Optimization of sustainable control strategies against blue rot in table grapes under cold storage conditions

Abstract

Cold storage conditions do not inhibit the development of Penicillium expansum, a wound pathogen that causes significant losses in terms of quantity and quality in table grape´s production. The adoption of integrated strategies is recommended to enhance postharvest disease control and diminish reliance on synthetic fungicides and their adverse effects. Biocontrol is compatible with these purposes but to date there are no studies that have assessed the combination of different antifungal strategies by using statistical Mixture Design Models (MDM) and optimizing through the Response Surface Methodology (RSM). The aim of this work was optimizing a compatible combination of antimicrobials agents (antimicrobial substances and UV-C light exposure) with native biocontrol yeasts looking for an integrated strategy to reduce the disease severity (DS) caused by P. expansum on table grapes at 2 ±1°C. Three psychrotrophic yeast isolates belonging to the species Metschnikowia pulcherrima (Mp22, Mp36, Mp43) and four P. expansum (PSS4, PSS6, PRG3, PRG2) pathogen isolates were used. Isolates sensitivity was evaluated under in vitro assays with chemical and physical antimicrobial agents. An augmented simplex-centroid mixture design was selected and RSM was used to optimize the compatible combination of biocontrol yeasts and sodium bicarbonate (NaHCO3) to control P. expansum DS on Superior Seedless grape clusters under cold storage conditions. A Special Cubic model best fitted the data from the response variable (p < 0.0001; R2=0.9334). The combination of yeasts (Mp22, Mp36) and NaHCO3, after optimization, reduced 90% the DS in grape bunches stored for 30 days at 2±1 °C (validation assays). Results obtained in the present work suggest biocontrol integrating M. pulcherrima yeasts and NaHCO3 effectively reduces the growth of P. expansum in table grapes. The use of MDM and RSM is a methodological novelty in biocontrol studies that leads to more precise integrating strategies against fungal diseases on table grapes under cold storage conditions.