Abstract

PATHOGENICITY REDUCTION OF RHIZOCTONIA BY PHYLLOSPHERE MODIFICATION OF ADHATODA VASICA LEAVES

Debojit Saha*, Rishika Chakraborty, Arpan Majumdar, Joyce D. John and Kasturi Biswas, Arup Kumar Mitra

Abstract

Adhatoda vasica is an important medicinal plant, commonly found in Asia. The plant contains a quinazoline alkaloid, Vasicine in all its parts. The Adhatoda vasica leaves that were collected from a garden near Hari Singh Marg (Jammu) had lesions which were yellow and irregular in nature. Inoculation of the infected parts of the leaves on Potato Dextrose Agar slants, followed by incubation, produced profuse black mycelial growth. The fungus causing the infection was identified to be Rhizoctonia spp on the basis of spore morphology. Inductive coupled plasma mass spectroscopic analysis reported the presence of Lead while Cadmium was found in negligible amount. In-vivo test applying Koch’s postulates was performed which showed that percentage germination of the spore had decreased in presence of lead (88.89%) and fungicide Carbendazim (94.4%). The in-vitro slide bio assay test substantiated the above result. Both Lead (10ppm) and Carbendazim (1500ppm) was found to reduce the fungal biomass by 45.29% and 99.4% respectively. On performing HPLC and Vasicine spectral assay with fresh and infected leaves, it was found that Vasicine content had reduced by a substantial amount (60%) in the infected leaf. Hence, Rhizoctonia leaf spot constitutes a potential threat to this important medicinal plant. An increase in metal concentration resulted in a decrease in fungal biomass, elucidating the possible use of metal stress as a controlling agent against the infection. As the vasicine content is greatly reduced in infected Adhatoda vasica leaves, its medicinal value is affected. This can simply be controlled by Carbendazim spray and Lead salt dusting.

Keywords: Rhizoctonia spp, Adhatoda vasica, lead ,Carbendazim, Koch’s postulates, Vasicine.