Optimizing storage methods for Neoscytalidium dimidiatum and effects of culture media and light regime on mycelial growth and sporulation

Neoscytalidium dimidiatum is the causal agent of stem and fruit canker, which is the most destructive pathogen on dragon fruit (Hylocereus spp.) worldwide. This study aimed to identify culture media and light conditions that promote rapid mycelial growth and sporulation of the pathogen and to determine the best storage method that can efficiently preserve N. dimidiatum. Four culture media (potato dextrose agar, malt extract agar, oatmeal agar, and V8 juice agar) were investigated under three light regimens (12-hour photoperiod, continuous light, and continuous darkness) at 25 °C. Additionally, the effect of storage method on recovery, mycelial growth, spore production, and pathogenicity of N. dimidiatum isolates was investigated after two and eight months. Results demonstrated that potato dextrose agar (PDA) consistently supported optimal growth and sporulation of N. dimidiatum, regardless of light conditions; and continuous light exposure significantly enhanced spore production. Furthermore, storage method significantly influenced the biological characteristics of N. dimidiatum. Subculture at 25 °C and storing mycelia on filter paper at −20 °C proved to be the best method for preserving N. dimidiatum. Other storage methods resulted in a low recovery rate, poor mycelial growth and sporulation, and reduced pathogenicity in fruits. These findings underscore the importance of media selection and storage methods in maintaining the viability and virulence of N. dimidiatum [for conservation purposes], thereby enhancing further research on this pathogen and the management of dragon fruit canker disease.