European Journal of Sustainable Agroecosystems

Background: Fusarium wilt caused by Fusarium oxysporum f. sp. capsici is a major disease limiting sustainable pepper (Capsicum annuum L.) production worldwide with yield losses from 30 to 80% in susceptible cultivars. The increasing pathogen resistance to chemical fungicides and environmental concerns have resulted in increased demand for sustainable biological disease management strategies. The indigenous plant growth-promoting rhizobacteria (PGPR) are the promising eco-friendly alternative for disease suppression and crop productivity enhancement.
Objective: The present study aimed to determine efficacy of native PGPR isolates against Fusarium wilt, soil biological health and growth, physiological performance and yield of pepper under greenhouse and field conditions.
Methods: A two-year investigation was carried out under semi-controlled greenhouse conditions followed by validation under open field conditions. Nine treatment combinations of four indigenous PGPR strains (Bacillus subtilis, Pseudomonas fluorescens, Streptomyces lividans and Bacillus megaterium) and their consortium were evaluated against Fusarium oxysporum challenge inoculation applied 30 days after transplanting. The incidence and severity of disease, plant growth, fruit yield, activities of antioxidant enzymes (POD, PPO, CAT and SOD), total phenolic content, carbon of rhizosphere microbial biomass, activities of soil enzymes (dehydrogenase, phosphatase and arylsulfatase), indices of microbial diversity and dynamics of PGPR populations through quantitative polymerase chain reaction were assessed.
Results: The PGPR consortium showed the highest disease suppression, reducing the disease incidence by 74.2% and disease severity by 68.5% than pathogen-inoculated control. PGPR application increased plant height by 45–52% and fruit yield by 38–41% in the study. There were significant improvements in the antioxidant defense enzymes and total phenolic content which suggest enhanced induced resistance. Rhizosphere microbial biomass carbon increased by 42% with significant increases in the activity of dehydrogenase, phosphatase and arylsulfatase, suggesting the improvement of soil biological activity. Successful colonization and persistence of the introduced PGPR strains in the rhizosphere was confirmed by quantitative polymerase chain reaction. The sustainability indicators of the soil, such as the microbial quotient and metabolic diversity indices also showed significant improvement under PGPR treatments.
Conclusion: Native PGPR especially in consortia have shown to be effective against Fusarium wilt and at the same time have improved soil biological health, plant response to pathogens, and yield of pepper. The combined effects of the utilization of PGPR for pathogen control, improving rhizosphere performance, and enhancing crop productivity reveal their utilization in PGPR bioinoculants as sustainable alternatives to chemical fungicides. This study proves the advantages of native PGPR for being an eco-friendly component of integrated pest management system and sustainable production of pepper, especially in tropical and subtropical regions.