Madras Agric. J., 100 (Special Issue): 126-130, May 2013 Proceedings of the First Agricultural Graduate Student Conference 2013 on Food Safety and Food Security, May 2-3, 2013, SPGS, TNAU, Coimbatore *Corresponding author email: ramyabharu@gmail.com Induction of Defense Enzymes and Proteins in Tomato Plants by Bacillus Subtilis EPCO16 Against Fusarium oxysporum f. sp. lycopersici S.A. Ramyabharathi*, B. Meena and T. Raguchander Department of Plant Pathology, Centre for Plant Protection Studies, Tamil Nadu Agricultural University, Coimbatore - 641003 The biocontrol agent Bacillus subtilis EPCO16 is studied as an effective endophytic biocontrol agent in the management of plant diseases besides promoting plant growth. The eficacy of B. subtilis EPCO16 was tested for the induction of systemic resistance against tomato Fusarium wilt. B. subtilis EPCO16 in liquid and talc formulation on the induction of proteins and defense enzymes viz., phenylalanine ammonia lyase, catalase and phenolics in tomato plants infected with Fusarium oxysporum f. sp. lycopersici was studied under glass house condition. Activities of these enzymes increased in seed treatment, seedling dip and soil application of EPCO16 in liquid formulation on tomato plants challenged with the pathogen. The defense related proteins viz. phenylalanine ammonia lyase (PAL), catalase and phenolics were analysed spectrophotometrically. Activities of these enzymes reached maximum at the 7th day after challenge inoculation. The present study has helped in identifying an isolate B. subtilis EPCO16 with higher ability to induce defense related compounds in tomato plants against F. oxysporum f. sp. lycopersici. Key words: Fusarium wilt, Bacillus subtilis, Proteins, Defense enzymes Tomato is one of the most important solanaceous vegetable crops grown worldwide. One of the most important diseases of tomato in the warm regions of the world is Fusarium wilt. In India, the yield loss up to 45 per cent was recorded (Kalpana, 2008 and Manikandan et al., 2010) due to F. oxysporum f. sp. lycopersici. Several soil fungicides are being used as short term management of soil borne diseases. In addition, they cause reduction in beneicial soil microbes, harmful effect on human being and contamination of ground water. Use of biocontrol agents has been shown to be eco-friendly and effective against many plant pathogens and pest. Induced systemic resistance (ISR) activates multiple defense mechanisms that include increased activity of pathogenesis related (PR) proteins like Chitinase, β-1,3-glucanase and peroxidase (PO) (Maurhofer et al., 1994; Xue et. al., 1998), and also the accumulation of low molecular weight substances called phytoalexins (Van Peer and Schippers, 1992). Chitinases and β-1,3-glucanases are a structurally and functionally diverse group of hydrolytic enzymes involved in defense reactions of plants against pathogens (Jackson and Taylor, 1996). PO and phenylalanine ammonia lyase (PAL) are the key enzymes involved in phenylpropanoid metabolism (Vidhyasekaran et al., 1997). Accumulating evidences suggest that the organisms under most scrutiny for potential use in biological control of pest and diseases are bacteria belonging to the genera Pseudomonas and Bacillus (Powell and Rhodes, 1994; Ramamoorthy et al., 2001). Further, plant growth promoting endophytic bacteria (PGPE), especially Bacillus subtilis (EPCO16) have been developed commercially as a talc based formulation and tested against several crop diseases (Rajendran et al., 2006, 2007). The objective of the present study is to study the induction of various defense related genes implicated in strengthening plant cell walls by Bacillus subtilis in response to infection by Fusarium oxysporum f sp. lycopersici. Materials and Methods Plant materials and pathogen The seeds of tomato (cv. PKM1) were obtained from the Department of Vegetable Crops, Horticulture College and Research Institute, Tamil Nadu Agricultural University (TNAU), Coimbatore, Tamil Nadu, India. The pathogen was isolated from the tomato roots showing typical symptoms of Fusarium wilt by using potato dextrose agar (PDA) medium. Biocontrol agents The endophytic bacterial strain B. subtilis EPCO16 was isolated from cotton (Rajendran et al., 2006) and found to be effective in reducing several plant pathogens (Rajendran and Samiyappan, 2008; Rajendran et al., 2011; Senthil et al., 2011; Sundaramoorthy et al ., 2012; Sundaramoorthy and Balabaskar, 2012; Thilagavathi et al., 2012). Authenticated Bacillus subtilis EPCO16 (Accession Number. EF139864) , strain was obtained from