New Insights into Dutch Elm Disease: Cell Wall Compositional, Ecophysiological, Vascular and Nanomechanical Assessments JAROSLAV  ÏURKOVIÈ 1* , FRANTIÐEK KAÈÍ K 2 , MIROSLAVA MAMOÒOVÁ 3 , RASTISLAV LAGAÒA 3 , INGRID ÈAÒOVÁ 1 , JOSEF URBAN 4,5 AND JANA KRAJÒÁKOVÁ 6 1 Department of Phytology, Technical University in Zvolen, 96053 Zvolen, Slovakia 2 Department of Chemistry and Chemical Technologies, Technical University in Zvolen, 96053 Zvolen, Slovakia 3 Department of Wood Science, Technical University in Zvolen, 96053 Zvolen, Slovakia 4 Department of Forest Botany, Dendrology and Geobiocoenology, Mendel University in Brno, 61300 Brno, Czech Republic 5 Siberian Federal University, 660041, Krasnoyarsk, Russia 6 Scion, 49 Sala Street, Rotorua 3046, New Zealand * Corresponding author, e-mail: jaroslav.durkovic@tuzvo.sk Ïurkoviè, J., Kaèík, F., Mamo òová, M., Lagaòa, R., Èaòová, I., Urban, J. and Kraj òáková, J. 2019. New Insights into Dutch Elm Disease: Cell Wall Compositional, Ecophysiological, Vascular and Nanomechanical Assessments. Baltic Forestry 25(1): 1014. Abstract Comprehensive assessments were made of the chemical profiles of woody cell wall components, and leaf growth, ecophysiological, vascular and nanomechanical traits for two Dutch elm hybrids Groeneveld and Dodoens which possess contrasting tolerances toward Dutch elm disease. Upon infection with Ophiostoma novo-ulmi ssp. americana × novo-ulmi, medium-molecular weight macromol- ecules of cellulose were degraded in both hybrids. A loss of crystalline and non-crystalline cellulose regions occurred in parallel. In Groeneveld plants, syringyl-rich lignin provided a far greater degree of protection from cellulose degradation, but only guaiacyl-rich lignin in Dodoens plants was involved in a successful defence against the fungus. Unexpectedly, we found a very high proportion of non-significant differences between the infected and non-infected plants of Dodoens, including similarities in leaf growth, leaf gas exchange and leaf midrib vascular traits, as well as in the nanomechanical properties of the cell walls of tracheary elements such as modulus of elasticity, adhesion and energy dissipation. Three years after initial inoculations, except for a few traits such as leaf slenderness, relative chlorophyll content, transpiration rate and sap flow density in branches, we found no evidence of a decrease in leaf trait performances among the infected plants of Dodoens, despite the occasional persistence of fungal hyphae in the lumens of leaf midrib tracheary elements. Keywords: cellulose degradation, nuclear magnetic resonance, modulus of elasticity, Ophiostoma novo-ulmi, syringyl to guaiacyl ratio in lignin, transpiration Introduction Fungal metabolites and Dutch elm disease The pathogenic Ophiostoma novo-ulmi isolates spread within the secondary xylem vessels of infected trees, causing the formation of vessel plugs due to ty- loses and gels (Ouellette et al. 2004), which ultimately results in foliar wilting and subsequent tree death (Newbanks et al. 1983). This wilt syndrome is apparently a result of interactions between fungal metabolites and the tree (Scheffer et al. 1987). The fungus produces hydrophobin cerato-ulmin (Temple et al. 1997), a phyto- toxic peptidorhamnomannan (Strobel et al. 1978, Sticklen et al. 1991), tissue-invading structures which are thought to be involved in cavitation of the water column and al- teration of parenchyma cells (Ouellette et al. 2004), and cell wall degrading enzymes such as glucanases, glucosidases (Przybyù et al. 2006), xylanases, laccases (Binz and Canevascini 1996a,b), exo-glycanases and glycosidases (Svaldi and Elgersma 1982). Several ana- tomical parameters of wood have been found to be re- lated to Dutch elm disease (DED) resistance, and their possible use in early screening has been outlined. ISSN 2029-9230 10 2019, Vol. 25, No. 1 (49) J. ÏURKOVIÈ ET AL. BALTIC FORESTRY NEW INSIGHTS INTO DUTCH ELM DISEASE /.../