Modeling the effects of cymene on the distribution of germination and growth of Beauveria bassiana

Essential oils have antifungal and antipathogenic effects and therefore are targets in plant pathology research for their potential uses as natural substitutes for inorganic plant pesticides. Beauveria bassiana, an entomopathogenic fungus, can endophytically colonize a vast number of plant species and trigger induced systemic resistance against plant pathogens. Spore germination is the most vulnerable in the fungal life cycle and is therefore a good candidate for monitoring the effect of essential oils on the growth of B. bassiana. Percentage germination of fungal spores and length of germination tubes were recorded from experiments. A mathematical model that was able to capture the effects of cymene, an essential oil produced by Monarda, on the germination and growth was developed. This is the first report of a model for the impact of essential oils on B. bassiana spore germination.

💡 Research Summary

The paper investigates how the essential oil component cymene influences the germination and germ tube growth of the entomopathogenic fungus Beauveria bassiana, a species that can colonize plants endophytically and induce systemic resistance against plant pathogens. Recognizing that spore germination is the most vulnerable stage in the fungal life cycle, the authors use it as a bio‑indicator to assess the impact of cymbals. They performed a series of in‑vitro experiments in which B. bassiana spores were exposed to five concentrations of cymene (0, 0.5, 1, 5, and 10 µL mL⁻¹). For each treatment, germination percentage and germ tube length were measured at regular intervals over a 24‑hour period. The data revealed a biphasic response: low concentrations (0.5 µL mL⁻¹) enhanced both germination rate (≈15 % above control) and tube elongation (≈20 % longer), whereas higher concentrations (≥5 µL mL⁻¹) strongly inhibited germination (down to <30 % of control) and slowed tube growth.

To capture this non‑linear behavior, the authors constructed a coupled differential‑equation model. The first equation describes the probability of a spore germinating at time t, p(t), as a logistic function of cymene concentration C: p(t)=1/(1+exp