Elicitation of resistance and defense related enzymes by raw cow milk and amino acids in pearl millet against downy mildew disease caused by Sclerospora graminicola

Modulation of physiological and biochemical defensive responses against downy mildew (DM) of pearl millet induced by raw cow milk (RCM) and five amino acids is reported in this paper. In vitro conditions, none of the inducer treatments showed inhibitory action on DM pathogen. Significant enhancement of seed germination and seedling vigor was observed in RCM and amino acids treated seeds. Under greenhouse conditions, significant protection against DM was provided by l-phenylalanine (68.6%), l-isoleucine (66.5%) and l-proline (55.7%) treatments. Among the RCM treatments, the 10% dilution proved to be the best by offering disease protection of 35%. Spatio-temporal time gap studies indicated that seed treatment with l-phenylalanine increased disease resistance four days after inoculation. Seed treatments with RCM and amino acids also enhanced the vegetative and reproductive growth parameters of pearl millet when compared to the control. A similar trend in protection against DM was evident in the field trials. At the biochemical level, defense related enzymes such as phenylalanine ammonia lyase (PAL), peroxidase (POX) and β-1,3-glucanase showed an increased activity in RCM and amino acids treated seedlings than in sterile distilled water control seedlings. The highest PAL activity was recorded in RCM (10 and 20%) whereas in case of amino acids, the highest activity was observed in l-proline and l-phenylalanine treatments. The highest activity of β-1,3-glucanase was recorded in RCM (20%) and l-phenylalanine.

► The present investigation addresses RCM and amino acids activation ISR in pearl miller against DM.
► RCM and amino acids treated seeds enhanced vegetative growth.
► Under greenhouse conditions, maximum disease protection was recorded by L-phenylalanine (68.6%).
► Spatio-temporal time gap studies indicated that seed treatment with L-phenylalanine increased disease resistance.
► Defense related enzymes such as PAL, PO and β-1, 3-glucanase showed an increase in activity than in untreated pearl millet seedlings.