This study investigated how salicylic acid (SA) mediates the response of melon (Cucumis melo) seeds to salt stress using physiological and transcriptomic methods. The effects of SA on the antioxidant enzymes, osmoregulatory substances, and transcriptome of melon seeds under salt stress were investigated using sodium chloride (NaCl, 100 mmol·L⁻¹) as the stress stimulant and SA + NaCl (0.25 mmol·L⁻¹ + 100 mmol·L⁻¹) as the alleviation treatment. The results showed that SA positively influences salt tolerance by increasing the activity of superoxide dismutase activity (SOD) and catalase activity (CAT) while decreasing proline content (Pro). Differentially expressed genes (DEGs) were identified by transcriptome data analysis, of which 2958 were up-regulated, and 2157 were down-regulated. These genes were mainly involved in the mitogen-activated protein kinase (MAPK) signaling pathway and plant hormone signal transduction, lipid metabolism (linoleic and α-linolenic fatty acid metabolism), biosynthesis of secondary metabolites (phenylpropanoid pathway and flavonoid biosynthesis), and related pathways. Further analysis revealed that SA might alleviate salt stress by initiating a series of signaling pathways under salt stress, participating in lignin biosynthesis to improve cell wall stability, and positively regulating lipoxygenase (LOX) genes. These results provide valuable information and new strategies for future salt resistance cultivation and high melon yield.

Leaf stalk-stem angle is an important agronomic trait influencing melon architecture, photosynthetic efficiency, and crop yield. However, the mechanisms governing leaf stalk-stem angle, particularly in melon, are not well understood. In this study, we explored the comparative transcriptome in the expanded architecture line Y164 and the compact plant architecture line Z151 at 30 days after pollination. Phytohormones were measured at the leaf stalk-angle site at the same time in these two lines using liquid chromatography (LC) tandem mass spectrometry (MS) (LC-MS/MS). The phytohormones and transcriptomes were jointly analyzed. Differential hormone profiling revealed that the levels of 1-aminocyclopropane-1-carboxylate (ACC) and 12-oxophytodienoic acid (OPDA) in the large-angled line Y164 were significantly higher than those in the small-angled line Z151. These differences were quantified as 2.1- and 2.8-fold increases, respectively. Conversely, the content of isopentenyl adenosine (IPA) was significantly elevated in Z151, with a 3.8-fold higher concentration relative to Y164. Transcriptome analysis identified a total of 1709 differently expressed genes (DEGs), with a predominant enrichment in the Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways related to photosynthesis and plant hormone signal transduction. Similarly, photosynthesis and the hormone metabolic process were predominantly enriched in the biological process of Gene Ontology (GO) terms. Further integration of transcriptome and hormone analyses substantiated the close relationship between melon leaf stalk-stem angle and phytohormones, especially ACC, OPDA and IPA. Selected DEGs from phytohormone signal transduction were validated. Detailed analysis of DEGs highlighted the potential role of genes such as GH3s (LOC103490488, LOC103490483), SUARs (LOC107991561, LOC103497281 and LOC103489067), ARFs (LOC103503893, LOC103493078) and five genes in abscisic acid pathway. In summary, our findings strongly suggest a direct correlation between phytohormones and the leaf stalk-stem angles in melon.

Continuous cropping obstacles in watermelon are closely linked to rhizosphere microbial imbalance, posing a major threat to the sustainability of the industry in Xinjiang. Exogenous additives are widely used to regulate soil health, yet comprehensive comparisons of their mechanisms and effects remain limited. In this study, a field experiment was conducted under continuous watermelon cropping conditions in Xinjiang to evaluate the impact of eight treatments, including chemical fertilizer (NPK) alone and its combination with organic fertilizer (NPKM), glucose (NPKG), oxalic acid (NPKOA), amino acids (NPKGA), citric acid (NPKCA), and acetic acid (NPKAA), with unfertilized soil as the control (CK). Treatment effects were assessed through soil physicochemical analysis, fruit quality evaluation, and high-throughput sequencing (16S rRNA and ITS). Among all treatments, NPKM showed the greatest improvement in soil fertility, increasing soil organic matter by 13.91%, total nitrogen by 23.08%, and single fruit weight by 35.75% compared to CK. NPKGA also enhanced fruit weight (+33.06% vs. CK) and increased catalase activity, while oxalic acid exhibited the strongest activation of alkaline phosphatase. Microbiome analysis revealed that NPKM and NPKAA significantly reshaped both bacterial and fungal community structures. NPKM enriched beneficial taxa such as unclassified Chitinophagaceae and Lophotrichus, whereas NPKCA enriched the biocontrol bacterium Pseudomonas chlororaphis. Soil organic matter and total nitrogen were identified as key environmental drivers, showing significant positive correlations with core bacterial genera (Dokdonella) and negative correlations with the pathogenic fungus Alternaria. Collectively, this study elucidates the distinct mechanisms of various additives by linking treatment-specific microbial shifts to key soil factors and crop performance, providing a theoretical and technical framework for mitigating watermelon continuous cropping obstacles through rhizosphere environmental regulation.