Cucumber (Cucumis sativus L.), sensitive to cold stress, is one of the most economically important vegetables. Here, we systematically investigated the roles of exogenous glycine betaine, chitosan, and chitosan oligosaccharide in alleviating cold stress in cucumber seedlings. The results showed that 50 mg·L⁻¹ chitosan oligosaccharide had the best activity. It effectively increases plant growth, chlorophyll content, photosynthetic capacity, osmotic regulatory substance content, and antioxidant enzyme activities while reducing relative electrical conductivity and malondialdehyde levels in cucumber seedlings under cold stress. To reveal the protective effects of chitosan oligosaccharide in cold stress, cucumber seedlings pretreated with 50 mg·L⁻¹ chitosan oligosaccharide were sampled after 0, 3, 12, and 24 h of cold stress for transcriptome analysis, with distilled water as a control. The numbers of differentially expressed genes in the four comparison groups were 656, 1274, 1122, and 957, respectively. GO functional annotation suggested that these genes were mainly involved in “voltage-gated calcium channel activity”, “carbohydrate metabolic process”, “jasmonic acid biosynthetic”, and “auxin response” biological processes. KEGG enrichment analysis indicated that these genes performed important functions in “phenylpropanoid biosynthesis”, “MAPK signaling pathway—plant”, “phenylalanine metabolism”, and “plant hormone signal transduction.” These findings provide a theoretical basis for the use of COS to alleviate the damage caused by cold stress in plant growth and development.

The plant glutathione S-transferases (GSTs) are versatile proteins encoded by several genes and play vital roles in responding to various physiological processes. Members of plant GSTs have been identified in several species, but few studies on cucumber (Cucumis sativus L.) have been reported. In this study, we identified 46 GST genes, which were divided into 11 classes. Chromosomal location and genome mapping revealed that cucumber GSTs (CsGSTs) were unevenly distributed in seven chromosomes, and the syntenic regions differed in each chromosome. The conserved motifs and gene structure of CsGSTs were analyzed using MEME and GSDS 2.0 online tools, respectively. Transcriptome and RT-qPCR analysis revealed that most CsGST members responded to cold stress. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analyses for differentially expressed CsGSTs under cold stress revealed that these genes responded to cold stress probably through “glutathione metabolism.” Finally, we screened seven candidates that may be involved in cold stress using Venn analysis, and their promoters were analyzed using PlantCARE and New PLACE tools to predict the factors regulating these genes. Antioxidant enzyme activities were increased under cold stress conditions, which conferred tolerance against cold stress. Our study illustrates the characteristics and functions of CsGST genes, especially in responding to cold stress in cucumber.

Phosphorus utilization by crop plants is often limited, thereby resulting in large accumulations of residual phosphorus fertilizer in the soil. Trichoderma fungi function as natural decomposition agents that can contribute to increasing decomposition and promoting nutrient absorption in plants. In this study, we developed a novel fertilizer application strategy that reduces phosphate fertilizer and increases Trichoderma and examined its effects on the growth, nutrient absorption, and fruit quality of pepper (Capsicum annuum L.). We compared the efficacies of eight treatments: P100 = standard dose application of phosphorus fertilizer; P85 = 85% dose; P70 = 70% dose; P0 = no phosphorus fertilizer; and the TP100, TP85, TP70, and TP0 treatments, in which a Trichoderma mixture was added to the P100, P85, P70, and P0 treatments, respectively. The combined fertilizer application strategy stimulated plant growth, increased chlorophyll content, improved yield, and enhanced nutrient absorption. Additionally, the strategy improved pepper fruit quality by increasing the contents of soluble proteins, soluble sugars, vitamin C, capsaicin, and capsanthin. A comprehensive analysis indicated that the TP85 treatment was the optimal fertilization regime for pepper. This study provides a novel fertilizer application strategy for pepper that not only ensures good plant growth but also protects soil health.

Cucumbers (Cucumis sativus L.) are a global popular vegetable and are widely planted worldwide. However, cucumbers are susceptible to various infectious diseases such as Fusarium and Verticillium wilt, downy and powdery mildew, and bacterial soft rot, which results in substantial economic losses. Grafting is an effective approach widely used to control these diseases. The present study investigated the role of wax and the phenylpropanoid biosynthesis pathway in black-seed pumpkin rootstock-grafted cucumbers. Our results showed that grafted cucumbers had a significantly higher cuticular wax contents on the fruit surface than that of self-rooted cucumbers at all stages observed. A total of 1132 differently expressed genes (DEGs) were detected in grafted cucumbers compared with self-rooted cucumbers. Pathway enrichment analysis revealed that phenylpropanoid biosynthesis, phenylalanine metabolism, plant circadian rhythm, zeatin biosynthesis, and diterpenoid biosynthesis were significantly enriched. In this study, 1 and 13 genes involved in wax biosynthesis and the phenylpropanoid biosynthesis pathway, respectively, were up-regulated in grafted cucumbers. Our data indicated that the up-regulated genes in the wax and phenylpropanoid biosynthesis pathways may contribute to disease resistance in rootstock-grafted cucumbers, which provides promising targets for enhancing disease resistance in cucumbers by genetic manipulation.

Cucumber is an important vegetable crop, and grafts often affect the quality and wax loss in cucumber fruit and affect its value. However, their metabolites and molecular mechanisms of action remain unclear. Metabolome and transcriptome analyses were conducted on the fruit peels of self-rooted plants (SR) grafted with white seed pumpkin (WG). The results showed that there were 352 differential metabolites in the fruit peels of the SR and WG. The transcriptome analysis showed 1371 differentially expressed genes (DEGs) between the WG and SR. These differentially expressed genes were significantly enriched in plant hormone signal transduction, cutin, suberin, wax biosynthesis, phenylpropanoid biosynthesis, and zeatin biosynthesis. By analyzing the correlation between differential metabolites and differentially expressed genes, six candidate genes related to the synthesis of glycitein, kaempferol, and homoeriodictyol were identified as being potentially important. Key transcription factors belonging to the TCP and WRKY families may be the main drivers of transcriptional changes in the peel between the SR and WG. The results of this study have provided a basis for the biosynthesis and regulation of wax loss and quality in grafted cucumbers and represents an important step toward identifying the molecular mechanisms of grafting onto cucumber fruit.

Global food security is facing numerous severe challenges. Population growth, climate change, and irrational agricultural inputs have led to a reduction in available arable land, a decline in soil fertility, and difficulties in increasing crop yields. As a result, the supply of food and agricultural products is under serious threat. Against this backdrop, the development of new technologies to increase the production of food and agricultural products and ensure their supply is extremely urgent. Agricultural nanotechnology, as an emerging technology, mainly utilizes the characteristics of nanomaterials such as small size, large specific surface area, and surface effects. It plays a role in gene delivery, regulating crop growth, adsorbing environmental pollutants, detecting the quality of agricultural products, and preserving fruits and vegetables, providing important technical support for ensuring the global supply of food and agricultural products. Currently, the research focus of agricultural nanotechnology is concentrated on the design and preparation of nanomaterials, the regulation of their properties, and the optimization of their application effects in the agricultural field. In terms of the research status, certain progress has been made in the research of nano-fertilizers, nano-pesticides, nano-sensors, nano-preservation materials, and nano-gene delivery vectors. However, it also faces problems such as complex processes and incomplete safety evaluations. This review focuses on the horticultural industry, comprehensively expounding the research status and application progress of agricultural nanotechnology in aspects such as the growth regulation of horticultural crops and the quality detection and preservation of horticultural products. It also deeply analyzes the opportunities and challenges faced by the application of nanomaterials in the horticultural field. The aim is to provide a reference for the further development of agricultural nanotechnology in the horticultural industry, promote its broader and more efficient application, contribute to solving the global food security problem, and achieve sustainable agricultural development.