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Montana Agricultural Experiment Station; Montana Wheat and Barley Committee; Hatch project (MONB00298)

Polyphenol oxidase (PPO) activity is a factor in time-dependent discoloration of Asian noodles. At least two major genes Ppo - A1 and Ppo - D1 control kernel PPO activity in wheat. The goal was to determine the relative importance of allelic variation for Ppo - A1 and Ppo - D1 on Chinese raw noodle color profile and kernel and flour characteristics using a winter wheat recombinant inbred population segregating for Ppo - A1 and Ppo - D1 . Ppo - A1 allelic variation explained 80% and Ppo - D1 allelic variation explained 2% of the variation in kernel PPO activity. The low PPO allele at each locus gave noodles that were brighter (greater L*), more yellow (greater b*) and more red (greater a*) at 24 h, and noodles with less change in L* but more change in a* and b* with time (0–24 h). The two loci combined explained 27, 35, and 17% of variation in L*, a*, and b* at 24 h, and 51, 55, and 58% of the variation in change in L*, a*, and b* with time, respectively. Allelic variation at Ppo - D1 explained a larger percentage of variation than did Ppo - A1 in each case except b* at 24 h where the two loci explained equal amounts.

Polyphenol oxidase (PPO) (EC.1.14.18.1) activity has been shown to be related to time-dependent discoloration of Asian noodles. Our objective was to determine the impact of divergent selection for PPO activity on agronomic, milling, bread baking, and Chinese raw noodle quality traits in winter wheat (Triticum aestivum L.) populations. Progeny from seven winter wheat populations were selected for high or low PPO activity by the L-3,4-dihydroxyphenylalanine (L-DOPA) assay on whole kernel meal on the basis of a single replication with equal number of high and low lines in each population. The selected lines were evaluated in replicated trials in multiple environments. Agronomic, milling, bread baking, and Chinese raw noodle traits were measured for all entries. The high versus low PPO classification was confirmed from replicated trials with no overlap between low and high PPO lines for any of the populations. Divergent selection had no impact on agronomic traits except for heading date where low PPO lines averaged 1 d later to head than high PPO lines. Flour ash averaged 0.11 g kg -1 higher for low compared with high PPO lines, but flour protein and flour yield did not differ between groups. The low PPO selection group had weaker dough, as reflected by lower mixograph tolerance, and lower crumb grain scores. Chinese raw noodle texture was altered by divergent selection so that the low PPO group produced noodles that were less elastic, sticky, and chewy than the high PPO group. Chinese raw noodles became darker (lower L*), more yellow (greater b*), and more red (greater a*) with time. Low PPO lines averaged less change in L* (8.9 vs. 9.6) but more change in b* (-7.70 vs. -7.02) and a* (-0.74 vs. -0.62) than high PPO lines over 24 h. Whether these changes in noodle color and texture are desirable may depend on the type of noodle and regional and personal preferences.