|Nilthong, Somrudee Onto -|
|Baenziger, Stephen -|
Submitted to: Euphytica
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 8, 2012
Publication Date: August 28, 2012
Repository URL: http://ttp://handle.nal.usda.gov/10113/55918
Citation: Nilthong, S., Graybosch, R.A., Baenziger, S.P. 2012. Inheritance of polyphenol oxidase activity in wheat breeding lines derived from matings of low polyphenol oxidase parents. Euphytica. DOI 10.1007/s10681-012-0777-y. Interpretive Summary: Polyphenol oxidase is an enzyme found in all plants, and is responsible for undesirable reactions that lead to discoloration of food products. Polyphenol oxidase activity results in commonly observed discoloration in cut fruit such as apples and avocados. Polyphenol oxidase also is active in wheat grain, especially in the bran layers. When wheat is milled, some of the bran typically carries into the white flour portion. Residual polyphenol oxidase can result in discoloration of refrigerated and fresh products, especially Asian noodles and pre-formed “whomp” biscuits. Low levels of polyphenol oxidase are mandatory in newly developed hard white winter wheat cultivars. This study was conducted to investigate the inheritance of polyphenol oxidase activity in wheat cultivars identified as having low levels in the grain. The results demonstrated that common (bread) wheat cultivars can be developed with levels as low as those observed in durum wheats, typically considered polyphenol oxidase-free. The results also demonstrated that previously reported DNA markers for the trait will give erroneous predications in some genetic backgrounds, calling into question once again the utility of marker assisted selection in plant breeding and suggesting molecular biologists review fundamental genetic concepts such as recombination.
Technical Abstract: Polyphenol oxidase (PPO) in grain plays a major role in time-dependent discoloration of wheat (Triticum aestivum L.) products, especially fresh noodles. Breeding wheat cultivars with low or nil PPO activity can reduce the undesirable product darkening. The low PPO line PI 117635 was crossed to two low PPO cultivars, IDO580 and IDO377s to determine whether matings between wheats with low levels of grain PPO would result in complementation, and lines with still lower or nil PPO would be generated. A population derived from PI 117635/IDO580 displayed no variation in PPO activity among the progeny. In the F3:4 populations derived from PI 117635/IDO377s and the reciprocal IDO377s/PI 117635 normal distributions of low to high PPO activity were observed. Field-grown populations (F3:5; F3:6) derived from IDO377s crosses were analyzed for PPO activity and used to determine whether lines with nil PPO activity were generated. Of the 239 lines, 154 lines were verified to have PPO activity that was not significantly different from the low PPO durum (T. turgidum var durum) cultivar ‘Ben’. The average kernel PPO activity of the experimental lines with different PCR fragments amplified by STS markers showed that the populations were fixed for a putative low PPO allele at Ppo-A1. Using markers for Ppo-D1, it was found that the average PPO activity of lines with the 490-bp PCR fragments from PPO29 was significantly lower than that of lines with 560-bp fragments from STS01. These results disagreed with that predicted from previous reports for markers for Ppo-D1 alleles. Thus, breeders should exercise caution making selections using markers for alleles at Ppo-D1, as known markers might predict erroneous phenotypes and genotypes in some wheat backgrounds.