Silk coated seeds may work on previously unsuitable land

Published on Feb. 8, 2020

New research from the Massachusetts Institute of Technology (MIT) may open up areas of land to farming that are currently considered unsuitable for agriculture.

The research, partly supported by the Mohammed VI Polytechnique University-MIT Research Program, Office of Navel Research and Office of the Dean of Graduate Fellowship Research, discovered a protective seed covering that also supplies essential nutrients to germinating plants. 

Past research sparks idea

            During previous research, MIT Professor of Civil and Environmental Engineering Benedetto Marelli discovered an unlikely ally in silk as a way to coat seeds used for food crops and extend their shelf life.

            From this, Marelli and graduate students Augustine Zvinavashe and Hui Sun’s study was born.

            According to MIT, the study found silk treated with a bacteria that naturally produces nitrogen fertilizer helps germinating plants develop. Results from the study have shown seeds can grow successfully in soils that are too salty for untreated seeds to develop.

            “Back when I was doing some research on silk seed coating to extend shelf life, I stumbled on biofertilizers that can be used to increase the amount of nutrients in the soil,” explains Marelli. “These fertilizers use microbes that live symbiotically with certain plants and convert nitrogen from the air into a form that can be readily taken up by plants.” 

            Marelli points out this not only provides a natural fertilizer to plant crops, it also avoids problems found when using other fertilizing approaches.

“One of the big problems with nitrogen fertilizers is they have a big environmental impact because they are very energetically demanding to produce,” he says. “Artificial fertilizers may also have a negative impact on soil quality.”

Creating a new mixture

Nitrogen-fixing bacteria, also known as rhizobacteria, occur naturally in soils around the world. With different local varieties found in different regions, they are very hard to preserve outside of their natural soil environment, according to MIT.

However, since silk can preserve biological material, Marelli and his team decided to try it out on rhizobacteria.

            “We came up with the idea to use them in our seed coating and once the seeds were in the soil, they would resuscitate,” says Marelli.

Despite the promising outcome, preliminary tests did not go as well as expected, as the bacteria weren’t preserved as well as Marelli and his team had hoped.

            That’s when Zvinavashe came up with the idea of adding a trehalose to the mix.

According to MIT, trehalose is a type of sugar in which some organisms use to survive in low-water conditions.

Seed coating process 

Marelli explains the silk, bacteria and trehalose were suspended in water and then they simply soaked the seeds in the solution for a few seconds to produce an even coating. He notes the seeds were tested at both MIT and a research facility operated by the Mohammed VI Polytechnique University in Ben Guerir, Morroco.

            “The plants receiving ongoing fertilizer production from the bacteria developed in better health than those from untreated seeds and grew successfully in soil from fields that are presently not productive for agriculture,” Marelli explains. 

            Marelli notes this coating can potentially be applied to seeds via dipping or spray coating and either process can be done at ordinary ambient temperature and pressure. 

            “The process is fast, easy and it might be scalable to allow for larger farms and unskilled growers to make use of it,” Zvinavashe says. “The seeds can be simply dip-coated for a few seconds to produce a coating that is just a few micrometers thick.”

            “We use ordinary silk that is water soluble, so as soon as it is exposed to the soil, the bacteria are released,” Marelli says. “However, the coating still provides enough protection and nutrients to allow the seeds to germinate in soil with a salinity level that would ordinarily prevent their normal growth”

            He continues, “With this technology we are seeing plants growing where otherwise nothing grows.”

Further research

Marelli explains legume crops, such as common beans and chickpeas, have been the focus of their research so far because rhizobacteria normally provide fertilizer to legume crops. 

However, Marelli says it may be possible to adapt them to work with other kinds of crops as well, which is part of the team’s ongoing research.

            “There is a big push to extend the use of rhizobacteria to non-legume crops,” Marelli explains. “However, even if limited to legume crops, the method could still make a significant difference to regions with large areas of saline soil.”

            Marelli says he hopes this process will open up areas now considered unsuitable for agriculture. 

He also notes, the next step in their research will be working on developing new coatings that could not only protect seeds from saline soil, but also make them more resistant to drought, using coatings that absorb water from the soil. 

            Information in this article was compiled from an article in Science Daily titled Coated seeds may enable agriculture on marginal lands. This article can be found at sciencedaily.com. Marelli and his team’s findings were originally published in the PNAS journal in November.

            Hannah Bugas is the assistant editor for the Wyoming Livestock Roundup. Send comments on this article to roundup@wylr.net.