Grapes, Wine, and Climate Change

Will there be good wine available in the future?

by Mike Miller

Spoiler alert: Yes!! (See especially the section on Marine Microbes below)

A number of approaches have been taken to drought and heat in the prime grape growing regions of the world in order to ensure a continuing supply of good quality wines. Among them are:

Rootstocks: The use of roots instead of own-rooted vines started in the latter part of the nineteenth century, primarily as a response to the problem of phylloxera that was leading to the destruction of European vineyards. With use, it was learned that many rootstocks also imparted significant resistance to nematodes, another grapevine pest.

Starting in the 1980’s it was observed that some rootstocks fared better under drought conditions than others, and growers began making decisions based on these early drought tolerance observations. The results were not always satisfactory. For example, rootstock 110R was shown to be somewhat drought tolerant. It had a deep root structure, and could source water from deep soils or deep aquifers better than most others. It did have one shortcoming, a vigorous growth habit that resulted in a heavy canopy. This meant there was extra pruning work required to ensure that the extra water went into the grapes themselves rather than just into much larger plants. Another drawback with 110R was its use in sandier soils where there was little water retention in the deep root area as well as the shallow root area. Here, with the addition of modest irrigation, a rootstock with an extensive shallow, fine root structure fared much better. Other work on these plant/root/soil interactions has been proposed and is underway. (1)

A recent study on some root physical properties may help in the selection of the better rootstocks for use in drier conditions. As the soil dries, the normal reaction of roots is to shrink as there is less water available to transport to the leaves and fruit. Bartlett (2) found that rootstocks that had less physical shrinkage when transitioning from wet soil conditions to dry soil conditions fared better in supporting the plant during drought conditions. Perhaps a key attribute of drought tolerant rootstocks is the ability or their roots to maintain physical contact with the soil as the soil dries.

Rhizospheric Microorganisms: Another technique being studied is the use of rhizospheric bacteria and fungi to reduce the negative impact of a low water environment on grapevines. These studies are in their in their infancy, but are showing promising results. In one study soil microorganisms from hot, dry soil in Senegal were injected into the soil around the roots of plants being grown in Italy. The results were better horizontal root growth, and better ability to absorb limited soil moisture. (3) During drought stress, plants produce excess ethylene as part of a mechanism to slow growth. Another study found that injecting the soil with bacteria that produce an ethylene degrading biochemical helped plants achieve better growth during drought stress conditions than in the absence of these bacteria. (4) Other studies are underway, and are showing that in addition to improving drought stress resistance, the bacteria are improving both soil texture and soil nutrient levels as well. (5)

Marine Microbes: The most interesting recent study involved the use of marine rhizobacteria collected from coastal salt marshes and inoculated in grapevine soils. The test grapevines were then exposed to significant heat stress (rather than water stress) and evaluated for a variety of plant health and growth parameters. One of the two bacteria combinations tested showed grapevines with improved heat stress tolerance versus an uninoculated control. The second bacteria combination showed grapevines with “heatwave amelioration.” Essentially, those plant showed little if any negative impacts from their exposure to excess heat. Leaf cell structure and several leaf biochemicals were relatively unchanged from unstressed control plants

This is huge! Although further studies, such as how to optimize the bacterial inoculum, how frequently and how long to apply it are needed. Also, the process must be evaluated at the vineyard level, and the grapes and wines made from them must be evaluated to ensure there are no surprises. Nevertheless, this and work described above provide valuable tools to counter our changing weather patterns.

In conclusion, the answer to the question of will we have good wine in the future is YES! With the work underway and recent breakthroughs, despite warmer temperatures in many areas and less rain in some than we are used to, winegrapes will continue to grow well in traditional growing areas, and there will likely be some new growing areas opening up as well.

(1) Fichtl, L., et al., (2023). Towards grapevine root architectural models to adapt viticulture to drought, Frontiers in Plant Science 14 1162506.

(2) Bartlett, M. K., et al., (2022). Root pressure–volume curve traits capture rootstock drought tolerance. Annals of Botany, 129(4), 389-402.

(3) Zoppellari, F., et al., (2014). Improvement of drought tolerance in maize (Zea mays L.) by selected rhizospheric microorganisms. Ital J Agrometeorol, 18(1), 5-18. Duan, B. et al., (2021). 1-Aminocyclopropane-1-Carboxylate deaminase-producing plant growth-promoting rhizobacteria improve drought stress tolerance in grapevine (Vitis vinifera l.). Frontiers in Plant Science, 12, 706990.

(4) Duan, B., et al., (2021). 1-Aminocyclopropane-1-Carboxylate deaminase-producing plant growth-promoting rhizobacteria improve drought stress tolerance in grapevine (Vitis vinifera l.). Frontiers in Plant Science, 12, 706990.

(5) Bhat, B. A., et al., (2022). The role of plant‐associated rhizobacteria in plant growth, biocontrol and abiotic stress management. Journal of Applied Microbiology, 133(5), 2717-2741

(6) Carreiras, J., et al., (2023). Improving Grapevine Heat Stress Resilience with Marine Plant Growth-Promoting Rhizobacteria Consortia. Microorganisms, 11(4), 856.

Comments or questions: mmiller@morethanadrink.com