Fungal Elicitor-Mediated Induction of Innate Immunity in Catharanthus roseus Against Leaf Blight Disease Caused by Alternaria alternata

Catharanthus roseus (L.) G. Don has a broad range of medicinal importance besides its ornamental exterior. In the present work, biotic (fungal) elicitor was prepared from the broth culture of Alternaria alternata (Fr.) Keissl. and applied to detached leaves of one natural variety (rosea) and one synthetic cultivar (Victory red) of C . roseus to induce defense responses. Results showed that fungal elicitor (FE) was able to induce the defense response in both the cases. Defense-related enzymes like peroxidase, polyphenol oxidase, phenylalanine ammonia-lyase, and β-1,3 glucanase showed higher activity along with higher accumulation of total phenol and total flavonoid over the water-treated control sets. The important signaling molecule nitric oxide (NO) was also monitored both biochemically and using fluorescence microscopy. In order to find out the involvement of nitric oxide in this defense responses, different NO modulators were applied to check the defense response in both rosea and victory red. The obtained results showed potential involvement of NO in FE-induced defense responses. We have also checked the efficacy of this elicitor-induced defense responses against Alternaria leaf blight disease in the natural variety and cultivar of C . roseus . The lower amount of disease development and cell death in elicitor treated natural variety and cultivar of C . roseus confirms the protective role of this biotic elicitor against Alternaria leaf blight disease.