and has the capacity to inhibit the production of various mycotoxins. Fungal susceptibility to this peptide was shown to greatly vary according to the species and even the strain. We found that TC3 is highly efficient when applied at the spore stage and has a strong anti-germination activity. Using a FITC-labeled TC3 peptide and confocal microscopy, we showed that TC3 has strong affinity for the conidia surface and surrounds these fungal structures. While this study provides further arguments supporting the huge potential of TC3 as a novel and efficient anti-fungal agent, it also highlights the need for further studies to ensure that the application of TC3 in wheat fields will not induce a shift in Fusarium population such as in mycotoxin profile contaminating grains.