Nanotechnologies, biological and physical tools for gray mold management

Botrytis cinerea causes gray mold in more than 1,400 different hosts and heavy economic losses in in both preharvest and post-harvest resulting in the second most important pathogen worldwide. Due to economic importance, gray mold control is traditionally based on the application of synthetic fungicides, but it dramatically increases the risk of developing fungicide-resistant populations and amplifies the negative impacts on human health and the environment. To address the challenge of sustainable control, innovative physical control means, based on microwave (MWs), pulsed electric filed (PEF) and UV-C, as well as new biocontrol agents and bio-based nanocarriers were evaluated. The effect of increasing microwave-specific energy stages (7.3 to 18.1 Kj‧kg -1), PEF exposure times (1 to 20 minutes) and UV-C (90 to 300 mJ) were evaluated against conidia suspension of B. cinerea. MWs treatment effectively inhibited conidial germination by 98–100% already at 7.3 Kj‧kg -1. While PEF treatment showed significant efficacy from 15 minutes of exposure at a voltage of 10 kv, a pulse frequency of 200 Hz, a power of 3 kW and a pulse current of 40A. UV-C at 300 mJ totally inhibit conidia germination. Additionally, the efficacy of 37 different microorganisms isolated from aqueous extracts of halophytic plants (Suaeda maritima, Crithmum maritimum, Salicornia perennis) and ornamental species (i.e Kalanchoe daigremontiana) was evaluated through dual culture assays on nutrient agar. After 10 days, all the tested microorganisms caused reduced fungal radial growth by 50–65%. Furthermore, liposome loaded with the fungicide Fludioxonil were developed. Three types of vesicles composition and two production methods were compared for Encapsulation Yields, Drug Loading Content and Zeta potentials and B. cinerea control in terms of conidia germination, germ tube elongation and colony radial growth. The Extruded PEGylated liposomes were the optimal compromise of active substances release and pathogen control, showing low effectiveness on conidia germination (22.7% at 0.3µg·ml-1), but a high effectiveness on germ tube elongation and colony radial growth (respectively 7.7% and 68% at 0.01 µg·ml-1). Finally, an ancient Calabrian germplasm confidentially called ‘Francesina’ of wine-grapevine and proved to be highly tolerant to gray mold on filed was in vitro established and its genetic characterization is ongoing. These findings suggest that combining physical, biological and nanotechnologies could offer effective and eco-friendly complements or alternatives to conventional fungicides.