Photosynthetic markers reveal recovery of Pisum sativum from pathogen infection following fungicide treatment

Many plant-pathogen interactions can severely compromise plant growth and productivity, highlighting the need for effective strategies to prevent or mitigate infection and limit disease progression. Pathogen infection disrupts photosynthesis and carbon metabolism; however, the physiological consequences of fungicides, both beneficial and potentially phytotoxic, remain insufficiently characterised despite their widespread use in crop protection. After preliminary experiments in Arabidopsis thaliana , we investigated the impact of Ascochyta pisi infection on Pisum sativum and evaluated the efficacy of tebuconazole applied preventively or curatively. Determining the best time to apply the fungicide to the crops appears to be crucial. Photosynthetic function was assessed by PAM chlorophyll fluorometry, and pigment content and the abundance of selected chloroplastic proteins (cFBP1, TRX f, PsaC, D1/PsbA, and LHCII) were also determined. Infection caused a marked decline in Y(II) photosynthetic performance, accompanied by cFBP1 and TRX f decreased, and an induction of PsaC (PSI), the D1/PsbA protein (PSII), and LHCII. Curative tebuconazole application partially restored photosynthetic and metabolic functions, whereas preventive treatment did not fully counteract infection-induced alterations. Principal component analysis, integrating all measured variables, clearly separated the treatments and supported a stronger curative than preventive effect of the fungicide under the conditions tested. This combined physiological and biochemical approach enables robust comparisons across treatments and helps identify trade-offs between disease suppression and host performance. Overall, these results provide an integrative and quantitative framework using an effective and reliable methodology for assessing plant physiological responses to biotic stress and inform more sustainable crop protection strategies, particularly under increasing climate pressure in Mediterranean agroecosystems.