Light spectrum modulation of corm development and starch biosynthesis in saffron (Crocus sativus L.): insights into CsSUS1, CsPhol, and SBE gene expression

Abstract Saffron ( Crocus sativus L.), prized for its culinary, cosmetic, and medicinal uses, faces challenges such as climate change and resource-intensive farming. Controlled environment agriculture (CEA) offers a solution by optimizing growing conditions, particularly for producing large daughter corms essential for yield. This study investigated the impact of various light spectra—blue (B), red (R), and far-red (FR) combinations (1B:1R, 1B:1FR, 1B:2R:1FR, and 1R:1FR)—on saffron growth, photosynthesis, and carbohydrate biosynthesis genes (i.e., CsSUS1 , CsPhol , SBE ). Results showed that R and FR light enhanced leaf growth and photosynthesis but reduced underground biomass, while a balanced R and FR light increased daughter corm production. Molecular analysis indicated that FR light elevated soluble carbohydrates but decreased carbohydrate storage. The highest CsSUS1 expression occurred under 1R:1FR light, whereas CsPhol and SBE , associated with starch biosynthesis, were upregulated under 1B:1R light. A strong correlation was observed between CsSUS1 expression and soluble carbohydrate content. In summary, FR light promotes vegetative growth while reducing starch accumulation, resulting in smaller daughter corms. In contrast, R and B light enhance starch-related gene expression, increasing daughter corm size. These findings underscore the potential of light spectrum manipulation in CEA to optimize saffron corm production with minimal resource input.