Use of X-ray microdensitometry for assessing the resistance to fungus C. puteana of a hybrid larches population

The aim of this research was to utilize the X-ray microdensitometry to determine the natural durability and its variability of a hybrid larch population. The method was applied on slices obtained by increment cores collected on standing trees before cutting them down. The methodology was discussed also in order to propose as a new screening method especially suited for trees populations. X-ray microdensitometry proved to be really interesting for screening purposes but showed, in presence of severe decay, high density due to collapsed cell walls during the conditioning at 65% RH and 20°C. Unfortunately, the X-ray microdensitometry could not able to distinguish, by the means of resistance to Coniophora puteana, the inter-trees variability within the larch population after 8 weeks of contact with fungus. This difficulty was due to severe decay and consequent collapse of wood cells that determined an increase of density. A further development could be the reduction of the exposure time to the fungus in order to limit the decay but still to allow the expression of within-population variability for natural durability.