Biochemical and Molecular Basis of Chemically Induced Defense Activation in Maize against Banded Leaf and Sheath Blight Disease

Maize is the third most vital global cereal, playing a key role in the world economy and plant genetics research. Despite its leadership in production, maize faces a severe threat from banded leaf and sheath blight, necessitating the urgent development of eco-friendly management strategies. This study aimed to understand the resistance mechanisms against banded leaf and sheath blight (BLSB) in maize hybrid "Vivek QPM-9". Seven fungicides at recommended doses (1000 and 500 ppm) and two plant defense inducers, salicylic acid (SA) and jasmonic acid (JA) at concentrations of 50 and 100 ppm, were applied. Fungicides, notably Azoxystrobin and Trifloxystrobin + Tebuconazole, demonstrated superior efficacy against BLSB, while Pencycuron showed limited effectiveness. Field-sprayed Azoxystrobin exhibited the lowest BLSB infection, correlating with heightened antioxidant enzyme activity (SOD, CAT, POX, β-1,3-glucanase, PPO, PAL), similar to the Validamycin-treated plants. The expression of defense-related genes after seed priming with SA and JA was assessed via qRT-PCR. Lower SA concentrations down-regulated SOD, PPO, and APX genes but up-regulated CAT and β-1,3-glucanase genes. JA at lower doses up-regulated CAT and APX genes, while higher doses up-regulated PPO and β-1,3-glucanase genes; SOD gene expression was suppressed at both JA doses. This investigation elucidates the effectiveness of certain fungicides and plant defense inducers in mitigating BLSB in maize hybrids and sheds light on the intricate gene expression mechanisms governing defense responses against this pathogen.