Influence of culture media and environmental factors on mycelial growth and conidial production of Diplocarpon mali

Aim:  To identify media and environmental conditions suitable for rapid mycelial growth and sporulation of Diplocarpon mali. Methods and Results:  Liquid shake cultures were used to evaluate effects of media and environmental conditions on mycelial growth and conidial production of D. mali. Carrot sucrose broth (CSB), potato and carrot dextrose broth (PCDB) and potato and carrot sucrose broth (PCSB) were most favourable for rapid mycelial growth. PCDB, PCSB, PCB (potato and carrot broth) and carrot dextrose broth (CDB) were favourable for conidial production. All carbon sources tested and peptone favoured for mycelial growth. Carbon and nitrogen sources tested did not significantly stimulate conidial production. The optimum temperature for mycelial growth and conidial production was 25°C. No mycelial growth occurred at 5 or 30°C, but D. mali survived at these temperatures. Active mycelial growth occurred at pH 5–7, and pH 5–8 was favourable for sporulation. Conclusions:  PCDB and PCSB incubated at 25°C for 14 day are recommended for mycelial growth and conidial production of D. mali. Significance and Impact of the Study:  The information generated in this study will facilitate mycological and pathological research on D. mali and Marssonina leaf blotch of apple caused by D. mali.