Botryosphaerialean fungi causing canker and dieback of tree hosts from Mount Yudu in China

New species and records of Botryosphaeriales (Dothideomycetes) associated with tree dieback in Beijing, China

Botryosphaeriales species are important pathogens that have worldwide distribution. In this study, 23 Botryosphaeriales strains were isolated from 13 host species during a dieback disease survey in Beijing, China. Based on morphological and phylogenetic analyses, six Botryosphaeriales species were identified, including two new species named Dothiorellahortiarborum sp. nov. and Phaeobotryonfraxini sp. nov., and four new host records: Aplosporellaginkgonis from Cotinuscoggygriavar.cinereus, A.javeedii from Acermiyabei, Acertruncatum, Forsythiasuspensa, Lagerstroemiaindica, Sambucuswilliamsii, Syringavulgaris, Ulmuspumila, Xanthocerassorbifolium, A.yanqingensis from Acertruncatum, and Do.acericola from Forsythiasuspensa, Ginkgobiloba, and Syringaoblata. This study enriches the species diversity associated with tree dieback in Beijing, China, and contributes to the further study of the taxonomy of this order.

Morphology and molecular analyses reveal three new species of Botryosphaeriales isolated from diseased plant branches in China

The Botryosphaeriales represents an ecologically diverse group of fungi, comprising endophytes, saprobes, and plant pathogens. In this study, taxonomic analyses were conducted based on morphological characteristics and phylogenetic analyses of multi-gene sequence data from four loci (ITS, LSU, tef1-α, and tub2). Thirteen isolates obtained from Beijing and Yunnan Province were identified as seven species of Botryosphaeriales, including Aplosporellajaveedii, Dothiorellaalpina, Phaeobotryonaplosporum and Ph.rhois, and three previously undescribed species, namely Aplosporellayanqingensis, Dothiorellabaihuashanensis, and Phaeobotryonplatycladi. Additionally, the new records of Dothiorellaalpina from the host species Populusszechuanica, Phaeobotryonaplosporum from Juglansmandshurica, and Phaeobotryonrhois from Populusalbavar.pyramidalis are included.

Identification and pathogenicity of six fungal species causing canker and dieback disease on golden rain tree in Beijing, China

Golden rain trees (Koelreuteria paniculata) are largely cultivated because of their important ornamental, medicinal, and economic value. However, they are affected by canker and dieback disease to a large extent. To determine the fungi associated with canker and dieback disease of golden rain trees, isolations were obtained from diseased branches and twigs during 2019 and 2020 in greenbelts and nurseries in Beijing, China. Isolates were identified as six species (Allocryptovalsa castaneicola, Botryosphaeria dothidea, Cytospora koelreutericola sp. nov., Dothiorella acericola, Eutypella citricola, and Peroneutypa scoparia) based on morphological features and phylogenetic analyses of ITS, act, rpb2, tef1-α, and tub2. The results of pathogenicity tests indicated that all fungi produced discoloration and Botryosphaeria dothidea was highly aggressive to golden rain tree. In conclusion, this study explored the taxonomy, phylogeny, and pathogenicity of different fungal species associated with canker and dieback disease on golden rain tree and provided fundamental knowledge to improve disease management.

The Potential Fungal Pathogens of Euonymus japonicus in Beijing, China

Euonymus japonicus tolerates the dry and frigid climate of Beijing, China, and effectively filters out particles during the winter. However, fungal infestation frequently causes extreme illness and can even lead to shrub death. In this study, 104 diseased E. japonicus specimens were collected from seven districts in Beijing. Seventy-nine isolates were identified as 22 fungal species in seven genera. The species were Aplosporella hesperidica, A. javeedii, A. prunicola, Botryosphaeria dothidea, Colletotrichum aenigma, Co. euonymi, Co. euonymicola, Co. gloeosporioides, Cytospora ailanthicola, C. albodisca, C. diopuiensis, C. discotoma, C. elaeagni, C. euonymicola, C. euonymina, C. haidianensis, C. leucostoma, C. sophorae, C. zhaitangensis, Diaporthe eres, Dothiorella acericola, and Pestalotiopsis chaoyangensis. On the basis of morphological and phylogenetic analyses, Colletotrichum euonymi, Co. euonymicola, Cytospora zhaitangensis, and Pestalotiopsis chaoyangensis were introduced as novel species. Colletotrichum euonymi, Co. euonymicola, and Pestalotiopsis chaoyangensis were subsequently confirmed as pathogens of E. japonicus leaves by pathogenicity testing. This study provides an important assessment of the fungi associated with diseases of E. japonicus in Beijing, China.

Re-Evaluating Botryosphaeriales: Ancestral State Reconstructions of Selected Characters and Evolution of Nutritional Modes

Botryosphaeriales (Dothideomycetes, Ascomycota) occur in a wide range of habitats as endophytes, saprobes, and pathogens. The order Botryosphaeriales has not been subjected to evaluation since 2019 by Phillips and co-authors using phylogenetic and evolutionary analyses. Subsequently, many studies introduced novel taxa into the order and revised several families separately. In addition, no ancestral character studies have been conducted for this order. Therefore, in this study, we re-evaluated the character evolution and taxonomic placements of Botryosphaeriales species based on ancestral character evolution, divergence time estimation, and phylogenetic relationships, including all the novel taxa that have been introduced so far. Maximum likelihood, maximum parsimony, and Bayesian inference analyses were conducted on a combined LSU and ITS sequence alignment. Ancestral state reconstruction was carried out for conidial colour, septation, and nutritional mode. Divergence times estimates revealed that Botryosphaeriales originated around 109 Mya in the early epoch of the Cretaceous period. All six families in Botryosphaeriales evolved in the late epoch of the Cretaceous period (66-100 Mya), during which Angiosperms also appeared, rapidly diversified and became dominant on land. Families of Botryosphaeriales diversified during the Paleogene and Neogene periods in the Cenozoic era. The order comprises the families Aplosporellaceae, Botryosphaeriaceae, Melanopsaceae, Phyllostictaceae, Planistromellaceae and Saccharataceae. Furthermore, current study assessed two hypotheses; the first one being "All Botryosphaeriales species originated as endophytes and then switched into saprobes when their hosts died or into pathogens when their hosts were under stress"; the second hypothesis states that "There is a link between the conidial colour and nutritional mode in botryosphaerialean taxa". Ancestral state reconstruction and nutritional mode analyses revealed a pathogenic/saprobic nutritional mode as the ancestral character. However, we could not provide strong evidence for the first hypothesis mainly due to the significantly low number of studies reporting the endophytic botryosphaerialean taxa. Results also showed that hyaline and aseptate conidia were ancestral characters in Botryosphaeriales and supported the relationship between conidial pigmentation and the pathogenicity of Botryosphaeriales species.

Molecular characterization of a novel victorivirus isolated from the phytopathogenic fungus Phaeobotryon rhois

Phaeobotryon rhois is an important pathogenic fungus that causes dieback and canker disease of woody hosts. A novel mycovirus, tentatively named "Phaeobotryon rhois victorivirus 1" (PrVV1), was identified in P. rhois strain SX8-4. The PrVV1 has a double-stranded RNA (dsRNA) genome that is 5,224 base pairs long and contains two open reading frames (ORF1 and ORF2), which overlap at a AUGA sequence. ORF1 encodes a polypeptide of 786 amino acids (aa) that contains the conserved coat protein (CP) domain of victoriviruses, while ORF2, encodes a large polypeptide of 826 aa that contains the conserved RNA-dependent RNA polymerase (RdRp) domain of victoriviruses. Our analysis of genomic structure, homology, and phylogeny indicated that PrVV1 is a novel member of the genus Victorivirus in the family Totiviridae. This is the first report of the complete genome sequence of a victorivirus that infects P. rhois.

Re-evaluation of the Fungal Diversity and Pathogenicity of Cytospora Species from Populus in China

Poplar is widely cultivated in China because of its strong ecological adaptability, fast growth, easy reproduction, and short rotation period. However, it suffers from severe threat from canker disease caused by Cytospora species. The present study revealed the presence of Cytospora species from Populus in China. A total of six species of Cytospora were isolated from Populus in six provinces in China, including five known species (C. ailanthicola, C. chrysosperma, C. donglingensis, C. paratranslucens, and C. sophoriopsis) and one novel species (C. populi) based on morphological and phylogenetic analyses of ITS, act, rpb2, tef1-α, and tub2 gene sequences. Cytospora ailanthicola, C. chrysosperma, C. paratranslucens, and C. sophoriopsis are confirmed as pathogens by pathogenicity tests of which C. paratranslucens showed the strongest virulence, followed by C. ailanthicola, C. chrysosperma, and C. sophoriopsis. The mycelial growth rates of isolates from the six species had 22.5 to 27°C as the optimum temperatures, and the optimum pH values were 5.9 to 7.1. The effectiveness of six carbon sources on the mycelial growth showed that colonies grew the fastest in the presence of fructose and grew the slowest using xylose. This study represents a significant evaluation of Cytospora causing poplar canker disease in China.