The abilities of three pectinase-deficient mutants of Verticillium albo-atrum to infect and cause symptoms in tomato plants were compared to the wild type. Symptoms were absent, less severe or appeared later in plants infected with the mutants. However, each isolate apart from C23, a secretory mutant, colonized plants to levels comparable to that of the wild type. This implies that pectinases, particularly endo-pectin lyase, are virulence factors but probably not determinants of pathogenicity, because colonization can proceed in their absence.
Durrands, P., & Cooper, R. M. (1988). The role of pectinases in vascular wilt disease as determined by defined mutants of Verticillium albo-atrum. Physiological and Molecular Plant Pathology, 32(3), 363-371. https://doi.org/10.1016/S0885-5765(88)80030-4