Effect of Acibenzolar-S-methyl (ASM) pre-treatment in inducing resistance against Pythium aphanidermatum infection in Curcuma longa

In vitro experiments were carried out to test the efficacy of plant activator Acibenzolar-S-methyl (ASM a benzothiadiazole derivative trade name Bion 50WG) against rhizome rot disease of turmeric (Curcuma longa L) caused by Pythium aphanidermatum The plant activator was applied as a liquid rhizome pretreatment followed by inoculation with P aphanidermatum Cell death activities of pathogenesis related (PR) proteins such as cysteine protease (EC 3 4 22) peroxidases (EC 1 11 1 7) both soluble and tonically bound (IB) trypsin inhibitor (EC 34 21 1) and chymotrypsin inhibitor (EC 3421 4) were monitored Rhizome pre-treatment was effective in controlling P aphanidermatum infection Anatomical observation of turmeric rhizomes indicated the presence of calcium oxalate deposits in infected tissue and an accumulation of starch grains in response to infection by P aphanidermatum Pathogen infection also Induced new basic polypeptides corresponding to 180 and 41 0 kDa Induction of protease protease inhibitors soluble and tonically bound peroxidase activity was observed after ASM pre-treatment and P aphanidermatum infection ASM treatment also enhanced activities of proteases and peroxidase in rhizomes already infected with P aphanidermatum Increases in enzyme activities and protease inhibitors occurred much more rapidly and were enhanced in P aphanidermatum infected rhizomes that were previously treated with ASM suggesting that increased activities of peroxidases and protease inhibitors may play a key role in restricting the development of disease symptoms on the rhizomes infected with P aphanidermatum as evidenced by a reduction in cell death Hence pretreatment with ASM suppress the P aphanidermatum induced oxidative damage through higher accumulation of peroxidases and induced defense through activities of protease inhibitors thereby protected turmeric rhizomes from rhizome rot disease (C) 2010 Elsevier Ltd All rights reserved