Fungal endophytes promote wheat (Triticum aestivum L., genotype-PBW-343) growth and enhance salt tolerance through improvement of ascorbate-glutathione cycle and gene expression

Abstract Background and aims Wheat (Triticum aestivum L.) faces considerable challenges in terms of growth and productivity due to soil salinity, which is a major constraint to agricultural success. This study investigated the potential of fungal endophytes to enhance wheat growth and improve salt tolerance by influencing the ascorbate-glutathione cycle and gene expression. Methods Experiments were conducted, usingwheat seedlings (PBW-343) inoculated with endophytic fungi (Cladosporium parahalotolerant and Aspergillus medius)isolated from salt-tolerant wheat genotypes (KRL-210, KRL-213 and KRL-19) fromthe previous study. Endophytic fungi were used individually and in combination. Fifteen days seedlings exposed to 100 mM NaCl in the presence and absence of fungal endophytes. To elucidate the molecular mechanism, gene expression analysis was performed on key genesAPX, SOD, GR, DHAR, and MDHAR. Results Seedlings treated with endophytic fungi (consortia form)significantly enhanced the sugar, protein, chlorophyll, carotenoid content, and chlorophyll fluorescence (Fv/Fm)compared to control under salt stress. The O2- and lipid peroxidation levels were significantly reduced in plants inoculated with fungal endophytes. Salt stress increased APX, SOD activities and decreased GR, MDHARand DHAR activities.Endophytic fungi inoculated with salt-stressed seedlings enhanced the above-mentioned indicators compared to the salt-stressed plants without fungal endophytes, as well as in the ratios of AsA/DHA and GSH/GSSG.Endophytic fungienhanced the transcript levels of SOD, DHAR, APX, GR, and MDHAR genes compared to the control Conclusions The present study found that the expression levels of several genes associated with the ascorbate-glutathione cycle were upregulated in endophyte-inoculated plants, indicating a more efficient antioxidant system capable of scavenging reactive oxygen species.