Distribution of horseradish peroxidase activity in horseradish plants

Thirty horseradish (Armoracia rusticana Gaertn., Mey., & Scherb.) cultivars from eight countries in Europe and North America and from advanced lines developed at the Univ. of Illinois were evaluated for horseradish peroxidase (HRP; electrical conductivity 1.11.1.7, donor:hydrogen peroxide oxido-reductase) activity. Nearly 86% of the activity was present in the taproot and lateral roots and 14% in the leaf petiole, but there was no activity in the leaf blade, The 30 cultivars were divided into three groups with high (eight cultivars), medium (13 cultivars), and low (nine cultivars) activities [11.58 to 16.97, 7.19 to 9.79, and 2.88 to 6.91 mu mol.min(-1).g(-1) fresh weight (FW), respectively]. The cultivars with the highest activity were 819-A from the Illinois and 810-A from Switzerland with 16.97 and 16.67 mu mol.min(-1).g(-1) FW, respectively. The cultivar with the lowest HRP activity was 244-A from the United States with 2.88 mu mol.min(-1).g(-1) FW. Cultivar 819-A also had the highest protein concentration (1.92 mg.g(-1) FW). When HRP activity was expressed per milligrams of protein, cultivar 167-A, also known as 'Bohemian', had the highest activity and cultivar 243-A had the lowest (5.35 and 0.83 mu mol.min(-1).mg(-1) protein, respectively).