New species of the Diaporthales from eastern Asia and eastern North America

Unravelling Diaporthe Species Associated with Woody Hosts from Karst Formations (Guizhou) in China

Though several Diaporthe species have been reported in China, little is known about the species associated with nature reserves in Guizhou province. During a survey of fungi in six nature reserves in Guizhou province of China, thirty-one Diaporthe isolates were collected from different woody hosts. Based on morphology, culture characteristics and molecular phylogenetic analysis, these isolates were characterized and identified. Phylogenetic analysis of internal transcribed spacer region (ITS), combined with translation elongation factor 1-alpha (tef), β-tubulin (tub), calmodulin (cal) and histone H3 (his) gene regions identified five known Diaporthe species and seven distinct lineages representing novel Diaporthe species. The details of five known species: Diaporthe cercidis, D. cinnamomi, D. conica, D. nobilis and D. sackstonii are given and the seven new species D. constrictospora, D. ellipsospora, D. guttulata, D. irregularis, D. lenispora, D. minima, and D. minusculata are introduced with detailed descriptions and illustrations. This study revealed a high diversity of previously undescribed Diaporthe species associated with woody hosts in various nature reserves of Guizhou province, indicating that there is a potential of Diaporthe species remains to be discovered in this unique landform (Karst formations) in China. Interestingly, the five known Diaporthe species have been reported as pathogens of various hosts, and this could indicate that those newly introduced species in this study could be potentially pathogenic pending further studies to confirm.

Phylogenetic Analysis and Development of Molecular Tool for Detection of Diaporthe citri Causing Melanose Disease of Citrus

Melanose disease caused by Diaporthe citri is considered as one of the most important and destructive diseases of citrus worldwide. In this study, isolates from melanose samples were obtained and analyzed. Firstly, the internal transcribed spacer (ITS) sequences were used to measure Diaporthe-like boundary species. Then, a subset of thirty-eight representatives were selected to perform the phylogenetic analysis with combined sequences of ITS, beta-tubulin gene (TUB), translation elongation factor 1-α gene (TEF), calmodulin gene (CAL), and histone-3 gene (HIS). As a result, these representative isolates were identified belonging to D. citri, D. citriasiana, D. discoidispora, D. eres, D. sojae, and D. unshiuensis. Among these species, the D. citri was the predominant species that could be isolated at highest rate from different melanose diseased tissues. The morphological characteristics of representative isolates of D. citri were investigated on different media. Finally, a molecular tool based on the novel species-specific primer pair TUBDcitri-F1/TUBD-R1, which was designed from TUB gene, was developed to detect D. citri efficiently. A polymerase chain reaction (PCR) amplicon of 217 bp could be specifically amplified with the developed molecular tool. The sensitivity of the novel species-specific detection was upon to 10 pg of D. citri genomic DNA in a reaction. Therefore, the D. citri could be unequivocally identified from closely related Diaporthe species by using this simple PCR approach.

Diaporthe is paraphyletic

Previous studies have shown that our understanding of species diversity within Diaporthe (syn. Phomopsis) is limited. In this study, 49 strains obtained from different countries were subjected to DNA sequence analysis. Based on these results, eight new species names are introduced for lineages represented by multiple strains and distinct morphology. Twelve Phomopsis species previously described from China were subjected to DNA sequence analysis, and confirmed to belong to Diaporthe. The genus Diaporthe is shown to be paraphyletic based on multi-locus (LSU, ITS and TEF1) phylogenetic analysis. Several morphologically distinct genera, namely Mazzantia, Ophiodiaporthe, Pustulomyces, Phaeocytostroma, and Stenocarpella, are embedded within Diaporthe s. lat., indicating divergent morphological evolution. However, splitting Diaporthe into many smaller genera to achieve monophyly is still premature, and further collections and phylogenetic datasets need to be obtained to address this situation.

Families of Diaporthales based on morphological and phylogenetic evidence

Diaporthales is an important ascomycetous order comprising phytopathogenic, saprobic, and endophytic fungi, but interfamilial taxonomic relationships are still ambiguous. Despite its cosmopolitan distribution and high diversity with distinctive morphologies, this order has received relativelyiaceae, Macrohilaceae, Melanconidaceae, Pseudoplagiostomaceae, Schizoparmaceae, Stilbosporaceae and Sydowiellaceae. Taxonomic uncertainties among genera are also clarified and recurrent discrepancies in the taxonomic position of families within the Diaporthales are discussed. An updated outline and key to families and genera of the order is presented.