23 July 2021
Seeds of success in a water jacket
Published online 9 July 2021
A coating of biodegradable natural polymers can help seeds germinate in dry and challenging conditions.
The prospects for germinating seeds in semi-arid and sandy soils are being improved by learning a lesson from nature. Researchers in the US and Morocco have developed a biopolymer seed coating that can respond to challenging soil and climate conditions, improving the seeds’ ability to germinate and thrive.
The coating has been inspired by chia and basil seeds, which produce a natural water-retaining gel that promotes germination, regulates nutrient entry and facilitates interactions with beneficial microorganisms.
Researcher Benedetto Marelli says that the team’s coating can be programmed to meet a specific need, such as the ability to grow in dry soil.
“As climate change effects become ever present, we need to find strategies to adapt our agri-food system while making it more resilient and sustainable,” he says.
Marelli and colleagues at the Massachusetts Institute of Technology in the US developed the seed coating together with co-workers at the Mohammed VI Polytechnic University in Morocco.
After looking carefully at what nature already provides for chia and basil seeds, the team found success with a double-layered coating of natural biopolymers combined with beneficial bacteria. The inner layer is composed of silk and the sugar trehalose, and carries rhizobacteria that form mutually beneficial relationships with many plants. The outer layer of pectin and carboxymethylcellulose acts as a water jacket that retains moisture and swells after sowing.
The system was tested using seeds of the common bean (Phaseolus vulgaris) at an experimental farm in Ben Guerir, Morocco. The coating allowed more healthy plants to develop under water-limitation stress in drought-prone marginal soils.
Professor Leónie Bentsink, a seed biologist at Wageningen University in the Netherlands, who was not involved in the research, comments: "This is a promising investigation towards improving seedling establishment in challenging environments. I foresee however that it will be an expensive technology.” She queries whether the increase in harvestable product will justify the costs.
To assess the commercial viability of their approach, the researchers now plan to run larger field studies in Morocco. They also intend to tailor the seed coatings to achieve better growth in specific environments.
Marelli accepts that to offer a significant advance they will need to demonstrate that the coating technology works with many different types of seeds.
“Our goal is to have an impact on communities that need these technologies to guarantee food security and enhance wealth, especially in marginal and drought prone lands, such as some areas of the Middle East,” Marelli says.
Zvinavashe, A. T. et al. Programmable design of seed coating function induces water-stress tolerance in semi-arid regions. Nat. Food https://doi.org/10.1038/s43016-021-00315-8 (2021).