Elucidating the effects on polyphenol oxidase activity and allelic variation of polyphenol oxidase genes on dough and whole wheat-derived product color parameters

Polyphenol oxidase (PPO) activity is a primary cause of the development of unattractive dark brown discoloration of wheat-based end products. The present study aims to evaluate a set of 41 diverse wheat genotypes grown at three different locations in India for grain phenol color reaction, PPO activity and molecular marker-based characterization of alleles of PPO genes. Relationships among these parameters were analyzed along with the effects of grain PPO activity on dough and chapati color at different time intervals. The mean PPO activity ranged from 7.42 to 27.57 min(-1 )g(-1) 10(-3) among the genotypes and it showed a significant negative correlation with color brightness (L*) of dough rested for 0 min (r = -0.406), 15 min (r = -0.406), 2 h (r = -0.502) and 4 h (r = -0.551) and whole wheat flour-derived chapati rested for 2 h (r = -0.267) and 4 h (r = -0.424). The overall quality color score was negatively correlated with PPO activity (r = -0.863) and showed a positive correlation with both dough and chapati visual color measured at different time intervals. PPO activity in the genotypes carrying different alleles was found to be Ppo-A1a>Ppo-A1b; Ppo-B2d>Ppo-B2a; and Ppo-D1b>Ppo-D1a. The allelic constitution Ppo-A1bPpo-B2aPpo-D1a and Ppo-A1bPpo-B2dPpo-D1 was found to produce the lowest PPO activity, and thus these alleles are recommended to be used in marker assisted breeding for low PPO activity genotypes to minimize the discoloration of wheat-based end-products.