Jasmonic and Salicylic Acid-mediated Defence Enhancement in Maize under Soybean Intercropping for Aflatoxin Suppression

Background: Aflatoxin contamination in maize, mainly caused by Aspergillus flavus, poses a serious threat to food safety and crop value in tropical regions. Conventional control measures are increasingly inadequate under changing climatic conditions This study evaluated the integrated effects of soybean intercropping and foliar application of jasmonic acid (JA) and salicylic acid (SA) on biochemical, molecular and ecological defence responses in maize. Methods: A two-year field experiment (2022-2023 and 2023-2024) was conducted at Punjab, India, in a randomized complete block design (RCBD) with four representative treatment combinations: T1 - Sole maize (control), T2 - Sole maize + JA (100 µM), T3 - Maize + soybean intercropping (2:2 row) and T4 - Maize + soybean + JA + SA (1 mM). Treatments were assessed for aflatoxin B1 and B2 content, endogenous hormone levels (JA and SA), antioxidant enzymes (POD, SOD, CAT), PR protein (β-1,3-glucanase), gene expression (PR1, PR5), rhizospheric microbial diversity, soil moisture and temperature. Results: Significant differences were observed among treatments. Aflatoxin content was highest in T1 (38.6 µg kg-1) and lowest in T4 (16.9 µg kg-1), which was below the FSSAI threshold of 20 µg kg-1. T4 also recorded the maximum JA (320.6 ng g-1) and SA (310.9 ng g-1) levels, the highest antioxidant enzyme activities (POD: 2.85, SOD: 3.02, CAT: 2.77 U mg-1 protein) and the strongest β-1,3-glucanase activity (3.54 µg glucose eq. mg-1 protein). Defence-related genes PR1 and PR5 were upregulated 3.6- and 3.3-fold, respectively, in T4 compared with the baseline in T. Rhizospheric microbial diversity increased from 6.1 log CFU g-1 (T1) to 8.2 (T4), while soil moisture improved from 14.8% to 20.4% and soil temperature decreased from 32.4oC to 29.8oC. These findings demonstrate the potential of combining legume intercropping with phytohormonal priming as a biologically intensive and climate-resilient strategy for aflatoxin mitigation in maize.