Abstract Bacterial pustule disease, incited by Xanthomonas citri pv. glycines ( Xcg ), represents a significant phytopathological constraint limiting soybean productivity across major cultivation zones in India, with epidemiological reports documenting moderate-to-severe disease intensities causing considerable yield losses. The present study evaluated the in vitro antibacterial efficacy and in vivo prophylactic potential of Moringa oleifera Lam. extracts against Xcg under controlled conditions. Key physiological and biochemical parameters, including leaf number per plant, soluble protein, total soluble carbohydrate, and photosynthetic pigment content, were quantitatively assessed to determine host plant responses to pathogen challenge and extract treatment. In vitro bioassay results demonstrated that seed extract at 500 µg/mL elicited the most pronounced antibacterial activity, producing a zone of inhibition of 18.86 mm. Under greenhouse pot trial conditions, seed extract treatment significantly enhanced plant height, carbohydrate, chlorophyll, and carotenoid accumulation relative to inoculated controls. Soluble protein and carbohydrate concentrations exhibited a concentration-dependent decline at elevated extract doses, a trend similarly observed with the reference antibiotic streptomycin, suggesting potential phytotoxic effects at supraoptimal concentrations. At the highest evaluated concentration, seed extract formulation SE5 significantly reduced disease severity (DS) to 20.34% and achieved a percentage efficacy of disease control (PEDC) of 75.46%. Furthermore, the bioactive phenolic compound cinnamic acid, identified as a principal constituent of the seed extract, demonstrated a comparable zone of inhibition of 18.95 mm against Xcg , substantiating the mechanistic role of hydroxycinnamic acid-class phenolics in pathogen suppression. Collectively, these findings establish the phytotherapeutic potential of M. oleifera seed extracts and cinnamic acid as promising biopesticidal agents, warranting validation through large-scale field experimentation and integration into sustainable soybean crop protection and management strategies.
Khan et al. (Fri,) studied this question.