Plant-growth promoting rhizobacteria Azospirillum partially alleviate pesticide-induced growth retardation and oxidative stress in wheat (Triticum aestivum L.)

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.