Abstract:

The cucumber endophytic Chaetomium strain Ch1001 has shown its ability to suppress root knot nematode, Meloidogyne incognita, when applied as seed treatment. However, its optimum application dose, which is an important parameter for practical use in order to obtain robust seedlings as well satisfied nematode control efficacy has not been determined. In this paper, the root viability, defense related enzymes activity as well root knot nematode control efficacy were tested after cucumber seeds were inoculated with Ch1001 at 1×103, 1×104, 1×105, 1×106, 1×107, 1×108ascospores/seed respectively at sowing. Results indicated that root viability was not influenced by Ch1001 when the inoculum dose was at or lower than 1×105 ascospores/seed, but increased significantly at the inoculum dose of 1×106 and1×107 ascospores/seed， and decreased dramatically at 1×108 ascospores/seed. PAL and chitinase activity did not enhance after Ch1001 treatment， POD and CAT activity significantly increased at 1×105, 1×106 and 1×107 ascospores/seed，indicating that Ch1001 induced resistance related to active oxygen metabolism. The root knot nematode M. incognita control efficacy was positively correlated to seed treatment dose, the galls formation was significantly inhibited at 1×104, 1×105, 1×106 and 1×107 ascospores/seed treatment, the satisfied inhibition reached at 1×106 and 1×107 ascopores/seed treatment, which were 45.3% and 57.0% respectively. Based on the above results, the dose at 1×107 ascospores/seed was optimum for practical use because of the enhanced root viability, defense related enzymes activity as well as the lowest nematode invasion.