Molecular characterization and phylogenetic analyses of Lophodermella needle pathogens (Rhytismataceae) on Pinus species in the USA and Europe

Abstract

Increasing prevalence of conifer needle pathogens globally have prompted further studies on pathogen identification and a better understanding of phylogenetic relationships among needle pathogens. Several Lophodermella species can be aggressive pathogens causing needle cast in natural pine forests in the USA and Europe. However, their relationships with other Rhytismataceae species have historically been based on similarities of only limited phenotypic characters. Currently, no molecular studies have been completed to elucidate their relationships with other Lophodermella needle pathogens. This study collected and sequenced three gene loci, namely: internal transcribed spacer, large ribosomal subunit, and translation elongation factor 1-alpha, from five Lophodermella needle pathogens from North America (L. arcuata, L. concolor, L. montivaga) and Europe (L. conjuncta and L. sulcigena) to distinguish phylogeny within Rhytismatacaeae, including Lophophacidium dooksii. Phylogenetic analyses of the three loci revealed that all but L. conjuncta that were sampled in this study consistently clustered in a well-supported clade within Rhytismataceae. The multi-gene phylogeny also confirmed consistent nesting of L. dooksii, a needle pathogen of Pinus strobus, within the clade. Potential synapomorphic characters such as ascomata position and ascospore shape for the distinct clade were also explored. Further, a rhytismataceous species on P. flexilis that was morphologically identified as L. arcuata was found to be unique based on the sequences at the three loci. This study suggests a potential wider range of host species within the genus and the need for genetic characterization of other Lophodermella and Lophophacidium species to provide a higher phylogenetic resolution.

Needle pathogens of Rhytismataceae: Current knowledge and research opportunities for conifer foliar diseases

“…Molecular studies further supported the phylogenetic placement of some rhytismataceous needle pathogens previously classified based on morphology such as the Lophodermium on pines (Ortiz-García et al, 2003) and Lophodermella (Ata et al, 2021) clades.…”

“…Molecular studies further supported the phylogenetic placement of some rhytismataceous needle pathogens previously classified based on morphology such as the Lophodermium on pines (Ortiz‐García et al., 2003) and Lophodermella (Ata et al., 2021) clades. However, genetic attributes of a few species (e.g., Elytroderma deformans , Lirula exigua , Lophodermella conjuncta ) have challenged their current taxonomic classification (Ata et al., 2021; Fan et al., 2012; Ortiz‐García et al., 2003) and thus need further validation. Molecular analyses further revealed polyphyly of some Rhytismataceae genera such as Lophodermium Chevall.…”

“…However, genetic attributes of a few species (e.g., Elytroderma deformans, Lirula exigua, Lophodermella conjuncta) have challenged their current taxonomic classification (Ata et al, 2021;Fan et al, 2012;Ortiz-García et al, 2003) and thus need further validation. Molecular analyses further revealed polyphyly of some Rhytismataceae genera such as Lophodermium Chevall.…”

“…Increasingly, the diversity of Rhytismataceae needle pathogens has been questioned, as species previously classified as non‐rhytismataceous or those morphologically similar with other relatives yet genetically distinct have been identified through molecular research. Examples of these include the transfer of Lophophacidium dooksii from Phacidiaceae to Rhytismataceae and the identification of a potentially new Lophodermella species on Pinus flexilis E. James that is morphologically similar yet genetically unique from Lophodermella arcuata (Darker) Darker (Ata et al., 2021). Molecular data of more rhytismataceous needle pathogens is needed to further improve species classification and accurate diagnosis of needle diseases, and to use phylogeny to better understand the genetics controlling pathogenicity‐related traits and lifestyles within the family.…”

“…The generic taxonomy based on morphology within Rhytismataceae has been recognized to be inconsistent with phylogeny (Johnston et al, 2019;Lantz et al, 2011). Genetic studies of some species (e.g., Elytroderma deformans (Weir) Darker, Lirula exigua S. Kaneko, Lophodermella conjuncta (Darker) Darker) have demonstrated the current taxonomic classification to be inadequate (Ata et al, 2021;Fan et al, 2012;Ortiz-García et al, 2003). The research on genus Rhytisma Fr.…”