Abstract
Lecanosticta acicola causes the disease known as brown spot needle blight (BSNB), on Pinus species. The pathogen is thought to have a Central American centre of origin. This was based on the morphological variation between isolates believed to represent L. acicola from native Pinus spp. Two species of Lecanosticta, L. brevispora and L. guatemalensis, have recently been described from Mexico and Guatemala respectively based on morphology and sequence-derived phylogenetic inference. However, the putative native pathogen, L. acicola, was not found in those areas. In this study, the species diversity of a large collection of Lecanosticta isolates from Central America was considered. Phylogenetic analyses of the BT1, ITS, MS204, RPB2 and TEF1 gene regions revealed six species of Lecanosticta, four of which represented undescribed taxa. These are described here as Lecanosticta jani sp. nov. from Guatemala and Nicaragua, L. pharomachri sp. nov. from Guatemala and Honduras, L. tecunumanii sp. nov. from Guatemala and L. variabilis sp. nov. from Guatemala, Honduras, and Mexico. New host and country records were also found for the previously described L. brevispora and L. guatemalensis. Lecanosticta acicola was not found in any of the samples from Central America, and we hypothesize that it could be a northern hemisphere taxon. The high species diversity of Lecanosticta found in Mesoamerica suggests that this is a centre of diversity for the genus.
Highlights
Brown spot needle blight (BSNB) or Lecanosticta needle blight is an important needle disease on Pinus species
In Guatemala, 22 isolates were obtained from Pinus oocarpa, P. maximinoi, and P. tecunumanii needles that were collected in the Alta Verapaz District, 16 isolates were obtained from P. oocarpa needles collected in Chiquimula, 35 isolates from P. pseudostrobus needles collected in the Chimaltenango District in the Tecpán Municipality, eight isolates from P. tecunumanii needles collected in the Baja Verapaz District, 29 isolates from P. tecunumanii and P. oocarpa needles collected in the Jalapa District, and seven isolates from P. maximinoi needles in Coban and other regions (Table 1)
New regions of occurrence and host range emerged for Lecanosticta spp. with eight of the nine species occurring in Mesoamerica
Summary
Brown spot needle blight (BSNB) or Lecanosticta needle blight is an important needle disease on Pinus species. The disease is characterised by brown spots on necrotic yellow lesions at the points of infection and die-back of the needles from the apex, which often leads to premature defoliation (Ivory 1987). BSNB is caused by the fungal pathogen, Lecanosticta acicola (Siggers 1944). The fungus is a well-known pathogen in the USA and has been recorded in Central America, Colombia, Europe as well as Asian countries including China, Japan and Korea. Lecanosticta acicola is regarded as an A2 quarantine pathogen in Europe and Colombia where it is present as well as an A1 quarantine pathogen in the rest of. South America (COSAVE), Africa (IASPC) and the Eurasian Economic Union countries where it has yet to be recorded (https://gd.eppo.int/taxon/SCIRAC/categorization). L. acicola has been discovered in various new locations and on new hosts in Europe during the past decade (Jankovsky et al 2009; Markovskaja et al 2011; Anonymous 2012; Hintsteiner et al 2012; Adamson et al 2015; Janoušek et al 2016; Ortíz de Urbina et al 2017; Mullett et al 2018; Cleary et al 2019; Sadiković et al 2019)
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