ABSTRACT
Calli raised from mature embryos of susceptible wheat cultivar WH 542 were used in the present study as in vitro bioassay system to study the influence of disease determinant(s) of Karnal bunt (Tilletia indica), a semi-biotrophic fungal pathogen of wheat. Influence of elicitor and conditioned medium (CM) prepared from fungal cultures of T. indica was investigated on induction of programmed cell death (PCD). Induction of PCD was observed as hypersensitive response (HR) in terms of browning at localized regions of callus cultures and induction of proteolytic enzyme(s). Elicitor treated calli showed higher induction of protease activity than untreated and CM-treated cultures, which showed not much change in the activity. It was further substantiated by gel protease assay and activation of caspase-3 like protein(s) in callus cultures that clearly suggested the presence of signaling molecule(s) in the fungal elicitor preparation rather than in conditioned medium. This study further demonstrated that only elicitor preparation possesses such molecule(s), which might be cell wall bound components, rather than secretory in nature as CM was unable to induce PCD in wheat callus cultivars.