Abstract:

【Objective】 Grain polyphenol oxidase (PPO) activity is highly related to the brown discoloration of wheat based end-products. Studying on the variation of PPO activity and the distribution of allelic genes in Chinese wheat micro-core collections could take good advantage of germplasm and improve the appearance quality of wheat flour food. 【Method】 In this study the variation of PPO activity and the distribution of PPO allelic genes were detected by the method of biochemistry and gene-based markers in 251 Chinese wheat micro-core collections growning in Hefei and Fengyang in 2004-2005 crop season. 【Result】 The results showed that most cultivars were with low PPO activity and the rate of varieties with PPO activity below 200 was 47.01% and the variation of PPO activity was affected by genotype and locations and interaction between them. Four genotypes, PPO-2Aa1/PPO-2Da2 (a1a2), PPO-2Aa1/PPO-2Db1 (a1b1), PPO-2Aa1/PPO-2Db2 (a1b2), and PPO-2Ab1/PPO-2Db2 (b1b2), were detected in Chinese wheat micro-core collections. Cultivars with the genotype a1a2 have the lowest PPO activity while the cultirars with the genotype b1b2 have the highest, with genotype a1b2 and genotype b1a2 have the intermediate. The effect of interaction between marker genotypes and locations on PPO activity was not significant (P＜0.05). The frequency of PPO allelic genes on two wheat chromosomes 2A and 2D was different. The frequency of allelic genes 2Aa1 and 2Ab1 on chromosome 2A was most alike, while the frequency of 2Da2 was almost four times than that of 2Db2 on chromosome 2D. The effect of haplotype of PPO genes on the same chromosome on PPO activity was PPO-2Aa1＜PPO-2Ab1 and PPO-2Da2＜PPO-2Db2. The mean value of PPO activity of cultivars from South China Winter Wheat Region was significantly (P＜0.01) lower than that of cultivars from the three spring wheat regions and cultivars imported from aboard. Cultivars from the five winter wheat regions gave significantly (P＜0.01) lower PPO activity than cultivars from the three spring wheat regions of China. PPO activity of landrace was significantly (P＜0.01) lower than that of bred varieties and cultivars imported from aboard. The PPO activity and genotypes of primal parents in Chinese wheat cultivars was also analysized in this study. 【Conclusion】Variation of PPO activity in Chinese wheat micro-core collections is obvious, and the allelic variation of PPO genes induced a significant effect on grain PPO activity. The distribution of wheat grain PPO activity and genotypes have a close relationship with wheat regions and wheat primary parents.

Key words: common wheat (Triticum aestivum), micro-core collections, polyphenol oxidase, allelic variation