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Two sets of tobacco plants are shown. The control group on the left were untreated while the bigger plants on the right were treated with TC09.

KEARNEYSVILLE — There’s a fungus among us – and that’s a good thing.

Research conducted at the Appalachian Fruit Research Station in Kearneysville has demonstrated that an airborne fungus can dramatically accelerate plant growth if a germinating plant is near the fungus as it emits volatiles or gases.

The fungus, called Cladosporium sphaerospermum strain TC09, is often referred to simply as TC09. It’s harmless and is found in indoor environments. TC09 is virtually unnoticeable and is not known to cause any diseases or ailments in animals or plants.

“This is a game-changer for agriculture and for research that seeks innovative ways to accelerate plant growth,” said USDA scientist Chris Dardick, who works at the Appalachian Fruit Research Station in Kearneysville. “Its implications are far-reaching and will help ARS’ commitment to deliver cutting-edge scientific advances for American farmers and producers.”

As Dardick explained, TC09 is a relatively new species of fungi and scientists are still learning about it.

“It’s a fungus that was identified kind of serendipitously,” he said.

Dardick, who has a doctorate degree in molecular and cell biology, said that what initially appeared to be a contaminant found near a plant as part of an unrelated project, was later found to be a fungus after scientists noticed that the plants near TC09 were growing at a faster rate.

“The scientist then cultured the fungus and tested it, and it turned out that it was somehow stimulating the plants to grow faster,” he said.

It’s still unclear as to what TC09 actually does that makes plants grow faster. Dardick said it’s likely that the fungus releases some kind of a gas or a volatile compound that aids in the growth of plants. He described it as almost a hormonal reaction in the plants.

“Over the past three or four years we’ve been working with this thing, trying to study it and figure out exactly how what it does,” he said.

TC09 doesn’t form or grow on plants like the mold you may find on cheese or bread. Its mere presence seems to make the plants grow without any direct contact.

The “how” of this process has scientists a bit perplexed, but the end results are clear.

Dardick explained that when young plants at the seedling stage are exposed to this magical fungus for 10 to 20 days, “they’ll grow anywhere from four times to 30 times larger than they would without the stimulation.”

The research on TC09 began around four years ago when it was first discovered. Since then, scientists have used tobacco and pepper plants as models to study the conditions for accelerated plant growth once exposed to TC09. Following a relatively short duration of exposure at the seedling stage, the plants began to sense the fungi’s emissions. USDA scientists were then able to stimulate extremely rapid plant growth, earlier flowering and fruit yield increases.

The effects of TC09 were largely correlated with the duration of exposure. Visual observation indicated that plants with TC09 exposure for 10 days exhibited substantially more vigorous growth, thicker stems, larger leaves and a more robust root system relative to plants without fungal exposure.

Results also showed that treated plants flowered 20 days sooner and pepper plants yielded up to 213 percent more fruit that was ready for harvest three weeks earlier than untreated plants. More recent studies have shown similar research results for numerous other crops such as lettuce, arugula, kale, basil and other leafy greens.

Also, unlike other microbial species that have been tested, the researchers showed that TC09 does not induce defense or stress responses in exposed plants. Scientists hope to identify the specific volatiles and gases that stimulate plant growth in future research.

Research on microbial “biostimulants” that enhance plant growth has recently intensified because they provide an eco-friendly, cost-effective and sustainable strategy to benefit agriculture.

Real-world applications

The most effective use of TC09 is in controlled environments, like for example, greenhouses. Dardick pointed to the practice of urban agriculture, where companies are popping up in inner-city locations where they grow plants, like lettuce and other vegetables hydroponically in greenhouse-like environments.

“It’s that kind of industry where we expect this to initially have the most potential impact,” he said. “But in other areas such as starter plants, like growing seedlings for Home Depot or places like that where you’re trying to get many plants started quickly, there’s the potential for impact there as well.”

The USDA has patented the technology and has tested it with a number of different crops and all kinds of different herbs, including basil, lettuce, arugula and kale. It’s also been tested on strawberries, tomatoes and peppers.

Dardick pointed out that the reason why the USDA patented TC09 was to keep one company from owning it outright and blocking other groups from using it. The USDA wants this technology to be available to as many farmers as possible. “The government doesn’t necessarily patent technologies on the idea of making a profit,” he said. “It’s to help get the ideas commercialized.”

Most companies also want some kind of technology protection to invest in developing a product. So far, the USDA has issued two commercial evaluation licenses, which, for a small fee, allows companies to use the technology and see if it works for them. There’s also interest from a few more.

A new field

TC09 isn’t the only microbe out there that encourages plant growth. Dardick said that the field is in the midst of a steady growth trend.

“There have been other microbes of an identified fungi and bacteria that do this that have been identified in the last 10 years,” he said. “It’s kind of a growing field. There are many new products going on the market, particularly with things that are applied directly to the seeds, the soil or the plant themselves.” Most of these are microbes that physically colonize the plant roots or the plant itself, and they will also help promote growth or help it defend itself against diseases.

“This idea that there are gases or volatiles they produce are relatively new, so there aren’t any products like that on the market yet, but there’s been a number of scientific publications showing that different species of microbes can have this activity.”

USDA scientists will continue to study TC09 and seek practical strategies to apply it during commercial crop production, particularly for urban and indoor agricultural systems. They are awaiting approval of a patent and commercial evaluation license and partnered with NASA to apply this research technology to spaceflight conditions.

This research was supported in part by grants from USDA-ARS, ARS’ Appalachian Fruit Research Lab, and the Oak Ridge Institute for Science and Education.

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