Propolis and Lentinula edodes extracts can control the angular leaf spot of strawberry by different mechanisms

Strawberry leaf spot caused by Xanthomonas fragariae is one of the main limiting diseases of crops in Brazil, but there are not efficient control strategies. Additionally, the global demand for pesticide-free foods has stimulated research to find low toxicity products to control plant pathogens. Thus, strawberry plants were sprayed with Lentinula edodes polysaccharides (PSHII), propolis extracts (GP1), acibenzolar-s-methyl (ASM) or distilled water (control) and inoculated with the bacterium. Leaf samples were collected to determine phenylalanine ammonia lyase (PAL) and superoxide dismutase (SOD) activities. Antimicrobial activity was checked, based on the effect of the products on CFU and bacterial biofilm. In the cv. Albion, the propolis source GP1 reduced the AUDPC by more than 95%, compared to control, when applied 3 days before inoculation, but PSHII did not differ from control. For cv. San Andreas, GP1 significantly reduced the disease only at 7 days after inoculation. PSHII or ASM promoted significant reduction in all evaluations. Only GP1 inhibited the CFU and biofilm formation of the bacterium and promoted increases in PAL and SOD activities, while PSHII and ASM increased SOD activity. The data suggest that such products have potential for use in programs for control of strawberry diseases.