The New Foundation for Eco-Friendly Seed Treatments

Dr. Greg Welbaum has spent decades conducting agricultural research, but the professor of horticulture at Virginia Tech hopes to spend the rest of his career studying something new: the microbial ecology of seeds.

Vegetables are covered with bacteria. In light of the recent wave of food safety scares, learning about bacteria-covered vegetables may seem scary. Yet it’s the nature of life. Bacteria are everywhere in our environment, including on seeds. Until recently, scientists knew bacteria were present on seeds, but struggled to ascertain the type of bacteria.

Microbial ecology of seeds is an exciting new field made possible by emerging technologies. Suddenly, researchers have the ability to look at bacteria that were previously unidentifiable or difficult to study by sequencing their DNA. Some of the bacteria, of course, are threatening, because they may cause plant disease. However, other bacteria may be friendly.

As probiotic bacteria, like acidophilus and bifidus, benefit the human digestive tract and human health, some bacteria benefit seed and plant health. Today, Welbaum and his colleagues are looking for beneficial organisms that reside on seeds and can either stimulate germination or protect the seeds from pathogens.

“In conventional agriculture, the attitude is to sterilize seeds or apply fungicides to kill off organisms on the seed,” says Welbaum. “I think there’s an emerging picture now that having certain microbes on the seed is actually healthy.”

Welbaum’s theory is that some beneficial bacteria inhibit more harmful bacteria from populating the seed. He cites Trichoderma as one example of a fungus that helps control disease naturally. This approach is more natural and ecological; it offers an alternative to chemical seed treatments that the agricultural industry has relied on for so long to protect and enhance the propagation of the seed.

Pyrosequencing is one new technique making it possible for Welbaum and other scientists to sequence all the bacteria on a seed. In the past, researchers could only identify bacteria that would grow on culture plates. Pyrosequencing allows researchers to extract the DNA from the bacteria and do DNA sequencing to discover all the bacteria present. “We’re not limited,” exclaims Welbaum. “This is a very exciting development that will allow us to study exactly what’s going on with seeds.”

One of the challenges is to separate the plant DNA from the bacterial DNA. This task requires great care, because the researcher must make sure to isolate the bacterial DNA. Some bacteria are tightly attached to the outside of the plant, while other bacteria may actually reside on the inside of the plant. These endophytic bacteria, which reside inside plants, are particularly difficult to isolate.

Welbaum expects to see a lot of breakthroughs and some progress in protecting the food supply. Seed treatments are just one aspect of a very large picture with a lot of scientists working on it right now. Researchers have no proof that seeds can transmit human pathogens, like salmonella and E. coli. Still, Welbaum and his team are hoping to find a dominant bacteria residing on seed that would work as a seed treatment to protect plants from E. coli, listeria and human pathogens that are problematic on vegetable seeds and crops like spinach and lettuce.

Welbaum is conducting his current research with food scientist and bacteriologist Dr. Monica Ponder from Virginia Tech’s food science department. Their project is still in its infancy.

The author is a freelance writer based in Massachusetts and a monthly contributor to Growing.