Technical Yearbook 2023

How to fight water stress with a new foliar treatment A dual synergistic approach is required to manage extended or unpredictable water stress. On the one hand, planning of long-term strategies to be implemented during the planting phase; on the other, identifying flexible and timely techniques applicable during the season. The use of new natural foliar applications based on the action of specific microbial derivatives, such as inactivated yeasts and bacterial extracts, is a state-of-the-art cultivation strategy.

Specifically, LalVigne ProHydro™, based on the selected wine yeast derivative ( Saccharomyces cerevisiae ) and L-proline of natural origin ( Corynebacterium glutamicum ), was developed to improve vine response to water stress. Its preventive use achieves a dual action, ensuring high photosynthetic activity and avoiding excessive slowdown of basic plant metabolism, while preparing the plant to cope with water stress consequences. How the new foliar treatment works The water inside the plant moves, because of the negative water potential gradient, shifting from the soil to the atmosphere through roots, stems, shoots and leaves. In the event of water shortage, resources may be insufficient to ensure transpiration, photochemical reaction and cell turgor, three aspects that will be inhibited to varying degrees and dynamics. In these situations, the vine puts strategies in place to adapt to limiting conditions, such as increasing leaf angle and folding leaf margin, to escape exposure to direct light, or various chemical-physical rearrangements to regulate the water and biochemical balance of its tissues. These include the accumulation of proline, an osmotically active amino acid which, in the case of stress, is synthesised in chloroplasts and accumulated in the cytoplasm at concentrations equal to 10 times those of the pre-stress situation. Proline fosters osmotic adjustments necessary for maintaining cell turgor and draws water from the organelles with higher water potential. In addition, day-night proline turnover encourages reducing power (NADP+) accumulation and prevents the formation of reactive oxygen species, toxic molecules that cause yellowing and necrosis of stressed leaves. In 2020, potted Pinot noir vines were treated with LalVigne ProHydro™ and compared with an untreated control sample. From one day before treatment and at

PHOTO 1. Impact of water stress; even if water becomes available later, the plant is no longer able to recover pre stress photosynthesis rates. Extensive R&D conducted by Lallemand (patent pending) has led to the development of several specific formulations that can optimise vineyard performance in terms of improving tolerance to abiotic stresses (Giordano et al ., 2021) and phenolic and aromatic maturation (Pastore et al ., 2020).

FIGURE 2. Percentage of endogenous proline accumulation in response to treatment with LalVigne ProHydro™ at 1 kg/ha. A single treatment induced a constant accumulation of over 170% for the next 14 days, equal to a constant increase of 1.26 micromoles per day per g of weight.

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TECHNICAL YEARBOOK 2023