Metabolic fingerprinting to discriminate diseases of stored carrots

Abstract Volatile metabolites from headspace gas of carrot cv. Vita‐treat inoculated with water or four different pathogens Botrytis cinerea , Erwinia carotovora subsp. carotovora , Aspergillus niger and Fusarium avenaceum were profiled using gas chromatography and mass spectrometry to develop a technology to discriminate diseases. The inoculation of carrot roots with water or different pathogens released a total of 137 different volatile metabolites. Among them, 39 compounds were relatively consistent and 11 were specific to one or more diseases/inoculations. E. carotovora subsp. carotovora produced seven disease‐specific metabolites: 1‐butanol, 3‐methyl; 1‐pentanol; 1‐propanol, 2‐methyl; 2,3‐butanedione; boronic acid, ethyl; butane, 1‐methoxy‐3‐methyl; and ethane, ethoxy. Some metabolites were disease/inoculation discriminatory and were not detected in all treatments: 1,2‐dimethoxy‐ethene was common in carrots inoculated with E. carotovora subsp. carotovora and B. cinerea , while 2‐butanone, 3‐chloro‐4‐hydroxy‐1,4‐diphenyl was common in carrots inoculated with E. carotovora subsp. carotovora , F. avenaceum and water‐inoculated control. The significant mass ions, based on univariate analysis, from a total of 150 (46–195 m / z ) and compounds from a total of 32 were further subjected to stepwise discriminant analysis and discriminant analysis. The models for 3 days after inoculation (DAI) were better than those for 6 DAI and 3 + 6 DAI, where up to 90% of the observations were correctly classified into respective inoculations. The disease‐discriminatory compounds from different diseases/inoculations and discriminant analysis models developed here have the potential for the early detection and discrimination of postharvest diseases of carrot cv. Vita‐treat, after validation under commercial conditions.