Comparative Antifungal Potential of Stem Extracts of Four Quinoa Varieties against Macrophomina phaseolina
Iqra Haider Khan, Arshad Javaid
Abstract
Quinoa (Chenopodium quinoa Willd.) is native to South America and is recently introduced in Pakistan.Previous studies revealed that wild species of Chenopodium from Pakistan hold antifungal potential against a seed-and soil-borne notorious plant pathogen Macrophomina phaseolina.In the present study, quinoa stem was assessed for its antifungal potential against this destructive plant pathogen.Diseased mungbean plants were collected for the procurement of fungal pathogen and methanolic stem extracts (1, 2, 3, 4 and 5%) of four varieties of quinoa were examined in vitro for their antifungal properties.Different extracts showed profound antifungal activity and reduced fungal biomass by 48-89%.Quinoa variety V7 showed the best results against the pathogen and minimized its growth by 80-89%.Methanolic extract of this variety was fractionated with four organic solvents on the basis of increase in their polarities.Eight concentrations ranging from 1.562 to 200 mg mL -1 were used in antifungal bioassays for each fraction.Each concentration of n-hexane and chloroform fraction arrested growth of the pathogen by 100%.Ethyl acetate and n-butanol fractions were proved less antifungal with 66-100% and 52-100% decline in pathogen's biomass, respectively.GC-MS study of n-hexane and chloroform fractions revealed the presence of predominant antifungal compounds viz., 9,12-octadecadien-1-ol, (Z,Z)-(22.23%)followed by 8,11-octadecadienoic acid, methyl ester (16.68%); 1,2-benzedicarboxylic acid, diisooctyl ester (12.48%); and hexadecanoic acid,2-hydroxy-1-(hydroxymethyl) ethyl ester (10.99%).To conclude, n-hexane and chloroform fractions of stem extract of V7 variety of quinoa possess effective antifungal constituents against the pathogen.