BASF plans to launch biofungicide seed treatment

bacillus subtillus
Bacillus subtillus strain UD 1022, which was patented by the University of Delaware —photo courtesy University of Delaware

The Environmental Protection Agency has registered Velondis, a biological fungicide seed treatment that BASF initially will label for soybeans.

A key part of the product is based on research conducted by the University of Delaware into a specific strain of a naturally occurring beneficial microbe, Bacillus subtillis BU1814. The university has patented the particular organism as B. subtillus strain UD 1022.

The bacterium colonizes plant roots and the surrounding soil or rhizosphere. At the same time, it produces a biofilm and antimicrobial compounds that promote systemic resistance within the plant, according to a news release. The result is suppression of pathogens that attach to the root system.

Millions of stomata, consisting of microscopic pores surrounded by guard cells, cover the above-ground parts of plants. The pores resemble tiny mouths, or doors, which the guard cells open and close to allow carbon dioxide, oxygen, water and minerals in and out of the plant.

Pathogens also can slip through these stomata and begin infecting the plant. However, as University of Delaware researchers confirmed, this invasion is halted when Bacillus subtilis is present in the soil where the plant is rooted.

The finding was based on tests of approximately 3,000 Arabidopsis plants inoculated with the foliar pathogen Pseudomonas syringae pathovar tomato DC3000 during a year-long period. P. synringae pv. tomato is responsible for bacterial speck in tomatoes.

When a foliar pathogen attacks, the plant recruits Bacillus subtilis to help and helps its multiplication. The Bacillus subtilis bacteria bind to the plant’s roots and prompt abscisic acid and salicylic acid signaling pathways to close the stomata.

Abscisic acid and salicylic acid are important hormones involved in plant defense. When a plant encounters adverse environmental conditions, such as drought, for example, abscisic acid triggers the stomata to shut tightly to prevent the plant from dehydrating.

“Many bacterial pathogens invade plants primarily through stomata on the leaf surface,” Harsh Bais, assistant professor of plant and soil sciences, said in a university news release. “But how do plants fight off infection? In our studies of the whole plant, we see this active enlistment by Bacillus subtilis, from root to shoot.”

Strikingly, the research team’s data revealed that of different root-associated soil bacteria tested, only Bacillus species were effective in closing the stomata and for a prolonged period.

“We know only 1 to 5 percent of what this bug Bacillus subtilis can do, but the potential is exciting,” Bais said, pointing out that there is increasing commercial interest in inoculating crop seeds with beneficial bacteria to reduce pathogen infection. “Just as you can boost your immune system, plants also could be supercharged for immunity.”

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