In planta validation of nitric oxide mediated defense responses in common bean against Colletotrichum gloeosporioides infection

摘要

Our present study demonstrates an in planta approach of defense responses in bean plants against the devastating pathogen Colletotrichum gloeosporioides (Penz.) Penz. and Sacc. Recent evidences suggest the function of nitric oxide (NO) as a strong signaling molecule in many plant pathogen interactions. Standing at this point, the effect of NO durability in activation plant defense is poorly understood. Progression and establishment of the pathogen in the host has been confirmed by bright field and scanning electron microscopy. Biochemical studies indicated that during the pathogenesis, the NO content induced up to 12 days after pathogen inoculation, then gradually declined. Induction in NO content was positively correlated with different defense related enzyme activities and antimicrobial compounds like, total phenol and total flavonoid content. Chlorophyll content was also reduced as the pathogen progressed gradually. Lipid peroxidation and proline content are important stress-related markers were thus also estimated. Cell death was also found to increase with disease progression. Overall study suggests that during early stages of pathogen progression NO produce rapidly to intensify host defense but when virulent pathogen well established in the host cell NO production hampers significantly and as a consequence host defense mechanism also become down-regulated. So, durability and maintenance of NO level is one of the key factors of host resistance against pathogen.