Abstract

PHYSIOLOGICAL AND BIOCHEMICAL CHARACTERIZATION OF SENNA ALATA (L.) ROXB. LEAF EXTRACT - A PLANT BASED FUNGICIDE AGAINST ALTERNARIA LEAF SPOT IN SESAME

Lubaina, A.S. and Murugan K.*

ABSTRACT

Fungicidal effect of Senna alata aqueous leaf extracts was evaluated in vivo and in vitro on Alternaria sesami, the causative of Alternatia leaf spot disease. Sesame (Sesamum orientale L.) the oldest oil crop, cultivated all over world especially in Indian and African subcontinent. Among the different diseases that attack sesame crop, Alternaria leaf spot is one of the serious threat leading to significant reduction in yield. Chemical control of disease disturbs, environment, subvert ecology, degrade soil productivity, mismanage water resources. Because of the above constraints, the use of plant extracts in the management of plant diseases is gaining global significance. Perusal of earlier literature indicated that many attempts have been made in exploiting host resistance, modified cultural practices and application of biocontrol. Induced resistance is an alternative to systemic disease resistance response of plants. Methodologies include hydro-distillation of Senna alata leaf using clevenger apparatus, in vitro and in vivo plants (4 weeks after sowing- WAS) inoculation with conidial suspension of Alternaria sesami containing 1 x 103 conidial/ml followed by spraying Senna alata extracts (10%) from 5WAS. Both pot and field experimental condition are designed to evaluate disease severity and incidence, changes in the activity of defence related enzymes such as phenylalanine ammonia lyase (PAL), peroxidase (POX), polyphenol oxidase (PPO) and total phenolic content after 24 h from the last spray. Two fold increase in activities of these defence related enzymes was observed in sesame after S. alata leaf extract treatment suggesting induce resistance against the pathogen infection in the host than the control. In vitro analysis showed remarkable MIC and MFC which in turn supports in vivo results. Both field and pot culture aqueous extract treatment of S. alata decreased the incidence and severity of disease in sesame. Hence there is immense scope to integrate S. alata aqueous leaf extract for eco-friendly management of Alternaria leaf spot of sesame. Further work is required to confirm the efficacy of the extracts in large scale field under different agroclimatic conditions to determine the potentiality of the ingredient present in extracts and its mode of action.

Keywords: Alternaria leaf spot, Plant extract Induced resistance, Phenylalanine ammonia lyase, Peroxidase, Poly phenol oxidase.