Wheat (Triticum aestivum L.) is a crucial global food crop. The intensive crop farming, monoculture cultivation, and impact of climate change affect the susceptibility of wheat cultivars to biotic stresses, mainly caused by soil fungal pathogens, especially those belonging to the genus Fusarium. This situation threatens yield and grain quality through root and crown rot. While conventional chemical fungicides face resistance issues and environmental concerns, biological alternatives like seed priming with natural metabolites are gaining attention. Polyamines, including putrescine, spermidine, and spermine, are attractive priming agents influencing plant development and abiotic stress responses. Spermine in particular shows potential for in vitro antifungal activity against Fusarium. Optimising spermine concentration for seed priming is crucial to maximising protection against Fusarium infection while ensuring robust plant growth. In this research, we explored the potential of the polyamine spermine as a seed treatment to enhance wheat resilience, aiming to identify a sustainable alternative to synthetic fungicides. Our findings revealed that a six-hour seed soak in spermine solutions ranging from 0.5 to 5 mM did not delay germination or seedling growth. In fact, the 5 mM concentration significantly stimulated root weight and length. In complementary in vitro assays, we evaluated the antifungal activity of spermine (0.5–5 mM) against three Fusarium species. The results demonstrated complete inhibition of Fusarium culmorum growth at 5 mM spermine. A less significant effect on Fusarium graminearum and little to no impact on Fusarium oxysporum were found. The performed analysis revealed that the spermine had a fungistatic effect against the pathogen, retarding the mycelium growth of F. culmorum inoculated on the seed surface. A pot experiment with Bulgarian soft wheat cv. Sadovo-1 was carried out to estimate the effect of seed priming with spermine against infection with isolates of pathogenic fungus F. culmorum on plant growth and disease severity. Our results demonstrated that spermine resulted in a reduced distribution of F. culmorum and improved plant performance, as evidenced by the higher fresh weight and height of plants pre-treated with spermine. This research describes the efficacy of spermine seed priming as a novel strategy for managing Fusarium root and crown rot in wheat.

Dehydrins are stress-inducible proteins with protective functions, characterized by high hydrophilicity, thermostability, and a low degree of secondary structure. They stabilize cellular membranes, preserve macromolecule conformation, and support enzymatic and structural protein functions. Their accumulation in plant tissues under drought is regulated by abscisic acid (ABA)-dependent and ABA-independent pathways. Ethylene plays a key role in stress adaptation, but its relationship with dehydrin accumulation remains unclear. This study investigates how ethylene influences dehydrin expression in Arabidopsis thaliana during prolonged dehydration using transcript profiling and immunodetection in wild-type (Col-0), ethylene-constitutive (ctr1-1), and ethylene-insensitive (ein3eil1) mutants. Comparative analyses showed increased survival of ctr1-1 plants under dehydration stress, likely due to reduced oxidative damage. Analysis of dehydrin-coding genes identified multiple Ethylene Response Factor (ERF) binding sites, flanking the transcription start sites, which suggests a fine-tuned ethylene-dependent regulation. The ability of ethylene signaling to either suppress or stabilize particular dehydrins was demonstrated by RT-qPCR and immunodetection experiments. Under drought stress, ethylene signaling appeared to suppress root-specific dehydrins. A Y-segment-containing protein with approximate molecular weight of 20 kDa showed decreased levels in ctr1-1 and higher accumulation in ein3eil1, indicating that ethylene signaling acts as a negative regulator. These results provide new information on the dual role of ethylene in dehydrin control, highlighting its function as a molecular switch in stress adaptive responses.

Photosynthesis is a primary plant physiological process, which can easily be affected by various environmental factors, including biotic stressors. The exogenous application of different substances like plant growth regulators might benefit this process both under normal and stress conditions. It is well known that the polyamine spermine positively modulates photosynthesis. We evaluated the effects of 5 mM spermine seed priming on photosynthesis-related parameters in wheat (Triticum aestivum L.) plants grown from Fusarium culmorum-infected seeds. Under no stress conditions, the spermine seed priming improved leaf gas exchange, chlorophyll a fluorescence, and leaf pigment content compared to the control. In non-primed seedlings exposed to the pathogen, these parameters were significantly affected. The most substantial reductions were seen in the net photosynthetic rate (56%), transpiration rate (63%), and stomatal conductance (58%). In plants cultivated from seeds primed with spermine the pathogen’s adverse effect on the assessed parameters was mitigated. Our study demonstrates the efficacy of spermine seed priming in sustaining photosynthetic activity in wheat plants exposed to biotic stress induced by Fusarium culmorum.

Melatonin is a naturally occurring compound that regulates many aspects of plant growth and development. Recently, its stress-protective potential has been extensively studied. This study investigates the effect of exogenous melatonin on non-enzymatic antioxidants, gene expression, and activity of key antioxidant enzymes in young winter wheat plants subjected to 5 days of drought. Melatonin was root-supplemented 24 h before or after the stress. The parameters were analyzed in the leaves of two Bulgarian cultivars at the end of drought, and after recovery. Drought activated both enzymatic and non-enzymatic antioxidant defense in both cultivars, with distinct responses reflecting their tolerance. The drought-tolerant cv. Gines showed marked increase in total phenolics, thiol containing compounds, catalase (CAT) and glutathione reductase (GR) activities, and catalase (CATA, CAT3) and class III peroxidase (POX2) transcript levels. The less tolerant cv. Fermer exhibited more limited induction, primarily involving CATA, CAT3 and GR transcripts and the glutathione pool. Melatonin pre-treatment generally attenuated drought-induced antioxidant responses. This effect was more pronounced in cv. Fermer, where the most drought-responsive parameters were also the most alleviated by melatonin, whereas in cv. Gines only CATA expression, and CAT and GR activities were significantly influenced, suggesting cultivar-dependent modulation of antioxidant systems by melatonin. During recovery, both pre- and post-drought melatonin applications produced comparable effects on the antioxidant defense. The post-treatment selectively enhanced the studied transcripts in a cultivar-specific manner.

Our study investigated the protective effects of seed priming with 5mM polyamine spermine (Spm) on the biochemical and transcriptional responses of winter wheat during Fusarium culmorum infection. We tested the effects of the priming in two age groups of plants via two pathogen infection approaches. In the seed-inoculated plants, infection with F. culmorum induced severe cellular damage and oxidative stress, as evidenced by increase in electrolyte leakage, thiobarbituric acid reactive substances, and hydrogen peroxide levels. The pathogen also triggered metabolic changes in the plants by elevating reducing sugars, free proline, total osmotically active solutes and peroxidase activity, while at the same time suppressing the activity of catalase. On the other hand, the 5 mM Spm seed priming significantly mitigated this pathogen-induced damage. The priming effectively lowered most oxidative stress biomarkers and reduced the over-accumulation of osmolytes. Spm also restored the suppressed catalase activity, stabilized superoxide dismutase activity and altered the pathogen-mediated transcriptional response of the tested defence enzymes. Furthermore, spermine priming enhanced glutathione S-transferase activity in infected 30-day-old plants. Overall, our findings demonstrate that 5 mM spermine seed priming modulates the physiological response to F. culmorum in wheat by optimizing antioxidant enzyme activity and returning the studied metabolic parameters to near control levels.