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Climate change-induced weather events, such as extreme temperatures, prolonged drought spells, or flooding, pose an enormous risk to crop productivity. Studies on the implications of multiple stresses may vary from those on a single stress. Usually, these stresses coincide, amplifying the extent of collateral damage and contributing to significant financial losses. The breadth of investigations focusing on the response of horticultural crops to a single abiotic stress is immense. However, the tolerance mechanisms of horticultural crops to multiple abiotic stresses remain poorly understood. In this review, we described the most prevalent types of abiotic stresses that occur simultaneously and discussed them in in-depth detail regarding the physiological and molecular responses of horticultural crops. In particular, we discussed the transcriptional, posttranscriptional, and metabolic responses of horticultural crops to multiple abiotic stresses. Strategies to breed multi-stress-resilient lines have been presented. Our manuscript presents an interesting amount of proposed knowledge that could be valuable in generating resilient genotypes for multiple stressors.

Boron (B) is an essential trace element required for the physiological functioning of higher plants. B deficiency is considered as a nutritional disorder that adversely affects the metabolism and growth of plants. B is involved in the structural and functional integrity of the cell wall and membranes, ion fluxes (H+, K+, PO43−, Rb+, Ca2+) across the membranes, cell division and elongation, nitrogen and carbohydrate metabolism, sugar transport, cytoskeletal proteins, and plasmalemma-bound enzymes, nucleic acid, indoleacetic acid, polyamines, ascorbic acid, and phenol metabolism and transport. This review critically examines the functions of B in plants, deficiency symptoms, and the mechanism of B uptake and transport under limited B conditions. B deficiency can be mitigated by inorganic fertilizer supplementation, but the deleterious impact of frequent fertilizer application disrupts soil fertility and creates environmental pollution. Considering this, we have summarized the available information regarding alternative approaches, such as root structural modification, grafting, application of biostimulators (mycorrhizal fungi (MF) and rhizobacteria), and nanotechnology, that can be effectively utilized for B acquisition, leading to resource conservation. Additionally, we have discussed several new aspects, such as the combination of grafting or MF with nanotechnology, combined inoculation of arbuscular MF and rhizobacteria, melatonin application, and the use of natural and synthetic chelators, that possibly play a role in B uptake and translocation under B stress conditions.

Brassinosteroids (BRs) are important in plant resistance to chilling stress. However, limited information is available regarding the specific mechanisms involved at proteomic level. We utilized the iTRAQ proteomic approach, physiological assays and information obtained from cellular ultrastructure to clarify the underlying molecular mechanism of BRs to alleviate chilling stress in pepper (Capsicum annuum L.). Foliar application of 24-epibrassinolide (EBR) improved photosynthesis and improved cell structure by presenting a distinct mesophyll cell and chloroplast with well-developed thylakoid membranes in the leaves of pepper seedlings. We identified 346 differentially expressed proteins (DEPs), including 217 up-regulated proteins and 129 down-regulated proteins in plants under chilling (Chill) and Chill + EBR treated plants. Most of the DEPs were related to multiple pathways, including photosynthesis, carbohydrate metabolism, energy metabolism, protein biosynthesis, amino acid synthesis, redox and stress defence (ascorbate peroxidase, glutathione peroxidase and superoxide dismutase). Up-regulated DEPs were associated with the photosynthetic electron transfer chain, oxidative phosphorylation, GSH metabolism pathway, Calvin cycle and signaling pathway. The physiochemical analysis showed that EBR treatment improved the tolerance of pepper seedlings to chilling stress.

Soil salinity adversely affects the growth and yield of crops, including cucumber, one of the most important vegetables in the world. Grafting with salt-tolerant pumpkin as the rootstock effectively improves the growth of cucumber under different salt conditions by limiting Na+ transport from the pumpkin rootstock to the cucumber scion. High-affinity potassium transporters (HKTs) are crucial for the long distance transport of Na+ in plants, but the function of pumpkin HKTs in this process of grafted cucumber plants remains unclear. In this work, we have characterized CmHKT1;1 as a member of the HKT gene family in Cucurbita moschata and observed an obvious upregulation of CmHKT1;1 in roots under NaCl stress conditions. Heterologous expression analyses in yeast mutants indicated that CmHKT1;1 is a Na+-selective transporter. The transient expression in tobacco epidermal cells and in situ hybridization showed CmHKT1;1 localization at plasma membrane, and preferential expression in root stele. Moreover, ectopic expression of CmHKT1;1 in cucumber decreased the Na+ accumulation in the plants shoots. Finally, the CmHKT1;1 transgenic line as the rootstock decreased the Na+ content in the wild type shoots. These findings suggest that CmHKT1;1 plays a key role in the salt tolerance of grafted cucumber by limiting Na+ transport from the rootstock to the scion and can further be useful for engineering salt tolerance in cucurbit crops.

Background Low temperature stress severely limits the growth and development of pepper ( Capsicum annuum L.). Brassinolides (BRs) and carotenoids play key roles in alleviating low-temperature stress. At present, the research on the regulatory relationship between BRs and carotenoids remains rather limited. In this study, CaBZR1 (Brassinazole-Resistant 1), a key transcription factor of BR signaling pathway, and CaLCYB (Lycopene β-Cyclase), a carotenoid synthesis gene, were silenced using virus-induced gene silencing (VIGS) technology. The role of BR-mediated carotenoid regulation of cold tolerance was explored. Results The results showed that after silencing CaBZR1 and CaLCYB respectively, the carotenoid content, the activities of antioxidant enzymes including superoxide dismutase (SOD), peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX), as well as the chlorophyll fluorescence parameter (Fv/Fm) all decreased significantly. The levels of superoxide anion (O₂⁻), hydrogen peroxide (H₂O₂) and malondialdehyde (MDA) increased significantly, leading to oxidative damage to membrane lipids. The expressions of cold-responsive genes such as CaFbox1 (F-box protein 1), CaMBF1 (Multiprotein Bridging Factor 1) and CaNAC3 (NAC domain containing protein 3) were significantly reduced. Exogenous spraying of EBR alleviated the damage in CaBZR1 and CaLCYB -silenced plants under low-temperature stress. Conclusions These results emphasize that carotenoids and BRs enhance cold resistance in pepper by enhancing antioxidant enzyme activities, scavenging reactive oxygen species (ROS) and transcriptional responses. This study provides new insights into the interactions between BR signaling and carotenoid metabolism under low-temperature stress and offers a potential strategy for improving low-temperature tolerance in crops.

Background Powdery mildew is a disease with one of the most substantial impacts on cucumber production globally. The most efficient approach for controlling powdery mildew is the development of genetic resistance; however, few genes associated with inherent variations in cucumber powdery mildew resistance have been identified as of yet. Results In this study, we re-sequence 299 cucumber accessions, which are divided into four geographical groups. A genome-wide association study identifies 50 sites significantly associated with natural variations in powdery mildew resistance. Linkage disequilibrium analysis further divides these 50 sites into 32 linkage disequilibrium blocks containing 41 putative genes. Virus-induced gene silencing and gene expression analysis implicate CsGy5G015960 , which encodes a phosphate transporter, as the candidate gene regulating powdery mildew resistance. On the basis of the resequencing data, we generate five CsGy5G015960 haplotypes, identifying Hap.1 as the haplotype most likely associated with powdery mildew resistance. In addition, we determine that a 29-bp InDel in the 3′ untranslated region of CsGy5G015960 is responsible for mRNA stability. Overexpression of CsGy5G015960 Hap.1 in the susceptible line enhances powdery mildew resistance and phosphorus accumulation. Further comparative RNA-seq analysis demonstrates that CsGy5G015960 Hap.1 may regulate cucumber powdery mildew resistance by maintaining a higher H 2 O 2 level through the depletion of multiple class III peroxidases. Conclusions Here we identify a candidate powdery mildew-resistant gene in cucumber using GWAS. The identified gene may be a promising target for molecular breeding and genetic engineering in cucumber to enhance powdery mildew resistance.

Background Pepper ( Capsicum annuum L.) is a vegetable crop of significant economic importance, but its yield and quality are severely affected by the combined stress of low temperature and low light (LL), particularly in greenhouse environments. Despite this, the physiological and molecular mechanisms underlying pepper’s response to LL stress remain poorly understood. In this study, we conducted physiological and transcriptomic analyses on two pepper genotypes: Y2, a LL-sensitive genotype, and Y425, a LL-tolerant genotype. These genotypes were subjected to LL stress conditions (10 °C/5°C, 100 µmol m⁻²s⁻¹) and control (CK) conditions (28 °C/18°C, 300 µmol m⁻²s⁻¹). Results Three days after treatment, the phenotypes of the two pepper genotypes began to show clear distinctions, with Y425 seedlings exhibiting greater root length, shoot fresh weight, and root fresh weight compared to Y2. Additionally, comparative transcriptome analysis of leaf samples from both genotypes identified a total of 13,190 differentially expressed genes (DEGs). Gene Ontology (GO) enrichment analysis revealed that genes associated with photosynthesis, osmotic stress response, reactive oxygen species response, and other GO terms potentially contribute to LL tolerance. Moreover, three key pathways involved in the response to LL stress were identified: photosynthesis-antenna proteins, zeatin biosynthesis, and circadian rhythm pathways. The key DEGs in these pathways were expressed at higher levels in Y425 as compared with Y2. Furthermore, physiological indicators such as chlorophyll fluorescence parameters, chlorophyll content, osmoregulatory substances, and antioxidant enzyme activities decreased under LL stress; however, the reduction was significantly greater in Y2 compared to Y425, further validating the molecular findings from the transcriptome analysis. Conclusion This study identified significant physiological and transcriptomic differences in two pepper genotypes under LL stress. It highlighted key pathways and provide novel insights into the molecular and physiological mechanisms of pepper’s LL tolerance. These results emphasize the importance of optimizing greenhouse conditions for better crop productivity.

A fungus F. sp. (FON) is the causal organism of wilt in watermelon. In this study, we evaluated the effect of wheat intercropping on the wilt of watermelon. Our results showed that wheat intercropping decreases the incidence of wilt of watermelon, likely due to the secretion of coumaric acid from the roots of wheat that dramatically inhibits FON spore germination, sporulation, and growth. The secretion of -hydroxybenzoic acid, ferulic acid, and cinnamic acid from the roots of watermelon stimulates FON spore germination, sporulation, and growth. The secretion of phenolic acids and organic acids from the roots of watermelon is also promoted by FON infection. However, secretion of phenolic acids and organic acids from the roots of watermelon is substantially reduced under wheat intercropping systems. FON infection increases the accumulation of free and conjugated salicylic acid (SA) in watermelon grown under wheat intercropping systems through isochorismate (ICS) and phenylalanine ammonia-lyase (PAL) pathways. Furthermore, wheat intercropping up-regulates the expression of disease-and defense-responsive genes and improves the activities of corresponding pathogenesis-related (PR) enzymes in the roots of watermelon. In conclusion, the secretion of coumaric acid from the roots of wheat and changes in the composition of phenolic acid and organic acid secretion from the roots of watermelon suppress wilt of watermelon under wheat intercropping system. Meanwhile, wheat intercropping also enhanced the resistance of watermelon to FON by up-regulating the expression of disease-and defense-responsive genes in watermelon.

Background Fruit drop and quality deterioration are major constraints limiting date palm ( Phoenix dactylifera L.) productivity, particularly under environmental constraints. While plant growth regulators (PGRs), particularly synthetic auxins like 2,4-Dichlorophenoxyacetic acid (2,4-D), have demonstrated potential in managing these physiological limitations, cultivar-specific responses and optimal application protocols remain insufficiently characterized. Results This study evaluated the impact of foliar-applied 2,4-D at three concentrations (25, 50, and 75 mg/L) on fruit retention and quality traits in two date palm cultivars under field conditions. Application of 2,4-D, particularly at 50 mg/L during the kimri stage, significantly improved key agronomic parameters, including bunch weight, fruit and pulp weight, fruit length and width, and moisture content. Fruit quality parameters such as total soluble solids (TSS), total sugars, reducing and non-reducing sugars, ascorbic acid, and tannins were also enhanced. Furthermore, antioxidative enzymes peroxidase and catalase, flavonoids, and phenolic content were significantly higher compared to the untreated control. Among the tested cultivars, differential responses were observed, with one cultivar consistently showing superior outcomes in terms of fruit quality. Conclusion The exogenous application of 2,4-D demonstrated a positive effect on reducing fruit drop and enhancing both physical and quality traits in date palm cultivars. These findings suggest that 2,4-D can serve as an effective tool in sustainable date palm production by improving yield and fruit quality under stress conditions.