Polygalacturonase, Pectate Lyase and Pectin Methylesterase Activity in Pathogenic Strains of Phytophthora capsici Incubated under Different Conditions.

Pectolytic enzymes are found mainly in fungi and bacteria. The most widely occurring enzymes are polygalacturonase (PGs), pectin methylesterase (PMEs) and pectate lyase (PLs) produced during the infection process and during culturing. The secretion of these enzymes results in the disorganization of the plant cell walls, which is responsible for the pathogenicity of the pathogens. These enzymes degrade the pectin of plants causing maceration of plant tissues and the enzyme activity increases under favourable environmental conditions. We have found that Phytophthora capsici, a pathogenic oomycete, produces levels of these three enzymes equal to those produced by soft-rotting Erwinia chrysanthemi. The activity of PGs, PLs and PMEs was investigated at the optimum temperature, pH and ionic strength in highly pathogenic P. capsici strains cultivated in two kinds of liquid medium containing either crude pepper extracts plus pectin or pectin as the carbon source. Virulence tests and enzymes activity showed that there was a high correlation between the enzyme activity and the pathogenicity of P. capsici. The effects of different carbon sources on the enzyme activity showed that pepper extract plus pectin was the best source for the carbon source. [ABSTRACT FROM AUTHOR]