Holistic understanding of the response of grapevines to foliar application of seaweed extracts

Abstract

Viticulture is highly dependent on phytochemicals to maintain good vineyard health. However, to reduce their accumulation in the environment, green regulations are driving the development of eco-friendly strategies. In this respect, seaweeds have proven to be one of the marine resources with the highest potential as plant protective agents, representing an environmentally-friendly alternative approach for sustainable wine production. The current work follows an interdisciplinary framework to evaluate the capacity of Ulva ohnoi and Rugulopteryx okamurae seaweeds to induce defense mechanisms in grapevine plants. To our knowledge, this is the first study to evaluate Rugulopteryx okamurae as a biostimulator . This macroalgae is relevant since it is an invasive species on the Atlantic and Mediterranean coast causing incalculable economic and environmental burdens. Four extracts (UL1, UL2, RU1 and RU2 developed from Ulva and Rugulopteryx, respectively) were foliar applied to Tempranillo plants cultivated under greenhouse conditions. UL1 and RU2 stood out for their capacity to induce defense genes, such as a PR10, PAL, STS48 and GST1, mainly 24 hours after the first application. The increased expression level of these genes agreed with i) an increase in trans-piceid and trans-resveratrol content, mainly in the RU2 treated leaves, and, ii) an increase in jasmonic acid and decrease in salicylic acid. Moreover, an induction of the activity of the antioxidant enzymes was observed at the end of the experiment, with an increase in superoxide dismutase and catalase in the RU2-treated leaves in particular. Interestingly, while foliar fungal diversity was not influenced by the treatments, alga extract amendment modified fungal composition, RU2 application enriching the content of various groups known for their biocontrol activity. Overall, the results evidenced the capacity of Rugulopteryx okamurae for grapevine biostimulation, inducing the activation of several secondary metabolite pathways and promoting the abundance of beneficial microbiota involved in grapevine protection. While further studies are needed to unravel the bioactive compound(s) involved, including conducting field experiments etc., the current findings are the first steps towards the inclusion of Rugulopteryx okamurae in a circular scheme that would reduce its accumulation on the coast and benefit the viticulture sector at the same time.

SEAWINES: Use of macroalgae as biostimulants against fungal diseases in grapevines

“…3). Importantly these extracts were also the ones with highest capacity for phytoalexin production, inducing stilbene biosynthesis (data not shown) [8]. An induction of the activity of the antioxidant enzymes was also observed with an increase in SOD and CAT in the RU2-treated leaves in particular (data not shown).…”

“…2). In particular, the upregulation of genes in RU2 treated samples was in general more evident after 24 hours, suggesting that this algal extract is triggering a fast response [8]. The most induced gene was the one coding for Ribonuclease-like PR10 protein, mainly in UL1 and RU2, which has been shown to be induced by pathogen attack in a wide variety of plant species [8], suggesting that grapevines could recognize the algae extract compounds as an elicitor of plant defence [9].…”

“…Sporobolomyces, known for their antifungal activity [11], were particularly abundant in the RU2 samples compared with the water-treated leaves. It was also noteworthy that Debaryomyces hansenii was significantly enriched in UL2 (0.68% relative abundance), and particularly in RU2 leaves (2%), while it was almost absent in the remaining treatments [8]. Several strains within this genus exhibit antagonistic activity against fungal phytopathogens through diverse mechanisms, such as competition for nutrients and space, mycoparasitism, the secretion of antifungal substances (e.g.…”

“…Greenhouse experiments to evaluate the biostimulant capacity of the extractsTempranillo (Vitis vinifera L.) grapevine plants grown under greenhouse were treated either with one or two applications of Ulva and Rugulopteryx extracts (UL1, UL2, RU1 and RU2). The response of the plants was studied by collecting leaves at different time points (24, 48 and 144 hours after treatments, Fig.1,[8]). …”

Nature‐based strategies to regenerate the functioning and biodiversity of vineyards

“…Most of these nonmicrobial biostimulants are foliar applied. Algal extracts have also commonly been used to improve the yield of vineyards, although other by‐products of the agrifood industry, including pruning remains and vinification waste, as well as the by‐products of vegetable production, are also an important source of bioactive ingredients (Jindo et al, 2022; Zarraonaindia et al, 2023).…”