Yeast species interactions and composition modulate leaf rust severity in Populus trichocarpa.
Romero-Jiménez MJ, Pérez-Pazos E, Leopold DR, Lebeis SL, Busby PE
Plant Microbiome
The wild black cottonwood trees lining Pacific Northwest rivers and riparian trails are silently shaped by invisible yeast communities on their leaves — and this research reveals those microbes can either shield the trees from rust disease or make it worse depending on who's in the mix.
Scientists tested different combinations of tiny yeasts (single-celled fungi) living on the leaves of black cottonwood trees to see how they affected a rust disease. They found that some yeasts fight the disease, some make it worse, and most do nothing — and when you mix yeasts together, the outcome can flip entirely. Crucially, just having more types of yeasts on a leaf doesn't automatically make the tree healthier.
Key Findings
Individual yeasts fell into three categories: antagonists that reduced rust severity, facilitators that worsened it, and neutrals — with most falling into the neutral category.
Yeast community composition matters more than diversity: a rust-promoting yeast was neutralized when other yeasts were added, but adding yeasts to a rust-fighting community paradoxically increased disease severity.
Strong competition between yeast species was confirmed in lab tests, suggesting that competitive dynamics — not just each microbe's individual effect — drive the disease outcomes seen in mixed communities.
chevron_right Technical Summary
Not all microbes in a plant's leaf community are equally helpful against disease — it depends on which specific microbes are present and how they interact with each other, not just how many there are.
Abstract Preview
Plant microbiomes are recognized for increasing defence against pathogens. Yet, identifying the role of beneficial microbes beyond their individual effects remains poorly explored. In a series of i...
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Populus trichocarpa, the black cottonwood, western balsam-poplar or California poplar, is a deciduous broadleaf tree species native to western North America. It is used for timber, and is notable as a model organism in plant biology. The tree is notable for the seed-carrying cottony fluff it rele...