The influence of lulo (Solanum quitoense Lam) fruit maturity stage on polygalacturonase and pectate lyase secretion by Colletotrichum acutatum

The influence of the lulo fruit maturity stage on the secretion of polygalacturonase (PG) and pectate lyase (PL) enzymes by Colletotrichum acutatum was determined. The study was performed using in vitro assays in the presence of exocarp and cell walls (CW) of the fruit at three different ripening stages (unripe, semi-ripe and ripe). The results showed that PG behaves as a constitutive enzyme and is only induced by semi-ripe CW, while PL is induced with the exocarp of lulo fruits at the three maturation stages, although its activity was highest with semi-ripe fruit. This enzymatic behavior might be related to the quiescent stage of the pathogen in the fruit, as C. acutatum remains quiescent until maturation begins. The profiles of PL induction were different in the presence of the CW and the exocarp inducers, whereas PG levels barely varied, indicating that the process of obtaining the CWs may eliminate a compound that contributes to the induction of PL secretion.