Lactuca sativa mediated chitinase activity and resistance in pearl millet against Sclerospora graminicola

Pearl millet seeds were treated with latex extracts (L1- 50 µl, L2- 100 µl and L3- 200 µl) ofAsclepias curassavica, Calotropis gigantea, Croton sp., Eucalyptus alba, Morus alba,Nerium odoratum, Lactuca sativa and Tridax procumbens were applied on pearl millet seeds for 3 and 6 h to evaluate their role in growth promotion and downy mildew resistance. Latex extracts of all tested plants improved vegetative parameters when compared with the control. L. sativa (L2) at 3 h showed 38 and 18% increase in seed germination and vigor, respectively, over the control. Plant height, shoot fresh and dry weight, number of tillers and leaf surface area also increased upon latex treatment. Green house studies indicated that L. sativa required four days after challenge inoculation to build up maximum resistance and offered 54% protection against downy mildew. Resistance induction was evident with increased activities of phenylalanine ammonia lyase (PAL) (four fold), peroxidase (POX) (three fold) and chitinase (three fold) in L. sativa(L2) treated seedlings challenged with the pathogen as compared to control seedlings.   Key words: Downy mildew, induced resistance, Lactuca sativa, pearl millet, plant extracts, Sclerospora graminicola.