Iodine nanocitrate seed priming modulates contrasting genotypes of wheat PSII responses to phytopathogenic infection and improves productivity.

Abstract

While not classified as essential, iodine can be a beneficial element, helping to modulate redox balance and enhance stress tolerance. We assessed whether seed treatment with iodine nanocitrate affects PSII photochemical parameters (F₀, Fv/Fm), pigment composition, and wheat yield under pathogen inoculation in field conditions, while monitoring ambient air quality and short-term temperature variability. The experimental design included the following factors: (i) cultivars (Zelma, Zymoyarka); (ii) seed priming (control, iodine nanocitrates (I-0.5%)); and (iii) infection background (uninoculated, phytoplasma-like pathogen (Acholeplasma laidlawii), bacterial pathogen Pseudomonas syringae pv. atrofaciens (Psa). F₀ and Fv/Fm were measured at 7-day intervals. Treatment effects were tested within cultivar × date using a one-way ANOVA with Tukey's HSD; factorial effects of date, cultivar, and variant were assessed using ANOVA models. RESULTS: Seed priming with I-0.5% showed strong temporal and cultivar dependence in Fv/Fm, with significant date-related shifts and cultivar- and variant-dependent patterns. Variant separation was clearer in Zymoyarka, while Zelma showed generally lower intradate divergence. Pigment composition revealed contrasting cultivars' strategies: Zymoyarka exhibited pigment depletion, most strongly at I-0.5%+Psa, whereas Zelma typically increased chlorophyll and carotenoid content after inoculation and priming. Flag leaf area was consistently larger in Zelma and was mainly genotype-driven. Grain yield increased at I-0.5% in both cultivars, reaching statistical significance in Zymoyarka. CONCLUSIONS: Iodine nanocitrate priming can alter PSII functional status and pigment balance in a cultivar-specific manner under pathogen inoculation in the context of monitored ambient air pollution quality. Agronomic benefits (yield) were most pronounced in Zymoyarka, which also showed stronger within-date Fv/Fm divergence among variants and a depletion/remodeling-type pigment response (most evident under I-0.5% + Psa), consistent with greater physiological sensitivity/plasticity of this cultivar under the prevailing field load.