A novel molecular marker for the polyphenol oxidase gene located on chromosome 2B in common wheat

Polyphenol oxidase (PPO) is a major cause of time-dependent darkening and discoloration in Asian noodles and other wheat-based products. One of the best ways to reduce this undesirable darkening is to breed new wheat cultivars with low PPO activity using efficient and reliable markers. Based on the sequence of a PPO gene SSPPO-B1 (GenBank accession no. AB254804) located on chromosome 2B of common wheat, 26 pairs of primers were designed to detect polymorphisms between wheat cultivars with low and high PPO activity. F-8, one of these primer pairs, amplified double fragments (band “a” of approximately 400 bp and band “b” of approximately 600 bp) in the cultivars with low PPO activity, and a single fragment (only band a) in the cultivars with high PPO activity. The differences between the fragments a and b include five indels and several single nucleotide polymorphisms, which occurred in intron II of the PPO gene. F-8 can be used as a sequence-tagged site marker to discriminate between two alleles Ppo-B1a (GQ303713) and Ppo-B1b (AB254804). The screening of 284 accessions of the core collection of Chinese wheat germplasms using the marker F-8 showed that the double fragments were present in 188 accessions, and the single fragments were present in the remaining 96 accessions. Statistical analysis revealed that the cultivars with the double fragments had significantly lower mean PPO activity than those with the single fragments. We also screened the 284 accessions using two additional markers, PPO18 for Ppo-A1 on chromosome 2A and STS01 for Ppo-D1 on chromosome 2D. Results showed that the combination of markers F-8, PPO18, and STS01 could reliably predict PPO activity. These markers can be used in wheat breeding programs for low PPO activity selection to improve the quality of wheat-based products.