For a sustainable environment, plant-growth-promoting rhizobacteria (PGPR) are natural resources considering as one of the most important fungicides' alternatives inducing resistance to plant diseases.& nbsp;The aim of the present work is to investigate the synergistic promotion effect of a PGPR mixture composed of Paenibacillus sp. strain B2 (PB2) and Arthrobacter spp. strain AA (AA), referred hereafter as Mix-2, on the wheat growth, resistance to Zymoseptoria tritici (teleomorph Mycosphaerella graminicola), the causal agent of Septoria tritici blotch (STB) and drought stress.& nbsp;The results of the quantitative real-time polymerase chain reaction (qPCR) showed a helpful effect of AA for wheat-root external and internal colonization with PB2. Interestingly, in non-stress conditions, the inoculation of wheat grains with Mix-2 (PB2:AA, 1:1), at sowing, showed an increase in almost all tested cultivars for foliar and root dry biomasses. Under drought stress, contrarily to PB2 in single inoculation, Mix-2 induced a significant tolerance in all tested cultivars for plant dry biomass and root length. On the other hand, both PB2 alone and Mix-2 induced resistance against Z. tritici with at least 50% of protection efficiency in all tested cultivars. However, Mix-2-root colonization and-induced resistance were observed at the most mature wheat growth stage. Moreover, Mix-2-induced resistance is characterized by the upregulation of gene markers of the basal defense, defense and cell rescue, reactive oxygen species, jasmonic acid, and phenylpropanoids & phytoalexins pathways. Pathogenesis-related protein 1 (PR1), chitinase, glucanase, and flavonoides are possible gene markers for wheat resistance selection to STB.& nbsp;To conclude, the endophyte PGPR' consortium of AA and PB2 is a wheat growth promoter and inducer of a durable-systemic resistance to Z. tritici and genotype-independent tolerance to drought stress.
