Application of Cu-Chitosan Nanocomposites to Stimulate Growth and Induce Defense in Maize (Zea mays L.) against PFSR Disease

Post-flowering stalk rot (PFSR), associated with Fusarium verticillioides, affects maize production and requires effective disease-management approaches. This study evaluated copper–chitosan nanocomposites (CuCH-NCPs) for their effects on PFSR severity, selected growth traits and defence-related enzyme activities in maize (Zea mays L.) under pot conditions. CuCH-NCPs were synthesised by ionic gelation and characterised for particle size, polydispersity index and zeta potential. Seeds of the susceptible maize variety 'Surya local' received CuCH-NCP treatments, followed by foliar sprays at 45 and 65 days after sowing. Disease severity, percentage efficacy of disease control (PEDC), plant height, stem diameter, root length, root number and the activities of peroxidase (POX), polyphenol oxidase (PPO) and phenylalanine ammonia-lyase (PAL) were assessed. The 0.10% treatment had the lowest reported disease severity (24.7%) and the highest PEDC (48.1%), whereas control plants showed 47.8% disease severity. The greatest plant height (89.2 cm) and stem diameter (5.66 mm) were recorded at 0.02%. Defence-enzyme activities varied across concentrations and observation times, with the 0.14% treatment showing increases in POX, PPO and PAL following the first foliar spray. The findings indicate that CuCH-NCP treatment was associated with reduced PFSR severity and concentration-dependent changes in maize growth and defence responses. Further field evaluation is needed to determine whether these effects are maintained under agricultural conditions.