Inheritance of grain polyphenol oxidase (PPO) activity in multiple wheat (Triticum aestivum L.) genetic backgrounds

Abstract

Grain polyphenol oxidase (PPO) activity can cause discoloration of wheat (Triticum aestivum L.) food products. Five crosses (PI 117635/Antelope; Fielder/ NW03681; Fielder/Antelope; NW07OR1070/Antelope; NW07OR1066/OR2050272H) were selected to study the genetic inheritance of PPO activity. STS markers, PPO18, PPO29 and STS01, were used to identify lines with putative alleles at the Ppo-A1 and Ppo-D1 loci conditioning low or high PPO activity. ANOVA showed significant genotypic effects on PPO activity (P \ 0.0001) in all populations. The generations and generation 9 genotype effects were not significant in any population. A putative third (null) genotype at Ppo-A1 (no PCR fragments for PPO18) was discovered in NW07OR1066 and NW07OR1070 derived populations, and these had the lowest mean PPO activities. Results demonstrated that both Ppo-A1 and Ppo-D1 loci affect the kernel PPO activity, but the Ppo-A1 has the major effect. In three populations, contrary results were observed to those predicted from previous work with Ppo-D1 alleles, suggesting the markers for Ppo-D1 allele might give erroneous results in some genetic backgrounds or lineages. Results suggest that selection for low or null alleles only at Ppo-A1 might allow development of low PPO wheat cultivars.

Genetic characterization and expression analysis of wheat (Triticum aestivum) line 07OR1074 exhibiting very low polyphenol oxidase (PPO) activity

“…These findings suggest the Ppo-1 and Ppo-2 orthologous A genome loci contribute more transcripts and, therefore, likely more functional PPO enzyme than Ppo transcripts from either the B and D genome combined. This is in accordance with prior work indicating that Ppo-A1 allelic variation has the greatest effect on kernel PPO activity (Raman et al 2005;Sun et al 2011;Nilthong et al 2012) and upon Chinese raw noodle color (Martin et al 2011) compared to Ppo-D1 allelic variation. However, since the Ppo-1 and Ppo-2 orthologous genes are separated by just 10 cM (Beecher et al 2012), genetic linkage may confound previously reported results examining the relative importance of Ppo-A1 and Ppo-D1 allelic variation upon kernel PPO activity.…”

“…All PCRs were performed in a total volume of 25 µL as described above. PPO18 was multiplexed with the primer combination PB5 and CAT 3.4 (Swan et al 2006) to distinguish between the putative null allele (Nilthong et al 2012) and alleles conditioning high and low activity at the Ppo-A1 locus (Sun et al 2011). The primer combination PB5 and CAT 3.4 amplifies a portion of the Pinb-D1 gene which was used as an internal control for genomic DNA quality (Fig.…”

“…Paralogous gene family Ppo-1 members consisting of Ppo-A1 and Ppo-D1 are localized to the long arm of homeologous chromosomes 2A and 2D, respectively (Sun et al 2011;He et al 2007). Ppo-A1 and Ppo-D1 allelic variation is associated with kernel PPO activity variation (Sun et al 2011;He et al 2007;Wang et al 2009;Martin et al 2011;Nilthong et al 2012). The sequence-tagged site (STS) marker PPO18, amplifies a 685 bp (Ppo-A1a) and 876 bp (Ppo-A1b) fragment corresponding to genotypes associated with high and low PPO activity, respectively (Sun et al 2011).…”

“…Nilthong et al (2012) described these wheat lines as containing a putative null genotype at the Ppo-A1 locus but did not characterize any mutations in other Ppo genes. The goals of the present study were: (1) characterize mutations present at additional Ppo loci that explain the substantial reduction in kernel PPO activity present in a putative null Ppo-A1 genetic background; (2) create novel functional markers encompassing mutations found within newly characterized alleles; (3) assess the allelic impact of the newly characterized alleles on kernel PPO activity; and (4) characterize the expression profile of kernel-expressed Ppo genes in a putative null Ppo-A1 genetic background.…”

Gas Separation by Polymer Membrane

“…The kinked ether linkage and the absence of polar groups suppress efcient chain packing and densication, resulting in a relatively large fractional free volume in PPO, as seen in table 1. The high free volume and the ease of rotation of the phenyl rings about the ether linkages contribute to high diffusivity and permeability [25]. …”