Intraspecific variability in growth and in vitro production of plant cell wall-degrading enzymes among argentinean isolates of Colletotrichum graminicola, a maize pathogen

Background and aims: Colletotrichum graminicola (Glomerellaceae, Glomerellales), the causal agent of maize (Zea mays) anthracnose, as many other fungal pathogens, relies on its battery of cell wall degrading enzymes (CWDEs) to make its way through the cell walls of the host, and thus the production of these enzymes is considered a virulence factor. Since this disease is relatively new in Argentina, little is known about the capacity of CWDEs production in native isolates. The aim of this work was to investigate if there is intraspecific variability in growth and in vitro production of several extracellular CWDEs among Argentinean fungal isolates of C. graminicola. M&M: Eight isolates of C. graminicola (obtained from symptomatic maize plants growing in different geographical locations) were tested in vitro to evaluate growth capacity and polygalacturonase, polymethylgalacturonase, β-glucosidase and laccase production, using two different liquid culture media.  Results: Polygalacturonase, polymethylgalacturonase and β-glucosidase production greatly varied among isolates and culture media. Laccase activity was detected only in three isolates. Utmost enzymatic titres attained were respectively 250, 280, 45 and 63 U/l. The observed intraspecific variability in CWDEs in vitro production is consistent with the high variability found at genetic level when assessing ISSR markers. Conclusions: The isolates of C. graminicola evaluated showed notable differences in CWDEs production, not associated with a differential growth. This indicates a large intraspecific variability, which might be considered when choosing a method to deal with this pathogen.