Unleashing Soil Microbes

The far-reaching consequences of climate change are beginning to infiltrate every aspect of our lives, with perhaps none more vital than the sustenance gracing our dinner tables. Among these challenges, droughts emerge as a significant menace to our global food supply, casting a particularly ominous shadow over crops like maize, wheat, and rice, which are especially susceptible to the ravages of dry weather. To counteract this looming threat, scientists have spent decades attempting to fortify plants against drought's grip, employing cutting-edge techniques such as genetic modification. While these endeavors have achieved some success, it's becoming increasingly clear that genetically modified plants are not the sole answer. Surprisingly, an uncomplicated remedy may have been at our fingertips all along: the microorganisms residing in the soil, constituting a plant's microbiome.

For those who've inadvertently neglected to water their plants, the havoc that drought can wreak is all too familiar. What's disheartening is that the damage inflicted by drought isn't easily rectified even after water returns. While certain molecular, structural, and physiological changes triggered by drought can revert to normalcy with rainfall, many leave behind indelible physical scars. Consequently, even brief episodes of drought can yield enduring consequences. During dry spells, plants grapple with a diminished ability to extract essential nutrients from the soil. Their leaves wither, reducing the surface area available for photosynthesis, and their cells fail to elongate as usual. These cumulative effects culminate in stunted growth, reduced edible yield, and a less-than-appealing taste. Astonishingly, the impact of a single growing season marred by drought can reverberate throughout the food supply chain for years.

With the global population on the rise, agriculture is already teetering on the brink of its capacities. As climate change amplifies the frequency and severity of droughts, the challenge of feeding a burgeoning population with dwindling food resources intensifies. This challenge is manifesting itself in tangible ways. Across Europe, the combination of heatwaves and drought has driven the proportion of non-harvestable grain to nearly triple over the past six decades, soaring from 2.2% between 1964 and 1990 to over 7% between 1991 and 2015. In developing nations situated in tropical regions, the situation is even more dire, with wheat yields projected to plummet by approximately 15% in African and Southern Asian countries by 2050.

The urgency of the situation has thrust the quest to shield plants from drought-induced devastation into the spotlight for decades. While many plants possess inherent mechanisms to survive drought, extensive research has also focused on genetic modifications aimed at bolstering drought resilience. However, it's not solely the plants' genetic makeup that holds the key to their survival during dry spells—it's their microbial counterparts. Microbiomes, intricate communities of diminutive organisms, thrive within ecosystems, encompassing bacteria, fungi, algae, and more. While the term "microbiome" may evoke thoughts of the human body, plants harbor their own microbiomes. These encompass microorganisms residing both inside and outside the plant, as well as within the soil surrounding the roots.

These microbiomes play pivotal roles in stimulating plant growth, facilitating the conversion of nitrogen into forms usable by plants, and absorbing nutrients for transmission to their host plants. Astonishingly, certain microorganisms within these communities release molecules that contribute to drought resistance. Some bacteria emit plant growth regulators that influence energy metabolism, enhance photosynthesis, and fortify the antioxidant system. Others produce enzymes that foster growth by dampening the effects of ethylene, a stress-inducing hormone released when plants are under duress. Additionally, certain microbes secrete exopolysaccharides, constructing protective biofilms around plant roots to curb water loss.

However, these aren't generic growth stimulators; their impact on plant growth and crop yield appears to be negligible under normal conditions. Their potency only becomes apparent when drought strikes. Intriguingly, not all plants seem to host these beneficial microbial allies. Consequently, scientists are working diligently to harness the potential of these drought-resilient microbiomes, seeking to activate them consistently, particularly for crops intended for consumption. A notable example comes from China in 2017, where researchers introduced bacteria from drought-resistant desert plants into the soil of wheat cultivation. The result was wheat plants displaying less leaf curling, longer roots and shoots, increased chlorophyll and sugars, and an overall higher total weight under simulated drought conditions.

Similarly, in Milan in 2015, researchers achieved parallel outcomes by introducing bacteria from grapevine microbiomes to pepper plants. While large-scale implementation of plant microbiomes remains on the horizon, the potential of this approach is immensely promising. By infusing fertilizers or soil with these microorganisms, smaller farms and agricultural regions in the developing world could significantly boost yields and improve livelihoods. In this remarkable collaboration between minuscule organisms and crucial crops, a potent solution to a daunting global problem may well come from the tiniest of sources.