Uncovering the transcriptional molecular dynamics of shelf life extension and system acquired resistance induction to Fusarium pallidoroseum in melon fruits by the use of pulsed-light

Melon is a globally commercialized fruit, and Fusarium rot disease poses a significant threat to post-harvest losses. The conventional use of fungicides raises concerns about chemical residues, prompting exploration into alternative technologies such as Pulsed Light (PL). While PL has been effective in controlling infections in various fruits and vegetables, the precise physiological responses and molecular mechanisms in melon fruits remain incompletely understood. In this study, melon fruits infected with the Fusarium pallidoroseum were treated with different doses of PL (0, 6, 9, and 12 J cm-2), and the impact on both fungal control and fruit shelf life extension was investigated. The 9 J cm-2 dose emerged as the most effective in controlling fungal growth without causing damage, inducing beneficial responses. This optimal PL dose upregulated genes in the lignan biosynthesis pathway and the infection upregulated genes involved with systemic acquired resistance, triggered by the pipecolic acid. In this way, the PL treatment and the infection trigger a double mechanism of resistance in melon fruits. A second and third experiment focused on evaluating the extension of melon fruit shelf life and the safe manipulation window post-PL treatment. The results revealed an average shelf life extension of six days and a safe manipulation period of 24 hours. The extension in shelf life was associated with a deviation in information flux from the ethylene biosynthesis to upregulation of the polyamine biosynthesis pathway, which produces nitric oxide, a product that can inhibit ethylene biosynthesis and its action. Furthermore, the observed 24-hour safety period against fungal infection post-PL treatment was characterized as a memory response resistance caused by the upregulation of lignan biosynthesis, which is a potential and efficient alternative to chemical products like fungicides. Overall, this study provides insights into the transcriptional molecular mechanisms through which PL promotes systemic acquired resistance and extends the shelf life of melon fruits.