Antagonistic Actinomycete XN-1 from Phyllosphere Microorganisms of Cucumber to Control Corynespora cassiicola

Strain XN-1 isolated from the cucumber phyllosphere was tested for potential application as an antagonistic actinomycete against Corynespora cassiicola (Berk.& Curt.)Wei. The fungistatic activity of this strain was determined by inoculation of C. cassiicola on PDA plates, spore germination inhibition in culture filtrate and control tests on cucumber leaves. The spore germination and hyphal growth inhibition rate of the XN-1 fermentation filtrate against C. cassiicola can reach 96.50% and 51.17%, respectively, as well as the 63.54% of control effect on cucumber leaves. The stability of XN-1 fermentation filtrates was studied under the treatment of pH gradient, temperature gradient, and exposure to UV. The results showed the filtrates remained relatively stable in the range of those gradients. This experiment indicates that this exogenous actinomycete XN-1 has the potential to act as an antagonistic agent in controlling the occurrence and development of cucumber target leaf spot in the greenhouse. This also confirms that phyllosphere microorganisms play an important role in combating the infection of pathogens and have a promising future in developing the biocontrol products and methods.