Abstract Shade stress affects soybean yield in intercropping, but the molecular basis of cultivar‐specific tolerance is unclear. We analyzed shade‐tolerant (Guru) and sensitive (Heinong 53) soybeans under 30% and 70% shade using transcriptomic, physiological, and biochemical methods. Moderate shade (30%) initially promoted growth in Heinong 53, while 70% shade restricted growth in both. Guru maintained better physiology, with higher chlorophyll (2.8 vs. 2.1 mg/g), photosynthesis, and stable stomatal conductance. RNA‐seq identified 2596–7841 differentially expressed genes (DEGs), with severe shade causing more changes. Down‐regulated DEGs are linked to development and shade response; up‐regulated DEGs are involved in metabolism, including glucosinolate biosynthesis and protein export. Core shade responses included 279 up‐ and 388 down‐regulated DEGs across treatments. Shade tolerance involved metabolic reprogramming: Guru had higher sucrose content (30.2 vs. 13.8 mg/g) and sucrose synthase activity and increased nitrogen enzyme activity. Antioxidant enzymes showed cultivar‐specific strategies, with Guru having higher peroxidase and lower oxidative stress markers. Gene‐trait analysis linked 37 DEGs to photosynthesis and 28 to transpiration, indicating water use regulation. Key genes included calcium‐dependent kinases and histone deacetylases. Overall, shade tolerance involves maintaining photosynthesis, metabolic shifts favoring carbs, and stress responses, guiding development of tolerant cultivars and understanding plant adaptation in intercropping systems.
Zhang et al. (Wed,) studied this question.