17 October 2019
Shaking up salt-friendly agriculture
Published online 20 December 2017
Scientists look to the past for food security solutions.
Desalination is a partial solution, but it’s unlikely to provide enough freshwater. To close the gap, scientists in the region are looking to the wilderness and adapting and adopting ancient agricultural practices.
“Irrigated systems produce about a third of the world’s food, but they’re all unsustainable systems at the moment,” says Mark Tester, head of the SALTLAB at King Abdullah University of Science and Technology (KAUST). “Every groundwater aquifer that’s being used for irrigation is being depleted. This is very clearly documented and is a massive concern. There’s an imperative to change our current agricultural system.”
Reaching out to relatives
Tester believes part of the solution can be found in the wild relatives of crops.
During domestication, crop plants were bred for greater productivity and convenience, not durability. While our major crops do poorly in drought or salty water, some of their relatives grow well on poor soils and unreliable or low-quality water. For Tester, the genomes of these plants are a treasure trove which scientists and breeders can use to make crops more resilient.
Tester’s team has already had some success. Last year, they reported the discovery of a salt-tolerant barley strain. A lab in Germany had crossed domesticated barley with 25 wild strains from around the Middle East, creating an ideal resource for Tester, a population with “a balance between having plants that are domesticated enough to do reasonably well and sufficiently wild to find something interesting”.
Tester’s lab grew the partially wild barley lines at the International Center for Biosaline Agriculture (ICBA) in Dubai for two years with fresh and salty water. A single line descended from a plant in northeastern Iraq grew better than domesticated barley in the stressful conditions of the field trials — low quality soil, intermittent water stress, and high temperatures — and also did well when irrigated with saline water. The team has pinpointed the genetic location responsible for the plant’s stress tolerance and are now crossing it into commercial barley strains.
Another advance has come from a wild tomato strain found in the Galápagos Islands, which grows on exposed cliff faces constantly splashed by seawater. “That variety has got an incredible ability to maintain fruit production in saline conditions,” says Tester. The genetic regions responsible were identified by a student in his lab and are now being crossed into several commercial tomato varieties. The team is also sequencing a highly salt tolerant strain of currant tomato which they discovered during the project.
"We have to reevaluate and revisit how agriculture should be implemented for the future."
To discover valuable genomic resources, Tester’s lab combines modern sequencing technologies with a high-throughput plant characterization platform he established in Australia before moving to KAUST. By statistically analyzing precise differences in plants’ stress tolerance along with their genome sequence, the team identifies genomic regions linked with valuable traits, accelerating the pace of breeding.
With this technique, they’ve identified segments of the rice genome linked with tolerance. Tester also plans to use this approach to help domesticate quinoa, which currently has too much variation for large-scale industrial farming.
With a little help from little friends
Elsewhere at KAUST, Heribert Hirt is tackling the problem from a different angle. Rather than breed tougher plants, he aims to supplement them with microbes that can help them cope with adverse conditions.
To find these tiny helpers, Hirt turned to the desert and the plants that thrive there.
“The desert is actually a natural laboratory where an experiment has been going on for thousands of years with enormous pressure on plants to survive. As you go through the desert, nothing is growing and then suddenly you have a plant there. How does it do that?”
Along with international collaborators, Hirt is collecting microbes from desert plants and screening them to discover those which improve plants’ stress tolerance. They’ve identified a microbe which can improve yields by 20% under saline conditions, and this year his lab published its genome sequence.
Through the microbe’s genome, Hirt hopes to uncover the molecular language mediating its interaction with plants. “We know a lot about how pathogens and plants talk to each other, but we basically know nothing about how beneficial microbes and plants talk together,” says Hirt. “If we could actually understand that better, could we then predict what works together?”
Hirt believes that the low-cost, low-tech nature of microbial supplements makes this approach particularly useful for small-scale and subsistence farmers. Distributing the system to farmers in need is likely to pose a significant hurdle, but Hirt is reaching out to NGOs engaged with poor farmers throughout the world. “We are just at the brink of an ecological green revolution where microbes are coming into the game, where we can replace a lot of the chemicals that we have been using as fertilizers, herbicides, and pesticides,” he says. “But this also depends a lot on us scientists providing simple solutions for people.”
Improving the lot of small-scale farmers is also the aim of an agronomist at ICBA, Dionysia Lyra, who is working on a technique known as modular farming. “This modular farming approach is not really something new,” she says, explaining that fish and rice have long been grown together in the rice paddies of southeast Asia. Lyra’s goal is to develop a similar multi-component system for use in the Middle East, with the output of one component of the farm serving as the input for the next.
The project started with the observation that small-scale desalination is used on some farms to purify salty groundwater. The fresh water enables these farms to grow high-value crops, but the waste brine from the desalination is often poured back into the soil, further contaminating the groundwater. To break this cycle, Lyra and her team came up with a way to put the brine to use: fish farming. Not only does this produce fish for the farmer, but the fish waste serves as manure to fertilize the water, which is then used to irrigate salt-tolerant crops such as Salicornia.
According to Lyra, modular farms offer a resilience to climate that existing monoculture systems don’t have. “Taking into consideration the challenges of overpopulation, low-quality water resources, and degraded lands, we have to reevaluate and revisit how agriculture should be implemented for the future,” says Lyra.
By combining components, modular farms can use marginal land to provide protein and other nutrients. “They’re also sustainable because water efficiency is maximized and we’re trying to recycle the water and other components,” says Lyra.
Lyra is still refining the system, but she plans to eventually hold training for farmers, as well as developing a range of modular components which could be combined based on local conditions.
“It takes some time to see how the system works and to get all the components working in harmony,” she says. While the project is currently limited to the UAE, she hopes to expand to other regional countries such as Jordan, Tunisia, and Morocco. “To be able to feed the people in deserts and marginal environments, the farming communities need to be able to sustain themselves in terms of food, and these kinds of systems are perfect to cover those needs.”
By combining desalination with approaches that improve water use efficiency and take advantage of low quality water, farmers in the region may be able to improve their productivity in the face of difficult and worsening conditions.
In the long run, the aim is to develop a saltwater-based agricultural system in which farmers can irrigate salt tolerant crops with low-quality water in a sustainable and economically viable manner.