GC-MS Analysis of Headspace and Liquid Extracts for Metabolomic Differentiation of Citrus Huanglongbing and Zinc Deficiency in Leaves of 'Valencia' Sweet Orange from Commercial Groves

• Published in: Phytochemical analysis 2011-05, Vol.22 (3), p.236-246
• Main Authors: Cevallos-Cevallos, Juan Manuel, García-Torres, Rosalía, Etxeberria, Edgardo, Reyes-De-Corcuera, José Ignacio
• Format: Article
• Language: English
• Subjects: biomarker; Biomarkers; citrus; Citrus - chemistry; Citrus - metabolism; Citrus - microbiology; Gas Chromatography-Mass Spectrometry - methods; GC-MS; Huanglongbing; metabolomics; Metabolomics - methods; Plant Diseases - classification; Plant Diseases - microbiology; Plant Extracts - chemistry; Plant Leaves - chemistry; Plant Leaves - metabolism; Plant Leaves - microbiology; Principal Component Analysis; Solid Phase Microextraction - methods; Zinc - metabolism; zinc deficiency
• ISSN: 0958-0344; 1099-1565
• DOI: 10.1002/pca.1271

Introduction – Citrus Huanglongbing (HLB) is considered the most destructive citrus disease worldwide. Symptoms‐based detection of HLB is difficult due to similarities with zinc deficiency. Objective – To find metabolic differences between leaves from HLB‐infected, zinc‐deficient, and healthy ‘Valencia’ orange trees by using GC‐MS based metabolomics. Methodology – Analysis based on GC‐MS methods for untargeted metabolite analysis of citrus leaves was developed and optimized. Sample extracts from healthy, zinc deficient, or HLB‐infected sweet orange leaves were submitted to headspace solid phase micro‐extraction (SPME) and derivatization treatments prior to GC‐MS analysis. Results – Principal components analysis achieved correct classification of all the derivatized liquid extracts. Analysis of variance revealed 6 possible biomarkers for HLB, of which 5 were identified as proline, β‐elemene, (‐)trans‐ caryophyllene, and α‐humulene. Significant (P < 0.05) differences in oxo‐butanedioic acid, arabitol, and neo‐inositol were exclusively detected in samples from plants with zinc deficiency. Levels of isocaryophyllen, α‐selinene, β‐selinene, and fructose were significantly (P < 0.05) different in healthy leaves only. Conclusion – Results suggest the potential of using identified HLB biomarkers for rapid differentiation of HLB from zinc deficiency. Copyright © 2010 John Wiley & Sons, Ltd.