Inoculation of wheat seeds with spore-forming bacteria as a novel approach to enhance growth under climate change-induced stress conditions

Spore-forming bacteria (SFB) survive various environmental stress conditions by transforming into dormant endospores. In this study, we isolated 243 strains of SFB from the roots and rhizosphere soils of crops. The 16 S rRNA sequences of the selected 62 isolates identified Bacillus (45%), Priestia (31%), and Paenibacillus (24%). These Priestia and Paenibacillus isolates showed the capability for P solubilization, Priestia strains were capable of K solubilization and exhibited higher indole-3-acetic acid, while Bacillus strains showed strong siderophore production. Whole genome analysis of isolates, TTREn1 and TC-CSREp1, classified them as Priestia aryabhattai and Paenibacillus sp. Inoculation of wheat seedlings with the spores of 13 selected isolates improved shoot and root biomass under control and stress conditions (heat and drought) compared to uninoculated controls. Bacillus species, which showed higher biofilm formation among the three genera, colonized roots endophytically when inoculated as spores under drought stress, whereas the other isolates tested did not. Furthermore, spore inoculation modulated the expression of stress-related genes such as APX, CAT, and P5CS, with strong induction observed under heat stress and suppression under drought stress in most isolates. Our findings demonstrate the potential efficacy of spore inoculation in enhancing wheat plant growth resilience under heat and drought stress conditions.