Nectriaceae Species Associated with Root Rot of Nursery and Young Trees in Uruguay with as Novel Species.

Forestry constitutes an important agronomical activity in Uruguay, involving the cultivation of exotic trees mainly for cellulose pulp production with species Over the last decade, emerged as a species of interest for cellulose pulping. However, its rapid expansion has coincided with high mortality rates among young trees ranging from 5 to 85%, especially during the first and second summer after plantation. Disease surveys conducted on nine commercial fields and three nurseries in southern and eastern Uruguay yielded a collection of 25 isolates from root rot belonging to the Nectriaceae family. In this study, we aimed to identify and characterize these isolates employing phenotypical and molecular studies and to assess their pathogenicity on seedlings. Based on morphological features, the Nectriaceae isolates were subdivided into two groups, one resembling ( = 15) and the other -like ( = 10). DNA sequences of the partial histone H3 (), actin, calmodulin, RNA polymerase II second largest subunit, translation elongation factor 1-alpha (), and β-tubulin () genes were amplified for , as well as partial , , , and internal-transcribed spacer and intervening 5.8S () gene regions for the -like group. Based on phylogenetic analysis and phenotypical features, three species were identified and characterized: ( = 15), ( = 2), and a novel taxon which we describe here as sp. nov. ( = 8). The pathogenicity trials revealed that isolates from the three species significantly reduced both shoot and root dry weights of inoculated seedlings compared with control plants.