Relationship between the allelic variations at the<italic> Ppo-A1 </italic>and <italic>Ppo-D1</italic> loci and pre-harvest sprouting resistance in wheat

Abstract

<p indent=0mm><italic>Ppo-A1</italic> and <italic>Ppo-D1</italic> are the major genes that control the activity of polyphenol oxidase (PPO) in wheat. It has been reported that the activity of polyphenol oxidase affects pre-harvest sprouting (PHS) resistance, but the effect of different alleles/allelic combinations at the <italic>Ppo-A1</italic> and <italic>Ppo-D1 </italic>loci on PHS resistance remains unclear. The current study was carried out to elucidate the effects based on the germination index obtained from 248 Chinese wheat cultivars in a three-year trial in combination with genotypic data at the <italic>Ppo-A1</italic> and <italic>Ppo-D1 </italic>loci. Analysis of variation for the<italic> Ppo-A1 </italic>and <italic>Ppo-D1</italic> loci showed that year,<italic> Ppo-A1</italic> locus and<italic> Ppo-A1</italic> × <italic>Ppo-D1 </italic>interaction had significant effects on germination index. At locus <italic>Ppo-A1</italic>, germination index of cultivars carrying the allele <italic>Ppo-A1b</italic> of low PPO activity was 5.22% lower than that carrying the allele<italic> Ppo-A1a</italic> of high PPO activity on average. In contrast, the cultivars carrying the allele <italic>Ppo-D1a</italic> of low PPO activity had higher germination index than that carrying the allele<italic> Ppo-D1b</italic> of high PPO activity at locus<italic> Ppo-D1</italic>, but no significant differences between two alleles. Among the four allelic combinations, the cultivars with the <italic>Ppo-A1bPpo-D1b</italic> had the lowest germination index. The relationship between the alleles at locus <italic>Ppo-A1</italic> and PHS resistance had been verified in the Lunxuan 13 × Jimai 20 F₂ and F_2:3 segregation populations. There were significantly positive correlations between PPO activity / relative expression level of <italic>Ppo-A1</italic> gene and germination index. This study suggests that functional markers of allele<italic> Ppo-A1b </italic>can be effectively applied in marker-assisted selection for PHS resistance.