Investigation of some biochemical mechanisms involved in the resistance of faba bean (Vicia faba L.) varieties to Orobanche spp.

Abstract

Broomrapes are weedy root parasitic plants that cause important damage to the faba bean production. Genetic resistance is considered as the most desirable control method. In this study, we investigated some of the mechanisms involved in the resistance to Orobanche crenata and O. foetida for two Tunisian resistant varieties Najeh and Chourouk in comparison with the susceptible variety Badi. The results showed that, for Najeh and Chourouk, the Orobanche infestation did not significantly influence the plant growth as indicated by inconsiderable changes in the shoot and root dry weights, pod setting and chlorophyll and carotenoid contents. In comparison to Badi, both resistant varieties showed a reduced Orobanche attachments/tubercles number and dry weights, low H<sub>2</sub>O<sub>2</sub> and malondialdehyde (MDA) accumulation with increased levels of peroxidase activity in the roots. An Orobanche infestation was found to induce a significant decrease in the total lipid content and lipid unsaturation in the Badi leaves only. For resistant varieties, no significant changes were observed in these two parameters, which may indicate conservation and stability in the membrane fluidity. The resistance of Najeh and Chourouk was mainly associated with a relatively more efficient enzymatic antioxidative response and reduced lipid peroxidation that helped the plants to avoid the damaging effect of an Orobanche attack. Therefore, these two varieties could be used as a component of an integrated control strategy to improve the plant growth and productivity under an Orobanche infestation