Biostimulants in Viticulture: A Sustainable Approach against Biotic and Abiotic Stresses

Abstract

Climate change and disproportionate anthropogenic interventions, such as the excess of phytopharmaceutical products and continuous soil tillage, are jeopardizing viticulture by subjecting plants to continuous abiotic stress. One of the main physiological repercussions of abiotic stress is represented by the unbalanced redox homeostasis due to the overproduction of reactive oxygen species (ROS), ultimately leading to a state of oxidative stress (detrimental to grape quality). To these are added the direct and indirect damages caused by pathogens (biotic stresses). In light of this scenario, it is inevitable that sustainable techniques and sensitivity approaches for environmental and human health have to be applied in viticulture. Sustainable viticulture can only be made with the aid of sustainable products. Biostimulant (PB) applications (including resistance inducers or elicitors) in the vineyard have become interesting maneuvers for counteracting vine diseases and improving grape quality. These also represent a partial alternative to soil fertilization by improving nutrient absorption and avoiding its leaching into the groundwater. Their role as elicitors has important repercussions in the stimulation of the phenylpropanoid pathway by triggering the activation of several enzymes, such as polyphenol oxidase, lipoxygenase, phenylalanine ammonia-lyase, and peroxidase (with the accumulation of phenolic compounds). The present review paper summarizes the PBs' implications in viticulture, gathering historical, functional, and applicative information. This work aims to highlight the innumerable beneficial effects on vines brought by these products. It also serves to spur the scientific community to a greater contribution in investigating the response mechanisms of the plant to positive inductions.

Keywords: Trichoderma spp.; chitosan; humic and fulvic acids; phosphites; plant-growth-promoting rhizobacteria; protein hydrolysates; seaweed extracts.

Figure 1

Main effects of rising temperatures on the bunch [40,42,43].

Figure 2

Categories of plant biostimulants [94,102,103,104,105,106,107,108,109].

Figure 3

Main effects of biostimulants (PBs) on crops [33,74,111,112,113,114,115,116,117].

Figure 4

The main plant resistance responses induced at the systemic level. SAR is activated in healthy tissues, distant from the site of infection, and is mediated by SA. ISR is activated in the whole plant following the establishment of symbiosis with beneficial microorganisms at the rhizosphere level and is mediated by JA/ET [141,142,143].