Association of Polyphenol Oxidase Activities with Molecular Markers and Yellow Rust Resistance in Diverse Bread Wheat Genotypes

Polyphenol Oxidase (PPO) catalyses the undesirable browning of wheat products which is of significant concern in consumer acceptance perspectives. Another important yield-limiting cause for wheat crops is wheat rust (e.g., yellow rust), a source of great economic loss worldwide. The purpose of the current research was to screen conventional and synthetic bread wheat genotypes for their PPO activity and yellow rust resistance. Different genotypes differed significantly in total PPO activity and in their activities against different substrates (L-DOPA and Catechol). The synthetically derived bread wheat genotypes 1-279, showed the lowest (39.2 units/min/g) cumulative PPO activity. Ten genotypes each with the highest and lowest PPO activities were selected for testing their association with seven reported molecular markers. Intriguingly the PPO markers reported in literature could not clearly differentiate between contrasting cultivars. Association with yellow rust resistance was also investigated. Interestingly, the rust-resistant genotypes, including 1-263, Ch-43, 1-57 and Emat (all synthetic-derived), exhibited low PPO activity. The current study underpins that there is a need to search for more reliable PPO markers and to further validate association of low PPO activity with yellow rust.