Project description:Lettuce (Lactuca sativa L.) is a highly perishable horticultural crop with a relatively short shelf life due to leaf senescence that limits its commercial value and contributes to food waste. Postharvest senescence varies with influences of both environmental and genetic factors. Preharvest genetic factors can be indicative of postharvest quality. Discovery of additional preharvest markers to assess lettuce shelf life is an important step towards increasing the efficiency of lettuce breeding efforts for improved shelf life. We selected and evaluated three romaine lettuces with variable shelf lives with the aim of identifying preharvest markers of lettuce postharvest shelf life. We evaluated leaf morphological characteristics for each of the three cultivars. To assess molecular indicators of shelf life, we used an RNA sequencing approach to construct transcriptomic profiles of two of the cultivars, a short shelf life (SSL) breeding line 60184 and a long shelf life (LSL) cultivar ‘Okeechobee’ at maturity. We identified 552 upregulated and 315 downregulated differentially expressed (DE) genes between the genotypes. We found that 27 % of the DE lettuce genes had an Arabidopsis thaliana ortholog characterized as senescence-associated, indicating that variable expression of senescence-associated genes (SAGs) could serve as a tool for preharvest markers of postharvest shelf life. Notably, we identified several SAGs and functional groupings with highly differential expression between the cultivars. This includes several jasmonate ZIM-domain (JAZ), jasmonic acid (JA) signaling genes, chlorophyll a-b binding (CAB) chloroplast-associated genes, and cell wall modification genes including pectate lyases (PL) and expansins (EXP). This study presented an innovative approach for identifying molecular markers for preharvest factors linked to postharvest traits for prolonged shelf. These genes could potentially be developed further as preharvest predictors of shelf life for lettuce breeding

Project description: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.

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