Water fern gains more evidence as safe potential global food insecurity solution

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Is the floating freshwater fern commonly called Carolina azolla the potential answer to global food insecurity or a possible threat to humanity? On the heels of a study published earlier this year by researchers at Penn State on the plant's nutrition and digestibility, the team learned of concerns about the plant's potential toxin content.

The researchers joined an international effort to test Azolla and found that it does not contain cyanotoxins, potent toxins produced by a type of cyanobacteria, or blue-green algae, associated with the plant.

The team published their findings in the journal Plants.

"That finding suggests that azolla is food safe and has the potential to safely feed millions of people due to its rapid growth while free-floating on shallow fresh water without the need for nitrogen fertilizers," said Daniel Winstead, research technologist in Penn State's College of Agricultural Sciences and lead author on the earlier study. He works in the labs of Michael Jacobson, professor of ecosystem science and management, and Francesco Di Gioia, assistant professor of vegetable crop science.

"Azolla is an amazing plant that can double its biomass in two days and capture nitrogen from the air."

After the original study published, Winstead said, it was brought to his attention that the cyanobacteria that live inside azolla could produce powerful cyanotoxins that dissuade animals from eating the plant.

Cyanotoxins have been linked to neurodegenerative disorders including amyotrophic lateral sclerosis (ALS) and Parkinson's disease, liver and kidney failure, muscle paralysis and other severe health issues. Despite the threat of the toxins and the use and study of azolla, he explained they learned that no scientists had definitively tested for the presence of these toxins in azolla.

"I felt a sense of responsibility to help answer this question because we had just published about azolla's nutritional quality," Winstead said.

"I didn't want to be promoting the consumption of a potentially harmful plant. As I was preparing an experimental design, I was contacted by the Azolla Foundation about that organization's interest in our research. I reached out to them and asked if they knew anyone who was looking into azolla's toxicity from cyanotoxins."

Several weeks later he received an email saying a group of researchers was investigating the cyanobacteria-cyanotoxins in the azolla in question, and they invited Winstead to be a part of the study.

"Together, we analyzed the results and concluded that azolla, and more specifically a cyanobacterium that lives in cavities in the leaves of azolla, do not produce any of the main cyanotoxins," he said, explaining that the azolla's cyanobacterium is Nostoc azollae, an endosymbiont or organism that lives within or on the surface of another organism in a mutually beneficial relationship.

"More importantly, the known genes required to make these toxins are not even present within the genome of Nostoc azollae."

According to Winstead, this discovery adds to a growing body of evidence that azolla could be used broadly to solve several global challenges.

"It could help feed many people in need around the world as well as become a new source of biofertilizer and biodiesel," he said.

More information: Jonathan P. Bujak et al, Azolla as a Safe Food: Suppression of Cyanotoxin-Related Genes and Cyanotoxin Production in Its Symbiont, Nostoc azollae, Plants (2024). DOI: 10.3390/plants13192707

Provided by Pennsylvania State University