Exogenous Salicylic Acid Improves Fruit Yield and Quality of Lycium barbarum Under Summer High Temperature

Global warming poses an escalating threat to crop yield and quality, particularly for thermosensitive medicinal-edible plants such as goji berry (Lycium barbarum). Although salicylic acid (SA) is recognized for enhancing plant thermotolerance, its effects on fruit productivity and quality under summer high temperatures remain inadequately quantified. This study investigated the physiological, metabolic, and transcriptomic responses of field-grown Ningqi No. 7 (N7) goji berry to exogenous SA application under summer heat stress. SA treatment significantly increased fruit yield by 22%, while reducing leaf defoliation rate by 32%. Metabolite profiling revealed that SA elevated total soluble sugar content by 30% and flavonoid concentration by 14% but decreased total organic acid content by 16%. Transcriptomic analysis identified SA-induced differential expression of genes involved in sugar metabolism (phosphofructokinase), secondary biosynthesis (flavonoid and alkaloid related pathways), and stress responses (HSPs, E3 ubiquitin ligases, SRK2). These results demonstrate that exogenous SA enhances goji berry productivity and improves fruit taste (via increased sugar/organic acid ratio) and functional quality under summer high temperatures. Consequently, SA application thus represents a promising and cost-effective strategy for climate-resilient goji berry cultivation.