What question did this study set out to answer?

This study aims to evaluate the effectiveness of three bacterial endophytes in promoting plant growth and reducing plant disease caused by Phytophthora capsici.

April 25, 2026Open Access

Three Bacterial Endophytes Enhanced Plant Growth and Yield and Reduced the Severity of Phytophthora capsici in Bell Pepper and Tomato Plants in the Field

Key Points

This study aims to evaluate the effectiveness of three bacterial endophytes in promoting plant growth and reducing plant disease caused by Phytophthora capsici.
Field evaluation of three endophytic bacterial isolates: PRT (Bacillus subtilis), PSL (Bacillus amyloliquefaciens), and IMC8 (Bacillus thuringiensis) against Phytophthora capsici.
Comparison with two commercial biological fungicides and a water control.
Data collected on plant growth, disease severity, fruit number, fruit size, total yield, and disease incidence.
PRT showed the best overall performance in plant growth and yield metrics compared to other treatments.
PSL and Double Nickel were most effective in managing disease and promoting growth in tomatoes.
IMC8 resulted in larger fruit size but fewer fruits per plant in both crops.

Abstract

Naturally abundant endophytes colonize plants internally without causing harm to their host plants. Endophytes are likely to occupy the same ecological niches as phytopathogens and thus have a high potential to be effective biological control agents. Their demonstrated ability to suppress more than one plant pathogen suggests that they can offer a viable alternative to chemical fungicides and a strategy for decreasing the inoculum potential of soil-borne pathogens. Some biocontrol endophytes are also known to improve soil health and the overall health of plants. However, the results in greenhouse studies do not always translate to consistent field efficacy. In this study, the efficacy of three endophytic bacterial isolates (PRT (Bacillus subtilis), PSL (Bacillus amyloliquefaciens), and IMC8 (Bacillus thuringiesis) were evaluated against Phytophthora capsici in a field environment and compared with two commercial biological fungicides, Serenade® (Bayer Crop Science, St Louis MO, USA) and Double Nickel® (Certis Biologicals, Columbia, MO, USA), and water control. Plants were inoculated with the bacteria strains using seed treatment for early plant colonization before transplanting to a field infested with P. capsici. Treatments with commercial bio-fungicides followed label recommendations. Data on plant growth vigor, disease severity, number of fruits, fruit size, total yield per plant, and percent of diseased fruits displayed significant differences between the bacteria treatments. While PRT was the best treatment for most traits, followed by PSL on pepper, PSL and Double Nickel were the best treatments on tomatoes. IMC8 was best for plant vigor and larger fruit size, but with fewer fruits per plant on both crops. This study suggests bacterial isolates PRT, PSL, and IMC8 can provide additional products for growth promotion and P. capsici disease management in pepper and tomatoes.

Three Bacterial Endophytes Enhanced Plant Growth and Yield and Reduced the Severity of Phytophthora capsici in Bell Pepper and Tomato Plants in the Field

Key Points

Abstract

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