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The white-rot fungus Phellinus noxius is known to cause brown root rot disease (BRRD) in woody trees and shrubs. To understand the pathogenicity of P. noxius in herbaceous plants, we investigated 23 herbaceous weed and turfgrass species in 32 BRRD-infested sites in Taiwan and/or tested them by artificial inoculation. In the field survey, P. noxius was isolated from seven symptomless herbaceous species (i.e., Typhonium blumei, Paspalum conjugatum, Paspalum distichum, Oplismenus compositus, Bidens pilosa, Digitaria ciliaris, and Zoysia matrella). Potted plant inoculation assays suggested that P. noxius is able to infect Artemisia princeps, O. compositus, and Z. matrella but not Axonopus compressus, Eremochloa ophiuroides, Ophiopogon japonicus, or Cynodon dactylon. A. princeps plants wilted within 2 weeks postinoculation, but inoculated O. compositus and Z. matrella were asymptomatic, and P. noxius could be isolated from only inoculated sites. The colonization of P. noxius in the cortex and vascular cylinder of roots was visualized by paraffin sectioning and trypan blue staining of juvenile seedlings grown on water agar. To evaluate the effect of replantation for the remediation of BRRD-infested sites, P. noxius-inoculated wood strips were buried in soil with or without vegetation. After 4 weeks, P. noxius could be detected only in the bare soil group. For the control of BRRD, the herbaceous hosts should be removed around the diseased trees/stumps and non-host turfgrasses (e.g., A. compressus, E. ophiuroides, O. japonicus, or C. dactylon) planted to accelerate the degradation of P. noxius.

Brown blight, a destructive foliar disease of tea, has become a highly limiting factor for tea cultivation in Taiwan. To understand the population composition of the causal agents (Colletotrichum spp.), the fungal diversity in the main tea-growing regions all over Taiwan was surveyed from 2017 to 2019. A collection of 139 Colletotrichum isolates was obtained from 14 tea cultivars in 86 tea plantations. Phylogenic analysis using the ribosomal internal transcribed spacer, glutamine synthetase gene, Apn2-Mat1-2 intergenic spacer, β-tubulin, actin, calmodulin, and glyceraldehyde-3-phosphate dehydrogenase genes together with morphological characterization revealed three species associated with brown blight of tea; namely, Colletotrichum camelliae (95.6% of all isolates), C. fructicola (3.7%), and C. aenigma (0.7%). This is the first report of C. aenigma in Taiwan. The optimal growth temperatures were 25°C for C. camelliae and 25 and 30°C for C. fructicola and C. aenigma. Although C. fructicola and C. aenigma were more adapted to high temperature, C. camelliae was the most pathogenic across different temperatures. Regardless of whether spore suspensions or mycelial discs were used, significantly larger lesions and higher disease incidences were observed for wounded than for nonwounded inoculation and for the third and fourth leaves than for the fifth leaves. Wounded inoculation of detached third and fourth tea leaves with mycelial discs was found to be a reliable and efficient method for assessing the pathogenicity of Colletotrichum spp. within 4 days. Preventive application of fungicides or biocontrol agents immediately after tea pruning and at a young leaf stage would help control the disease.

Rice blast caused by Magnaporthe oryzae is a dangerous threat to rice production and food security worldwide. Breeding and proper deployment of resistant varieties are effective and environmentally friendly strategies to manage this notorious disease. However, a highly dynamic and quickly evolved rice blast pathogen population in the field has made disease control with resistance germplasms more challenging. Therefore, continued monitoring of pathogen dynamics and application of effective resistance varieties are critical tasks to prolong or sustain field resistance. Here, we report a team project that involved evaluation of rice blast resistance genes and surveillance of M. oryzae field populations in Taiwan. A set of International Rice Research Institute-bred blast-resistant lines (IRBLs) carrying single blast resistance genes was utilized to monitor the field effectiveness of rice blast resistance. Resistance genes such as Ptr (formerly Pita2) and Pi9 exhibited the best and most durable resistance against the rice blast fungus population in Taiwan. Interestingly, line IRBLb-B harboring the Pib gene with good field protection has recently shown susceptible lesions in some locations. To dissect the genotypic features of virulent isolates against the Pib resistance gene, M. oryzae isolates were collected and analyzed. Screening of the AvrPib locus revealed that the majority of field isolates still maintained the wild-type AvrPib status but eight virulent genotypes were found. Pot3 insertion appeared to be a major way to disrupt the AvrPib avirulence function. Interestingly, a novel AvrPib double-allele genotype among virulent isolates was first identified. Pot2 repetitive element-based polymerase chain reaction (rep-PCR) fingerprinting analysis indicated that mutation events may occur independently among different lineages in different geographic locations of Taiwan. This study provides our surveillance experience of rice blast disease and serves as the foundation to sustain rice production.

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 are 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. A 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 that S. vesicarium is associated with SLB in Sanxing. When inoculated onto Welsh onion leaves, the isolates caused symptoms identical to those observed in the field; therefore, S. vesicarium was reisolated and Koch’s postulates were confirmed. 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 plus pyraclostrobin, fluopyram, fluxapyroxad, and fluxapyroxad plus 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 support the sustainable management of SLB in Sanxing, Taiwan; however, further field assessments of the fungicides are warranted.

Brown root rot disease (BRRD), caused by

The white-rot fungus

Brown blight, a destructive foliar disease of tea, has become a highly limiting factor for tea cultivation in Taiwan. To understand the population composition of the causal agents

The Fusarium solani species complex (FSSC) comprises fungal pathogens responsible for mortality in a diverse range of animals and plants, but their genome diversity and transcriptome responses in animal pathogenicity remain to be elucidated. We sequenced and compared six chromosome-level FSSC clade 3 genomes of aquatic animal and plant host origins and revealed a spectrum of conservation patterns in chromosomes categorised into three compartments: core, fast-core (FC), and lineage-specific (LS). Each chromosome type varied in structural architectures, with FC and LS chromosomes containing significantly higher proportions of repetitive elements and methylation levels than core chromosomes, with genes exhibiting higher dN/dS and enriched in functions related to pathogenicity and niche expansion. Mesosynteny were detected between FC chromosomes of Fusarium genomes, indicating that these chromosomes were present in a common ancestor that predated FSSC species. These findings provide evidence that genome compartmentalisation was the outcome of multi-speed evolution amongst FSSC chromosomes. We further demonstrated that F. falciforme and F. keratoplasticum are opportunistic pathogens by inoculating Pelodiscus sinensis eggs and identified differentially expressed genes also associated with plant pathogenicity. These included the most upregulated genes encoding the CFEM (Common in Fungal Extracellular Membrane) domain. The study establishes genomic resources and an animal model for fungal pathogens of trans-kingdom hosts.

Brown root rot (BRR) caused by Phellinus noxius is a destructive tree disease in tropical and subtropical areas. To understand how BRR affects the composition of the plant rhizoplane-enriched microbiota, the microbiomes within five root-associated compartments (i.e., bulk soil, old/young root rhizosphere soil, old/young root tissue) of Ficus trees naturally infected by P. noxius were investigated. The level of P. noxius infection was determined by quantitative PCR. Illumina sequencing of the internal transcribed spacer and 16S rRNA revealed that P. noxius infection caused a significant reduction in fungal diversity in the bulk soil, old root tissue, and rhizosphere soil. Interestingly, Cosmospora was the only fungal genus positively correlated with P. noxius. The abundance and composition of dominant bacterial taxa such as Actinomadura, Bacillus, Rhodoplanes, and Streptomyces differed between BRR-diseased and healthy samples. Furthermore, 838 isolates belonging to 26 fungal and 35 bacterial genera were isolated and tested for interactions with P. noxius. Antagonistic activities were observed for isolates of Bacillus, Pseudomonas, Aspergillus, Penicillium, and Trichoderma. Cellophane overlay and cellulose/lignin utilization assays suggested that Cosmospora could tolerate the secretions of P. noxius and that the degradation of lignin by P. noxius may create suitable conditions for Cosmorpora growth. This article is protected by copyright. All rights reserved.