Phosphite-induced suppression of Pseudomonas bleeding canker (Pseudomonas syringae pv. aesculi) of horse chestnut (Aesculus hippocastanum L.)

摘要

Field trials were conducted using 4-year-old horse chestnut (Aesculus hippocastanum L.) to assess the efficacy of potassium and silicon phosphite as plant protection agents against the bacterial pathogen Pseudomonas syringae pv. aesculi (Pae) the causal agent of Pseudomonas bleeding canker of horse chestnut. Phosphites were applied preventatively, i.e. before Pae inoculation of trees, and curatively, i.e. after Pae inoculation of trees, and, as both a foliar spray (FS) and root drench (RD). Application of both phosphite forms induced positive effects on plant vitality (increased leaf chlorophyll content, leaf chlorophyll fluorescence (F_v/F_m)), enhanced defensive enzyme activity (beta-1,3-glucanase, peroxidase) and reduced Pae lesion size, the mainproxy of Pae success or aggressiveness. Preventative rather than curative phosphite application resulted in greater reductions in Pae severity. Little significance of mode of application (FS, RD) and phosphite anion (potassium, silicon) was demonstratedindicating both phosphites can be foliar applied or root drenched with similar degrees of resulting Pae control. Significant reductions in Pae severity recorded in this study gave credence to the potential of phosphites as an alternative or compliment to conventional bactericides for Pae control.