Fig. 1

Exogenously applied ethylene positively regulates H. brasiliensis resistance to E. quercicola. a Exogenously applied ethephon reduced H. brasiliensis infection. Ethephon at different concentrations was applied to the leaves for 24 h, followed by inoculation with E. quercicola conidia. Mock is distilled water used as the solvent of ethephon. Photographs were captured at 7 days post-inoculation (dpi). b Lesion area in leaves treated with different concentrations of ethephon was quantified at 7 dpi. Statistical differences are marked with asterisks compared to the mock (n = 9 leaf discs from 3 independent experiments. ** P < 0.01, Student’s t-test). c Reactive oxygen species (ROS) accumulation was visualized by 0.1% 3,3’-diaminobenzidine (DAB) staining in the infected leaf tissues with mock and 50 μM ethephon treatments. Photographs were captured at 48 h post-inoculation (hpi). Scale bars: 50 µm. Red arrows indicate the represented ROS accumulation. d Callose deposition was visualized by aniline blue staining in H. brasiliensis leaves treated with mock and 50 μM ethephon. Scale bars: 50 µm. Red arrows indicate the represented callose deposition. e, f The proportion of infected sites with ROS accumulation and callose deposition, respectively. Statistical differences are marked with asterisks compared to the mock (n = 9 leaf discs from 3 independent experiments. ** P < 0.01, Student’s t-test). g Abscisic acid (ABA), salicylic acid (SA), jasmonate (JA), and 1-aminocyclopropane-1-carboxylic acid (ACC) elicited by EqTub2-silenced strain in H. brasiliensis (FW: Fresh weight). Statistical differences are marked with asterisks compared to the samples at 0 hpi. (n = 9 leaf discs from 3 independent experiments. * P < 0.05, ** P < 0.01, Student’s t-test)