Mécanismes de tolérance de la symbiose fève-rhizobium au déficit hydrique Sélection des associations performantes et impact sur les cultures céréalières en rotation.

Abstract

The planet's natural resources have been overexploited in order to handle the growing human population, leading to significant loss of biodiversity, climate change and disruption of the nitrogen cycle. Since then, the water deficit has become one of the most uncontrolled and unpredictable constraints for agricultural production. Furthermore, soil microorganisms are known for their ability to mitigate abiotic stress and promote plant development which would be very valuable tools for sustainable agriculture in the era of climate change. To this end, the present work aimed to first evaluate the impacts of two different strains of Rhizobium leguminosarum (3841 and OL13) on the induction of terminal drought tolerance in two genotypes of Vicia faba, Aquadulce (AQD) and Maltait (MLT) grown in Algeria. Secondly, the PGPR (Plant Growth Promoting Rhizobacterial) effect of these two strains was evaluated for two varieties of Triticum durum, Waha (WH) and Oued zenati (OZ) under water deficit. To this end, we measured morphological, physiological parameters, accumulation of osmoprotectants, oxidative stress markers and enzymatic activities to evaluate the effect of R. leguminosarum inoculation on V. faba and T. durum under terminal water deficit conditions in greenhouse trials. On the first hand, the upregulation of antioxidant mechanisms and the production of compatible solutes in V. faba were activated differently depending on the Rhizobium strain. The MLT variety's tolerance to water deficit was improved by using the local Rhizobium strain OL13 compared to the common strain 3841. The symbiosis with the OL13 strain leads in particular to a much better production of proline and soluble sugar in the nodules, but also in the roots and leaves of MLT genotype. On the other hand, inoculated durum wheat plants also recorded better relative water content, increased osmoprotectant accumulation and antioxidant (peroxidase) responses, and decreased oxidative stress marker accumulation for both Rhizobium strains, compared to the un-inoculated plants. However, under water deficit, the co-inoculation by the two strains of Rhizobiums improved these parameters in comparison with the simple inoculation for only one of the two studied genotypes (OZ), which leads us to suppose that this variation in reactivity indicates a possibility of genotype effect. Overall, even if further research is still needed to understand how a Rhizobium strain can affect the accumulation of osmoprotectants or the cellular redox status in all plants, inoculation with selected Rhizobium strains could be a promising ecological strategy for legumes and cereals in the face of climate change.