Polyvinylpyrrolidone

Salicylic acid, hydrogen peroxide, catechol, guaiacol, polyvinylpyrrolidone, tris buffer, sodium phosphate, and di-sodium phosphate were purchased from Himedia, Bangalore, India. All chemicals used were of analytical grade (≥99% purity).

Protein content in fungicide-treated/untreated and PGPR-inoculated radish leaves were determined [43 (link)] using bovine serum albumin (BSA; HiMedia, Mumbai, India) as standard. For the assay, 1.0 g of fresh leaf was crushed in 3.0 mL of 50 mM phosphate buffer (pH = 7.8) containing 1 mM EDTA (HiMedia, Mumbai, India) and 2% w/v polyvinyl pyrrolidone (PVP; HiMedia, Mumbai, India). The extract was centrifuged at 10,000 ×g and set aside for 10 min at 4 °C. For protein estimation, 0.2 mL supernatant was placed in a glass test tube and the volume made up to 1.0 mL with double distilled water (DDW). To this, 4.5 mL of copper solution was added and kept for 10 min. Thereafter, 0.5 mL of Folin’s reagent (Thermo Fischer Scientific) was added to each tube and incubated for 30 min for color development. Protein content was recorded by measuring the absorbance at 660 nm against the calibration curve of BSA.