Effectiveness of various nematode-trapping fungi for biocontrol of the Meloidogyne incognita in tomato (Lycopersicion esculentum Mill.)

Abstract

The nine promising species of nematode-trapping fungi namely Dr. dactyloides, Dr. brochopaga, Da. gephyropaga, Da. phymatopaga, A. eudermata, A. oligospora, A. conoides, A. thaumasia and A. musiformis were isolated from the root-knots rhizosphere to compare their, in vitro nematode trapping ability against Meloidogyne incognita, ability to form conidial traps close to nematode infested soils and their effectiveness in reducing on M. incognita infection indices on tomato. The laboratory assays of nematophagous efficacy of nine nematode-trapping fungi against M. incognita revealed that Dr. dactyloides, Dr. brochopaga, D. gephyropaga and Da. phymatopaga seemed to be the most effective, with 73.2–99.8% trapping and killing of juveniles within 5 days of nematode and fungal interface. Conidial trap forming ability of different species of nematode-trapping fungi showed that Dr. dactyloides, Dr. brochopaga formed frequent formation of conidial traps without intermediate germ tubes whereas Da. phymatopaga and Da. gephyropaga formed adhesive traps on spore germ tubes in close vicinity of root-knot nematode infested soils and killed the nematode present on the agar discs. A. eudermata, A. oligospora, A. conoides, A. thaumasia and A. musiformis frequently germinated by germ tubes in soil and occasionally formed fewer traps. The pot experiment results showed that Dr. brochopaga and Dr. dactyloides, which dominantly formed conidial traps without an intermediate mycelial phase caused the highest decrease in the number of roots-knots (67.2–70.4%), females (80.5–85.8%) and eggs and juveniles (84.9–88.8%) of M. incognita followed by Da. gephyropaga and Da. phymatopaga which formed traps on conidial germ lings and mycelium. A. eudermata, A. oligospora, A. conoides, A. thaumasia and A. musiformis which formed poor conidial traps caused a moderate decrease in the number of root-knots (45.3–53.4%), females (55.5–61.1%), eggs and juveniles (52.9–60.1%) of M. incognita in comparison to control. This paper analyses the effective biocontrol of M. incognita by using different nematode-trapping fungi, especially conidial traps forming fungi and the fate of application of these species in the RKN-infested soil for management of M. ingocnita.