Abstract: 【Objective】The enzyme activity of polyphenol oxidase (PPO) in grain has been closely related to the brown discoloration of wheat (Triticum aestivum L.) based end-products, particularly for fresh noodles. The allelic variation of PPO genes on chromosome 2A and 2D and its effect on PPO activity were detected for improvement of the appearance quality of wheat based end-products and MAS for low PPO activity.【Method】One STS marker PPO18, which was located on wheat chromosome 2A and STS01 designed from a mRNA sequence (Genbank: AY515506) in this study, which was located on chromosome 2D were used to study the allelic variation of different PPO genes and its effect on PPO activity using 130 cultivars, which the PPO activity was measured in each of two crop seasons.【Result】The results showed that PPO alleles L1 and H1 at the STS01 locus and alleles L2 and H2 at PPO18 locus gave significantly different effect on wheat kernel PPO activity. The cultivars with allele STS01-H1 and PPO18-H2 had greater (P<0.01) PPO activity than the cultivars with STS01-L1 and PPO18-L2, meanwhile 32 cultivars with L1L2 gene gave very low PPO activity mostly. Allelic variation at STS01 and PPO18 loci can explain 63.06% of phenotypic variance for PPO activity. The effect of PPO genes on chromosome 2A and 2D on PPO activity appears cumulative. 【Conclusion】Wheat PPO activity was mainly effected by two PPO genes located on chromosome 2A and 2D. Using STS markers PPO18 and STS01 together in MAS could improve the effect of selection obviously in breeding program for low PPO activity.

Key words: Wheat (Triticum aestivum L.), Polyphenol oxidase activity, STS molecular marker, Alleic variation