Currently, in agriculture, there is a tendency towards the partial replacement of chemical pesticides with microbiological plant protection products. In this work, we tested the ability of plant-growth promoting bacteria from the genus Azospirillum to reduce the negative effects of high concentrations of six different pesticides on wheat characteristics. Of the seven Azospirillum strains studied, five showed high resistance to at least one pesticide, and Niveispirillum irakense (formerly classified as Azospirillum until 2014) was one of the most resistant strains to all pesticides. In most cases, catalase activity increased in resistant strains in the presence of pesticides. Furthermore, we demonstrated that some of the most resistant Azospirillum strains (including N. irakense, A. brasilense, A. picis, A. thiophilum, and A. baldaniorum) can counteract pesticide-induced growth inhibition, suppress oxidative stress, as evidenced by a decrease in iron-induced chemiluminescence and the amount of oxidative damage to wheat seedling mtDNA in a pot experiment. However, the bacteria had no positive effect on the chlorophyll content of wheat seedlings. Azospirilla were found in the rhizosphere of wheat roots 3 months after a wheat planting in the field experiment. Pesticides led to a slight decrease in their quantity in the rhizosphere. Additionally, bacterial inoculation mitigated the pesticide-induced decrease in wheat biomass.

The dose-dependent effect of the A.brasilense Sp7 lectin on the roots of 4-day-old wheat seedlings (Triticumaestivum L. cv. Saratovskaya 29) grown under simulated salt stress was studied. In the roots of wheat seedlings under salt stress, lectin increased the activity of peroxidase and superoxide dismutase, but decreased the activity of catalase. In the roots of stressed seedlings, lectin reduced the total protein content and lipid peroxidation causing membrane damage, but increased the content of secondary metabolites, such as the total amount of phenols and flavonoids. It was concluded that Azospirillum lectins are involved in adaptive changes in the roots of wheat seedlings, due to which the relationship between bacteria and their hosts can be regulated when soil and climatic factors change.