Evaluation of efficient Rhizobium isolates as biological control agents of Orobanche foetida Poir. parasitizing Vicia faba L. minor in Tunisia

B. Sifi, N. Abdi, M. Bouraoui, I. Hmissi, Z. Abbes

Abstract: Orobanche foetida is an important new agricultural biotic constraint which parasite grain legumes in Tunisia. Several broomrape control strategies have been developed, but without success. The present work aims to select the most efficient Rhizobium isolates for symbiotic nitrogen fixation and antagonist to O. foetida parasitism in faba bean. For this purpose, hydroponic co-culture and pots experiments were conducted using the commercial faba bean (Badï variety) and different Rhizobium isolates. Results showed that in hydroponic co-culture, O. foetida germination was significantly decreased (75%) only after inoculation with the Rhizobium isolate Mat. The percentage of reduction of tubercle number compared to the control reached 89% with this Rhizobium isolate tested. In pot experiments, only Bous.96 isolate reduced significantly the total tubercle number. The number of emerged parasites (stage 5) was significantly decreased with all Rhizobium isolates inoculation. A significant increase in faba bean shoot and root dry weight was recorded only with Mat isolate inoculation. No brownish radicals or necrosis in attached parasites was observed in the two trials. The two Rhizobium isolates (Mat and Bous.96) are potential candidates as inoculants production for plants growth promotion and chemical nitrogen fertilizer reduction. They would be a good tool to reduce parasitic infestation and to develop sustainable agriculture. The characterization of the resistance induced by these isolates against O. foetida and their use in field experiments is suggested.

Keywords: bio-control; Broomrape; faba bean; nitrogen fixation; Orobanche foetida; Rhizobium

Date published: 2019-07-23