Molecular and physico-chemical evaluation of enzymatic browning of whole meal and dough in a collection of tetraploid wheats

Many studies have demonstrated the role of polyphenol oxidase (PPO; E.C. 1.14.18.1) in darkening of wheat products. Even slight browning of pasta is a major hindrance to consumer acceptance. The aim of this research was to evaluate the variability of PPO activity, browning level, and protein content in a collection of more than 100 genotypes of tetraploid wheat, including cultivars and landraces. A molecular approach was followed to evaluate the efficiency of marker PPO18, discovered and used in common wheat, in detecting tetraploid wheat genotypes with low browning level. The data showed a significant genotype influence on the activity of the PPO enzyme, which was correlated with brown index of whole meal and dough, and with protein content. On the whole, the cultivars showed lower PPO activity, brown index, and protein content than landraces, but wide variability was present. Marker PPO18 detected four different alleles for Ppo-A1. The allele Ppo-A1f identified genotypes with high PPO activity and brown index, while the Ppo-A1b and null alleles were associated with the opposite characteristics. Hence, this marker can be used to select new tetraploid wheat cultivars with low browning level.