Cell death induced by fumonisin B1 in two maize hybrids: correlation with oxidative status biomarkers and salicylic and jasmonic acids imbalances

Fungal and plant secondary metabolites modulate host-pathogen interactions. However, the participation of fumonisin B1 (FB1) in the Fusarium verticillioides -maize pathosystem is unclear. In this work, cell death and the reactive oxygen species-phytohormone imbalance interplay as well as their correlation with the FB1 phytotoxicity in two maize genotypes with contrasting resistance to Fusarium ear rot were studied. Resistant (RH) and susceptible hybrid (SH) maize seedlings, grown from uninoculated seeds irrigated with FB1 (1 and 20 μg/mL), were harvested at 7, 14 and 21 days after planting, and were examined for electrolyte leakage (aerial parts) and for oxidative stress biomarkers (aerial parts and roots). The salicylic/jasmonic acid levels associated with cytotoxicity were further explored in seedlings exposed 24 h to FB1 (1 μg/mL) in hydroponics, with and without pre-treatment with the antioxidant ascorbic acid (AA). Cell death increased in RH and SH watered with 1 and 20 μg/mL of mycotoxin, respectively. Both toxin concentrations were pro-oxidant, and the major perturbations were found in roots. The overall plant stress, estimated by an Integrated Biomarker Response index, was higher in plants treated with 20 μg/mL of FB1, while treatment with 1 μg/mL caused more stress in RH at 21 days. Different phytohormone changes were found in both hybrids: salicylic acid increases (prevented by AA) in RH, and jasmonic acid decreases in both germplasms (although prevented by AA pre-treatment only in SH). Cell death induced by FB1 was associated with different phytohormonal regulatory mechanisms in both maize genotypes, some of which were mediated by the redox status.