Prospección de especies de Calonectria en viveros forestales de Uruguay

Over the past three decades, the forestry sector in Uruguay has experienced a significant growth, consolidating itself as the second largest agricultural export sector, with Eucalyptus being the most planted genus in the country. Nursery production is the first stage of the forestry sector, where plant production is exposed to various pathogens attacks. Species from the genus Calonectria cause diseases in nurseries such as damping-off, root rot, leaf spot, and stem canker, leading to significant economic losses. The aim of this study was to survey and identify Calonectria species present in Eucalyptus nurseries in the northern and central eastern regions of the country, based on molecular and morphological characterization techniques. Visits were made to three nurseries and a total of 123 samples were collected, including symptomatic Eucalyptus spp. seedlings, soil beneath benches, irrigation water, first-use substrate, and sand tray, covering all nursery stages. The pathogen was found in 11% of the samples, yielding resulting in a collection of 17 isolates being that were molecularly identified, together with 15 additional Calonectria strains previously isolated from other study, using the elongation factor and beta-tubulin gene regions. Based on the phylogenetic analysis, 24 isolates belong to the Calonectria candelabrum complex, and eight belong to Ca. cylindrospora complex. Within the former, all isolates were identified as Ca. pauciramosa, while the isolates from the latter are grouped into two clades (five and three), different from each other and from other known Calonectria species. This suggests that these could be new, undescribed species. Complementary, the morphological characterization revealed considerable diversity among Ca. pauciramosa isolates, whose structures matched descriptions reported in the literature. These findings are an important precedent for the phytosanitary status of the country´s forestry complex.