To protect a growing world population against food insecurity, the chickpea is one crop that humanity definitely wants on its side: highly productive and rich in protein and calories, this legume is already a staple for millions. But, it faces the growing specter of drought, which threatens 80% of chickpea agriculture that currently depends on rainwater worldwide. 

Now, researchers may have found a way to turn this valuable crop into an actual boon against climate change, by identifying several chickpea varieties that can survive drought. What’s more, they’ve identified the genetic machinery behind this resilience, which might be transferable to other crops.

Chickpeas have a natural genetic diversity, and it’s already known that there are some varieties that can cope well with drought, though it’s not well-understood why. The researchers were therefore eager to see what genetic treasures they might unearth, and so they began their work by selecting 36 chickpea genotypes, which they grew out as seedlings in field experiments—unusually, situated in the city of Vienna—under two conditions: well-watered, and very dry. 

Typically, drought affects a legume’s ability to fill its pods with large, healthy seeds (which form the peas that we ultimately eat.) The researchers carefully measured this pod-filling ability across the different chickpea genotypes under the two climate conditions. Then they combined it along with other traits to develop something called a ‘stress susceptibility index’, which allowed them to categorize the growing chickpea plants into four groups—ranging from most drought-resilient, to least. 

At the same time, they took leaf samples from each plant, and measured the presence of 63 metabolites within: metabolites are substances that are made or used as an organism breaks down food. These substances are essential for growth, and their presence and accumulation in plant tissue, especially during key growth phases like pod-filling, can therefore provide clues about how well that process is going. 

These experiments revealed, first of all, that of the 36 chickpea strains that the researchers tested out, at least 13 of them showed real potential to weather the severities of drought. These varieties scored low on the stress susceptibility index, partly because they were able to keep producing a large quantity of healthy seeds despite the difficult conditions. 

At the same time, the researchers showed from their leaf tissue analysis that three metabolites in particular changed in concentration during the pod-filling phase of the plant growth in drought-stressed chickpeas. These were L-threonic acid, fructose, and various sugar alcohols. This discovery suggested that they have a key role to play in insulating those plants against stress.

Digging further, the researchers found a clear correlation between the most drought-resilient chickpea plants, and the concentration of metabolites: more resilient strains showed bigger changes in those three metabolites, and others. That was especially true for the sugar alcohols, a byproduct of photosynthesis that is known to help plants cope better with environmental stress. Interestingly also, higher fructose levels in plants is associated with a stronger ability to absorb moisture from the soil—handy in water-scarce situations. 

Finally, the researchers carried out a genetic analysis to connect the dots between drought-resilience, and the genetic machinery that might enable this. This revealed over 300 sections of the genome that were linked to metabolites and metabolic processes involved in drought tolerance. This gives scientists a clue about where to look, in future research, for specific genes that may help them breed and engineer more climate-resilient legumes and other plants. 

An extra bonus of the research was that by carrying out their experiments in an urban setting, the researchers were also able to demonstrate that chickpeas can grow in cities—which could help expand access to this protein-rich food.

The study’s findings may only become more relevant as the world warms. According to the work, drought-related agricultural losses worldwide have cost almost $30 billion over the past ten years. That may only grow as projections show that freshwater availability could decline by up to 50% by 2050, under increasing climate variation, at the same time as water demand from agriculture grows to meet an expanding human population. 

These stats make a strong case for developing more capable crops, and chickpeas are the natural starting point, the researchers say. “With their high protein content and their drought resistance, legumes such as chickpeas are a food of the future.”

Weckwerth et. al. “Natural variation in the chickpea metabolome under drought stress.” Plant Biology Journal. 2024.

Image: Prathyush Thomas