Bio-agents: A source for initiation of defence enzymes in chilli infected with root-knot nematode, Meloidogyne incognita

The plant parasitic nematodes are major problem in chilli. Out of these, root-knot nematodes have been considered as severe constraint to chilli production. Root knot nematode particularly Meloidogyne incognita is widely distributed and ranked most destructive pathogen on vegetable crops in the world. Nematode infection in plant roots cause stress and in response to the infection a series of biochemical and physical reactions occur in plants. Plants synthesize certain compounds that are toxic to root-knot nematode. Resistance is usually associated with hypersensitive reaction (HR), a rapid and localized cell death in the infected plant in response to nematode attack. Reactive oxygen species (ROS) play an important role in plant defence and during pathogen attack. As a result, plants produce more ROS and accumulation of these components leads to HR in plant cells. Oxidative enzymes such as PO, PAL, PPO, SOD and CAT are reported to be involved in the mechanism of disease resistance. This research aimed to examine the effect of the application of bio-agents to the induction of defence enzymes peroxidase (PO), polyphenol oxidase (PPO), phenylalanine ammonia lyase (PAL) and super oxide dismutase (SOD) against M. incognita in chilli. This research was conducted with Completely Randomized Designs (CRD) using bio-agents Trichoderma viride, Trichoderma harzianum, Pochonia chlamydosporia and Paecilomyces lilacinus each @ 2g and 4g per kg and Pseudomonas fluorescens @ 4g/kg were added to soil. The results showed that the level of PO, PPO, PAL and SOD was increased in chilli roots with the application of all bio-agents as compared to untreated control but P. fluorescens and T. viride @ 4g/kg soil was found to be the best treatments. The level of PO and SOD were found highest while, PPO and PAL were found lowest in chilli roots during different time of observations i.e. 7th, 14th, 21th, 28th and 60th DAT. The enzyme activity showed gradual increase till 28 DAT in treated roots as compared to untreated ones but gradually decrease at 60 DAT. Among all the treatments application of P. fluorescens and T. viride @ 4g/kg soil was found to be the best treatments to improve plant growth and decrease number of galls and egg masses per plant, number of eggs per egg mass, nematode population/200cc soil and total nematode population over other treatment.