Culture media and temperature effects on Neofusicoccum mediterraneum: assessing mycelial growth and colony characteristics

In this study, Neofusicoccum mediterraneum, a highly aggressive plant pathogen with a broad host range, including Eucalyptus spp., was investigated to determine its optimum medium and temperature for mycelial growth and chlamydospore production. The results revealed differences in the growth behaviour of N. mediterraneum under different in vitro conditions. Potato Sucrose Agar (PSA) was determined to be the most favourable environment for mycelial growth, achieving the maximum growth rate (GR) of 100% after 3 days of incubation at 25 °C. This was closely followed by cultures on Malt Extract Agar (MEA), exhibiting a GR of 100% after 4 days of incubation at 25 °C, while both substrates displayed optimal growth within the temperature range of 25 to 30 °C. The General Linear Model (GLM) unveiled significant differences in the growth rate across the different media (P = 0.000) and temperatures (P = 0.000). The interaction effect (media*temperature) retained its high significance throughout all incubation days (P < 0.0001). The binomial distribution and multinomial logistic regression analysis revealed that colony texture was significantly influenced by both the media (P = 0.022) and the temperature (P = 0.008). Additionally, temperature affected significantly the surface colour (P = 0.015) and reverse colour (P = 0.023) of the colony. Production of chlamydospores was observed only on PSA at 20 °C, 25 °C, 30 °C and 35 °C and on PDA at 25 °C and 30 °C. Both the medium and temperature had notable influences on the pathogen's growth, highlighting their importance in understanding its biology and behaviour. These findings contribute to the understanding of the phenotypic plasticity exhibited by N. mediterraneum towards temperatures and growth substrates.