Carlos Eduardo Aucique-Perez

Leaf and spike diseases can significantly reduce wheat yield and grain quality. To mitigate these impacts, an integrated disease management approach can be adopted, incorporating measures such as the use of resistant cultivars, fungicides and nitrogen fertilization. This study aimed to evaluate the impact of these practices on chlorophyll a fluorescence, yield components, and the technological quality of wheat grains. The area under the disease progress curve (AUDPC) was correlated with the maximum efficiency of photosystem II (PSII) photochemistry (F_v/F_m), as measured at the dough development stage (ZGS80) under field conditions, which also affected quality parameters. Additionally, an increase in AUDPC values reduced the thousand kernel weight (TKW) and test weight (TW). Conversely, AUDPC values for tan spot, powdery mildew and leaf rust were positively related to ash content (affecting flour color), protein content (PC) and grain falling number. Both the recommended nitrogen rate (130 kg ha⁻¹) and the high rate (200 kg ha⁻¹) increased grain protein content (PC) and gluten index (GI), while maintaining dough stability and water absorption. Fungicide application increased flour lightness and yellowness. Overall, integrated disease management combining moderately resistant cultivars, fungicide applications and nitrogen fertilization reduced AUDPC values, increased F_v/F_m (indicating optimal physiological performance) and ensured yield components and maintenance of wheat technological quality.

Frequent and increasingly severe freezing events threaten citrus production in northern Florida, underscoring the need for strategies that enhance freezing resilience in citrus cultivars. Grafting scions onto tolerant rootstocks provides a physiologically integrative approach to improve stress tolerance. This study aims to elucidate how these interactions modulate physiological and metabolic responses under freezing stress, thereby identifying mechanisms that contribute to enhanced freeze resilience in citrus. Here, we grafted Citrus reticulata (cv. UF-950) onto eight rootstocks (Bitters, Blue-1, C-146, Sour Orange, UFR07TC, UFR09TC, UFR5, and US942) to evaluate scion–rootstock interactions under normal (20 °C) and freezing (−6 °C) conditions. Freezing stress caused a sharp increase in oxidative stress markers, lipid peroxidation, and membrane damage while reducing photosynthetic performance across most combinations. Antioxidant capacity, osmolyte accumulation, and carbon–nitrogen metabolic responses varied significantly among rootstocks, revealing strong genotype-dependent modulation of scion physiology. Among the tested combinations, UF-950 grafted onto UFR5 displayed the highest freezing tolerance, characterized by robust activation of antioxidant enzymes, elevated proline and glycine betaine accumulation, reduced oxidative damage, and sustained carbon–nitrogen metabolic fluxes under freezing stress. These results demonstrate that rootstock genotype governs the extent of scion defense activation and metabolic homeostasis under freezing conditions. Our findings identify UFR5 as a promising rootstock for enhancing freezing resilience in citrus and provide mechanistic insight into how scion–rootstock interaction orchestrates integrative stress tolerance pathways. Future work should focus on multi-omics dissection of rootstock-mediated signaling networks and long-term field validation to optimize rootstock selection for enhanced cold resilience under variable climatic conditions.

Putrescine (Put) is a promising small molecule‐based biostimulant to enhance plant growth and resilience, though its mode of action remains unclear. This study investigated the Put priming effect on Arabidopsis mutant lines (Atadc1, Atadc2, Atnata1, and Atnata2) under control conditions and salinity to understand its role in regulating plant growth.The Atadc2 mutant, characterized by reduced endogenous Put levels, showed insensitivity to Put priming without growth enhancement, which was linked to significant imbalances in nitrogen metabolism, including a high Gln/Glu ratio. Contrarily, the Atnata2 mutant exhibited significant growth improvement and upregulated AtADC2 expression, particularly under Put priming, highlighting these genes' involvement in regulating plant development.Put priming enhanced plant growth by inducing the accumulation of specific polyamines (free, acetylated, conjugated, or bound form) and improving light‐harvesting efficiency, particularly in the Atnata2 line. Our findings suggest that AtNATA2 may negatively regulate Put synthesis and accumulation via AtADC2 in the chloroplast, impacting light harvesting in photosystem II (PSII). Furthermore, the Atadc2 mutant line exhibited upregulated AtADC1 but reduced AcPut levels, pointing to a cross‐regulation among these genes. The regulation by AtNATA2 on AtADC2 and AtADC2 on AtADC1 could be crucial for plant growth and overall stress tolerance by interacting with polyamine catabolism, which shapes the plant metabolic profile under different growth conditions. Understanding the regulatory mechanisms involving crosstalk between AtADC and AtNATA genes in polyamine metabolism and the connection with certain SMBBs like Put can lead to more effective agricultural practices, improving plant growth, nitrogen uptake, and resilience under challenging conditions.

Nitrogen (N) and silicon (Si) are mineral elements that have shown a reduction in the damage caused by tan spot (Pyrenophora tritici-repentis (Ptr)) in wheat. However, the effects of these elements were studied separately, and the N and Si interaction effect on wheat resistance to tan spot remains elusive. Histocytological and biochemical defense responses against Ptr in wheat leaves treated with Si (+Si) at low (LN) and high N (HN) inputs were investigated. Soil amendment with Si reduced the tan spot severity in 18% due to the increase in the leaf Si concentration (around 30%), but it was affected by the N level used. The superoxide dismutase (SOD) activity was higher in +Si plants and inoculated with Ptr, leading to early and higher H₂O₂ and callose accumulation in wheat leaf. Interestedly, phenylalanine ammonia-lyase (PAL) activity was induced by the Si supplying, being negatively affected by the HN rate. Meanwhile, catalase (CAT), and peroxidase (POX) activities showed differential response patterns according to the Si and N rates used. Tan spot severity was reduced by both elements, but their interaction does not evidence synergic effects in this disease’s control. Wheat plants from −Si and HN and +Si and LN treatments recorded lower tan spot severity.

Plant diseases are a major threat to food security, causing drastic alterations in plant metabolism upon infection by pathogens. This often results in decreased biomass accumulation, slowed growth rates, and diminished yield components. Pathogens, through various lifestyles such as biotrophic, necrotrophic, and hemibiotrophic, disrupt photosynthesis, the primary metabolic process, via functional and structural damages. Furthermore, the CO₂ assimilation in plants is severely altered by pathogens regardless of their lifestyles. Photosynthetic determinations allow us to establish a perspective about the physiological impairment caused by pathogens related to alterations in the CO₂ flow from the atmosphere to carboxylation sites, stomatal limitations, and photosynthetic performance of photosystem II (PSII). From the changes in the energy, dissipation is possible to establish the functional status of the photochemistry machinery under stress conditions. For the above, chlorophyll a fluorescence (CF) and CF imaging (CFI) arose as a method highly sensible to determine the damage caused by pathogens in plants. This review shows a practical perspective on CF tools using visual method and rapid fluorescence induction kinetics (OJIP-test), for disease detection associated with plant-pathogen interaction studies from the physiological viewpoint, their implications for plant pathology research, applications for the plant phenotyping field, and biotic stress detection.

Biostimulants became a hotspot in the fight to alleviate the consequences of abiotic stresses in crops. Due to their complex nature, it is challenging to obtain stable and reproducible final products and more challenging to define their mechanism of action. As an alternative, small molecule-based biostimulants, such as polyamines have promoted plant growth and improved stress tolerance. However, profound research about their mechanisms of action is still missing. To go further, we tested the effect of putrescine (Put) and its precursor ornithine (Orn) and degradation product 1,3-diaminopropane (DAP) at two different concentrations (0.1 and 1 mM) as a seed priming on in vitro Arabidopsis seedlings grown under optimal growth conditions, osmotic or salt stress. None of the primings affected the growth of the seedlings in optimal conditions but altered the metabolism of the plants. Under stress conditions, almost all primed plants grew better and improved their greenness. Only Orn-primed plants showed different plant responses. Interestingly, the metabolic analysis revealed the implication of the N- acetylornithine and Orn and polyamine conjugation as the leading player regulating growth and development under control and stress conditions. We corroborated polyamines as very powerful small molecule-based biostimulants to alleviate the adverse abiotic stress effects.