Bacillus megaterium JPR68 modulates soil nitrogen uptake and suppress collar rot in Bhut Jolokia by triggering systemic resistance

Background and aims: Bhut Jolokia cultivation is constrained by collar rot and fungal diseases, and the role of PGPR in enhancing nitrogen uptake remains unclear. This study investigated the effects of Bacillus megaterium JPR68 on plant growth, oxidative stress regulation, and metabolism, and examined PR gene expression and nitrogen assimilation under Rhizoctonia solani stress, along with its impact on yield and soil health. Methods The study combined in vitro and in vivo (pot and field) experiments to assess BmJPR68 in Bhut Jolokia. In vitro assays evaluated seed dormancy, germination, and vigor, while greenhouse and field trials measured growth and yield. ROS localization, antioxidant enzymes, PR gene expression, and nitrogen assimilation were analyzed under pathogen stress. Fruit bioactives, capsaicinoids, fatty acids, nutrient content, total NPK uptake, and soil nutrients were quantified. Results Bacillus megaterium JPR68 (BmJPR68) associated with enhanced nitrogen assimilation in Bhut Jolokia by modulating internal signaling and transport systems, improving plant architecture and fruit yield. Treated plants showed upregulation of NR, NiR, NRT1.1, NRT1.2, NRT2.1, NRT2.2 , and GSH genes. GC-MS identified thirteen fatty metabolites, while improved nitrogen assimilation and collar rot resistance contributed to higher productivity. Conclusions The findings indicate that pre-treatment of Bhut Jolokia plants with BmJPR68 significantly enhances chili yield and capsaicin accumulation. Field trials validated these results, demonstrating improved plant growth, higher yield attributes, and elevated soil macro- and micronutrients. This study provides an effective and sustainable strategy for managing collar rot disease without relying on chemical fertilizers, while maintaining productivity through optimized plant architecture.