Relationship between the virulence of hop isolates of Verticillium albo-atrum and their in vitro secretion of cell-wall degrading enzymes

Abstract

The in vitro production of extracellular polygalacturonase, pectin lyase, and cellulase by hop isolates of Verticillium albo-atrum was studied. A total of 24 isolates belonging to the two pathotypes commonly described as fluctuating or progressive, according to the symptoms produced in certain susceptible hop cultivars, were grown in liquid shake cultures. The media used contained glucose, pectin or acetone-extracted hop tissue as a carbon source. The production of all three enzymes was significantly correlated with pathotype when the medium contained hop tissue. Pectin lyase production was also correlated with pathotype when pectin was used as the carbon source. The influence of carbon source on enzyme output and possible reasons for some exceptions to the correlations observed are discussed.