The era of mechanization (1.0) and absolute chemistry (2.0) belongs to the past, the era of biosolutions and precision viticulture (3.0) is at a rather advanced point, it is now necessary to quickly push on agromotics and digital agriculture ( viticulture 4.0), or more teleinformatics, mechatronics and business services, including decision support (DSS), to manage production cycles efficiently and economically, including emergencies and critical issues.
The vineyard communicates, sends signals that we do not understand or are no longer able to interpret. A missed dialogue that leads to serious consequences, especially in years affected by strong summer stresses. Indeed, it is paradoxical that in the era of advanced systems and technologically advanced innovations, a hot and dry summer, such as those of 2003, 2007, 2011, 2012, 2015, 2017, 2018 and 2020, is enough to send many wineries into crisis, with production also reduced by 70-80% and grape quality totally compromised. Yet it is since 2003 that despite the careful adoption of optimized cultivation systems considered valid in many areas, the vineyards have begun to send out signs of suffering, showing macroscopic anomalies both in the phenological phases and in the ripening of the grapes (Fig. 1).
The causes, direct and indirect, that contribute to these problems are many (Fig. 1), with different incidences depending on the cultivation area and the production model adopted, but which too often lead to the production of grapes with high sugar levels and decidedly alcoholic wines, with alcohol contents often higher than 15-16% vol. In this regard, it should be emphasized that both domestic and foreign consumers are registering a growing demand for wines with a moderate alcohol content, 12-13% vol., However, with freshness, lightness, balanced aromas, bright colors and the right flavor. The causes of this high alcoholic potential are due, on the one hand, to the artificially imposed, sometimes exaggerated, production containment and the concomitant need for correct phenolic maturation, ergo postponed harvests, and on the other hand by often penalizing summer weather courses, due to excess of temperature and water shortage, which in fact accelerate the technological ripening, slow down the phenolic ripening and cause excessive dehydration of the berries with consequent unwanted drying (Palliotti et al. 2014). Result: yield limitations, loss of acidity and varietal aromas, high pH values, decrease in color and microbiological stability of musts, typical over-ripening hints. In such conditions it is not even possible to resort to early harvests, as they would aggravate the situation and the wines would be unripe and unexpressed.
FLEXIBILITY AND NEW APPROACHES IN VINEYARD MANAGEMENT
There is no doubt that the climate change that has now been underway for some years is generating areas of cultivation where water shortages and thermal excesses are quite recurrent and in which, contrary to the maturation of phenols, the accumulation of sugars in musts is particularly fast and therefore requires a careful control. This is also necessary to avoid the final part of grape ripening coinciding with the hot periods, i.e. the end of August, and therefore avoid the dangerous losses of anthocyanins, aromatic precursors, organic acids as well as excessive dehydration and damage from sunburn. (sun-burn) (Fig. 2).
Climate change has increased the frequency of extreme weather phenomena, such as frosts, hailstorms, water bombs, excess heat and long periods of drought. Flexible management strategies are therefore required based on the presumable weather trend of the year. So far, innovations in precision viticulture have had little effect in avoiding the more extreme consequences of global warming, but something is changing. The new approach of the IoT (Internet of Thing) which essentially aims to network management software and a series of latest generation sensors and instruments, capable of detecting the physiological responses of plants with high precision, are leading to more attention to the plant and its union with the agro-ecosystem that hosts them (e.g. tensiometers, psychrometers, infrared thermometers, thermal cameras, multispectral and thermal cameras, NIR, dendrometers, sap-flow, fluorimeters, ray gas analyzers infrared, etc.). The integration of these measurements allows the management of fertilization, irrigation, phytosanitary protection interventions with greater efficiency, as well as the management of the canopy, the soil, the growth and ripening of the grapes and the harvest. It can therefore be said that we have started to straighten the antennas also inside the vineyard to pick up useful signals to guide management efficiently. But what signals does the vineyard emit in response to changes in environmental conditions?
WHY DO NOT YOU TALK?
While waiting for better clarification of the mechanisms of action that some compounds, volatile and non-volatile, produced and / or emitted by plants exercise for communication purposes, such as physical signals (electrical, acoustic, electromagnetic, etc.), volatomic footprint (volatile substances) , ionomic flux (constituted and active ions), joint action of some phytohormones (auxins, gibberellins, brassinazole, abscisic acid, etc.), it must be stressed that these obviously do not speak. And thank goodness, who knows what they would say following, for example, the treatments or mistreatments, of various kinds and more or less invasive, that all the researchers in the sector, including the writer, have inflicted and continue to inflict on plants without hesitation, of course. with the aim of increasing knowledge and finding technical solutions to specific problems. After all, for centuries plants have undergone often severe or even cynical manipulations, just think for example that in the second half of the 1800s, the French physiologist Claude Bernard (founder of experimental medicine and father of homeostasis) treating with diethyl ether (then used as anesthetic in the medical and veterinary field) a shrub capable of reacting to tactile and acoustic stimuli by closing the leaves on themselves, or the sensitive Mimosa pudica , demonstrated that this function was inhibited, just like human / animal pain during surgery, and formulated the following postulate: plants and animals share a common biological essence that is disrupted by anesthetics.
THE LANGUAGE OF SIGNS
Experience indicates that plants are capable of communicating, especially with the surrounding environment, expressing their “well-being / discomfort” through the language of “signs / symptoms” in accordance with a natural paradigm that can be equated with the “action” scheme – reaction “. Physically, Isaac Newton affirmed that to every action corresponds an equal and opposite reaction; biologically, plant organisms “act” according to a genetically pre-established program and “react” to external stimuli when they become problematic, for example excess / defect, absent / present, etc.
Contrary to natural biocoenoses (woods and forests), anthropized plant contexts, such as vineyards, where unfortunately the simplification and limitation of biodiversity still predominate today, must respond with greater problems and costs to a series of external stimuli that may come from the soil , from the troposphere and from both animal and plant parasites. As a result of limitations or excesses of many of these stimuli and depending on their intensity and duration, the plants counteract with visual manifestations, at first labile then gradually more and more manifest until reaching serious dysfunctions and even death of the affected tissues.
Here are a few simple and visually observable examples of “actions” (deficiencies or excesses) that induce deviations from normal metabolism and visible phenotypic “reactions” , which then require appropriate corrective actions:
- H 2 O deficiency in the soil (action) = stomatal closure, physiological limitations and stunted development (reaction)
- O 2 deficiency in the soil (action) = chlorosis of the leaves and reduced growth (reaction)
- Lack of light (action) = increase in photosynthetic pigments (chlorophylls and carotenoids) and in the expansion of the leaf blades and planophilicity of the same (reaction)
- Deficiencies of mineral elements (action) = symptoms at the foliar level typical for each macro and micro element (reaction)
- Lack of vigor (action) = stunted growth of the shoots, scarce emission of seedlings, chlorosis, small and limited number of berries (reaction)
- Excess of temperature (action) = chronic photoinhibitions of leaf tissues with chlorosis and necrosis and deep dehydration of the berries with browning and damage from burns (reaction)
- Excess of vigor (action) = spinning of the inflorescences, poor adjustment of the shoots and nutritional reserves not adequately reconstituted, insufficient composition of musts, greater sensitivity to fungal rot (reactions)
- Excess of light (action) = heliotropic movements of the leaves (reaction)
- Parasitic attacks (action) = production of phytoalexins and other secondary metabolites, volatile allelochemical compounds and specific acids (jasmonic and salicylic in particular) (reaction).
LOOKING TO UNDERSTAND (it is not anachronistic)
From simple observation, therefore, interesting inputs arrive, sometimes illuminating, at other times, in-depth studies and analyzes are required to identify the causes of the anomalous reactions.
The ongoing evolution of the sensor sector allows us to increase our perceptions. An increased sensitivity that can be used to precisely define the thread that binds actions to reactions and at the same time define behavioral models to finally face, with flexibility and precision, even the effects of climate change. In fact, the answer cannot be just genetic: the best breeding centers are looking for vines and rootstocks resistant to water and thermal stresses connected to the expected increase in average and maximum temperatures. Waiting for the epigenetic mechanisms underlying the resistances to be better clarified and which could be profitably exploited, for example that of an alleged “memory effect of long-term stress” through which, thanks to structural, genetic and biochemical modifications, the arboreal plants acquire over time, adaptability and resistance (Tombesi et al. 2018), it is useful to continue to use functional visual diagnostic methods, even if traditional, as well as obviously instrumental ones.
RESILIENCE GOAL
Who knows if these acquired resistances / resiliences are transmissible tout court , or if plants obtained agamically from subjects subjected to recurrent and severe stress, for example water and thermal stress, are really more resistant than those obtained from non-stressed plants. Speaking of resilience, biostimulants of natural origin are today a new frontier, as they represent innovative tools of growing interest to induce tolerance and / or resistance to both biotic and environmental stress and to optimize vineyard management. This class of compounds is also emerging due to the increase in biological and biodynamic cultivation systems which in fact, not being able to use chemical means, find a valid help in biosolutions. In addition to the latest generation biostimulants, represented by complex mixtures of various elements among which nucleic acids, vitamins, proteins, free amino acids, betaines, phytohormones, polysaccharides, alginic acid, diterpenes, macro and micronutrients stand out, among those used for a long time with there are arbuscular mycorrhizae (Glomus iranicum , Glomus intraradicens, etc.) and extracts of brown algae (Aschophyllum nodosum, Macrocystis integrifolia, Laminaria, Fucus, Ecklonia maxima, Sargassum, etc.), pure or mixed with specially selected yeasts, also defined as physioactivators, as they are capable of enhancing both the restart of the plant after any environmental stress and the accumulation of transcripts of genes responsible for inducing resistance against various fungal parasites. Certainly the advent of recent disciplines, such as phenotyping, and the use of new technologies, such as nuclear magnetic resonance and laser technologies, which allow the acquisition of very high resolution images, especially of lesser known organs, tissues and structures such as roots. , vascular system, cytoskeleton, etc., open new frontiers that will one day certainly be useful, but which undoubtedly require to be then accompanied by resolutive techniques to be applied in the field. In the meantime, it is wise to use, even in the age of advanced information and complex systems such as today, the useful information deriving from the skilful observation of the symptoms manifested by plants in difficulty in order to optimize production and its composition, sometimes to remove from serious dangers, such as death, tissues, organs and even the whole plant (Fig. 3).
