Microscopic studies showed that P. chlororaphis strain PA-23 inhibited the germination of S. sclerotiorum ascospores on petals while complete colonization of petals was observed 48 h after application of ascospores alone. Double application of PA-23 on canola plants challenged with the ascospores of S. sclerotiorum triggered increased levels of hydrolytic enzymes including chitinase and β-1,3-glucanase in canola plants. In addition, it also triggered the expression of the pathogenesis-related protein PR3.
Field studies over a period of two years indicated that disease control with PA-23 and BS6 was comparable to that achieved with the fungicide Rovral Flo® (iprodione). There was no significant difference between single- and double-spray application of PA-23 and BS6 in the management of canola stem rot. Results suggest that P. cholororaphis PA-23 and B. amyloliquefaciens BS6 can be used to control Sclerotinia stem rot of canola under field conditions.