Physiological and Molecular Effects of Calcium and Salicylic Acid on Fusarium graminearum-Infected Wheat Seedlings

Fusarium graminearum is among the most virulent pathogens attacking wheat plants and significantly lowering its production globally. The present work aims to shed light on the interactions between two priming solutions, calcium (Ca) or salicylic acid (SA), and F. graminearum inoculation depending on the growth rate, physiological attributes, and molecular responses in wheat seedlings. In a pot experiment, F. graminearum-pre-inoculated or inoculum-free sandy soil was used to germinate wheat kernels after priming them for 12 h in distilled water, 5-mM CaCl2, or 0.05-mM SA. The results demonstrated that F. graminearum inoculation decreased growth rate and chlorophyll content, but promoted carotenoids, stress markers (electrolytes leakage, lipid peroxidation, protein oxidation, hydrogen peroxide, and hydroxyl radical), antioxidant molecules (AsA, phenols, and flavonoids), osmolytes (GB, amino acids, and proline), and the antioxidant enzymes (CAT, GPX, SOD, PPO, and PAL). Additionally, the fungal infestation boosted the expression of CAT, GR, PR4, MT, and PCS genes. However, presoaking wheat kernels in Ca or SA solutions has contributed to mitigating the negative effects of fungal inoculation by restoring growth rate, chlorophyll content, and antioxidant capacity. It has also decreased the induced oxidative stress and downregulated the gene expression of F. graminearum-inoculated wheat seedlings. Consequently, by minimizing the negative repercussions of F. graminearum infestation, priming with Ca or SA could be used to appropriately stimulate growth and readjust the oxidative status of wheat seedlings.