Antagonistic effect of Fusarium oxysporum on Heterodera cruciferae

This study was conducted to investigate the effects of Fusarium oxysporum Schlecht. (isolate no. B6) on Heterodera cruciferae Franklin and its pathogenicity on cabbage plants. Fusarium oxysporum (B6) was isolated from cysts extracted from cabbage (Brassica olareacae L.) fields in Samsun (north part of Turkey). Healthy cysts obtained from mass culture in a growing chamber were placed on fungal colonies already formed in Petri dishes. The highest infection rate was observed 10 days after inoculation and reached 72%. Fusarium oxysporum also had the ability to penetrate through cysts wall. The effects of spore suspensions of Fusarium on H. cruciferae in cabbage plants were tested in pot experiments in growth chambers. Cabbages cyst nematode (CCN) eggs were first incubated in a fungal spore suspension (10(8)-10(9) spores/ml) for 5 min and then introduced into pots containing sterilized soil and 3-weeks-old healthy cabbage plants. A positive effect was observed on plant height, fresh weight, fresh root weight, length and leaf area. Nematode numbers in the root system decreased within 2 months after artificial inoculations with Fusarium-infected cysts. This suggests a negative, antagonistic effect between F. oxysporum and H. cruciferae.