Impact of chemical and alternative fungicides on grapevine berry transcriptome at harvest

Grapevine is one of the most important cultivated fruit crops worldwide, whose fruits are consumed fresh or dried as table grapes or used to produce beverage and nutraceutical products. Most grown grapevine varieties (Vitis vinifera cvs) are susceptible to fungal diseases, causing great yield losses and requiring numerous fungicide treatments. New products, such as biofungicides, resistance inducers and biostimulants may lead to the development of alternative crop protection strategies that are respectful of the environmental sustainability and food safety. In this work, the main aim was to evaluate the impact of biocontrol products such as laminarin, resistance inductors (i.e. fosetyl-Al and potassium phosphonate), electrolyzed water and a standard chemical fungicide (i.e. metiram), on the transcriptomic profile of Nebbiolo grape berries at harvest (Fig.1). In addition to a validation of the sequencing data through RT-qPCR, expression of selected genes in different cell-types of berry skin (i.e. epidermal and hypodermal layers) was verified using a laser microdissection (LMD) approach. Results showed that the considered antifungal treatments do not strongly affect the berry transcriptome profile, although differences among treatments were unveiled. The conventional one (i.e. metiram) led to a higher number of differentially expressed genes (DEGs) with respect to the other treatments, suggesting that this one could have a major impact on berry physiology with respect to the other antifungal treatments, which deserves to be further investigated to verify the effects on fruit quality and properties. In addition, results demonstrated that the LMD technique associated with targeted gene expression analysis, is a powerful tool to identify genes differentially expressed in the two-cell type populations forming the berry skin, leading to a better understanding of the specialized contribution of each tissue to berry physiology. Some candidate genes correlated to defense responses appeared in fact to be more or exclusively expressed in the external cell-type population.