Antioxidant Enzymatic Activity of Extracts from Hairy Roots of Root-Lesion-Nematode-Susceptible and -Resistant Cultivars of Medicago sativa

Diseases caused by phytoparasitic nematodes are still a heavy constraint on modern farming, causing losses in crop yields as well as increased production costs due to pest management. Root-lesion nematodes (RLNs) are soil-dwelling migratory endoparasites that infect the roots of several crop species. RLNs feed and reproduce in the cortical cells of affected plant roots typically characterized by development of necrotic spots. Injuries to plant tissues result in weakened plants that become more prone to attack from opportunistic pathogens. In alfalfa (Medicago sativa L.), resistance to Pratylenchus penetrans has been linked to increased transcription of key enzymes in the biosynthesis of phenylpropanoids, important molecules for countering oxidative stress. However, the mechanisms of resistance are still unknown. The present work analyzed indicators of oxidative stress in extracts from transgenic roots of susceptible (cv. Baker) and resistant (cv. MNGRN-16) alfalfa. On extracts of susceptible alfalfa transgenic roots, levels of lipid peroxidation were more than three times higher after seven and fourteen days of growth, while activity of guaiacol peroxidase (GPX) was approximately four times higher after fourteen and twenty-one days of growth, in comparison to the resistant cultivar. This suggests that resistance response may be dependent on plant redox state. Future work will focus on metabolomic characterization of these varieties in contact with RLNs.