Coordinated effects of root autotoxic substances and Fusarium oxysporum Schl. f. sp. fragariae on the growth and replant disease of strawberry

Effects of hydroxybenzoic acid, an important autotoxic substance in roots, on plant growth, photosynthesis and Fusarium oxysporum occurrence in succession cropping of strawberry were evaluated in this paper. It was found that plant growth was negatively regulated by hydroxybenzoic acid or inoculation with F. oxysporum. Compared with these single factor treatments, the combination of the hydroxybenzoic acid treatment and F. oxysporum inoculation caused more severe inhibition in plant growth, greatly enhanced the occurrence of disease symptoms, and significantly decreased the chlorophyll content, net photosynthetic rate, transpiration rate, stomatal conductance and intercellular CO₂ concentration. In the meantime, the chlorophyll fluorescence parameters in strawberry were also significantly affected. After the application of hydroxybenzoic acid, the original chlorophyll fluorescence rapidly increased, resulting in a combined corresponding decrease in the maximum chlorophyll fluorescence and the chlorophyll fluorescence transformation efficiency. The effects of hydroxybenzoic acid treatment on the above chlorophyll fluorescence parameters from inoculation were delayed. Similarly, the coordination of hydroxybenzoic acid and F. oxysporum showed an elevated negative effect on the degree of inhibition of leaf photosynthesis more than the single factor treatments.