Biofungicidal Potential of Melia azedarach Extracts against Alternaria spp. in Potato: Integrating Phytochemical Profiling with In Vitro and In Vivo Antifungal Efficacy

The development of sustainable alternatives to synthetic fungicides for controlling potato early blight, caused by Alternaria spp., is crucial for food security and environmental health. This study investigates the biofungicidal potential of Melia azedarach L. extracts. The aim was to compare the efficacy and phytochemical basis of methanolic extracts from M. azedarach seeds and leaves against Alternaria spp. The antifungal activity was evaluated in vitro using the poisoned food technique against three Alternaria isolates. The most potent extract was further tested on detached potato leaves (preventive and curative modes) and on whole potato plants under greenhouse conditions. Phytochemical profiling was conducted through TLC, quantification of total phenolics and flavonoids, and UPLC-ESI-MS/MS analysis. The seed extract demonstrated superior and consistent antifungal activity, achieving mycelial growth inhibition (MGI) of 77.8-78.6% in vitro, significantly higher than the leaf extract. In vivo trials confirmed significant disease suppression at the concentration 20%. Preventive application on detached leaves was more effective than curative. UPLC-ESI-MS/MS analysis revealed several major bioactive constituents in the seeds, including oleanolic acid, sinapic acid, oleuropein, and kojic acid. These compounds are known to contribute to membrane destabilization, enzyme inhibition, and the induction of oxidative stress in target pathogens. The seed extract of Melia azedarach demonstrates strong potential as a biofungicide against potato early blight. Its effectiveness appears to arise from a diverse array of bioactive molecules operating through multiple modes of action. Collectively, these results highlight its suitability for incorporation into sustainable potato disease management strategies.