Biological microbial strains matter both to the regulatory process and to performance in the field. The strain or culture of a given species of microbe is often not identified for biostimulant active ingredients, and most labels stop at genus and species, such as Bacillus subtilis.
Species identifies the organism. Strain identifies expected performance. And two strains of the same species can colonize roots differently, produce different metabolites and respond differently to soil and stress. The closer identification gets to the strain, the stronger the basis for efficacy, safety and claim specificity.
Other crop protection categories already work this way, and strain specificity is clearly accepted for insecticides, fungicides and nematicides, but genus and species are largely the accepted sufficient identifier for biostimulants. Which leads to two questions
- Is focus on strain a potential mitigant for the inconsistent performance image of biostimulants? And,
- Will biostimulant performance and regulatory timelines become more consistent if activity is identified by strain and not just by species?
Same Species, Different Organism
Microbial identity is a hierarchy and the closer identification gets to the strain, the stronger the basis for efficacy, safety and claim specificity.
- Genus: the broad taxonomic group.
- Species: names the microbe.
- Strain: distinguishes the exact culture.
- Trait evidence: links that culture to observed activity.
The published research on Bacillus shows why the last two rungs matter. The studies describe multiple elite strains within several Bacillus species. Each has its own profile of growth promoting traits, bioactive metabolites and field effects. The species name is a starting point, not proof that every strain will behave the same way.
The pattern holds well beyond Bacillus. Phosphate solubilization offers a sharper example. At least nine designated strains or isolates of Priestia megaterium have published phosphate-solubilization evidence, and they answer different questions.
Regulatory Expectations Are Not Yet Aligned
Today, some agencies treat strain as a key identifier for registration. Others accept species as enough to characterize efficacy and non-target effects. Requirements vary by agency, market and use case.
Market access is moving the same way. Import permits may increasingly follow the strain and permits for some countries may be evolving toward requiring more safety data on the strain rather than accept data for which strain or culture is not identified. Those requirements will likely shift country by country before becoming globally consistent.
When regulators make strain the minimum standard for biostimulant active ingredients, innovators should prepare for the most specific plausible standard, not the least demanding current one.
Can Strain Fix the Inconsistency Problem?
While strain identification won’t solve everything, it will address a root cause. Consistency improves when the evidence chain stays attached to the exact organism tested. When a product is described only by species, a grower can’t tell whether the trial data behind it came from the strain in the jug.
A strain-first approach follows four steps:
- Identify: Name the strain, not only the genus and species.
- Characterize: Connect that identity to traits, metabolites and activity.
- Validate: Test performance across crops, soils and environments.
- Claim: Make specific claims backed by strain-level data.
The commercial payoff is fewer unexplained performance swings, clearer differentiation from look-alike products, and stronger grower confidence. In a category still working to earn trust, that last one may matter most.
As knowledge evolves, the biostimulant developers will see requirements for regulatory approval, and grower adoption will also evolve toward specific claims with supporting data for the strain, not just the species. Getting there first is a competitive advantage.
Learn more by attending Fountas’ presentation on “Strain is Key in Biostimulant Development, Registration and Commercial Performance” at Biostimulants World Congress in the Science & Technical Track on Dec. 1, 2026, at 5:25 Pacific Time.
