Enhanced Performance of Endophytic Bacillus subtilis in Composition with Salicylic Acid Meliorated Simultaneous Drought and Fusarium Root Rot Stresses in Triticum aestivum L.

Plants are constantly faced with both abiotic and biotic stresses, which seriously reduce their productivity. We evaluated the potential of endophytic bacteria Bacillus subtilis (strain 10-4) alone, and when mixed with salicylic acid (SA), to meliorate drought and Fusarium root rot (FRR) stresses in Triticum aestivum L. All microbiological, molecular, and physio-biochemical parameters were assessed using classical and modern methods. The findings demonstrated B. subtilis 10-4 alone, and especially mixed with SA, significantly improved wheat growth and ameliorated the damaging influence of drought, FRR, and drought + FRR. An important contribution to observed growth-stimulating and protective effects of B. subtilis 10-4 and SA on plants revealed the ability of bacteria to produce auxins, siderophores, lipopeptides surfactin, and to colonize internal plant tissues. Additionally, bio-priming of seeds with B. subtilis 10-4 alone, and especially mixed with SA, decreased stress-induced (drought, FRR, drought + FRR) lipid peroxidation and amino acid proline accumulation in plants, thereby indicating a protective effect on plant cells against reactive oxygen species and osmotic damages. Current research provides novel insights into the potential and mechanism of B. subtilis 10-4 and SA in the mitigation of combined drought + FRR stresses in wheat.