Identification of active principle in the herbal extracts possessing bactericidal action against citrus canker, Xanthomonas axonopodis pv. Citri

Bactericidal action of some selected herbal extracts viz., Acalypha indica, Achyranthes aspera, Aloe vera, Azadirachta indica, Datura metal, Hibiscus rosasinensis, Nerium oleander, Ocimum sanctum, O. basilicum, Phyllanthus emblica, Polyalthia longifolia, Piper betle, Punica granatum, Solanum torvum and Solanum trilobatum were tested in vitro against the growth of citrus canker disease causing pathogen, Xanthomonas axonopodis pv. citri (Xac). The leaf extract of P. longifolia followed by A. aspera recorded the maximum growth inhibition of 9.77mm and 8.47mm diameter respectively. The 20–40% ammonium sulphate fraction of A. aspera and 40–60% fraction of P. longifolia exhibited inhibitory action on in vitro growth of the pathogen. The molecular weight of the fractions of leaf extracts was found to be 30 kDa and 19 kDa for P. longifolia and A. aspera respectively.