Biotic Stress Response of Local Host on Cassava Mosaic Virus and its Control with selected Essential Oils: An Experimental Approach

Abstract

Aim: The present investigation was done to study the antiviral property of essential oils collected from Cymbopogon flexuosus, Ocimum tenuiflorum, and Piper nigrum on the local lesion host Gomphrena globosa, which was mechanically infected with Cassava Mosaic Virus (CMV).Materials and Methods: Isolation of essential oils from the aerial parts of Cymbopogon flexuosus, Ocimum tenuiflorum, and Piper nigrum was done using GC/MS analysis. The pathogenicity assay was done with the viral inoculum prepared from Manihot esculenta leaves and was applied to the local host, Gomphrena globosa, at varying concentrations (100-500 ppm). Further, different biochemical assays, like estimation of photosynthetic pigments, flavonoid, proline, MDA, and aldehyde, were conducted to find out the biotic response of the local lesion host.Results: It was observed that concentrated viral inoculum (CMV-C) was effective in infecting the local lesion host. The local lesion host plant showed many morphological changes, like the presence of local necrotic lesions, yellowing of leaves, and early defoliation of leaves. The yield of the essential oils was 1.4% from C. flexuosus, 0.8% from O. tenuiflorum, and 0.6% from P. nigrum dried samples. The most effective oil in reducing the local lesion number was the oil isolated from C. flexuosus (97.2%), followed by O. tenuiflorum (94.4%) and P. nigrum (91.6%). Probit analysis data revealed that the LC50 value was minimum (133.116 ppm) in C. flexuosus oil, whereas it was maximum (172 ppm) in P. nigrum oil. From the result, it was observed that the inhibitory effect of the essential oil was dose-dependent. The dominant component (>60%) present in O. tenuiflorum and P. nigrum oil was sesquiterpenes. From the three essential oils tested, C. flexuosus oil showed high inhibition activity.Conclusion: Thus, it could be concluded that the essential oils from the tested plants can be used to control CMV infection in a controlled condition.

Keywords: Biotic stress; Cassava mosaic virus; Essential oils; Pathogenicity