Impact of Two Strains of Rhizobium leguminosarum on the Adaptation to Terminal Water Deficit of Two Cultivars Vicia faba

Abstract

Drought stress has become one of the most uncontrolled and unpredictable constraints on crop production. The purpose of this study was to evaluate the impacts of two different Rhizobium leguminosarum strains on terminal drought tolerance induction in two faba bean genotypes cultivated in Algeria, Aquadulce and Maltais. To this end, we measured physiological parameters-osmoprotectants accumulation, oxidative stress markers and enzyme activities-to assess the effect of R. leguminosarum inoculation on V. faba under terminal water deficiency conditions in greenhouse trials. Upregulation of anti-oxidative mechanisms and production of compatible solutes were found differentially activated according to Rhizobium strain. Drought stress resilience of the Maltais variety was improved using the local Rhizobium strain OL13 compared to the common strain 3841. Symbiosis with OL13 strain leads in particular to a much better production of proline and soluble sugar in nodules but also in roots and leaves of Maltais plant. Even if additional work is still necessary to decipher the mechanism by which a Rhizobium strain can affect the accumulation of osmoprotectants or cellular redox status in all the plants, inoculation with selected Rhizobium could be a promising strategy for improving water stress management in the forthcoming era of climate change.

Keywords: Rhizobium strains; antioxidants; drought stress; faba bean; osmoprotectants; symbiosis.

Figure 1

Dry matter yield responses to water deficiency. Seventy day-old Vicia faba plants, previously individually inoculated with Rhizobium strains (3841-light gray bars) and (OL13-dark gray bars), were grown under control conditions (Noted: NS) or under water limited conditions (Noted: S). (A) Shoot, (B) root plant dry weights (DWs) were measured after seventy day of growth. AQD: Aquadulce; MLT: Maltais. The values shown are the mean ± SD of three independent replicates. Differences in the data were considered significantly different at the 0.05 level of probability by Student-Newman-Keuls Test (indicated by different letters).

Figure 2

Stomatal conductance influenced by water deficit conditions. Seventy day-old Vicia faba plants, previously individually inoculated with Rhizobium strains (3841-light gray bars) and (OL13-dark gray bars), were grown under control conditions (Noted: NS) or under water limited conditions (Noted: S). AQD: Aquadulce; MLT: Maltais. The values shown are the mean ± SD of three independent replicates. Differences in the data were considered significantly different at the 0.05 level of probability by Student-Newman-Keuls Test (indicated by different letters).

Figure 3

Photosynthetic pigments content in leaves. Seventy day-old Vicia faba plants, previously individually inoculated with Rhizobium strains (3841-light gray bars) and (OL13-dark gray bars), were grown under control conditions (Noted: NS) or under water limited conditions (Noted: S). (A) Total Chlorophyll, (B) Total carotenoids. AQD: Aquadulce; MLT: Maltais. The values shown are the mean ± SD of three independent replicates. Differences in the data were considered significantly different at the 0.05 level of probability by Student-Newman-Keuls Test (indicated by different letters).

Figure 4

Proline content in leaves, roots and nodules. Seventy day-old Vicia faba plants, previously individually inoculated with Rhizobium strains (3841-light gray bars) and (OL13-dark gray bars), were grown under control conditions (Noted: NS) or under water limited conditions (Noted: S). (A) Leaves, (B) Roots and (C) Nodules. AQD: Aquadulce; MLT: Maltais. The values shown are the mean ± SD of three independent replicates. Differences in the data were considered significantly different at the 0.05 level of probability by Student-Newman-Keuls Test (indicated by different letters).

Figure 5

Soluble sugar content in leaves and roots. Seventy day-old Vicia faba plants, previously individually inoculated with Rhizobium strains (3841-light gray bars) and (OL13-dark gray bars), were grown under control conditions (Noted: NS) or under water limited conditions (Noted: S). (A) Leaves and (B) Roots. AQD: Aquadulce; MLT: Maltais. The values shown are the mean ± SD of three independent replicates. Differences in the data were considered significantly different at the 0.05 level of probability by Student-Newman-Keuls Test (indicated by different letters).

Figure 6

Superoxide dismutase activity in leaves, roots and nodules. Seventy day-old Vicia faba plants, previously individually inoculated with Rhizobium strains (3841-light gray bars) and (OL13-dark gray bars), were grown under control conditions (Noted: NS) or under water limited conditions (Noted: S). (A) Leaves, (B) Roots and (C) Nodules. AQD: Aquadulce; MLT: Maltais. The values shown are the mean ± SD of three independent replicates. Differences in the data were considered significantly different at the 0.05 level of probability by Student-Newman-Keuls Test (indicated by different letters).

Figure 7

Catalase activity in leaves, roots and nodules. Seventy day-old Vicia faba plants, previously individually inoculated with Rhizobium strains (3841-light gray bars) and (OL13-dark gray bars), were grown under control conditions (Noted: NS) or under water limited conditions (Noted: S). (A) Leaves, (B) Roots and (C) Nodules. AQD: Aquadulce; MLT: Maltais. The values shown are the mean ± SD of three independent replicates. Differences in the data were considered significantly different at the 0.05 level of probability by Student-Newman-Keuls Test (indicated by different letters).

Figure 8

Ascorbate peroxidase activity in leaves, roots and nodules. Seventy day-old Vicia faba plants, previously individually inoculated with Rhizobium strains (3841-light gray bars) and (OL13-dark gray bars), were grown under control conditions (Noted: NS) or under water limited conditions (Noted: S). (A) Leaves, (B) Roots and (C) Nodules. AQD: Aquadulce; MLT: Maltais. The values shown are the mean ± SD of three independent replicates. Differences in the data were considered significantly different at the 0.05 level of probability by Student-Newman-Keuls Test (indicated by different letters).

Figure 9

Guaiacol peroxidase activity in leaves, roots and nodules. Seventy day-old Vicia faba plants, previously individually inoculated with Rhizobium strains (3841-light gray bars) and (OL13-dark gray bars), were grown under control conditions (Noted: NS) or under water limited conditions (Noted: S). (A) Leaves, (B) Roots and (C) Nodules. AQD: Aquadulce; MLT: Maltais. The values shown are the mean ± SD of three independent replicates. Differences in the data were considered significantly different at the 0.05 level of probability by Student-Newman-Keuls Test (indicated by different letters).