Development and validation of a new co-dominant DNA marker for selecting the null allele of polyphenol oxidase gene Ppo-D1 in common wheat (Triticum aestivum L.)

Abstract

Polyphenol oxidase (PPO) is a key enzyme contributing to the time-dependent discoloration of wheat products. Developing cultivars with low PPO activity is one way to solve this problem. In this study, we focused on the Ppo-D1 gene, which has the second highest effect on grain PPO activity after the Ppo-A1 gene. Utilizing resequencing data, we found that the Ppo-D1 gene in the common wheat line ‘Fukuhonoka-NIL’, which exhibits low PPO activity, has an approximately 3 kb deletion in the 3′UTR and a 73 bp deletion in the third exon. The deletion in the third exon indicated that this allele was the ppo-D1d allele, previously identified in the wheat D genome progenitor, Aegilops tauschii Coss. Additionally, the ppo-D1d allele in ‘Fukuhonoka-NIL’ had very low expression, suggesting that this allele is non-functional. We developed a new co-dominant DNA marker for distinguishing the Ppo-D1a, Ppo-D1b and ppo-D1d alleles and demonstrated that F₂ plants homozygous for the ppo-D1d allele exhibited significantly lower grain PPO activity. Additionally, we determined that the ppo-D1d allele likely originated from Ae. tauschii ssp. tauschii (lineage 1) accessions. The ppo-D1d allele has not previously been found in common wheat (Triticum aestivum L., AABBDD genome), and thus the DNA marker developed in this study will be helpful for introducing this allele in common wheat breeding programs.