Analysis of the genetic effects of allelic variation at the Pod-A1, Pod-D1, and Pod-2D loci on peroxidase activity in wheat grains

Peroxidase (POD) activity in wheat grains strongly influences processing quality and the color of wheat-based products, and is therefore an important target for quality improvement. In this study, 151 wheat varieties (lines) from domestic and international sources were used to systematically characterize allelic variation at the Pod-A1, Pod-D1, and Pod-2D loci using molecular markers. Together with multi-year, multi-location measurements of grain POD activity, we evaluated the effects of individual alleles and their combinations on POD activity. Grain POD activity showed substantial genetic variation, with a mean of 674.39 U g⁻¹ min⁻¹, a range of 431.30-954.81 U g⁻¹ min⁻¹, and a coefficient of variation of 15.52%. Environment, genotype, and their interaction all had highly significant effects on POD activity (P < 0.01). All three loci significantly affected grain POD activity, and the favorable alleles were Pod-A1b, Pod-D1b, and Pod-2D-GG, respectively. In total, 12 allelic combinations were identified and classified into high-, medium-, and low-activity combination types based on grain POD activity. POD activity differed significantly among the three types (P < 0.05), whereas no significant differences were detected within each type. The genetic effects of the three loci on grain POD activity followed the order Pod-2D > Pod-A1 > Pod-D1. Grain POD activity increased significantly with the number of favorable alleles (R² = 0.9681, P < 0.05); varieties (lines) pyramiding 2-3 favorable alleles had significantly higher POD activity than those carrying 0-1 favorable allele (P < 0.05). Significant regional differences were observed in POD activity, allelic variation, and allelic-combination frequencies. Nine varieties, including Liangxing 66, Lankao 24, and Jimai 22, were identified as carrying all three favorable alleles and exhibiting POD activity above 800 U g⁻¹ min⁻¹. These findings provide a theoretical basis and germplasm resources for molecular marker-assisted breeding to optimize wheat grain POD activity.