Bioefficacy of Cymbopogon citratus in controlling grey blight disease in tea (Camellia sinensis) caused by Pestalotiopsis microspora

Abstract

Tea, a perennial shrub, is severely impacted by various biotic and abiotic stresses, among which grey blight, caused by Pestalotiopsis microspora, plays a major role in significant crop loss. In this study, out of 15 locally available plants, the ethyl acetate extracts of Cymbopogon citratus and Piper nigrum were scrutinised. The in vitro bioassay revealed that C. citratus at 5 mL/L and 10 mL/L completely inhibited P. microspora under the food poisoning technique. The minimum inhibitory concentration (MIC) of C. citratus extract was found to be 2 mg/mL. The GC-MS analysis confirmed the presence of 1-Iodo-2-methylundecane, Silane, trichlorooctadecyl-, and 1,3-Benzenedicarboxylic acid, bis(2-ethylhexyl) ester at higher levels, with saturated hydrocarbons as the most abundant class (48 %). The Elongation Factor 1-alpha (EF1) of Pseudopestalotiopsis theae was taken as the target protein, and a 3D model was built and validated with an active site containing 98 amino acid residues. The molecular docking results highlighted the compound 2,6-Dimethyl-6-trifluoroacetoxyoctane, having a binding affinity of −5.8 kcal/mol, compared to Carbendazim with −6.5 kcal/mol. Under visualisation, the ligands of 2,6-Dimethyl-6-trifluoroacetoxyoctane formed conventional hydrogen bonds at ILE60, CYS80, and ILE83, aiding in the interaction and stability of the ligand-protein complex. Finally, C. citratus established a satisfactory control of 61 % against grey blight disease, which was on par with the organic recommended schedule under field conditions. This study suggests a sustainable and environmental-friendly control measure by reducing synthetic chemical inputs through an integrated disease management (IDM) strategy.