Biochemical studies on plant tissues infected by Phytophthora palmivora (Butl.) Butl.

Lesion formation in tomato and eggplant fruits infected by Phytophthora palmivora could be classified into three phases associated with changes in hydrolytic enzymes in the tissues. Phenolase, arabinofuranosidase and endo-polygalacturonase activities were all higher than in healthy tissue. The enzymic effects seemed to be reflected in a fairly high loss of pectic materials in the infected tissue, especially the water-insoiuble components. There was a significant negative correlation (r = -0·56) between pH of tomato and the endo-polygalacturonase secretion in the infected tissues. Paper chromatographic analysis of host metabolites showed little or no qualitative differences between the sugar contents of healthy and of infected tomato tissues; there were also no qualitative differences in the amino acid and the phenolic contents. Chlorogenic acid was detected in healthy but not in infected eggplant tissues and lesion maturation was associated with its disappearance. Gradual browning of the lesion was probably also associated with changes in cell membrane permeability of infected tissue.