Researchers studying gray mold fungus in Spanish vineyards found a natural mutant strain (Bc116) that behaves differently from typical strains, particularly in response to light. Through genetic analysis, they identified that a mutation in the bcltf1 gene is responsible for this strain’s reduced ability to infect plants, increased spore production, and altered survival structure formation. Restoring the normal version of this gene reversed all these unusual characteristics, confirming bcltf1’s critical role in fungal development and disease-causing ability.