Reports show that phytohormone abscisic acid (ABA) is involved in reducing zucchini postharvest chilling injury. During the storage of harvested fruit at low temperatures, chilling injury symptoms were associated with cell damage through the production of reactive oxygen species. In this work, we have studied the importance of different non-enzymatic antioxidants on tolerance to cold stress in zucchini fruit treated with ABA. The application of ABA increases the antioxidant capacity of zucchini fruit during storage through the accumulation of ascorbate, carotenoids and polyphenolic compounds. The quantification of specific phenols was performed by UPLC/MS-MS, observing that exogenous ABA mainly activated the production of flavonoids. The rise in all these non-enzymatic antioxidants due to ABA correlates with a reduction in oxidative stress in treated fruit during cold stress. The results showed that the ABA mainly induces antioxidant metabolism during the first day of exposure to low temperatures, and this response is key to avoiding the occurrence of chilling injury. This work suggests an important protective role of non-enzymatic antioxidants and polyphenolic metabolism in the prevention of chilling injury in zucchini fruit.

Considering the importance of carotenoids in the human diet, their enhancement is a key trait in current breeding programs. This study assessed lutein, zeaxanthin, α-carotene, and β-carotene levels in the flesh of mature fruits from 257 global C. pepo accessions. Lutein and β-carotene were the most prevalent, with top accessions identified for each carotenoid. A panel of 120 accessions with reliable carotenoid contents and genetic diversity was analyzed using 23,111 GBS-generated SNPs in genome-wide association studies (GWAS). Three genomic regions (qtl1, qtl3, and qtl13) on chromosomes 1, 3, and 13 were significantly linked to carotenoid levels, with alternative alleles increasing the carotenoid content, leading to yellowish–orange flesh. Seven candidate genes were identified: CpTIC56, CpHSHP70, and CpPDL8, which regulate carotenoid biosynthesis in chloroplasts; CpSPX and CpPHO1, associated with phosphate homeostasis and carotenoid buildup; CpMYB106, co-expressed with carotenoid biosynthesis genes; and a CpPPR RNA-binding protein. RNA-seq data from yellow- and white-fleshed fruits supported their involvement in carotenoid accumulation. These results improve our understanding of the genetic control of carotenoid buildup in C. pepo fruit, supporting breeding efforts for improved nutritional quality.

Plant-based biostimulants are sustainable tools widely applied in agriculture to enhance plant physiology and stress resilience. Shelf-life extension has a pivotal role in postharvest as low-temperature storage of lettuce ( Lactuca sativa L.) often results in weight loss, surface damage, and a decline in quality and nutritional value. This study investigated the metabolic responses of lettuce to three commercial biostimulants, Ascophyllum nodosum extracts (Algae), plant-derived protein hydrolysate (PHs), and humic substances (Hum), applied via foliar spray (-S) and drip irrigation (-D). All treatments improved agronomic traits, with foliar-applied PHs (PHs-S) showing the most pronounced effects. Metabolomic profiling revealed treatment-specific shifts, particularly in secondary metabolites such as alkylphenols, flavonoids, and flavonoid glucosides, along with increased levels of sugars, polyols, vitamins, and phytohormones. In parallel, biostimulants positively influenced key agronomic parameters during lettuce growth, including plant diameter, chlorophyll content, and nitrogen balance index, with PHs applied via foliar spray showing the most pronounced effects. At harvest, these metabolic changes reflected a broader metabolic reprogramming, which appeared to contribute to improved postharvest traits, including reduced weight loss, enhanced leaf firmness, increased antioxidant capacity, and higher total phenolic content, particularly under Algae-D and PHs-S treatments. These biochemical changes suggest that biostimulants, particularly via foliar application, enhance antioxidant capacity, improve nutritional quality, and may contribute to extended shelf life in lettuce.

Cucurbita pepo is a monoecious species with female and male unisexual flowers on the same plant. The large size of its flowers makes this species a model for studying the regulation of sex determination and sex-associated developmental traits. Because male flowers appear at earlier stages of plant development than female flowers, the plant has evolved a system in which female flowers grow and open much faster than male flowers in order to synchronize male and female flowering for proper pollination and fertilization. In this paper, we show that this differential growth of female and male flowers is controlled by gibberellin (GA). We identify and characterize a loss-of-function mutation in the GA biosynthetic gene CpGA3ox1B, which results in a deficiency of active GA in various vegetative and reproductive organs. The dwarf phenotype of the ga3ox1b mutant is similar to that of other plants deficient in GA, but surprisingly, the GA mutation affects only the development of female flowers, which are much smaller, do not open, and are completely sterile. However, male flowers develop normally, reaching the same size and fertility as male WT flowers. In the WT, female flowers have higher expression of CpGA3ox1B than male flowers, causing them to accumulate more active GA and grow faster than male flowers. The mutant dwarf plant and flower phenotypes were rescued by GA3, but not ethylene or JA, indicating that the ga3ox1b flower did not reach the appropriate size to become sensitive to ethylene and JA, the hormones controlling petal expansion and flower opening in later stages of female flower development. The GA mutation does not affect ethylene-regulated sex determination at the earliest floral meristem, but it does affect the growth of the corolla and pistil once the meristem is determined to be a female flower. The transcriptomic changes and differential accumulation of other phytohormones in the WT and ga3ox1b female organs revealed that the function of GA depends on its interaction with other phytohormones, including auxin and cytokinin as GA synergists and ethylene, ABA, and JA as GA antagonists in the development of female floral organs. Completely opposite transcriptomic changes in the ovary of ga3ox1b and the ethylene-insensitive mutant etr2b demonstrate the mutual exclusion of ethylene and GA signaling at different stages of female flower development and highlight the importance of several transcription factors, such as MYB62, for the integration of ethylene and GA in the regulation of both sex determination and flower organ growth and development in C. pepo.