Sinorhizobium spp inoculation alleviates the effect of Fusarium oxysporum on Medicago truncatula plants by increasing antioxidant capacity and sucrose accumulation

• Published in: Applied soil ecology : a section of Agriculture, ecosystems & environment ecosystems & environment, 2020-06, Vol.150, p.103458, Article 103458
• Main Authors: Batnini, Marwa, Lopez-Gomez, Miguel, Palma, Francisco, Haddoudi, Imen, Kallala, Nadia, Zribi, Kais, Mrabet, Moncef, Mhadhbi, Haythem
• Format: Article
• Language: English
• Subjects: Antioxidant enzymes; F. oxysporum; Medicago truncatula; Nitrogen fixation; Sinorhizobium; Sucrose
• ISSN: 0929-1393; 1873-0272
• DOI: 10.1016/j.apsoil.2019.103458

In this study, the effect of the phyto-pathogenic fungus Fusarium oxysporum on Medicago truncatula-Sinorhizobium symbiosis performance was investigated. Fusarium oxysporum (KLR13) was inoculated on two genotypes of M. truncatula, one tolerant (Jemalong A17) and one susceptible (TN1.11), in symbiosis with Sinorhizobium meliloti (TII7), Sinorhizobium medicae (SII4) or fertilized with KNO3. Fungus infection reduced significantly biomass production and photosynthetic related parameters of non-symbiotic M. truncatula A17 and TN1.11. Reduction was less pronounced in A17, where a lower accumulation of H2O2 and lipid peroxidation (MDA) in concomitance to high activities of antioxidant enzymes, catalase (CAT), peroxidase (POD) and superoxide dismutase (SOD) was detected. In symbiosis, the fungus affected the nodule number and weight and inhibited the nitrogen fixing capacity (NFC), as well as the fructose and glucose contents. Nevertheless, inoculation with S. meliloti and S. medicae alleviated the effect of F. oxysporum on plant biomass production compared to the KNO3 fertilized plants. Moreover, the Sinorhizobium inoculation decreased H2O2 and MDA over-production caused by the fungal infection in leaves of both genotypes. This tolerance enhancing effect was more pronounced in S. medicae-TN1.11 symbiosis, where the relative maintenance of photosynthesis related parameters, growth capacity and NFC performance was concomitant to the induction of SOD and CAT activities and an increase of the sucrose content in leaves. For A17 genotype, both Sinorhizobium strains induced an increase of the proline and sucrose accumulation. In conclusion, F. oxysporum effect on M. truncatula was mitigated when plants were in symbiosis with Sinorhizobium species, mainly Sinorhizobium medicae that alleviated the oxidative stress and enhanced the accumulation of sucrose as energy source in TN1.11 genotype, which attenuates its susceptibility to F. oxysporum infection. •Fusarium oxysporum reduces biomass production within Medicago truncatula genotypes and induces oxidative stress in susceptible one.•Sinorhizobium meliloti and Sinorhizobium medicae inoculation alleviates Fusarium oxysporum effects.•S. medicae mitigates oxidative stress in susceptible genotype, enhances antioxidant enzymes and maintains the nitrogen fixing capacity.•S. meliloti and S. medicae increase the accumulation of proline and sucrose in M. truncatula genotypes infected with Fusarium oxysporum.