No abstract

Pleosporales species are important plant pathogens, saprobes, and endophytes on a wide range of economically important plant hosts. The classification of Pleosporales has undergone various modifications in recent years due to the addition of many families described from multiple habitats with a high level of morphological deviation. Numerous asexual genera have been described in Pleosporales that can be either hyphomyceteous or coelomycetous. Phoma- or coniothyrium-like species are common and have been revealed as polyphyletic in the order Pleosporales and linked with several sexual genera. A total of 31 pleosporalean strains were isolated in different regions of Taiwan between 2017 and 2018 from the leaves of Camellia sinensis plants with symptoms of leaf spot disease. These strains were evaluated morphologically and genotypically using multi-locus sequence analyses of the ITS, LSU, SSU, rpb 2, tef 1 and tub 2 genes. The results demonstrated the affiliation of these strains with the various families in Pleosporales and revealed the presence of one new genus ( Neoshiraia ) and eight new species ( Alloconiothyrium camelliae , Amorocoelophoma camelliae , Leucaenicola camelliae , L . taiwanensis , Neoshiraia camelliae , N . taiwanensis , Paraconiothyrium camelliae and Paraphaeosphaeria camelliae ). Furthermore, to the best of our understanding, Didymella segeticola , Ectophoma pomi and Roussoella mexican were reported for the first time from C. sinensis in Taiwan.

Camellia sinensis (L.) O. Kuntze, commonly known as tea, is widely cultivated around the world in tropical and subtropical areas. Tea is mainly manufactured using young shoots of tea plants. Therefore, it is essential to control foliar diseases. Grey blight disease is caused by Pestalotiopsis-like taxa and is known as one of the most destructive tea diseases. Although several studies have provided the groundwork for the fungal diseases associated with C. sinensis in Taiwan, grey blight disease has not been characterised based on diversity, molecular systematics, or pathogenicity. The goal of this study was to identify and characterise the causative agents of tea grey blight disease. A total of 98 Pestalotiopsis-like isolates associated with symptomatic leaves of C. sinensis from major tea fields in Taiwan were investigated. Based on phylogenies of single and concatenated DNA sequences (ITS, tub2, tef1-α) together with morphology, we resolved most of the Pestalotiopsis-like species in this study. The study revealed seven well-classified taxa and seven tentative clades in three genera, i.e., Pestalotiopsis, Pseudopestalotiopsis, and Neopestalotiopsis. One novel species, Ps. annellata, was introduced. Five new records – Ps. chinensis, Ps. camelliae-sinensis, P. camelliae, P. yanglingensis and P. trachicarpicola – were introduced for the first time in Taiwan. Ps. chinensis was the taxon most frequently isolated from C. sinensis in this study. Further, results of pathogenicity assessments exhibited that, with wound inoculation, all assayed isolates in this study were pathogenic on tea leaves. Ps. chinensis and Ps. camelliae-sinensis were identified as the major pathogens associated with grey blight disease of tea in Taiwan. This is the first study of the diversity, pathogenicity and characterisation of Pestalotiopsis-like fungi associated with tea grey blight disease in Taiwan.

The order Pleosporales comprises a miscellaneous group of fungi and is considered to be the largest order of the class Dothideomycetes. The circumscription of Pleosporales has undergone numerous changes in recent years due to the addition of large numbers of families reported from various habitats and with a large amount of morphological variation. Many asexual genera have been reported in Pleosporales and can be either hyphomycetes or coelomycetes. Phoma-like taxa are common and have been shown to be polyphyletic within the order and allied with several sexual genera. During the exploration of biodiversity of pleosporalean fungi in Taiwan, a fungal strain was isolated from mycelium growing on the fruiting body of an Ophiocordyceps species. Fruiting structures that developed on PDA were morphologically similar to Phoma and its relatives in having pycnidial conidiomata with hyaline conidia. The fungus is characterised by holoblastic, cylindrical, aseptate conidiogenous cells and cylindrical, hyaline, aseptate, guttulated, thin-walled conidia. Phylogenetic analysis based on six genes, ITS, LSU, rpb2, SSU, tef1 and tub2, produced a phylogenetic tree with the newly generated sequences grouping in a distinct clade separate from all of the known families. Therefore, a new pleosporalean family Tzeananiaceae is established to accommodate the monotypic genus Tzeanania and the species T.taiwanensis in Pleosporales, Dothideomycetes. The Ophiocordyceps species was identified as O.macroacicularis and this is a new record in Taiwan.

Welsh onion (Allium fistulosum L.) is one of the main and oldest vegetable crops grown in Taiwan. A severe epidemic of leaf blight in Welsh onion caused by a Stemphylium-like pathogen was found in Sanxing, Taiwan, from 2018 to 2020. However, correct species identification, biology and control of Stemphylium leaf blight (SLB) of Welsh onion is not well established. Therefore, the main objective of this study was to investigate the causal agent of SLB in Sanxing and evaluate the in vitro sensitivity of Stemphylium-like pathogen to commonly used fungicides. Phylogenetic analysis based on combining the internal transcribed spacer (ITS) region, and glyceraldedyhe-3-phosphate dehydrogenase (gapdh) and calmodulin (cmdA) gene sequences together with morphological features, identified S. vesicarium as associated with SLB in Sanxing. When inoculated onto Welsh onion leaves, the isolates caused symptoms identical to those seen in the field and S. vesicarium was reisolated, confirming Koch’s postulates. We observed a higher incidence of SLB symptoms on the oldest leaves compared with younger leaves. The maximum and minimum temperatures for in vitro mycelial growth and conidial germination (%) of S. vesicarium were 20 to 30°C and 5°C respectively. Sixteen fungicides were tested for their effectiveness to reduce the mycelial growth and conidial germination of S. vesicarium in vitro. Boscalid + pyraclostrobin, fluopyram, fluxapyroxad, fluxapyroxad + pyraclostrobin were highly effective at reducing mycelial growth and conidial germination in S. vesicarium. However, strobilurin fungicides (azoxystrobin and kresoxim-methyl) commonly used in Welsh onion production in Sanxing were ineffective. This study discusses the emergence of SLB caused by S. vesicarium in the foliar disease complex affecting Welsh onion and the management of the disease using fungicides with different modes of action in Taiwan. The research will underpin the sustainable management of SLB in Sanxing, Taiwan, however further field assessments of the fungicides are warranted.