Integrating Self-Endophytic Bio-Inoculant to Enhance Roselle Productivity Under Reduced Chemical Fertilization in Aswan, Egypt

Roselle (Hibiscus sabdariffa L.) is a valuable medicinal and economic crop widely cultivated in Egypt, with Aswan contributing 53% of the total area. On the other hand, sustainable agriculture increasingly relies on plant-microbe interactions, particularly endophytic microorganisms. This study investigated the potential of self-endophytic microbiomes as a bioformulation to reduce dependence on chemical fertilizers while enhancing roselle growth and productivity. A field experiment was conducted using different NPK fertilizer levels combined with a mixed self-endophytic inoculum. Results showed that replacing 25% of NPK with bio-inoculation significantly increased fruit number and shoot biomass by 25% and 15%, respectively. Also, using 75% NPK plus bio-inoculation improved seed weight and dry calyx yield by 35% and 16%, respectively, compared to full NPK. Additionally, this treatment enhanced chlorophyll a and b content by 15% and 23%. The highest carotenoid content was observed with 25% NPK plus bio-inoculant with 21% increase. These findings confirm that endophytic bacteria can colonize roselle tissues without causing harm, improve nutrient uptake, and boost productivity. This eco-friendly approach represents a promising strategy for sustainable roselle cultivation, reducing chemical input while maintaining high yields and supporting environmental health.