Scientia Horticulturae 207 (2016) 183–192 Contents lists available at ScienceDirect Scientia Horticulturae journal h om epage: www.elsevier.com/locate/scihorti Lactic acid bacteria mediated induction of defense enzymes to enhance the resistance in tomato against Ralstonia solanacearum causing bacterial wilt Narasimha Murthy Konappa a,∗ , Malini Maria a , Fazilath Uzma a , Soumya Krishnamurthy a , Siddaiah Chandra Nayaka b , Siddapura Ramachandrappa Niranjana b , Srinivas Chowdappa a a Department of Microbiology and Biotechnology, Jnanabharathi Campus, Bangalore University, Bangalore, 560 056, India b Department of Studies in Biotechnology, University of Mysore, Mysore, 570 006, India a r t i c l e i n f o Article history: Received 19 January 2016 Received in revised form 25 May 2016 Accepted 27 May 2016 Available online 14 June 2016 Keywords: Lactobacillus paracasei Ralstonia solanacearum Induced systemic resistance Tomato Bacterial wilt a b s t r a c t The biocontrol agent Lactic acid bacterium (LAB) was used against the bacterial wilt caused by Ralsto- nia solanacearum. The present investigation focuses on the role of defense related enzymes in imparting resistance to tomato plants against R. solanacearum. The LAB isolate was tested for its ability to induce the production of defense-related enzymes in treated tomato seedlings. Tomato seedlings were raised from LAB pretreated seeds, were challenge inoculated with R. solanacearum, harvested at different time intervals (0–72 h) and assayed for defense enzyme activity. The LAB treated seeds showed increase in ger- mination percentage (6%) and seedling vigour index (259) compared with control. Treatment of tomato seedlings with LAB isolate induced a significant amount of Peroxidase (POX), Polyphenol oxidase (PPO), Phenylalanine ammonialyase (PAL), total phenolics and -1,3-glucanase activities. The activities of PAL, POX, PPO and -1,3-glucanase reached maximum at 24 h, 24 h, 32 h and 24 h respectively after challenge inoculation. Increased accumulation of phenolics was noticed in plants pre-treated with LAB. Native PAGE analyses of POX and PPO were carried out for the time course of enzyme activities and the isoforms of POX and PPO were examined. In field study, ten isolates of R. solanacearum treated plots yielded an average of 32.4–50 kg/m 2 and LAB treated plots an average of 153.5 kg/m 2 . As compared to the control, LAB increased the yield by 15.3% (8.2 kg/m 2 ) and the pathogen infected plants and pre-treated with LAB gave an average of 55% (28.3 kg/m 2 compared to the infected plots). Field experiment results indicated that LAB exhibited 61.1% of disease reduction of bacterial wilt in tomato. © 2016 Elsevier B.V. All rights reserved. 1. Introduction Tomato (Lycopersicon esculentum) is a widely consumed veg- etable crop worldwide (Ronga et al., 2015), which is also an excellent source of vitamin A, vitamin C, iron and phosphorus. In tropical Asia it is an important cash crop of small farmers (Villareal, 1979) and tops the list of industrial crops because of its outstanding processing qualities. It is a short duration, high yielding crop, and hence it is economically important. Its area of cultivation is increas- ing steadily. The major constraint to tomato production in India is bacterial wilt caused by Ralstonia solanacearum (Yabuuchi et al., ∗ Corresponding author. E-mail addresses: n.murthy10@yahoo.com, n.murthy10@gmail.com (N.M. Konappa). 1995), with a host range exceeding 200 species covering over 50 families (Aliye et al., 2008). High pathogen variability, high survival rate under diverse environmental conditions and its extremely wide host range renders the disease difficult to control. Chem- ical treatments are short lived and less effective. Therefore, the stratagem of biocontrol has evolved itself as a promising approach to create long lasting effect and facilitating sustainable agricul- ture (Nagorska et al., 2007). Lactic acid bacteria (LAB) are known as probiotic organisms and are generally recognized as safe (Stiles and Holzapfel, 1997). Lactic acid bacteria are reported to produce various antibacterial compounds, such as acetic acid, lactic acid, hydrogen peroxide, several bacteriocins and even antifungal com- pounds (Ariyapitipun et al., 1999). Lactic acid bacterial cultures or their supernatants have been used as biological control agents on plant diseases in chilli, tomato and cucumber caused by Col- letotrichum capsici (El-Mabrok et al., 2012), Fusarium oxysporum and http://dx.doi.org/10.1016/j.scienta.2016.05.029 0304-4238/© 2016 Elsevier B.V. All rights reserved.