Foliar-applied honokiol exhibits basipetal translocation, offering a strategy for root disease management in...

Root diseases in crops are increasingly becoming the most difficult to control due to the challenge of fungicides reaching infection sites. Honokiol, a natural fungicidal product derived from Magnolia officinalis, is primarily biosynthesized in leaves and subsequently translocated to roots to resist pathogen infection.

In this study, honokiol applied to the leaves of Polygonatum cyrtonema Hua (PCH) could be transported downward to the roots and exhibited a control effect against root rot disease.

Subsequent research showed that concentration, temperature, pH, energy inhibitors (DNP, CCCP) and other agents (AgNO₃, BaCl₂, CaCl₂) significantly affect basipetal translocation of honokiol, suggesting that its translocation from leaves to roots is mediated by transport proteins. The distribution of honokiol in various parts of PCH was found as leaf > stem > root, indicating that honokiol was absorbed by the leaves and transferred to the roots through phloem. Translocation factor_root/stem value of honokiol in PCH was more than 1, indicating that honokiol was easy to transfer to the root. Subsequently, four potential transporter proteins, ABCB11, ABCG24, TIP1-2 and PIP1-3, were screened from Arabidopsis thaliana for molecular docking analysis, indicating a significant binding affinity between honokiol and transporter proteins having a binding energy of -12.83 kcal mol^-1, -10.70 kcal mol^-1, -9.38 kcal mol^-1 and -10.67 kcal mol^-1, respectively.

Foliar-applied honokiol exhibited pronounced basipetal translocation, efficiently moving from leaves to root tissues where root rot pathogens reside. This systemic redistribution enables targeted delivery of the antifungal compound honokiol to the infection site without direct soil application, minimizing environmental exposure.