Fungi of quarantine concern for China I: Dothideomycetes

Chionobium takahashii, gen. et sp. nov., associated with snow blight of conifers in Japan

Gremmenia abietis (Dearn.) Crous (syn: Phacidium abietis) was originally described in North America to accommodate the species associated with snow blight of Abies and Pseudotsuga spp. In Japan, this species was first observed on the dead needles on Abies sachalinensis and Picea jezoensis var. jezoensis in 1969. However, the identity of Japanese species was unclear due to the lack of molecular data and the absence of anamorph description. In this study, we collected fresh specimens from various conifer species (A. sachalinensis, A. veitchii, Pic. jezoensis var. jezoensis, Pic. jezoensis var. hondoensis, Pinus koraiensis, and Pin. pumila) in Japan and revised the taxonomy based on morphological and phylogenetic analyses. Phylogenetic analyses based on nuc rDNA internal transcribed spacer ITS1-5.8S-ITS2 (ITS), nuc 28S rDNA (28S), and RNA polymerase II second largest subunit (RPB2) regions indicated that the species belongs to Phacidiaceae. Conidiomata formed in vitro produced pyriform, hyaline conidia without mucoid appendage, which distinguished the species from phylogenetically related genera. Consequently, we established Chionobium takahashii to accommodate the snow blight fungus in Japan. Further phylogenetic analyses also indicated that C. takahashii includes several distinct clades corresponding to the host genera (Abies, Picea, Pinus). Morphological differences among those clades were unclear, suggesting that C. takahashii may contain host-specific cryptic species.

New Species of Didymellaceae within Aquatic Plants from Southwestern China

Members of Didymellaceae have a wide geographical distribution throughout different ecosystems, and most species are associated with fruit, leaf, stem and root diseases of land plants. However, species that occur in aquatic plants are not clearly known. During a survey of the diversity of endophytes in aquatic plants in Yunnan, Sichuan, and Guizhou provinces, we obtained 51 isolates belonging to Didymellaceae based on internal transcribed spacer region (ITS) sequences. Further, the phylogenetic positions of these isolates were determined by combined sequences composed of ITS, partial large subunit nrRNA gene (28S nrDNA; LSU), RNA polymerase II second largest subunit (rpb2) and partial beta-tubulin gene (tub2). Combining morphological characteristics and multi-locus phylogenetic analyses, two new varieties belong to Boeremia and 12 new species distributed into seven genera were recognized from 51 isolates, i.e., Cumuliphoma, Didymella, Dimorphoma, Ectophoma, Leptosphaerulina, Remotididymella, and Stagonosporopsis. Among these species, only one species of Stagonosporopsis and two species of Leptosphaerulina show teleomorphic stages on OA, but have no anamorphic state. Each new species is described in detail, and the differences between new species and their phylogenetically related species are discussed here. The high frequency of new species indicates that aquatic plants may be a special ecological niche which highly promotes species differentiation. At the same time, the frequent occurrence of new species may indicate the need for extensive investigation of fungal resources in those aquatic environments where fungal diversity may be underestimated.

Morphological and Phylogenetic Characterisations Reveal Four New Species in Leptosphaeriaceae (Pleosporales, Dothideomycetes)

Leptosphaeriaceae is a widely distributed fungal family with diverse lifestyles. The family includes several genera that can be distinguished by morphology and molecular phylogenetic analysis. During our investigation of saprobic fungi on grasslands in Yunnan Province, China, four fungal taxa belonging to Leptosphaeriaceae associated with grasses were collected. Morphological observations and phylogenetic analyses of the combined SSU, LSU, ITS, tub2, and rpb2 loci based on maximum likelihood and Bayesian inference were used to reveal the taxonomic placement of these fungal taxa. This study introduces four new taxa, viz. Leptosphaeria yunnanensis, L. zhaotongensis, Paraleptosphaeria kunmingensis, and Plenodomus zhaotongensis. Colour photo plates, full descriptions, and a phylogenetic tree to show the placement of the new taxa are provided.

Infection Characteristics and Physical Prevention Strategy of Panax notoginseng Round Spot Disease Caused by Mycocentrospora acerina

Panax notoginseng round spot disease (PRSD), caused by Mycocentrospora acerina, is the main leaf disease occurring in cultured P. notoginseng. Aiming to find a safe and efficient control method for PRSD, we studied the disease characteristics of PRSD and the optimal growth conditions of M. acerina and evaluated the efficacy of rain-shelter cultivation in PRSD control. Moreover, we described M. acerina based on morphological characterization and molecular analyses (ITS, ACT, LSU, and TEF-1α). The optimum temperature for M. acerina conidial germination was found to be 14 to 22°C. Furthermore, leaf surface wetness for at least 4 h is required for conidial germination, and conidia can successfully infect P. notoginseng when the leaf wetness lasts for more than 8 h. Additionally, rainwater splashing determines the conidial transfection distance, which is less than 2 m. Finally, our study revealed that rain-shelter cultivation is an effective and simple physical prevention strategy to control PRSD, with an average efficacy of up to 100%.

Neocosmospora rubicola, a stem rot disease in potato: Characterization, distribution and management

Potato (Solanum tuberosum L.) is one of the most important crops in maintaining global food security. Plant stand and yield are affected by production technology, climate, soil type, and biotic factors such as insects and diseases. Numerous fungal diseases including Neocosmospora rubicola, causing stem rot, are known to have negative effects on potato growth and yield quality. The pathogen is known to stunt growth and cause leaf yellowing with grayish-black stems. The infectivity of N. rubicola across a number of crops indicates the need to search for appropriate management approaches. Synthetic pesticides application is a major method to mitigate almost all potato diseases at this time. However, these pesticides significantly contribute to environmental damage and continuous use leads to pesticide resistance by pathogens. Consumers interest in organic products have influenced agronomists to shift toward the use of biologicals in controlling most pathogens, including N. rubicola. This review is an initial effort to carefully examine current and alternative approaches to control N. rubicola that are both environmentally safe and ecologically sound. Therefore, this review aims to draw attention to the N. rubicola distribution and symptomatology, and sustainable management strategies for potato stem rot disease. Applications of plant growth promoting bacteria (PGPB) as bioformulations with synthetic fertilizers have the potential to increase the tuber yield in both healthy and N. rubicola infested soils. Phosphorus and nitrogen applications along with the PGPB can improve plants uptake efficiency and reduce infestation of pathogen leading to increased yield. Therefore, to control N. rubicola infestation, with maximum tuber yield benefits, a pre-application of the biofertilizer is shown as a better option, based on the most recent studies. With the current limited information on the disease, precise screening of the available resistant potato cultivars, developing molecular markers for resistance genes against N. rubicola will assist to reduce spread and virulence of the pathogen.

Synopsis of Leptosphaeriaceae and Introduction of Three New Taxa and One New Record from China

Leptosphaeriaceae, a diverse family in the order Pleosporales, is remarkable for its scleroplectenchymatous or plectenchymatous peridium cells. Four Leptosphaeriaceae species were discovered and studied during the investigation of saprobic fungi from plant substrates in China. Novel taxa were defined using multiloci phylogenetic analyses and are supported by morphology. Based on maximum likelihood (ML) and Bayesian inference (BI) analyses, these isolates represent three novel taxa and one new record within Leptosphaeriaceae. A new genus, Angularia, is introduced to accommodate Angularia xanthoceratis, with a synopsis chart for 15 genera in Leptosphaeriaceae. This study also revealed a new species, Plenodomus changchunensis, and a new record of Alternariaster centaureae-diffusae. These species add to the increasing number of fungi known from China.