Effect of Chemical Applications to Peach Bark Wounds on Accumulation of Lignin and Suberin and Susceptibility toLeucostoma persoonii

Abstract

Fourteen extracts and chemical treatments were tested in the filed on orchard trees in May and June of 1987 for their effects on wound responses in the bark. Pruning wounds on 1-yr-old branches were treated and the wound sites were excised up to 14 days later for histological study and chemical analysis of lignin. Fungal cell wall extracts and cellobiose stimulated lignin synthesis and/or enhanced the wound response. In contrast, the commonly used sealants, Lac Balsam and white paint, retarded the wound response. In a second set of experiments, five treatments were tested in the laboratory for effects on wound response and susceptibility to Leucostoma persoonii. Branch segments were wounded and exposed to the treatment solutions for 72 hr before fungal inoculation. All treatments except calcium were associated with increased lignin formation before inoculation. Percentage of infection of twigs treated with GA3 + auxin was greater than the control, whereas twigs treated with cell wall extract from L. persoonii, cellobiose, and calcium exhibited fewer infections than the control. Canker length was reduced by all treatments. Lignin production following inoculation was related to the amount of disease present on the twigs, with increased lignin accompanying increased size of cankers.