Enzyme activity in wheat breeding lines derived from matings of low polyphenol oxidase parents

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 undesirable product darkening. The low PPO line PI 117635 was crossed to two low PPO wheats, IDO580 and 'IDO377s', to determine whether matings between wheats with low levels of grain PPO would result in complementation, such that lines with still lower or nil PPO would be generated. Progeny in a population derived from PI 117635/ IDO580 displayed no variation in PPO activity. In the F 3:4 populations derived from PI 117635/IDO377s, and the reciprocal IDO377s/PI 117635, normal distributions of low to high PPO activity were observed. Fieldgrown populations (F 3:5 ; F 3:6 ) derived from IDO377s crosses were analyzed for PPO activity and used to determine whether lines with nil PPO activity were generated. Of 239 lines, 154 were verified to have PPO activity that was not significantly different from the low PPO durum (Triticum turgidum var durum) cultivar 'Ben'. PCR analysis 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 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 when making selections using markers for alleles at Ppo-D1, as known markers might predict erroneous phenotypes and genotypes in some wheat backgrounds.

Determinants of wheat noodle color

“…demonstrated that in five different wheat populations, Ppo‐A1 and Ppo‐D1 alleles, as identified by molecular markers, were highly related to levels of kernel PPO activity. Nilthong et al . went on to show that crossing and selection could generate hexaploid wheat lines with PPO levels (by L‐DOPA) not different from the durum cultivar ‘Ben.’ Hystad et al .…”

“…Nilthong et al 129 demonstrated that in five different wheat populations, Ppo-A1 and Ppo-D1 alleles, as identified by molecular markers, were highly related to levels of kernel PPO activity. Nilthong et al 130 went on to show that crossing and selection could generate hexaploid wheat lines with PPO levels (by L-DOPA) not different from the durum cultivar 'Ben.' Hystad et al 75 showed that combining 'null' PPO alleles at PPO-A1 and PPO-D1 resulted in lower PPO activity, and brighter white salted noodles with lower discoloration (ΔL*).…”

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

“…Ppo-A2d contains a single aspartate to glycine mutation in the second exon at position 400 of the 577 residue polypeptide. Note that the use of complimentary STS markers PPO16/STS01 and PPO29 which discriminate between Ppo-D1 alleles associated with high (Ppo-D1b) and low (Ppo-D1a) PPO activity will give conflicting results in the 07OR1074 genetic background (Onto 2011;Nilthong et al 2012Nilthong et al , 2013. As the Ppo-D1f allele is identical in structure and nearly identical in sequence to the Ppo-D1b allele with the exception of a single SNP, PPO29 is unable to distinguish the high-PPO allele (Ppo-D1b) and null allele (Ppo-D1f) explaining erroneous results obtained in prior reports.…”

Molecular marker assisted screening for kernel polyphenol oxidase activity in wheat Triticum aestivum L.

“…The major genes governing kernel PPO activity have been reported to be present in wheat homeologous group 2 chromosomes (Jime´nez and Dubcovsky, 1999). The role of the PPO genes on chromosome 2AL and 2DL (i.e., PPOA1 and PPOD1) in regulating kernel PPO activity has been established (Sun et al, 2005;Chang et al, 2007;He et al, 2007;Wang et al, 2009) and the PPOA1 locus has been found to have major effect in determining kernel PPO activity (Raman et al, 2007;Beecher and Skinner, 2011;Martin et al, 2011;Nilthong et al, 2013). In order to facilitate marker assisted selection (MAS), reproducible gene-based sequence tag site (STS) markers have been developed for the PPOA1 and PPOD1 loci.…”

“…In order to facilitate marker assisted selection (MAS), reproducible gene-based sequence tag site (STS) markers have been developed for the PPOA1 and PPOD1 loci. However, the possibility of erroneous prediction of alleles at PPOD1 locus using the developed markers has been indicated (Nilthong et al, 2013). In the recent past, 4 QTLs for PPO activity on chromosomes 2AL, 3BS, 4BL and 7DL has been documented to explain 64.1-89.0 % of the total phenotypic variance across environments (Zhai et al, 2016).…”