Molecular, Metabolic, and Physiological Response to Progressive Biotic Stress Caused by Cucumber Mosaic Virus and Turnip Mosaic Virus in saffronTitle

The economic value of saffron stigma is primarily due to three crucial apocarotenoids: crocin, picrocrocin, and safranal, which contribute to its color, flavor and aroma. These compounds make saffron highly sought after in various industries. Plant viruses like Cucumber mosaic virus (CMV) and Turnip mosaic virus (TuMV) are significant threats to agricultural crops worldwide, causing economic losses. To elucidate the influence of viral stress on the quality of saffron, morphological, physiological, biochemical and molecular indexes were assessed. Under the stress of both viruses, typical viral symptoms appeared. The lowest content of leaf pigments, flowering performance, petal anthocyanin, greenness and photosynthesis properties were observed in plants infected with CMV and TuMV. According to High performance liquid chromatography (HPLC) analysis, CMV inoculation led to the highest reduction in crocin and safranal content, while inducing the highest increase in picrocrocin compared to the mock treatment. Gene expression analysis involved in the biosynthesis of crucial secondary metabolites showed a high correlation with the content of each metabolite. CMV inoculation caused the lowest expression of CsALDH31l and the highest expression of CsUGT709G1 compared to the mock. Our findings demonstrate the associations between virus stress and changes in the metabolism of the saffron medicinal plant.