Low concentration of Paecilomyces variotii extracts promote the growth and disease resistance of pepper

Paecilomyces variotii extract “ZhiNengCong” (ZNC) has been confirmed to be a high activity plant immune inducer, but its application effect and appropriate concentration in different crops and different environmental conditions need to be further verified. This study set up six treatments, including three ZNC concentration levels (0, 5, and 20 ng/mL) and two Ralstonia solanacearum (Rs) inoculation levels (with and without), to explore the effect of ZNC application on the growth and disease resistance of peppers. The results showed that ZNC application (particularly 5 ng/mL ZNC) increased the basal biomass of the pepper plant and promoted root growth. 5 ng/mL ZNC can improve photosynthetic performance (net photosynthetic rate, transpiration rate and chlorophyll content averagely increased 20.2%, 33.7% and 16.0%, respectively) and antioxidant enzyme activities (particularly, catalase activity averagely increased 38.9%) of peppers more efficient than 20 ng/mL. Moreover, 5 ng/mL ZNC significantly increased Rs resistance of pepper, while 20 ng/mL ZNC did not show this effect. In conclusion, 5 ng/mL ZNC had the most significant effects on the growth-promoting and disease resistance of peppers, indicating good application prospects in agricultural practice.