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PLoS Pathogens Jun 2023Satellites associated with plant or animal viruses have been largely detected and characterized, while those from mycoviruses together with their roles remain far less...
Satellites associated with plant or animal viruses have been largely detected and characterized, while those from mycoviruses together with their roles remain far less determined. Three dsRNA segments (dsRNA 1 to 3 termed according to their decreasing sizes) were identified in a strain of phytopathogenic fungus Pestalotiopsis fici AH1-1 isolated from a tea leaf. The complete sequences of dsRNAs 1 to 3, with the sizes of 10316, 5511, and 631 bp, were determined by random cloning together with a RACE protocol. Sequence analyses support that dsRNA1 is a genome of a novel hypovirus belonging to genus Alphahypovirus of the family Hypoviridae, tentatively named Pestalotiopsis fici hypovirus 1 (PfHV1); dsRNA2 is a defective RNA (D-RNA) generating from dsRNA1 with septal deletions; and dsRNA3 is the satellite component of PfHV1 since it could be co-precipitated with other dsRNA components in the same sucrose fraction by ultra-centrifuge, suggesting that it is encapsulated together with PfHV1 genomic dsRNAs. Moreover, dsRNA3 shares an identical stretch (170 bp) with dsRNAs 1 and 2 at their 5' termini and the remaining are heterogenous, which is distinct from a typical satellite that generally has very little or no sequence similarity with helper viruses. More importantly, dsRNA3 lacks a substantial open reading frame (ORF) and a poly (A) tail, which is unlike the known satellite RNAs of hypoviruses, as well as unlike those in association with Totiviridae and Partitiviridae since the latters are encapsidated in coat proteins. As up-regulated expression of RNA3, dsRNA1 was significantly down-regulated, suggesting that dsRNA3 negatively regulates the expression of dsRNA1, whereas dsRNAs 1 to 3 have no obvious impact on the biological traits of the host fungus including morphologies and virulence. This study indicates that PfHV1 dsRNA3 is a special type of satellite-like nucleic acid that has substantial sequence homology with the host viral genome without encapsidation in a coat protein, which broadens the definition of fungal satellite.
Topics: RNA, Satellite; RNA Viruses; Pestalotiopsis; RNA, Double-Stranded; Phylogeny; RNA, Viral; Genome, Viral; Fungal Viruses; Open Reading Frames
PubMed: 37285391
DOI: 10.1371/journal.ppat.1010889 -
Journal of Fungi (Basel, Switzerland) May 2023Black spot needle blight is a serious conifer disease of var. occurring in Northeast China, which is usually caused by the plant pathogenic fungus . From the diseased...
Black spot needle blight is a serious conifer disease of var. occurring in Northeast China, which is usually caused by the plant pathogenic fungus . From the diseased pine needles collected in Honghuaerji, the strain YJ-3 was isolated and identified as the phytopathogen, and its culture characteristics were studied. Then, we generated a highly contiguous 48.36-Mbp genome assembly (N50 = 6.62 Mbp) of the strain YJ-3 by combining the PacBio RS II Single Molecule Real Time (SMRT) and Illumina HiSeq X Ten sequencing platforms. The results showed that a total of 13,667 protein-coding genes were predicted and annotated using multiple bioinformatics databases. The genome assembly and annotation resource reported here will be useful for the study of fungal infection mechanisms and pathogen-host interaction.
PubMed: 37233276
DOI: 10.3390/jof9050564 -
BMC Microbiology May 2023To explore the community composition and diversity of the endophytic fungi in Taxillus chinensis, samples of the parasites growing on seven different hosts, Morus alba,...
BACKGROUND
To explore the community composition and diversity of the endophytic fungi in Taxillus chinensis, samples of the parasites growing on seven different hosts, Morus alba, Prunus salicina, Phellodendron chinense, Bauhinia purpurea, Dalbergia odorifera, Diospyros kaki and Dimocarpus longan, were isolated. The strains were identified by their morphological characteristics and their internal transcribed spacer (ITS) sequences.
RESULTS
150 different endophytic fungi were isolated from the haustorial roots of the seven hosts with a total isolation rate of 61.24%. These endophytic fungi were found to belong to 1 phylum, 2 classes, 7 orders, 9 families, 11 genera and 8 species. Among of them, Pestalotiopsis, Neopestalotiopsis and Diaporthe were the dominant genera, accounting for 26.67, 17.33 and 31.33% of the total number of strains, respectively. Diversity and similarity analyses showed that the endophytic fungi isolated from D. longan (H'=1.60) had the highest diversity index. The highest richness indexes were found in M. alba and D. odorifera (both 2.23). The evenness index of D. longan was the highest (0.82). The similarity coefficient of D. odorifera was the most similar to D. longan and M. alba (33.33%), while the similarity coefficient of P. chinense was the lowest (7.69%) with M. alba and D. odorifera. Nine strains showed antimicrobial activities. Among them, Pestalotiopsis sp., N. parvum and H. investiens showed significant antifungal activity against three fungal phytopathogens of medicinal plants. At the same time, the crude extracts from the metabolites of the three endophytic fungi had strong inhibitory effects on the three pathogens. Pestalotiopsis sp., N. parvum and H. investiens had the strongest inhibitory effects of S. cucurbitacearum, with inhibitory rates of 100%, 100% and 81.51%, respectively. In addition, N. parvum had a strong inhibitory effect on D. glomerata and C. cassicola, with inhibitory rates of 82.35% and 72.80%, respectively.
CONCLUSIONS
These results indicate that the species composition and diversity of endophytic fungi in the branches of T. chinensis were varied in the different hosts and showed good antimicrobial potential in the control of plant pathogens.
Topics: Humans; Fungi; Loranthaceae; Endophytes; Biodiversity; Anti-Infective Agents; Phylogeny
PubMed: 37173641
DOI: 10.1186/s12866-023-02878-x -
Plant Disease May 2023Weizhi Xun and Changwang Wu contributed equally to this work In October 2020, bayberry (Myrica rubra (Lour.) S. et Zucc.) leaves that beginning to wither were collected...
Weizhi Xun and Changwang Wu contributed equally to this work In October 2020, bayberry (Myrica rubra (Lour.) S. et Zucc.) leaves that beginning to wither were collected in Wencheng County (N27°50', E120°03'). In the county, 4,120 ha of bayberry were planted, of which 58% were affected by the disease, and the severity of leaf disease per plant was 5 to25%. Bayberry leaves leaves were intensely green at first, then gradually turned yellow and brown,and completely withered. The leaves did not fall off at the beginning of the symptoms, but did fall after 1 to 2 months. To identify the pathogen, 50 diseased leaves with typical symptoms were collected from 10 diseased trees. Leaves with necrotic-tissue were firstly washed with sterilized water, and then tissue at the disease-/ healthy-tissuejunction removed with sterile surgical scissors. The tissues were soaked in 75% ethanol for 30 s, followed by 5% sodium hypochlorite solution for 3 to 4 min, rinsed with sterilized water 4 times, and placed on sterilized filter paper. The tissue was placed on PDA medium and cultured in an incubator at 25℃ (Nouri et al. 2019). After the colonies grew around the tissue, mycelia with the same morphology was selected and placed on fresh PDA. A pure culture of the pathogen was obtained after repeating the last process several times. The isolatedcolonies were white, with a round edge and a light-yellow back. Conidia were straight or slightly curved, with 3 to 4 septations. The internal transcribed spacer (ITS) regin translation elongation factor 1-α gene (TEF1-α), and beta-tubulin gene (β-TUB)(Chaiwan et al. 2020; Li et al. 2021; Chen et al. 2020; Chen et al. 2018) of the two strains were amplified and sequenced, and the sequences were uploaded to Gen bank (GenBank accession number.ACCC 35162: ITS OP891011, TEF1-α OP903533, β-TUB OP903531; ACCC 35163: ITS OP891012, β-TUB OP903534, TEF1-α OP903532). BLAST alignment indicated that the ITS sequence of strain ACCC 35162 had 100% identity with NR_147549.1, the TEF sequence had 100% identity with MT552449.1, and the TUB sequence had 99.87% identity with KX895323.1; the ITS sequence of strain ACCC 35163 had 100% identity with NR_147549.1, the TEF sequence had 100% identity with MT552449.1, and the TUB sequence had 99.86% identity with KX895323.1. A Phylogenetic tree using maximum likelihood/rapid bootstrapping run on XSEDE based on the above three sequences inferred that the two strains were identical to P. kenyana (Miller et al. 2010). The strain was preserved in the Agricultural Culture Collection of China (Preservation numbers: ACCC 35162, ACCC 35163). Following Koch's rule, six healthy plants leaves were inoculated with conidial suspensions (106 conidia mL-1) and mycelial plugs (5 mm),and then placed in an artificial climate chamber (25℃, 90% humidity, 16-h light), sterile PDA and sterile water were used as blank controls. The same treatment was applied to fresh bayberry leaves under laboratory conditions, and brown spots were observed after three days. There were no symptoms in the control group. The experimental symptoms were similar to those in the field. Using the previous method, the same fungus was reisolated from the diseased leaves and again identified as P. kenyana. As far as we know, this is the first report causing disease on P. kenyana infecting bayberry in China, this disease seriously affected the yield and quality of bayberry and caused economic losses to farmers.
PubMed: 37172979
DOI: 10.1094/PDIS-03-23-0450-PDN -
Plant Disease May 2023Pandanus amaryllifolius, also known as pandan, is a perennial herb, growing in Indonesia, China and the Maluku Islands (Wakte et al. 2009). It is the only plant with...
Pandanus amaryllifolius, also known as pandan, is a perennial herb, growing in Indonesia, China and the Maluku Islands (Wakte et al. 2009). It is the only plant with aromatic leaves in the Pandanaceae. It is widely used in food, medicine, cosmetics and other industries, and is also known as "Oriental Vanilla." Pandan is planted in Hainan province over 1,300 ha and is the main plant intercropped among the forest trees. From 2020, the leaf spot was surveyed for three years. Diseased leaves occurred on 30 to 80% of the surveyed plants, with an incidence of 70% and yield losses of 40%. The disease occured from mid-November to April and was most severe at low temperatures and humidity. Initial symptoms were pale green spots, that formed dark brown, nearly circular lesions. As the lesions expanded, their centers became greyish white, with yellow halos at the junction of the diseased and healthy tissue. When the humidity was high, there were small black spots scattered in the center of the lesion. Symptomatic leaf samples were collected from four different sites. The leaf surface was disinfested with 75% ethyl alcohol for 30 s and washed with sterile distilled water three times. Samples from the junction of diseased and healthy tissue (0.5 × 0.5 cm) were removed and placed on potato dextrose agar (PDA) medium containing 100 µg/mL of cefotaxime sodium and cultivated in a dark incubator at 28°C. After two days, hyphal tips from the edges of growing colonies were transferred to fresh PDA plates for further purification. Following Koch's postulates, colonies from strains were used as inoculum in pathogenicity tests. Colonies with 5 mm diameter were inoculated upside onto fresh and healthy pandan leaves via wounding method (pinpricked by sterilized needles) and non-wounding method. Sterilized PDA was used as control. All plants were setted three replicates and were incubated at 28℃ for 3 to 5 days. When symptoms on leaves similar to those in the field appeared, the fungus were reisolated The colonies formed on PDA were also consistent with the original isolate (Scandiani et al, 2003). After seven days, the colony covered the whole petri dish with white, petal-shaped growth with a slight concentric, annular bulge in the center, irregular edges, with black acervuli emerging at a later stage of colony growth. Conidia were fusiform, 18.1±1.6 × 6.4±0.3 μm, showing four septations and five cells, the middle three cells were brownish black to olivaceous, and the apical cell colorless with two to three filaments, 21.8±3.5 μm long. The caudate cell was colorless with one stalk 5.9±1.8 μm long (Zhang et al. 2021; Shu et al. 2020). According to the colony and conidia characteristics, the pathogen was initially identified as Pestalotiopsis spp. (Benjamin et al. 1961). To confirm the pathogen identity, we used the universal primers ITS1/ITS4, targeting primers EF1-728F/EF1-986R and Bt2a/Bt2b sequences (Tian et al. 2018). The sequences of the PCR products were deposited in NCBI GenBank with accession numbers OQ165166 (ITS), OQ352149 (TEF1-α) and OQ352150 (TUB2). BLAST results showed that the sequences of the ITS, TEF1-α and TUB2 genes shared 100% homology with the sequences of Pestalotiopsis clavispora. The maximum likelihood method was used in the phylogenetic analysis. The result showed that LSS112 was clustered with Pestalotiopsis clavispora with a support rate of 99%. Based on morphological and molecular characteristics, the pathogen was confirmed as Pestalotiopsis clavispora. To our knowledge, this is the first report of leaf spot of pandan caused by Pestalotiopsis clavispora in China. This research will be immediately helpful for the diagnosis and control the disease on pandan.
PubMed: 37157095
DOI: 10.1094/PDIS-02-23-0302-PDN -
Plant Disease Apr 2023Faba bean (Vicia faba L.) is a cool-season legume crop, planted worldwide as an essential source of protein-rich foods, vegetables, and animal feeds. In China, the total...
Faba bean (Vicia faba L.) is a cool-season legume crop, planted worldwide as an essential source of protein-rich foods, vegetables, and animal feeds. In China, the total cultivated area of faba bean in 2019 was 839,618 square hectometers (hm2) and the production was 1,740,945 tons (t) (Ji et al. 2022). In May 2021, a leaf spot disease on faba bean plants with about 80% disease incidence was observed in a 0.3 ha commercial field located at Zunyi City (27°31'43.80″ N, 106°23'34.27″ E), Guizhou Province, China. The leaves of the early affected plants appeared circular dark brown spots, which then rapidly develop into large irregular shaped lesions if conditions remain favorable. Severe infection can result in extensive defoliation of plants and lesions on pods. Symptomatic leaves were collected and cut into small pieces, surface sterilized with 75% ethanol for 30 s followed by 2% NaClO for 1 min, rinsed with sterile distilled water three times, and incubated on PDA plates amended with streptomycin sulfate (0.5 mg/L) at 25°C for 2-4 days. Two purified cultures were obtained through single-spore culture. Colonies on PDA attaining 62 mm diam after 2 weeks, white or pale red, edge undulate, with dense aerial mycelium on the surface, fruiting bodies black to reddish brown. Conidia fusoid to ellipsoid, 4-septate, straight to slightly curved, 18.5-22 × 6-7 μm (av. = 20 × 7 μm, n = 30); basal cell obconic, hyaline, 3.5-5 μm long, with a single appendage, 2.5-6 μm; three median cells doliiform, verruculose, olivaceous with slightly red (second cell from base 4-5 μm long; third cell 4.5-5.5 μm long; fourth cell 3-5.5 μm long); apical cell conical, hyaline, 2.5-4 μm long, with 1-3 tubular appendages, 13-22.5 μm long. The morphological characters of our studied specimens fit well with Pestalotiopsis rosea (Maharachchikumbura et al. 2012). For molecular identification, the internal transcribed spacer (ITS) region, partial β-tubulin (tub2) and translation elongation factor 1-alpha (tef1-α) genes were amplified and sequenced using primer pairs ITS5/ITS4 (White et al. 1990), T1/Bt-2b (Glass and Donaldson 1995) and EF1-728F/EF-2 (Carbone and Kohn 1999). The DNA sequences of two isolates GUCC 195257 (OP364052, OP391714, OP391713) and GUCC 195258 (OP364053, OP391716, OP391715) were deposited in GenBank. The BLAST searches revealed that these sequences had 99% (537/539 bp), 100% (453/453 bp), 99% (591/593 bp), 99% (537/539 bp), 100% (453/453 bp) and 99% (574/576 bp) nucleotide identity to the ex-type strain of P. rosea (JX399005, JX399036, JX399069), respectively. In addition, multi-locus phylogenetic analysis showed that both isolates clustered with P. rosea with full statistical support. The phylogenetic relationship of Pestalotiopsis species supported the identification of our isolates as P. rosea. In the pathogenicity test, the leaves of ten healthy 2-week-old faba bean plants were spray inoculated with a conidial suspension (1 × 106 conidia/ml) of the two isolates. Another set of five plants that were sprayed with sterilized distilled water served as the controls. Treated plants were kept at 25°C in a greenhouse with a photoperiod of 12 h and 70% relative humidity. After one week, all inoculated leaves showed symptoms similar to those of the infected faba bean observed in the field, whereas controls were symptomless. The pathogenicity test was performed twice with similar results. The fungus was reisolated from the inoculated plants and identified as P. rosea by morphological and molecular evidence, thus confirming Koch's postulates. To our knowledge, this is the first report of P. rosea causing leaf spot on faba bean in the world. Pestalotiopsis species are well-known phytopathogens that can cause a variety of diseases, including leaf spots, chlorosis, and various postharvest (Wang et al. 2019). The results of this study not only contribute to accurately identify this disease in the fields of faba bean production, but also provide an important reference for developing specific control measures.
PubMed: 37081628
DOI: 10.1094/PDIS-12-22-2920-PDN -
International Journal of Molecular... Feb 2023The effectiveness of nitric oxide (NO) for control of grey spot rot cause by in harvested loquat fruit and its probable mechanisms have been investigated. The results...
The effectiveness of nitric oxide (NO) for control of grey spot rot cause by in harvested loquat fruit and its probable mechanisms have been investigated. The results showed that NO donor sodium nitroprusside (SNP) did not evidently inhibit mycelial growth and spore germination of , but resulted in a low disease incidence and small lesion diameter. SNP resulted in a higher hydrogen peroxide (HO) level in the early stage after inoculation and a lower HO level in the latter period by regulating the activities of superoxide dismutase, ascorbate peroxidase and catalase. At the same time, SNP enhanced the activities of chitinase, β-1,3-glucanase, phenylalanine ammonialyase, polyphenoloxidase, and total phenolic content in loquat fruit. However, SNP treatment inhibited the activities of cell wall-modifying enzymes and the modification of cell wall components. Our results suggested that NO treatment might have potential in reducing grey spot rot of postharvest loquat fruit.
Topics: Nitric Oxide; Disease Resistance; Hydrogen Peroxide; Eriobotrya; Nitroprusside; Fruit
PubMed: 36901799
DOI: 10.3390/ijms24054369 -
Plant Disease Mar 2023American ginseng ( L.) is an herbaceous perennial understory plant. It was listed as endangered species by the Convention on International Trade in Endangered Species of...
American ginseng ( L.) is an herbaceous perennial understory plant. It was listed as endangered species by the Convention on International Trade in Endangered Species of Wild Fauna and Flora (McGraw et al. 2013). Leaf spot symptoms were observed on 6-year-old cultivated American ginseng on a research plot (8 x 12 ft raised bed under a tree canopy) in Rutherford Co., TN in July 2021 (Fig. 1a). Symptomatic leaves were exhibiting light brown leaf spots with chlorotic haloes 0.5 to 0.8 cm in diameter, mostly confined within or bounded by veins. As the disease progressed, leaf spots expanded and coalesced into irregular shapes with necrotic centers, resulting in a tattered appearance of the leaf. Disease severity was about 50 to 80% of leaf area and incidence was 10% out of 20 plants. Plant tissues were surface sterilized with 10% NaOCl for 60s and washed thrice with sterile water and plated on potato dextrose agar (PDA). Colony growth of the isolates FBG880 and FBG881 on PDA were round, white, thick, and flocculent at the front of the plate and showed a yellowish-ringed shape on the back 10 days after incubation at 25°C (light/dark: 12/12h). Acervular conidiomata containing abundant conidia were observed on PDA. They were globose, 1.0 to 1.8 mm in diameter, and found as solitary or aggregated clusters. Conidia contained five cells (average 13.03±3.50 x 14.31±3.93 µm, = 30). The middle three cells were light brown to brown. The basal and apical cells were nearly triangular, and transparent, with two to three (7:3 ratios, respectively) apical appendages (average 13.27±3.27 µm) and a basal appendage (average 4.50±0.95 µm, = 30). To determine pathogen identity, total DNA was extracted using DNeasy PowerLyzer Microbial Kit from fungal colonies on PDA (isolates FBG880 and FBG881). The ribosomal internal transcribed spacer (ITS) region, beta-tubulin (BT), and translation elongation factors 1-α (EF1) genetic markers were amplified using ITS1/ITS4 (White et al. 1990), T1/T2 (Stefańczyk et al. 2016), and EF1/EF2 (O'Donnell et al. 1998), respectively. The sequences (GenBank accession nos. ITS: OQ102470 and OQ103415; BT: OQ107059 and OQ107061; and EF1: OQ107060 and OQ107062) are 100% similar to (CSUFTCC16 and CFCC53882) (Jiang et al. 2022; Li et al. 2021) (Fig. 2). Based on morphology and molecular characteristics, the isolates were identified as . To conduct the pathogenicity trial, six healthy 1-year-old American ginseng plants, germinated from seeds and grown in the greenhouse were spray inoculated with a conidial suspension (1×10 conidia/ml) (FBG880). Six control plants were sprayed with sterile water. All plants were covered with plastic bags and incubated in a greenhouse set at 21 to 23°C, 70% relative humidity and 16-h photoperiod. After 48 h, bags were removed and plants were maintained under the same conditions. After one month, while control plants remained asymptomatic (Fig. 1b), inoculated plants started to exhibit symptoms resembling those in the research plot (Fig. 1c). Fungal isolates resembling in cultural characters were consistently recovered from inoculated plants and their identity as was confirmed by DNA sequencing. To our knowledge, this is the first report of leaf spot disease caused by on American ginseng. Identification of this pathogen and confirmation of its pathogenicity are fundamental to future disease management approaches.
PubMed: 36890123
DOI: 10.1094/PDIS-01-23-0078-PDN -
Journal of Fungi (Basel, Switzerland) Feb 2023tolerates the dry and frigid climate of Beijing, China, and effectively filters out particles during the winter. However, fungal infestation frequently causes extreme...
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 specimens were collected from seven districts in Beijing. Seventy-nine isolates were identified as 22 fungal species in seven genera. The species were , , , , , , , , , , , , , , , , , , , , , and . On the basis of morphological and phylogenetic analyses, , , , and were introduced as novel species. , , and were subsequently confirmed as pathogens of leaves by pathogenicity testing. This study provides an important assessment of the fungi associated with diseases of in Beijing, China.
PubMed: 36836386
DOI: 10.3390/jof9020271 -
Taxonomic Advances from Fungal Flora Associated with Ferns and Fern-like Hosts in Northern Thailand.Plants (Basel, Switzerland) Feb 2023Ferns are one of the most significant plant groupings that comprise a substantial proportion of the plant flora due to the fact of their great diversity, especially in...
Ferns are one of the most significant plant groupings that comprise a substantial proportion of the plant flora due to the fact of their great diversity, especially in tropical areas. The biodiversity of fungi associated with ferns and fern-like hosts has also received little attention in studies. Plant samples were collected from diseased and dead plants of ten fern or fern-like species from Chiang Rai in northern Thailand. Forty-one isolates were selected from the obtained isolates for molecular and morphological analysis, with a focus on pathogenic fungal genera and consideration of the diversity in host and geographical location. Twenty-six species belonging to seven genera (, , , , , , and ) in six families were identified. Thirty new hosts, eight new geographical hosts, and one new species, , are described. , , , , and were isolated for the first time from leaf spots. Additionally, new reservoirs and geographical locations for species previously isolated from leaf spots or whose pathogenicity was established were found. However, more studies are necessary to prove the pathogenicity of the fungi isolated from the leaf spots and to identify the fungi associated with other species of ferns.
PubMed: 36771768
DOI: 10.3390/plants12030683