Kinetic of the production of polygalacturonase and pectin lyase by two closely related Formae speciales of Fusarium oxysporum

Abstract

The kinetic of the in vitro production of polygalacturonase and pectin lyase of two closely related fungi, Fusarium oxysporum f.sp. lycopersici and F. oxysporum f.sp. radicis-lycopersici, was examined under various culture conditions such as the source of carbon, the pH, and the age of cultures. Over a 5-day period, the production of these enzymes by various isolates of the same forma specialis (f. sp.) of F. oxysporum was not significantly different ( P ≥ 0.05). However, the amount of the enzymes produced differed markedly between both f. sp. The different carbon sources added to the culture media, such as citrus pectin, apple pectin, tomato cell wall fragments, and d-galacturonic acid, proved to be higher pectinase inducible substrates than sucrose and glucose. For both fungi, polygalacturonase and pectin lyase activities were optimal at pH 5.0 and 8.0, respectively. Furthermore, pectin lyase production had a partial Ca 2+ requirement in contrast to polygalacturonase production which was limited by Ca 2+. In most experiments performed, the production of polygalacturonase appeared superior with F. oxysporum f.sp. radicislycopersici than with F. oxysporum f.sp. lycopersici. On the other hand, pectin lyase production of F. oxysporum f.sp. lycopersici was approximately 10-fold greater than that by F. oxysporum f.sp. radicis-lycopersici in media supplemented with d-galacturonic acid.