Biofertilizer alters primary and secondary metabolism in winter-grown lettuce in a cultivar-dependent manner

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Abstract

In this study, we evaluated the effects of biofertilizer on primary and secondary metabolites in lettuce. Green 'Aleppo' and red 'Murai' cultivars were grown in an unheated greenhouse during winter production under biofertilizer and control (no fertilization) conditions. Main effects of cultivar showed that red 'Murai' exhibited higher total antioxidant capacity (TAC), total phenolic content (TPC), and total carotenoid content, myo-inositol, malic, propionic, and citric acids, and higher concentrations of chicoric and chlorogenic acids, caffeoylquinic acid glucoside, along with all quantified flavonoids except kaempferol. In contrast, green 'Aleppo' showed higher fructose, sucrose, total sweetness index (TSI), total soluble solids (TSS), shikimic acid, fumaric acid, lactucopicrin, and lactucopicrin-15- oxalate. Biofertilizer application significantly increased glucose by 42.9%, fructose by 39.1%, and sucrose by 57.8%, resulting in a 40.5% increase in TSI. Furthermore, malic acid increased significantly by 23.2% and fumaric acid by 36.0%, whereas myo-inositol and propionic acid significantly decreased by 23.3% and 21.6%, respectively. Biofertilizer also reduced major phenolic compounds, including chicoric acid (66.9%), chlorogenic acid (81.2%), and caffeoylquinic acid glucoside (32.6%), along with TPC (19.4%) and TAC (54.0%). All principal flavonoids were significantly reduced (30.1–70.8%) when averaged across cultivars, whereas sesquiterpene lactones showed no significant biofertilizer main effect, and lactucin was the predominant lactone. Significant cultivar × biofertilizer interactions revealed contrasting metabolic responses between cultivars. EM Aktiv reduced phenolic acids and flavonoids in 'Murai', whereas in 'Aleppo', these compounds were generally maintained or enhanced in a compound-dependent responses, alongside increases in sugars and selected organic acids. Lactones showed a crossover response, increasing under EM treatment in 'Aleppo' but decreasing in 'Murai'. These results demonstrate that lettuce responses to biofertilizer treatment are strongly cultivar- dependent, highlighting the importance of genotype selection in determining metabolic responses under biofertilizer application. Overall, these changes may indicate altered allocation between primary and secondary metabolism under winter conditions.

Keywords

Lactuca sativa / effective microorganisms / winter season / spectrophotometric assays / sugars / organic acids / phenolic acids / flavonoids / sesquiterpene lactones / HPLC/LC/MS/DAD

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