Colletotrichum lindemuthianum, causal agent of bean anthracnose is one of the most destructive fungal bean diseases that potentially have an enormous economic impact on bean cultivation worldwide. To obtain novel insights into how bean regulates its defense pathways to react efficiently against this invading pathogen, cvs Khomein and Naz representing contrasting interactions were investigated by histochemical and real-time quantitative RT-PCR (RT-qPCR) approaches. Our histochemical analysis conducted at 24, 48, 72 and 96 h post inoculation (hpi) demonstrated that hydrogen peroxide (H2O2) may have a bifunctional role in establishing the incompatibility and compatibility. This free radical (H2O2) can, therefore, be elevated at an early stage (24 hpi) of the incompatible context to arrest fungal growth, whereas H2O2 was promoted at the late stage (72 hpi) of the compatible context to facilitate the infection process. Additionally, we demonstrated that O2− probably plays an essential function in launching the resistance response since O2− increased significantly at 36 hpi in incompatible interaction compared with that of the compatible interface. Our expression analysis showed that the expression of six defense-related genes are differentially regulated regarding the types of interactions, shedding light on how the beans adaptively regulate defense pathways. This study contributes to a better understanding of the kinetics of reactions triggered following C. lindemuthianum infection and may be applied to develop novel strategies to manage bean anthracnose effectively.
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