Optimizing maize late wilt disease management: A comparative assessment of bacterial biocontrol and Azoxystrobin...

Maize (Zea mays L.) is one of the world's most widely cultivated and economically important cereal crop, serving as a staple food and feed source in over 170 countries. However, its global productivity is threatened by late wilt disease (LWD), a disease caused by Magnaporthiopsis maydis, that spreads through soil and seeds and can cause severe yield losses. This study evaluated the efficacy of an integrated management strategy combining the biocontrol agent Pseudomonas sp. D1 with the fungicide azoxystrobin. Maize plants were subjected to five treatments: non-infected control (NI), infected (I), infected treated with azoxystrobin (Az), with bacteria (B), or both (Az-B). Morphometric, physiological, biochemical, nutrient, and lipidomic parameters were assessed in roots and shoots 23 days after sowing. Pseudomonas sp. D1 alone significantly enhanced plant growth, increasing shoot length by 23 % and root fresh weight by 76 % compared to infected plants, and reduced conidia by 65 %. It also improved biochemical responses, including a 2.5-fold increase in phenolics and 34 % reduction in root lipid peroxidation, likely through a combination of antibiosis and induction of resistance in maize plants, as evidenced by induction of antioxidant enzyme activity, phenolic compounds production and alterations in lipid profile. The Az-B treatment improved some physiological traits, notably protein content and lipid peroxidation reduction in shoots. In roots Az-B treatment reduced visible decay compared to the bacterial treatment alone, however no differences were observed between the two treatments in the lipid profile and biochemistry of roots. Biochemical responses diverged: bacterial inoculation increased phenolic and starch levels in roots, while azoxystrobin mainly altered catalase, glutathione s-transferase, and protein oxidation. Lipidomic analysis revealed infection-related depletion of key lipid classes, including galactolipids and branched fatty acid esters of hydroxy fatty acids (FAHFAs), which were partially restored by bacterial treatment. These findings demonstrate the advantage of early-stage (23 DAS) lipidomic and nutrient profiling to detect infection-induced changes and treatment efficacy before symptom development and underscore the effectiveness of Pseudomonas sp. D1 as a sustainable alternative to chemical fungicides, reducing the environmental risks associated with azoxystrobin use.