Effect of Environmental Factors on Spore Germination, Spore Survival, and Growth of Gloeosporium musarum

SUMMARYOptimum temperature for growth, sporulation and conidial germination in G. musarum was in the range of 27–30°. The rate of germination was somewhat slower in light than in the dark, but under optimum conditions, maximum percentage of germination was obtained in both instances within 8 hours. Spores germinated in 6–12 hours at 98–100% relative humidity, but germination was delayed for 24–48 hours at 96%; germination failed to occur at 92%. Lowered oxygen tension slowed spore germination. Completely anaerobic conditions prevented spore germination, but did not prevent growth of the mycelium on agar medium. Mycelial growth was limited in an atmosphere of CO2, and there was evidence for CO2 toxicity. Optimum pH for spore germination was about pH 6, but germination occurred over the pH range of 4--10. Conidia survived on glass beads for 60 or more days, except over Drierite, where they survived less than 16 days. Germinated spores with appressoria were found to be more resistant to solutions of 0.25% sodium hypochlorite than were nongerminated spores.