title: Leaf trait dissimilarities between Dutch elm hybrids with a contrasting tolerance to Dutch elm disease.
abstract: OBJECTIVE
  Previous studies have shown that Ophiostoma novo-ulmi, the causative agent of Dutch elm disease (DED), is able to colonize remote areas in infected plants of Ulmus such as the leaf midrib and secondary veins. The objective of this study was to compare the performances in leaf traits between two Dutch elm hybrids 'Groeneveld' and 'Dodoens' which possess a contrasting tolerance to DED. Trait linkages were also tested with leaf mass per area (LMA) and with the reduced Young's modulus of elasticity (MOE) as a result of structural, developmental or functional linkages.
  
  
  METHODS
  Measurements and comparisons were made of leaf growth traits, primary xylem density components, gas exchange variables and chlorophyll a fluorescence yields between mature plants of 'Groeneveld' and 'Dodoens' grown under field conditions. A recently developed atomic force microscopy technique, PeakForce quantitative nanomechanical mapping, was used to reveal nanomechanical properties of the cell walls of tracheary elements such as MOE, adhesion and dissipation.
  
  
  RESULTS
  'Dodoens' had significantly higher values for LMA, leaf tissue thickness variables, tracheary element lumen area (A), relative hydraulic conductivity (RC), gas exchange variables and chlorophyll a fluorescence yields. 'Groeneveld' had stiffer cell walls of tracheary elements, and higher values for water-use efficiency and leaf water potential. Leaves with a large carbon and nutrient investment in LMA tended to have a greater leaf thickness and a higher net photosynthetic rate, but LMA was independent of RC. Significant linkages were also found between the MOE and some vascular traits such as RC, A and the number of tracheary elements per unit area.
  
  
  CONCLUSIONS
  Strong dissimilarities in leaf trait performances were observed between the examined Dutch elm hybrids. Both hybrids were clearly separated from each other in the multivariate leaf trait space. Leaf growth, vascular and gas exchange traits in the infected plants of 'Dodoens' were unaffected by the DED fungus. 'Dodoens' proved to be a valuable elm germplasm for further breeding strategies.
authors.affiliation: Department of Phytology, Technical University, Zvolen, Slovakia. jaroslav.durkovic@tuzvo.sk
authors.forename: Jaroslav
authors.initials: J
authors.lastname: Durkovic
authors.forename: Ingrid
authors.initials: I
authors.lastname: Canová
authors.forename: Rastislav
authors.initials: R
authors.lastname: Lagana
authors.forename: Veronika
authors.initials: V
authors.lastname: Kucerová
authors.forename: Michal
authors.initials: M
authors.lastname: Moravcík
authors.forename: Tibor
authors.initials: T
authors.lastname: Priwitzer
authors.forename: Josef
authors.initials: J
authors.lastname: Urban
authors.forename: Milon
authors.initials: M
authors.lastname: Dvorák
authors.forename: Jana
authors.initials: J
authors.lastname: Krajnáková
mesh_terms: D002678:Chimera; D002734:Chlorophyll / Q000378:metabolism; D000077194:Chlorophyll A; D060467:Disease Resistance; D005470:Fluorometry / Q000379:methods; D018625:Microscopy, Atomic Force; D008855:Microscopy, Electron, Scanning; D055156:Ophiostoma / Q000502:physiology*; D010788:Photosynthesis / Q000502:physiology; D010935:Plant Diseases / Q000276:immunology / Q000382:microbiology*; D018515:Plant Leaves / Q000254:growth & development / Q000276:immunology* / Q000382:microbiology / Q000502:physiology; D018526:Plant Transpiration / Q000502:physiology; D014197:Trees; D034403:Ulmus / Q000254:growth & development / Q000276:immunology* / Q000382:microbiology / Q000502:physiology; D014934:Wood / Q000254:growth & development / Q000276:immunology / Q000382:microbiology / Q000502:physiology; D052584:Xylem / Q000254:growth & development / Q000276:immunology / Q000382:microbiology / Q000502:physiology
chemical_list: D002734:Chlorophyll; D000077194:Chlorophyll A