Penicillium–sesame interactions: A remedy for mitigating high salinity stress effects on primary and defense metabolites in plants

• Soil salinity reduced the sesame plant growth.
• Penicillium sp. NICS01 reduced oxidative stress induced by high salinity in sesame.
• It enhanced the pigments, sugars, fatty acids and ions in stressed plants.
• It regulated amino acids, lipid peroxidation and salicylic acids in stressed plants.
• Fungus induced metabolic changes might be possible to mitigate the stress effects.

Salinization of agricultural land is increasing, and reduces the yield of crop plants. The introduction of plant growth-promoting and salt-tolerant microbes to soil can protect plants from salt effects. This study examined the primary and defense metabolites in sesame plants associated with Penicillium sp. NICS01, which mitigates oxidative stress induced by high salinity. Salt tolerance in Penicillium sp. NICS01 was observed in medium supplemented with 5.0% and 7.5% NaCl. The role of this fungus in mitigating against high salinity (150 mM NaCl) was tested on salt-stressed sesame plants. Salt stress decreased the length and weight of sesame shoots, but applying Penicillium sp. NICS01 significantly (p ≤ 0.05) increased these parameters in plants grown under salt-stress conditions by enhancing photosynthetic pigment levels (chlorophylls and carotenoids), sugar concentrations (sucrose, glucose, and fructose), fatty acid contents (palmitic acid, linolenic acid, arachidic acid, and cis-11-eicosenoic acid), and ionic transport (K and Ca, (p ≤ 0.05)). In addition, salt-induced oxidative damage was reduced by lowered lipid peroxidation (5%) and salicylic acid (15%) and Na (18%) contents, and raised peroxidase activity (more than five-fold), while amino acid (Thr, Gly, Val, Met, Ile, Leu, Tyr, Phe, Arg, Asp, Ser, Asn, Glu, Ala, and GABA) synthesis was regulated by the fungal interaction. Asp, Thr, Ser, Glu, Ala, and Arg contents were significantly (p ≤ 0.05) enhanced in salinity affected plants due to the effect of fungal inoculation. Our findings revealed that Penicillium sp. NICS01 regulates the biosynthesis of primary and defense metabolites in sesame plants under salt stress, suggesting that this fungus can ameliorate damage caused by salt stress in crop plants.