Abstarct: Abstract A Two-Year Study light is a crucial factor in photosynthesis and plant growth, directly affecting crop yield and the efficiency of biological processes. Simultaneously, symbiotic fungi significantly improve nutrient absorption and enhance plant resistance to various environmental conditions. This study was conducted from 2021 to 2022 at the experimental farm and environmental stress laboratory of Sari Agricultural Sciences and Natural Resources University in two stages: preliminary (laboratory) and complementary (pot and field experiments). The preliminary experiment, designed as a completely randomized trial, aimed to identify the best bio-priming treatment among 22 symbiotic fungi. The complementary experiment investigated the effects of these treatments under natural conditions in both field and pot trials (to enable more detailed and controlled evaluations of specific traits) in a split-plot design within a randomized complete block design (RCBD) with three replications. The main factors in the complementary experiment included shading during the flowering stage (R1) at five levels (20%, 40%, 50%, 70%, and 100% natural light) and fungal symbiosis treatments selected from the preliminary stage as sub-factors at four levels: control (no inoculation), and inoculation with single and combined symbiotic fungi, Bjerkandera adusta (ST1) and Chaetomium globosum (SE2). Laboratory results revealed that B. adusta (ST1) outperformed the control and other fungi in all traits measured, increasing germination percentage, germination speed up to 50%, and root and shoot lengths compared to the control. Similarly, C. globosum (SE2) exhibited higher germination percentage and speed relative to the control and other fungi. Pot and field experiments demonstrated that reducing light intensity by 50% enhanced certain morphological and vegetative traits, including plant height, root fresh weight, and leaf area at both R3 and R6 stages. However, reduced light intensity decreased chlorophyll content at all measurement stages, leading to reduced photosynthesis and growth. Symbiosis with B. adusta (ST1), C. globosum (SE2), and their combination improved vegetative, morphological, and physiological traits. Chlorophyll a and b content in inoculated plants increased significantly by 18% to 55% under 70% light intensity. Enzyme activities of catalase and guaiacol peroxidase were elevated under 20% light in plants inoculated with B. adusta (ST1) and C. globosum (SE2), indicating enhanced plant capacity to combat oxidative stress. At 70% light intensity, the number of pods per plant, seeds per pod, and seed yield were higher in plants inoculated with B. adusta (ST1) and the combined fungal treatment compared to the control. In conclusion, this research demonstrated that the most significant improvements in traits such as seed yield, seeds per pod, pods per plant, and chlorophyll content occurred in symbiotic plants under 70% light intensity. Thus, the use of the symbiotic fungi tested in this study is recommended for enhancing soybean productivity, especially in regions with reduced light intensity.