Evaluation of imide substance from Streptomyces atratus PY-1 for the biocontrol of Phytophthora blight

Phytophthora blight is one of the most serious diseases of pepper production and causes serious losses of yields and even complete harvest failures. Pepper growers are heavily dependent on fungicides, but there are concerns about the risks they pose to farm workers, consumers, non-target organisms and the environment. There are also problems with the development of strains resistant to fungicides. The objective of this study was to evaluate Streptomyces atratus PY-1 as a biocontrol agent to manage diseases caused by Phytophthora capsici . Strain PY-1 inhibited the growth of P. capsici mycelia on agar plates. The main active component of strain PY-1 was imide substance, and the concentration of imide substance in strain PY-1 fermentation liquor was 2.64 mg/mL. Simultaneously, the imide substance in fermentation liquor can cause the mycelia to rupture, become deformed and lose the ability to infect plants. These compounds strongly inhibited the activity of P. capsici in pots. The ability of imide substance to control pepper blight was 95.44% after dilution by 500, which was similar to that of 2,000-fold dilution of 50% Dimethorpho WP. The imide substance still inhibited the oomycete by 62.93% when diluted 5,000-fold, and there was no significant difference among the three repeated tests. Therefore, it could be used as a potential agent to control pepper blight.