Interaction between Fusarium culmorum and Ditylenchus dipsaci in purple and yellow onion

Summary

This study examined the interaction between the crown rot fungus Fusarium culmorum and the stem nematode Ditylenchus dipsaci in onion under controlled conditions. Both D. dipsaci and F. culmorum reduced plant growth and bulb weight when applied individually. However, simultaneous or sequential coinoculation did not increase disease severity compared with F. culmorum alone, indicating that D. dipsaci does not contribute to F. culmorum-induced basal rot in onion. In single nematode inoculations, the reproduction factor (RF) was higher in yellow onion (10.7) than in purple onion (9.6). In combined inoculations, RF values ranged from 8.3-9.5 in yellow onion and 5.4-6.4 in purple onion. Notably, F. culmorum significantly reduced D. dipsaci population density and RF in both cultivars, suggesting an antagonistic interaction. This is the first report demonstrating suppression of D. dipsaci by F. culmorum in onion, highlighting its potential relevance for integrated nematode management.