Ameliorative effects of endophytes on morphological, biochemical and molecular changes in Glycine max (L.) merrill....

Endophytes provide a wide range of benefits to host plants when the plants encounter unfavorable biotic and abiotic stress conditions. The current study aims to examine the impact of externally applied Sinorhizobium meliloti NOR1, Talaromyces flavus AVRF3 and coinoculum on soybean plants under drought stress conditions. The treatments were evaluated for their influence on morphological and physiological traits, biochemical parameters and gene expression levels. The isolated endophytic bacterial and fungal inoculum enhanced soybean seed germination and improved tolerance to artificial drought stress under in vitro conditions. The colonization of endophytic colonies in soybean plants was confirmed through reisolation and scanning electron microscopy analysis. Gas chromatography and mass spectrometry analysis revealed that endophytic cultures contain various organic volatile compounds that promote plant growth and tolerance to abiotic stress conditions. The soybean plants treated with endophytic inoculum showed significant improvements in shoot length, fresh and dry weights of shoots and roots compared to the control plants. The beneficial effect of endophytic treatments led to an increase in primary and secondary metabolites and the activities of antioxidant enzymes in soybean plants under drought stress conditions. Additionally, root inducing gene of GmPIN1A was increased by S. meliloti NOR1, while T. flavus AVRF3 and coinoculum treatments enhance the expression of GmPIF under both drought stress and normal conditions. This is one of the few studies that examine the impact of endophytes on soybean plants subjected to drought stress. The findings suggest that both endophytic bacterial and fungal inoculum application reprograms the photosynthetic pigments, biochemical contents and antioxidant expression of drought stress affected soybean plants and improve their plant growth under drought stress conditions.

The online version contains supplementary material available at 10.1007/s12298-025-01639-6.