Characterization of the capacity of yeast cell wall extracts to induce grapevine tolerance to combined biotic and drought stresses

Grapevine (Vitis vinifera L.) is one of the most cultivated perennial tree crops. Grapevine cultivation in Italy faces some biotic and abiotic stresses such as Botrytis cinerea causing gray mould disease, and drought stress, respectively. Several fungicide applications are needed to control the pathogen and reduce economical losses due to B. cinerea infection. Synthetic fungicides cause adverse effect in terms of environmental impact, health hazard, and high cost to farmers. Therefore, the searching for sustainable alternatives to the use of chemical control is crucial. The most significant environmental element affecting agricultural growth and yield is water availability. Climate change's erratic precipitation patterns and rising temperatures are anticipated to make droughts more common in many areas, increasing the strain on freshwater supplies and posing significant difficulties for agriculture. The yeast-derived product Romeo (Sumitomo chemical) is currently available on the market as resistance inducer effective against various grapevine pathogens such as B. cinerea and Plasmopara viticola. Previous research demonstrated that another yeast-derived product Cultus (Coccitech SRL) proved effective in inducing grapevine tolerance to B. cinerea in controlled conditions. In this work we tested the capacity of Cultus and Romeo in reducing the recovery face of grapevine plants from drought stress. Afterwards, we studied the effect of drought on the aggressiveness of B. cinerea in grapevine, and we evaluated the capacity of the yeast extracts in reducing B. cinerea infection in grapevine plants subjected to drought. Finally, we investigated the expression of molecular markers related to water stress and pathogenesis to shed light on the mechanisms activated by yeast-treated grapevine plants in response to B. cinerea and drought.