Submitted to: Journal of Theoretical and Applied Genetics
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/5/2012
Publication Date: 5/2/2012
Publication URL: http://naldc.nal.usda.gov.d2.nal.usda.gov/download/54471/PDF
Citation: Beecher, B.S., Carter, A.H., See, D.R. 2012. Genetic Mapping of a new family of Seed-Expressed Polyphenol Oxidase genes in Wheat (Triticum aestivum L.). Journal of Theoretical and Applied Genetics. 124:1463-1473. Interpretive Summary: Many agricultural plant products suffer from browning and discoloration caused by the action of an enzyme called polyphenol oxidase (PPO). Wheat based products are no exception. Some wheat based doughs, particularly alkaline noodles, can become progressively more discolored and dull during processing. These products are considered less desirable by the consumer. In order to minimize PPO content of flour and thus maintain the bright color of the product, wheat processor must employ measures that reduce profitability. Therefore there is considerable desire to genetically minimize the PPO content of wheat. This is complicated by the fact that wheat contains many PPO genes, only some of which are important for wheat quality. In order to efficiently reduce wheat PPO we must first identify and characterize which genes contribute to wheat PPO activity. Recently, we identified a major new family of important wheat PPO genes. Here, we determined the genetic location of these three new genes. In addition we identified additional regions of the wheat genome that might also be important for wheat kernel. PPO activity.
Technical Abstract: Polyphenol oxidase (PPO) enzymatic activity is a major cause in time-dependent discoloration in wheat dough products. The PPO-A1 and PPO-D1 genes have been shown to contribute to wheat kernel PPO activity. However it has been shown that wheat contains multiple PPO genes. Recently a novel PPO gene family consisting of the PPO-A2, PPO-B2, and PPO-D2 genes has been described. The PPO-A2 and PPO-D2 genes were shown to be more highly expressed in developing kernels than their PPO-A1 and PPO-D1 paralogous counterparts. In this study, the Louise X Penawawa mapping population was used to genetically map all five of the PPO genes known to be expressed in wheat kernel. All map to the long arm of homeologous group 2 chromosomes. PPO-A2 was found to be located 8.9 cM proximal to PPO-A1 on the long arm of chromosome 2A. Similarly, PPO-D1 and PPO-D2 were separated by 10.7 cM on the long arm of chromosome 2D. PPO-B2 mapped to the long arm of chromosome 2B and was the site of a novel QTL for polyphenol oxidase activity. Four other PPO QTL were identified in this study. One QTL corresponds to the previously described PPO-D1 locus, while the remaining three are located on chromosome 2B.