Harnessing Microbes for Drought-Resistant Crops: A Promising Solution

Climate change is poised to disrupt virtually every aspect of our lives, including the very sustenance on our dinner tables. Among the looming threats, droughts stand out as a major peril to our global food supply. This concern is amplified by the vulnerability of essential crops such as maize, wheat, and rice to dry weather. In response to this challenge, researchers have invested decades in high-tech approaches like genetic modification to bolster the drought resistance of plants. While these efforts have yielded some success, genetically modified plants aren't the sole remedy. Surprisingly, a straightforward solution may have been right under our fingertips all along: the soil-dwelling microbes that constitute a plant's microbiome.

For those who've experienced the unintentional neglect of watering their plants, the havoc that drought can wreak is familiar. Regrettably, the consequences of drought don't dissipate with the return of water. Although certain molecular, structural, and physiological changes triggered by drought may revert to normal with rain, many leave behind irreversible physical damage. Thus, even brief droughts can impose enduring consequences. During periods of drought, plants struggle to extract vital nutrients from the soil. Their leaves wither, reducing the surface area available for photosynthesis, while their cells fail to elongate as usual. The culmination of these effects results in stunted growth, diminished edible mass, and lackluster taste. Remarkably, a single growing season impacted by drought can reverberate through the food supply for years.

As the global population burgeons, agriculture is already straining its limits. With the intensification and increased frequency of droughts attributed to climate change, the challenge of nourishing more people with dwindling food resources looms ever larger. Evidently, this predicament is already unfolding. In Europe, heatwaves and droughts have caused the proportion of non-harvestable grain to nearly triple over six decades, surging from 2.2% between 1964 and 1990 to over 7% between 1991 and 2015. The situation is bleaker in developing tropical nations, where wheat yields are projected to plummet by approximately 15% in African and Southern Asian countries by 2050.

Given the gravity of the issue, scientists have long been exploring avenues to shield plants from the ravages of drought. Many plants have innate mechanisms to endure drought, and substantial research has delved into genetic alterations to augment drought resistance. Yet, the solution isn't confined solely to the genetic code of plants. It also resides in their microbial neighbors. Microbiomes, those intricate communities of minuscule organisms, thrive within ecosystems, comprising bacteria, fungi, algae, and more. While the term "microbiome" often evokes thoughts of the human body, plants too have microbiomes. These encompass microorganisms residing both inside and outside the plant and within the soil surrounding its roots.

These microbiomes play pivotal roles, stimulating plant growth, facilitating nitrogen transformation into plant-usable forms, and absorbing nutrients for transmission to their hosts. Intriguingly, certain microbes within these communities release molecules that contribute to drought resistance. Some bacteria secrete plant growth regulators that impact energy metabolism, bolster photosynthesis, and enhance the antioxidant system. Other bacteria produce enzymes that foster growth by quelling ethylene, a stress-inducing hormone released during plant distress. Additionally, some microbes secrete exopolysaccharides, which construct a protective biofilm around the plant's roots, curtailing water loss.

Yet, these aren't mere all-purpose growth-promoters. In normal conditions, their impact on plant growth and crop yield seems negligible. Their effects only manifest when drought strikes, and intriguingly, not all plants seem to harbor these supportive microbial companions. Thus, scientists are meticulously crafting strategies to harness these drought-resisting microbiomes and stimulate their consistent activation, especially for food-producing crops. A noteworthy example took place in 2017 when Chinese researchers introduced bacteria from drought-resistant desert plants into the soil of wheat cultivation. This intervention led to less leaf curling, lengthier roots and shoots, elevated chlorophyll and sugars, and an overall higher total weight in wheat plants subjected to simulated drought conditions.

Similarly, in Milan in 2015, researchers observed parallel outcomes by introducing bacteria from grapevine microbiomes to pepper plants. Although large-scale implementation of plant microbiomes remains on the horizon, the potential of this approach is immensely promising. By supplementing fertilizers or soil with these microbes, smaller farms and agricultural regions in the developing world could enhance yields and livelihoods. In this intriguing synergy between tiny organisms and vital crops, we might find a superlative solution to an imposing global problem.