Synergistic interaction between Meloidogyne incognita and Fusarium solani in black pepper, Piper nigrum L

The nematode-fungus disease complex is becoming a significant constraint in black pepper production in Kerala. Basic information on major nematodes and fungal pathogens associated with disease complex as well as histopathological and biochemical changes due to the interactive effects of both organisms, is essential for developing effective management strategies. Soil and root samples were collected from prominent black pepper-growing areas in Kannur, Idukki and Wayanad districts to document nematodes and fungal pathogens associated with black pepper. Plant parasitic nematodes, such as Meloidogyne incognita, Rotylenchulus reniformis, Radopholus similis, Helicotylenchus dihystera and Macroposthonia sp. and fungal pathogens such as Fusarium solani, F. oxysporum, Phytophthora capsici, Rhizoctonia sp. and Pythium sp., were associated with black pepper plants in surveyed areas. The disease severity was higher in regions where M. incognita co-existed with fungal pathogens. F. solani was the predominant pathogen along with M. incognita in the areas surveyed. Pot culture studies were conducted to investigate the interaction between nematodes and fungi. Plants inoculated with M. incognita 14 days before F. solani exhibited t h e highest (100 %) and early (24 days) disease incidence, as evidenced by the increased number of giant cells, distortion of vascular bundles and plugging of fungal mycelia in xylem vessels. The highest defense enzyme activity and phenol content were observed in plants inoculated with M. incognita + F. solani 14days after nematode inoculation. Results of the study highlighted that nematode infestation predisposes plants to fungal infection and synergistic interaction between nematode and fungal pathogen increases disease severity in field conditions.