Coating their seeds could fortify crops in arid regions

Individual species of plants thrive within set temperature ranges and as the world keeps on warming many plants may find it harder to cope. These include staple crops upon which the planet’s food supply depends.

Add to that increasing droughts from climate change in already semi-arid areas and we may have a crisis on our hands with seeds shriveling up and dying even before plants could sprout.

A team of scientists at the Massachussets Institute of Technology in the United States believe they have the answer to how to protect vulnerable seeds from water shortages as they germinate. The answer lies in covering seeds with protective layers through bioengineering.

“In semi-arid regions, water stress during seed germination and early seedling growth is the highest cause of crop loss,” the researchers explain.

However, the seeds of plants like chia and basil produce a mucilage-based hydrogel that helps them retain water while also regulating the intake of nutrients and facilitating interactions with beneficial microorganisms.

Taking their cue from these seeds, the scientists have developed a two-layered biopolymer-based coating with the aim of boosting seeds’ water-stress tolerance in the sandy soils of semi-arid areas lik Morocco.

A gel-like outer layer retains any moisture available while enveloping the seed inside while an inner coating contains microorganisms called rhizobacteria along with some nutrients. “When exposed to soil and water, the microbes will fix nitrogen into the soil, providing the growing seedling with nutritious fertilizer to help it along,” the scientists explain.

The double coating aimed at helping seeds withstand water shortages has been the fruit of years of research by Benedetto Marelli, a professor of civil and environmental engineering at MIT, and his colleagues who earlier developed a coating that help germinating seeds resist high salinity in the soil.

To test their invention in real-life settings, Marelli and his colleagues cultured common beans (Phaseolus vulgaris) in water-deprived conditions at an experimental farm in Ben Guerir, Morocco. Their coating on the bean seeds directed rhizobacteria to form root nodules, which boosted the plants’ ability to endure drought-like conditions as they continued to grow, they say.

“Because there is clear evidence that climate change is going to impact the basin of the Mediterranean area, we need to develop new technologies that can help to mitigate these changes in the climate patterns that are going to make less water available to agriculture,” the scientist says.

“Our idea was to provide multiple functions to the seed coating, not only targeting this water jacket, but also targeting the rhizobacteria. This is the real added value to our seed coating, because these are self-replicating microorganisms that can fix nitrogen for the plants, so they can decrease the amount of nitrogen-based fertilizers that are provided, and enrich the soil,” Marelli adds.

The coatings are fairly simple, which means that coated seeds could be deployed even at remote locations in the developing world.

“The system is so simple that it can be applied to any seed,” Marelli says. “And we can design the seed coating to respond to different climate patterns [and] it might even be possible to tailor coatings to the predicted rainfall of a particular growing season.”