Elucidating the role of effector protein as biomarker for enhanced resistance against pearl millet downy mildew disease

A variety of secreted effectors are used by fungal pathogens to evade, disrupt, or modify crucial elements of transcription, defense signaling, and metabolic processes to induce resistance against biotic stress in host plant. Induced resistance is a crucial component of managing downy mildew disease in Pennisetum glaucum. However, the underlying mechanisms of effectors and their host targets in biotrophic fungal infections are mainly unknown. In the current study, the effector protein 35983_g from Sclerospora graminicola was treated against the Pennisetum glaucum callus and seedlings of resistant and susceptible variety to downy mildew and compared with the control. Hypersensitivity response (HR), protein-cell wall cross-linking, lignin deposition, hydrogen peroxide (H2O2), phenylalanine-ammonia lyase (PAL) and peroxidase (POX) were evaluated in the both the varieties of Pennisetum glaucum. Experimental data demonstrated that effector protein induced HR, boosted the activity of the enzymes PAL and POX. Additionally, a histochemical examination showed that downy mildew resistant variety treated with effector protein had thicker cell walls due to lignin deposition than untreated cultivar. The identified oomycetes effector protein in this study can be used as a biomarker in breeding programmes to screen pearl millet downy mildew resistant lines across the globe.