Figure 8: Impact of Bio-arc and Nemastrol as biotic resistance inducers on peroxidase (PO) and polyphenol oxidase (PPO) activities in roots of sugar-beet var. Negma after 0, 3, 9 and 15 days of Meloidogyne incognita inoculation. A= peroxidase activity, B= polyphenol oxidase activity.