Molecular diagnosis and induced systemic protection against rhizome rot disease of ginger caused by Pythium aphanidermatum

Polyclonal antibodies and antigens of host and pathogen were used for early diagnosis of rhizome rot disease of ginger. Pythium aphanidermatum, a causal organism was detected in ginger rhizome after eight weeks of inoculation by agar gel double diffusion and immuoelectrophoretic tests, but only one week after inoculation by indirect ELISA (enzyme linked immunosorbent assay). Systemic protection against P. aphanidermatum was induced in ginger (Cv. Suprabha) by soaking rhizome seeds separately in selected synthetic chemicals or specific herbal extracts for 1 h prior to sowing. Among 12 plant defence activators tested, jasmonic acid (JA, 5 mM) and 10% leaf extract of Acalypha indica (ALE) reduced disease significantly, with concomitant increase of defence-related proteins (DRPs). Analysis of protein profiles of leaves of JA-treated and inoculated plants by SDS-PAGE and Image Master VDS-ID Gel Analysis Version 3.0 revealed 18 protein bands, including four DRPs having molecular masses 32, 24, 18 and 14 kDa respectively. At least four DRPs were detected in leaves of ALE-treated inoculated plants. Growth response of pathogen to both JA and ALE was evaluated in vitro. ALE stimulated growth, while JA inhibited growth at high concentration (0.5 mM) and slightly stimulated growth at low dose (0.005 mM). Results suggest their host-mediated role in induced systemic protection against disease.