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Plant Disease Sep 2022Euonymus japonicas is widely planted as an important landscape species throughout China. In June 2021, a serious gray blight disease was detected on E. japonicas in...
Euonymus japonicas is widely planted as an important landscape species throughout China. In June 2021, a serious gray blight disease was detected on E. japonicas in Henan Province (32°30'58" N, 112°19'44" E), causing severe defoliation of infected trees with a foliar disease incidence of 52 to 70% (n = 100). Gray spots initially appeared on leaves, gradually expanded into irregular white blotches with dark brown borders, eventually leading to wilting and death of the leaves. The junctions between the lesion and healthy tissue of infected leaves were cut into 3 × 3-mm pieces, surface sterilized with 1% NaClO solution for 1 min, rinsed in sterile water, and placed on PDA plates with 50 μg/ml of streptomycin. Three isolates (HY94, HY95, and HY98) were selected for subsequent experiments. The colonies reached 80-85 mm diam after 7 days at 25°C, with undulated margins, white to pale in color, with moderate aerial mycelium on the surface. Conidiomata were globose, solitary, and dark black. Conidia were ellipsoid, straight to slightly curved, 4-septate, 19 to 26.4 × 5 to 7.5 μm (n=100). The apical cell was cylindrical and hyaline, with 2 to 3 tubular apical appendages, unbranched, filiform, 2.5 to 3.5 μm in length. The basal appendage was single, unbranched, centric, 1.5 to 3 μm long. The characteristics were close to those of Pestalotiopsis spp. (Maharachchikumbura et al. 2013). The genomic DNA was extracted, and the rDNA internal transcribed spacer (ITS), the β-tubulin gene (TUB), and the translation elongation factor 1-alpha gene (TEF1) were amplified by primers ITS1/ITS4, Bt2a/Bt2b, and EF1-728F/EF1-986R, respectively (Carbone and Kohn, 1999). Sequences were submitted to GenBank with accession numbers OL840327-OL840329(ITS), OL961454-OL961456(TUB), and OL961448-OL961450 (TEF1). BLASTn analyses of ITS, TUB, and TEF1 sequences exhibited 99.46, 99.05, and 96.53% similarity to the sequences of Pestalotiopsis disseminata strain MEAN1166 (ITS, 548/551 bp; MT374688) (Silva et al. 2020), PSH2000I-066 (TUB, 418/422 bp; DQ333575), and TAP29O082 (TEF1, 250/259 bp; AB453850), respectively in GenBank. The three isolates formed a clade with the type strains, MEAN 1166 and MAFF238347 of P. disseminata in phylogenetic trees, being clearly seperated from other Pestalotiopsis spp. Based on morphological and molecular evidence, the pathogen was identified as P. disseminata (Maharachchikumbura et al. 2011). To fulfill Koch's postulates, pathogenicity was tested with three isolates. Ten healthy leaves of 5-year-old intact plants were used per isolate and inoculated with mycelial plugs on both nonwounded and wounded leaves. Control leaves were inoculated with agar plugs. The inoculated plants were placed at 28°C in a greenhouse (90% relative humidity). Distinct lesions were observed after 10 days. The pathogen reisolated was identical to that of the original cultures according to phenotype and ITS sequences. The control leaves showed no obvious symptoms. P. disseminata is known to cause disease on several important plants in China, such as Camellia japonica (Zhang et al. 2012), Pinus armandii (Hu et al. 2007), and Tripterygium wilfordii (Kumar et al. 2004). This is the first report of gray blight disease caused by P. disseminata on E. japonicas in China and worldwide. The fungal pathogen identification will provide valuable information for prevention and management of gray blight disease associated with E. japonicas.
PubMed: 36096099
DOI: 10.1094/PDIS-06-22-1373-PDN -
Plant Disease Aug 2022Nageia nagi (Thunb.) Kuntze is widely cultivated in China for its ornamental and economic value. In August 2019, a leaf spot was observed on N. nagi plants at the campus...
Nageia nagi (Thunb.) Kuntze is widely cultivated in China for its ornamental and economic value. In August 2019, a leaf spot was observed on N. nagi plants at the campus of Jiangxi Agricultural University (28°45'56″N, 115°50'21″E). Disease incidence was about 35%, and the diseased leaf rate was above 40%. The early symptoms were small spots on the edge or tip of the leaves. The spots gradually expanded and became reddish-brown, eventually developing large irregular lesions. Leaf pieces (5 × 5 mm) from the lesion borders were surfaced sterilized in 70% ethanol for 30 s, followed by 2% NaOCl for 1 min, and then rinsed three times with sterile water. Tissues were placed on potato dextrose agar (PDA) and incubated at 25°C (Zhang et al. 2021). Pure cultures were obtained by transferring hyphal tips to new PDA plates. Twenty-six isolates of Colletotrichum ssp. were obtained (isolation frequency about 82%). Three representative single-spore isolates (ZB-1, ZB-3, and ZB-7) were used for morphological studies and phylogenetic analyses. Colonies on PDA medium of the three isolates were white to gray in color with cottony mycelia. Conidia were single-celled, straight, hyaline, cylindrical, clavate, and measured 14.1-17.9 ×4.4-6.8 µm (15.6 ± 1.2 × 5.4 ± 0.3 µm, n = 100). Appressoria were brown to dark brown, ovoid to clavate, slightly irregular to irregular, and ranged from 5.7-9.3 × 4.6-6.9 µm (7.8 ± 0.2 × 5.6 ± 0.3 µm, n=100). Morphological features were similar to Colletotrichum siamense complex (Weir et al. 2012). The internal transcribed spacer (ITS) regions, actin (ACT), calmodulin (CAL), β-tubulin 2 (TUB2), chitin synthase (CHS-1), and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were amplified from genomic DNA for the three isolates using primers ITS1/ITS4, ACT-512F/ACT-783R, CL1/CL2, T1/Bt2b, CHS-79F/CHS-354R and GDF/GDR (Weir et al. 2012), respectively. Sequences of them deposited in GenBank under nos. OL826760 - OL826762 (ITS), OL830205 - OL830207 (ACT), OL830196 - OL830198 (GAPDH), OL830193 - OL830195 (TUB2), OL830199 - OL830201 (CHS-1), and OL830202 - OL830204 (CAL). A Blast search of GenBank showed that ITS, ACT, GAPDH, TUB2, CHS-1, and CAL sequences of the three isolates were identical to Colletotrichum siamense at a high level (Table 1). A maximum likelihood and Bayesian posterior probability analyses using IQtree v. 1.6.8 and Mr. Bayes v. 3.2.6 with the concatenated sequences placed ZB-1, ZB-3, and ZB-7 in the clade of C. siamense. Based on the multi-locus phylogeny and morphology, three isolates were identified as C. siamense. The pathogenicity of three isolates was tested on six N. nagi plants (three for inoculation, three for controls), which were grown in the field. Six healthy leaves were wounded with a sterile needle and inoculated with 10 µL of conidial suspension (1 × 106 conidia/mL) per plant. Healthy leaves were inoculated with ddH2O as a control by the same method. All the inoculated leaves were covered with plastic bags to keep a high-humidity environment for 2 days. The experiment was repeated three times. All the inoculated leaves showed similar symptoms to those observed in the field, whereas control leaves were asymptomatic for 8 days. C. siamense was reisolated from the lesions, whereas no fungus was isolated from control leaves. Up to now, Cephleuros virescens, Pestalotiopsis longisetula, Alternaria tenuissima, A. alternate, and Phoma glomerata could infect N. nagi (Zhou et al. 2015; Zhang et al. 2016), and cause leaf spots in China. To our knowledge, this is the first report of C. siamense causing leaf spots on N. nagi worldwide. This work provided crucial information for epidemiologic studies and appropriate control strategies for this newly emerging disease.
PubMed: 35947012
DOI: 10.1094/PDIS-06-22-1417-PDN -
Frontiers in Microbiology 2022Tea () is an important crop that is mainly used in the food industry. This study using the metabolome and microbiome investigates the resistance factors of wild tea...
Tea () is an important crop that is mainly used in the food industry. This study using the metabolome and microbiome investigates the resistance factors of wild tea plant resources against tea gray blight disease, which is caused by (Sawada) Steyaert. According to the interaction analysis of tea leaves and pathogenic fungus, the resistance of wild tea plant resource "R1" (Resistance 1) to tea gray blight disease was significantly higher than that of wild tea plant resource "S1" (Susceptibility 1). The difference between "R1" and "S1" in the metabolome was obvious. There were 145 metabolites that significantly changed. The phenolic acids and flavonoids were the major increased categories in "R1," and it included 4-O-glucosyl-sinapate and petunidin-3-o-(6"-o-p-coumaroyl) rutinoside. Six metabolic pathways were significantly enriched, including aminoacyl-tRNA biosynthesis, flavone, and flavonol biosynthesis. In terms of bacteria, there was no significant difference between "S1" and "R1" in the principal component analysis (PCA). was the major bacterial genus in "S1" and "R1." In addition, each of the two resources had its own predominant genus: was a predominant bacterial genus in "S1" and was a predominant bacterial genus in "R1." In terms of fungi, the fungal diversity and the abundance of the two tea plant resource samples could be distinguished clearly. The fungal component of "S1" was more abundant than that of "R1" at the genus level. x was the predominant fungal genus of "S1," and was the predominant fungal genus of "R1." The relative abundance of and were significantly different between "S1" and "R1." was identified as a potential biomarker. They correlated with some metabolites enriched in "S1" or "R1," such as L-arginine and quercetin-3-o-(2"-o-rhamnosyl) rutinoside-7-o-glucoside. Overall, phenolic acids, flavonoids, and could be functional metabolites or microorganisms that contributed to improving the resistance of wild tea plant resources to tea gray blight disease.
PubMed: 35910661
DOI: 10.3389/fmicb.2022.907962 -
Journal of Fungi (Basel, Switzerland) Jul 2022Amplicon sequencing is a powerful tool for analyzing the fungal composition inside plants, whereas its application for the identification of etiology for plant diseases...
Amplicon sequencing is a powerful tool for analyzing the fungal composition inside plants, whereas its application for the identification of etiology for plant diseases remains undetermined. Here, we utilize this strategy to clarify the etiology responsible for tea leaf brown-black spot disease (LBSD), a noticeable disease infecting tea plants etiology that remains controversial. Based on the ITS-based amplicon sequencing analysis, species were identified as separate from spp. and sp., which are concluded as the etiological agents. This was further confirmed by the fungal isolation and their specific pathogenicity on diverse tea varieties. Based on the morphologies and phylogenetic analysis constructed with multi-loci (ITS, LSU, and ), two novel species-tentatively named and as reference to their host plants-were proposed and characterized. Here, we present an integrated approach of ITS-based amplicon sequencing in combination with fungal isolation and fulfillment of Koch's postulates for etiological identification of tea plant disease, revealing new etiology for LBSD. This contributes useful information for further etiological identification of plant disease based on amplicon sequencing, as well as understanding, prevention, and management of this economically important disease.
PubMed: 35893150
DOI: 10.3390/jof8080782 -
Persoonia Jul 2022Novel species of fungi described in this study include those from various countries as follows: , , and on soil, from stem cankers of , from stem of , and from...
Novel species of fungi described in this study include those from various countries as follows: , , and on soil, from stem cankers of , from stem of , and from leaves of , as endophyte from roots of , from stem of , from leaves of × and from roots of , from intertidal wood and (incl. gen. nov.) on buds of , from a bark beetle gallery on and (incl. gen. nov.) from wood of , and (incl. gen. nov.) from bore dust of feeding on wood, (incl. gen. nov.) endophytic in roots of and on soil. , on soil and from soil. , from , on soil. , (incl. gen. nov.), and on dead culms of , on and (incl. gen. nov.) on , on dead culm of , on stems of , on dead culm of undetermined , (incl. gen. nov.) on dead leaves of and (incl. gen. nov.) on dead twigs of , from sand grains attached to a piece of driftwood on a sandy beach. , on the base of living and amongst dead leaves of and herbs. , (incl. gen. nov.) on living leaves of sp. and on twigs of , on soil, endophytic in roots of , on soil, from fluvial sediments, from a dead twig of , and in soil. , , and on soil. , , and on soil. , on overwintered stems of , from living leaves of and from a minute mushroom sporocarp. Morphological and culture characteristics are supported by DNA barcodes. : Crous PW, Boers J, Holdom D, et al. 2022. Fungal Planet description sheets: 1383-1435. Persoonia 48: 261-371. https://doi.org/10.3767/persoonia.2022.48.08.
PubMed: 38234686
DOI: 10.3767/persoonia.2023.48.08 -
Frontiers in Chemistry 2022Novel pyrazolecarbamide derivatives bearing a sulfonate fragment were synthesized to identify potential antifungal and antiviral agents. All the structures of the key...
Novel pyrazolecarbamide derivatives bearing a sulfonate fragment were synthesized to identify potential antifungal and antiviral agents. All the structures of the key intermediates and target compounds were confirmed by nuclear magnetic resonance (NMR) and high-resolution mass spectrometry (HRMS). The single-crystal X-ray diffraction of the compound showed that pyrazole carbamide is a sulfonate. The antifungal activities of the target compounds against Colletotrichum camelliae, Pestalotiopsis theae, Gibberella zeae, and Rhizoctonia solani were evaluated at 50 μg/ml. Among the four pathogens, the target compounds exhibited the highest antifungal activity against Rhizoctonia solani. The compound (EC = 0.45 mg/L) had higher antifungal activity than the commercial fungicide hymexazol (EC = 10.49 mg/L) against R. solani, almost similar to bixafen (EC = 0.25 mg/L). Additionally, the target compounds exhibited protective effects against TMV. Thus, this study reveals that pyrazolecarbamide derivatives bearing a sulfonate fragment exhibit potential antifungal and antiviral activities.
PubMed: 35815220
DOI: 10.3389/fchem.2022.928842 -
Journal of Fungi (Basel, Switzerland) May 2022Avocado () represents an important emerging tropical crop in Italy, especially in the southern regions. In this study, young plants of avocado showing symptoms of stem...
Avocado () represents an important emerging tropical crop in Italy, especially in the southern regions. In this study, young plants of avocado showing symptoms of stem and wood lesion, and dieback, were investigated. Isolations from symptomatic tissues consistently yielded colonies of -like species. The characterization of representative isolates was based on the observation of morphological characters, the effect of temperature on mycelial growth rate, and on the sequencing of three different gene regions, specifically ITS, , and . Phylogenetic analyses were conducted based on maximum parsimony and maximum likelihood approaches. The results showed the presence of two species, viz. and , the latter of which is here described as a new species. Pathogenicity tests were conducted using the mycelial plug technique on young potted avocado trees for both species. The results showed that both species were pathogenic to avocado. This study represents the first report of these two species affecting avocado and results in the description of a new species within the genus . Based on phylogeny, is combined in .
PubMed: 35736045
DOI: 10.3390/jof8060562 -
Plant Disease Aug 2022
Topics: Camellia sinensis; Gene Expression Profiling; Pestalotiopsis; Tea
PubMed: 35728096
DOI: 10.1094/PDIS-12-21-2698-A -
Plants (Basel, Switzerland) May 2022Val d'Agri is an important orchard area located in the Basilicata Region (Southern Italy). A phenomenon affecting cv. "Golden Delicious" apples which lead to tree death...
Val d'Agri is an important orchard area located in the Basilicata Region (Southern Italy). A phenomenon affecting cv. "Golden Delicious" apples which lead to tree death has been observed in the past several years in this area. This phenomenon has already been detected in about 20 hectares and is rapidly expanding. The symptoms observed were "scaly bark" and extensive cankers, mainly located in the lower part of the trunk, associated with wood decay. Dead plants ranged from 20% to 80% and, in many cases, trees were removed by farmers. In order to identify the causes of this phenomenon, investigations were started in autumn/winter 2019. In order to determine the possible causal agents, fungal and bacterial isolations, from symptomatic tissues, were performed in laboratory. Bacterial isolations gave negative results, whereas pure fungal cultures (PFCs) were obtained after 3-4 passages on potato dextrose agar (PDA) media. Genetic material was extracted from each PFC and amplified by PCR using three pairs of primers: ITS5/4, Bt2a/Bt2b and ACT-512F/ACT-783R. The amplicons were directly sequenced, and nucleotide sequences were compared with those already present in the NCBI GenBank nucleotide database. All isolated fungi were identified based on morphological features and multilocus molecular analyses. , and were most frequently isolated, while , spp. and were less frequently isolated. All nucleotide sequences obtained in this study have been deposited into the EMBL database. Pathogenicity tests showed that . was the most pathogenic and aggressive fungus, while sp. was demonstrated to be the less virulent one. All the investigated fungi were repeatedly reisolated from artificially inoculated twigs of 2-year-old apple trees, cv. "Golden Delicious", and subsequently morphologically and molecularly identified. The role played by the above-mentioned fungi in the alterations observed in field is also discussed.
PubMed: 35631798
DOI: 10.3390/plants11101374 -
Pathogens (Basel, Switzerland) May 2022causes crown rot in wheat. This study aimed to assess the effects of the bacterial strain QTH8 isolated from rhizosphere soil against . Bacterial strain QTH8 was...
causes crown rot in wheat. This study aimed to assess the effects of the bacterial strain QTH8 isolated from rhizosphere soil against . Bacterial strain QTH8 was identified as in accordance with the phenotypic traits and the phylogenetic analysis of 16S rDNA and gene sequence. Culture filtrates of bacterial strain QTH8 inhibited the mycelial growth of and resulted in mycelial malformation such as tumor formation, protoplast condensation, and mycelial fracture. In addition, bacterial strain QTH8 also inhibited the mycelial growth of , sp., , , , , , and . The active compounds produced by bacterial strain QTH8 were resistant to pH, ultraviolet irradiation, and low temperature, and were relatively sensitive to high temperature. After 4 h exposure, culture filtrates of bacterial strain QTH8-when applied at 5%, 10%, 15%, 20%, 25%, and 30%-significantly reduced conidial germination of . The coleoptile infection assay proved that bacterial strain QTH8 reduced the disease index of wheat crown rot. In vivo application of QTH8 to wheat seedlings decreased the disease index of wheat crown rot and increased root length, plant height, and fresh weight. Iturin, surfactin, and fengycin were detected in the culture extract of bacterial strain QTH8 by matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS). Bacterial strain QTH8 was identified for the presence of the , , , , , , and genes using the specific polymerase chain reaction primers. QTH8 has a vital potential for the sustainable biocontrol of wheat crown rot.
PubMed: 35631116
DOI: 10.3390/pathogens11050595