title: Fast Sampling, Analyses and Chemometrics for Plant Breeding: Bitter Acids, Xanthohumol and Terpenes in Lupulin Glands of Hops (Humulus lupulus).
abstract: BACKGROUND
  The valuable secondary metabolites in hops (bitter acids, xanthohumol, volatile monoterpenes and sesquiterpenes) are sequestered in lupulin glands (extracellular trichomes) which can be collected and analysed with little or no sample preparation.
  
  
  OBJECTIVE
  To determine whether high throughput screening of lupulin glands composition, by fast analyses and chemometrics, could be used for breeder selection of hops with key flavour attributes.
  
  
  METHODS
  Lupulin glands from 139 plants (39 cultivars/advanced selections) were analysed by Raman and1H NMR spectroscopy, and head-space solid-phase microextraction (HS-SPME) GC-FID. The digital X,Y-data were subjected to principal component analysis (PCA) and the results compared with conventional analyses of extracts of whole hops from the same plants. Quantitative1H NMR analyses were also done for the bitter acids.
  
  
  RESULTS
  Raman spectroscopy rapidly identified hops cultivars with high xanthohumol concentrations and high α:β bitter acid ratios.1H NMR spectroscopy was slower, requiring a solvent extraction, but distinguished cultivars by cohumulone content as well as α:β acid ratios. HS-SPME-GC rapidly distinguished aroma hops with high myrcene and farnesene contents, and pinpointed a novel selection with unusual sesquiterpenes. The quantitative NMR analyses showed correlations between bitter acid concentrations related to biosynthetic pathways.
  
  
  CONCLUSIONS
  Analysis of lupulin glands gave reliable results for the main quality indicators used by hops breeders, potentially avoiding harvesting, drying and solvent extracting whole hops. PCA of digital X,Y-data rapidly discriminated different hops chemotypes, and highlighted plants with potential for new flavourcultivars. Copyright © 2016 John Wiley & Sons, Ltd.
authors.affiliation: Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand.
authors.forename: Daniel P
authors.initials: DP
authors.lastname: Killeen
authors.affiliation: Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand.
authors.forename: Oliver C
authors.initials: OC
authors.lastname: Watkins
authors.affiliation: The New Zealand Institute for Plant & Food Research Limited, Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand.
authors.forename: Catherine E
authors.initials: CE
authors.lastname: Sansom
authors.affiliation: The New Zealand Institute for Plant & Food Research Limited, 55 Old Mill, RD 3, Motueka, 7198, New Zealand.
authors.forename: David H
authors.initials: DH
authors.lastname: Andersen
authors.affiliation: Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand.|Dodd-Walls Centre, University of Otago, Dunedin, New Zealand.
authors.forename: Keith C
authors.initials: KC
authors.lastname: Gordon
authors.affiliation: Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand.|The New Zealand Institute for Plant & Food Research Limited, Department of Chemistry, University of Otago, P.O. Box 56, Dunedin, New Zealand.
authors.forename: Nigel B
authors.initials: NB
authors.lastname: Perry
mesh_terms: D000143:Acids / Q000032:analysis*; D005419:Flavonoids / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry; D027582:Humulus / Q000737:chemistry* / Q000502:physiology; D000069600:Plant Breeding; D010936:Plant Extracts / Q000737:chemistry; D011427:Propiophenones / Q000032:analysis*; D066244:Proton Magnetic Resonance Spectroscopy; D013059:Spectrum Analysis, Raman; D013729:Terpenes / Q000032:analysis*
chemical_list: D000143:Acids; D005419:Flavonoids; D010936:Plant Extracts; D011427:Propiophenones; D013729:Terpenes; C104536:xanthohumol
keywords: GC; HS-SPME; Hops; Humulus lupulus; NMR; Raman; breeding; lupulin glands