The Effects of Propagation Techniques on Cell Wall Chemistry and Wood Anatomy in Micropropagated and Grafted Plants of the Dutch Elm Hybrid ‘Dodoens’

Determination of wood anatomy traits and the chemical attributes of plant cell walls is of great importance for the evaluation of both the effects of hybridization and the results of breeding strategies within the genus Ulmus , because these are both aimed at an enhanced tolerance to dutch elm disease (caused by Ophiostoma ulmi and O . novo-ulmi ) and to the improvement of trees having desired mechanical properties. The objective of this study was to determine whether the routinely applied vegetative propagation techniques of in vitro micropropagation or grafting would result in any change to lignin monomer composition and content, macromolecular traits of cellulose, neutral sugar composition, or the vascular and fiber anatomy traits in the stems of the dutch elm hybrid cultivar Dodoens (i.e., open-pollinated Ulmus glabra ‘Exoniensis’ × U . wallichiana P39). Propagation techniques appeared to have no direct effect on lignin monomer composition. The differences in the relative proportion of guaiacyl units in lignin between the stock types were not significant, showing that no advantage could be attributed to either stock type toward an enhanced tolerance to dutch elm disease. The micropropagated plants reached significantly higher values for 13 traits (32.5%), primarily associated with the relative proportion of d -glucose and the macromolecular traits of cellulose to compensate for a lower content of holocellulose. The grafts reached higher values for 10 traits (25%), including the relative proportions of d -xylose, d -mannose, and d -galactose. The effect of the rootstock might contribute to different amounts of these cell wall substances in the grafts. The grafts also reached a higher lignin content, which may provide minor advantages in terms of mechanical and physical properties to the cell walls of this stock type. Similarities between the stock types were found for 17 traits (42.5%). Both stock types formed compact homogeneous clusters clearly separated from each other in the multivariate wood trait analysis.