First Report of Alternaria alternata Causing Leaf blight on Epimedium sagittatum (Sieb. et Zucc.) Maxim. in China

Epimedium sagittatum (Sieb.et Zucc.) Maxim. is an important material of traditional Chinese medicine because of the rich content of flavonoids that are used to treat osteoporosis, liver cancer, and sexual dysfunction (Liu et al. 2013). A leaf blight was observed on E. sagittatum in Zhumadian City, China (32°58'12" N, 114°37'48" E, continental monsoon climate) in June 2021. Survey indicated that about 18% of the plants were infected in a 266-ha commercial planting area. The initial symptoms were white patches with tan borders, irregular in outline, with small black particles visible on the center of the lesions. In a week or so, patches extended throughout the leaf, and then leaves withered. Thirty leaves with symptoms collected from five different sites were cut into 5×5 mm pieces, and then surface-sterilized with 75% ethanol for 15 s followed by rinsing with double distilled water (ddH2O) three times. The pieces were then disinfested with 0.1% HgCl2 solution for 30 s, and rinsed with ddH2O, then placed onto potato-dextrose agar medium (PDA) and incubated in the dark for 3 d at 28°C. Eight fungal isolates were purified; of these, only the isolate HY2-1 infected the host plant and was selected for further morphological characterization. The colonies of HY2-1 were olive green with loose aerial hyphae on PDA. Conidiophores were single or branched, producing brown conidia in short chains. Conidia were obclavate, obpyriform, or ellipsoidal, 15.9-47.3 µm × 7.6-16.6 µm (n=50) and pale brown or dark brown with a short cylindrical beak at the tip that contained 1-5 transverse septa and 0-4 longitudinal septa. Morphological characteristics of the isolate were identical with those of Alternaria species (Huang et al. 2022). For molecular identification, the internal transcribed spacers (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) (Weir et al. 2012), major allergen Alt a 1(Alt a 1) and translation elongation factor 1-α gene (TEF) (Lawrence et al. 2013) were amplified and sequenced using the primers ITS4/5, GDF/GDR, Alt-F/R, and EF1-728F/986R, respectively. The results of the sequencing were uploaded to GenBank as ITS (OR418487), GAPDH (OR419792), Alt a 1 (OR419794), and TEF (OR419796), respectively. Phylogenetic analyses were performed by concatenating all the sequenced loci using the Bayesian method in Phylosuite (Zhang et al.2020). The phylogenetic tree indicated that the isolate belongs to the A. alternata clade with a bootstrap value of 75%. The pathogen was identified as A. alternata based on the morphological and molecular results. To satisfy Koch's postulates, a conidial suspension (106 conidia/mL) of the HY2-1 was prepared with ddH2O to infect the healthy plants. Ninety healthy leaves on 30 plants in pots were punctured using a sterilized needle, and then inoculated by spraying the conidial suspension on the wounded leaves in a greenhouse at 25°C and 80% relative humidity. The control plants were sprayed with ddH2O. The plants showed similar symptoms to the original infected plant 15 d after inoculation. The controls showed no symptoms. A pure culture of A. alternata was isolated and identified again as previously described. Leaf blight caused by A. alternata has been reported on Taro (Liu et al. 2020), Toona ciliata (Wang et al. 2023), etc. To our knowledge, this is the first report of E. sagittatum leaf blight caused by A. alternata in China. The results will help to develop effective control strategies for leaf blight on E. sagittatum.

First Report of Alternaria alternata Causing Leaf Spot on Oenothera biennis in China

Oenothera biennis is a versatile plant that can be used for both ornamental and medicinal purposes. Its potential in treating a range of diseases is noteworthy and has been studied extensively (Bayles et al. 2009). In September 2022, leaf spot on O. biennis was first observed in a 0.2 ha plant experimental demonstration land in Libo County (25°23'24″N, 108°4'22″E), Guizhou Province, China. The incidence of all O. biennis was about 60% over the 0.2 ha surveyed. Initially, red round or irregular spots appeared on the leaves, which then gradually turned dry yellow. To identify the cause, diseased tissues (5 mm2) from the margin of the lesions were surface disinfected by immersion in 75% ethanol for 30 sec, and 7% sodium hypochlorite for 1 min, and then rinsed three times with sterile distilled water (Sun et al. 2022). The tissues were cultured in potato dextrose agar (PDA) at 25℃. After 7 days, further purification was performed by transferring onto the new PDA and potato carrot agar (PCA) by single-spore isolation. After 8 days, the colonies on PDA were 80 mm in diameter, cotton-like in texture, dark green in color and nearly circular in shape with a white edge. The conidia on the PCA were short-chains, pear-shaped or oval, pale brown, smooth surface, 15.3-30.8 × 8.3-12.6μm (n = 150). Beaks were columnar or conical, 0-6.0 × 0-4.0μm (n = 100). Conidiophores were solitary straight or flexuous less branched, dark brown, and measured 14.0-60.5 × 3.0-4.5μm. Based upon morphological observations, all these characteristics were consistent with those of Alternaria alternata (Simmons 2007). To further identify the fungal species, internal transcribed spacer (ITS) rDNA regions, glyceraldehyde-3-phosphate dehydrogenase (gpd), Alternaria major allergen (Alt a 1), RNA polymerase second largest subunit gene (RPB2) and translation elongation factor 1-alpha (TEF 1) were amplified and sequenced using the primers ITS4/ITS5, RPB2-5F/RPB2-7CR, gpd1/gpd2, EF1-728F/EF1-986R, and Alt-for/Alt-rev (Woudenberg et al. 2015). Sequences were deposited in GenBank (ITS: OM319523; RPB2: OM849249; gpd: OM296248; TEF1: OM238124; Alt a 1: OM649813). The similarity of the representative isolate YJC and the type strain CBS 595.93 (ITS: KP124320; RPB2: KP124788; gpd: KP124175; TEF1: KP125096; Alt a 1: JQ646399) on the phylogenetic tree was 98%. Therefore, the fungus was identified as A. alternata by morphology and phylogenetic analysis. To confirm pathogenicity, a spore suspension (1 × 106 conidia/ml) of the representative isolate YJC was sprayed on the leaves of six healthy plants and six plants sprayed with distilled water as controls. The plants used in the experiment were covered with plastic bags for 48 h (Luo et al. 2012). After 8 days, all inoculated plants exhibited symptoms of the disease, while the control plants remained symptom-free. The experiment was conducted twice using the same approach. The fungus that has been inoculated was reisolated from the leaves of the infected plants and identified as A. alternata through morphological observation, thus fulfilling Koch's postulates. To the best of our knowledge, this is the first documented case of O. biennis leaf spot caused by A. alternata. This pathogen could pose a threat to O. biennis yield and result in economic losses. For further development of specific control measures, it is important to confirm the identity.

First Report of Alternaria alternata Causing Leaf Blight on Elsholtzia ciliata in China

Elsholtzia ciliata is an annual medicinal plant characterized to the family Lamiaceae Martinov. It is grown in most parts of China and has high economic value as a traditional Chinese medicine. In September of 2022, E. ciliata plants located at the planting base of traditional Chinses medicine in Daying county (30°35'40″N, 105°14 12″E), Sichuan Province, China, were recorded with leaf blight. The incidence of symptomatic plants was 15% (30 infected plants out of 200 surveyed). The symptoms included an irregular necrotic lesion at the tip of the leaf, which gradually expanded across the entire leaf. To elucidate the cause of the symptoms, 12 symptomatic leaves were sampled from four different plants and 5×5 mm section, including symptomatic and non-symptomatic tissue was excised. Tissue samples were disinfected in 75% ethanol for 30s, and 7% sodium hypochlorite for 1 min, and then rinsed three times with sterile distilled water (Sun et al. 2022). The sampled tissues were placed onto potato dextrose agar (PDA) and incubated at 25℃ in the dark. Seven days later, single spores were recovered onto fresh PDA (Zhu et al. 1992). Colonies on PDA initially appeared white, developing grayish-green conidia with white margins. Conidia (n=150) were collected and observed under the microscope. The conidia were smooth walled and dark brown, with pear-shaped, 12.1-31.4 × 5.0-9.4μm, with 3-5 transverse septa, 1-3 longitudinal or oblique septa. Conidiophores were thick, dark brown, simple with multiple conidial scars, 5.0-75.5 × 2.5.0-5.0μm. Based on morphological observations the 12 isolates were most similar to Alternaria alternata (Simmons 2007). The internal transcribed spacer (ITS) rDNA regions, glyceraldehyde-3-phosphate dehydrogenase (gpd), Alternaria major allergen (Alt a 1), RNA polymerase second largest subunit gene (RPB2) and translation elongation factor 1-alpha (TEF 1) were amplified and sequenced using the primers ITS4/ITS5, RPB2-5F/RPB2-7CR, gpd1/gpd2, EF1-728F/EF1-986R, and Alt-for/Alt-rev respectively (Woudenberg et al. 2015). The sequences of representative isolate (XR) were uploaded in GenBank (ITS: OM319521, RPB2: OM849248, gpd: OM296240, TEF1: OM238122, and Alt a 1: OM649814). The bootstrap value of the isolate and the type strain CBS 595.93 (ITS: KP124320, RPB2: KP124788, gpd: KP124175, TEF1: KP125096, and Alt a 1: JQ646399) on the phylogenetic tree was 99%. Therefore, based on morphology and phylogenetic analysis the fungus was identified as A. alternata. To verify pathogenicity, a spore suspension (1 × 106 conidia/ml) of the representative isolate XR was misted onto the foliage of six twenty-day-old non-symptomatic plants. Six additional plants were sprayed with distilled water and used as controls. The plants were covered with plastic bags for 48 h and incubated at a temperature of 28℃ in the dark. Eight days later, all inoculated plants demonstrated similar symptoms as recorded on the original source, while the control plants were symptomless. The experiment was repeated three times with similar results. A. alternata was re-isolated from the artificially inoculated plants, hence fulfilling Koch's postulates. To our best knowledge this is the first report of leaf blight caused by A. alternata in China on E. ciliate. The disease may be an economic threat and should be further monitored and studied.

First report of leaf spot disease caused by Alternaria alternata on Polygonatum cyrtonema Hua in Hunan Province of China

Polygonatum cyrtonema Hua, a perennial plant of the Asparagaceae family, is an important herb in Chinese medicine and is mainly grown in the Chinese provinces of Guizhou, Hunan, Yunnan, Anhui, and Zhejiang (Chen et al. 2021). In June 2021, a new case of leaf spot disease was detected in an 80 m2 plantation of P. cyrtonema on Xuefeng Mountain, Huaihua City, Hunan Province (27°17'30″N, 110°24'20″E). It infected almost 40% of the total planted area. Initially, irregular light brown spots appeared on the leaves, gradually turning dark brown and coalescing to form large necrotic areas, after which the affected plant turned yellow and eventually died. Ten disease samples were collected from ten plants in the plantation area. The leading edge of necrotic tissues were rinsed with sterile water and then disinfected with 3% hydrogen peroxide for 30 s, followed by 75% ethanol for 90 s, and rinsed three times with sterile water. Samples were then placed on water agar plates and incubated in the dark in a constant temperature incubator at 28 ℃ for 3-5 days. After mycelial growth was observed in the media, the hyphae were transferred to potato dextrose agar plates and incubated for 3-5 days at 28 ℃ in the dark. Ultimately, 12 purified fungal isolates were obtained, some of which were morphologically similar, including 10 that were Alternaria (83.3% isolation rate). Three representative isolates (HJYB1, HJYB2, and HJYB3) were selected for further study. The initial colonies were grayish green with white fluffy mycelia on the surface and a prominent white rim, which became brown with dense, cottony aerial mycelia as the colonies matured. The conidia were obpyriform or ellipsoidal, pale to dark brown, with 0-4 transverse and 0-3 longitudinal septa, some with a short cylindrical beak at the tip. They measured 11.826-28.873 × 6.231-26.018 μm (n = 100). To further confirm the identity of the isolates, their rDNA internal transcribed spacer region (ITS), β-microtubulin (TUB2) and translation elongation factor-1 (TEF-1) genes were amplified and sequenced using the ITS4/ITS5, TUB2F/R and EF-526F/1567R primers, respectively (Hong et al. 2006). The sequences were submitted to GenBank (ITS: OR513924, OR513964, OR519874; TUB2: OR526928, OR533421, OR526929; TEF: OR526926, OR533420, OR526927). A concatenated phylogenetic tree of the three genes showed that the isolate clustered significantly with Alternaria alternata. Based on morphological identification and phylogenetic tree analysis, the isolate was identified as A. alternata. We carried out pathogenicity tests on four uniformly growing P. cyrtonema plants. Three of these plants were used as experimental plants and one as a control. For each plant, three young leaves were selected and inoculated with 6 × 6 mm PDA blocks, while sterile PDA blocks were used as controls. The treated plants were subjected to 10 days of stable temperature in a climatic chamber set at 28°C, 80% constant relative humidity and 12 hours of light per day. The pathogenic lesions appeared and the pathogens re-isolated from the diseased leaves showed similar morphological characteristics to representative isolates and were confirmed as A. alternata by DNA sequencing, thus fulfilling Koch's postulates. A. alternata is the major causal agent of leaf spot on P. sibiricum (Zou et al. 2023) and Agrimonia pilosa (Jiang et al. 2023). As far as we know, leaf necrosis caused by A. tenuissima has been found on P. cyrtonema (Li et al. 2020). To our knowledge, this is the first report of A. alternata causing leaf spot disease in P. cyrtonema. These findings form the basis for the management of this leaf spot disease.

First Report of Alternaria Leaf Blight Caused by Alternaria alternata on Agrimonia pilosa in China

Agrimonia pilosa is widely distributed in East Asian countries, including China, Japan, Korea and Mongolia. It is a common medicinal plant with pharmacological effects such as procoagulant, antioxidant, anti-inflammatory. In September 2022, leaf blight was the first time observed on A. pilosa in a 2.6-ha A. pilosa plantation in Harbin, Heilongjiang Province, China. The incidence of the disease reached 80%, and almost every leaf had symptoms. Initially, yellow-to-brown spots appeared on the tips or edges of the leaves. As the disease progressed, the lesions gradually enlarged and merged. Finally, the whole leaf withered. To identify the causal agent, twenty symptomatic leaves were arbitrarily collected from ten diseased plants. Diseased leaf pieces that measured 5 mm2 were disinfested in 75% ethyl alcohol for 30 s and 7% NaOCl for 60 s, rinsed three times in sterile distilled water (Sun et al. 2022), and placed on potato dextrose agar (PDA). Ten fungal isolates obtained by single-spore isolations were selected for further study. Colonies of these isolates on PDA were off-white to black with abundant cotton-like aerial hyphae, and the colony diameter was 75 to 90 mm. The isolates produced conidia that were ovate to nearly oval, gray-to-black, with 1 to 4 transverse septa and 0 to 2 oblique septa, smooth surfaced, parietal cells extending into the beak, and measured 15.0 to 35.5 × 6.0 to 13.0 μm. Conidiophores were taupe, erect or curved, branched, with pronounced spore marks. All ten fungal isolates were morphologically similar to Alternaria alternata (Simmons 2007). Two representative isolates LYC and LYC01 were used for molecular identification. The internal transcribed spacer (ITS) region, RNA polymerase second largest subunit (RPB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-alpha (TEF1), and Alternaria major allergen (Alt a 1) were amplified with the primers ITS4/ITS5(White et al. 1990), RPB2-5F2/RPB2-7CR (Khodaei and Arzanlou 2013), gpd1/gpd2, EF1-728F/EF1-986R (Sun et al. 2023) and Alt-for/Alt-rev (Woudenberg et al. 2015). The resulting sequences were deposited in GenBank (ITS, OM319510, OQ788347; RPB2, OM296263, OQ862336; GAPDH, OM296236, OQ862337; TEF1, OM238113, OQ862338; Alta1, OM171260, OQ862339). Phylogenetic analyses showed 100% identity between LYC and LYC01 and the type strain CBS 121456. Thus, the fungus was identified as A. alternata based on morphology and molecular analysis. Pathogenicity tests were done by spraying conidial suspensions containing 106 conidia/ml of A. alternata isolates LYC and LYC01 on leaves of six healthy A. pilosa plants, separately. Another six plants were sprayed with sterile distilled water as control. Both groups of plants were covered with plastic bags and placed in a greenhouse maintained at 25⁰ C. Plastic bags were removed from plants after 48 h. Fifteen days later, the disease symptoms on the inoculated plants were similar to those observed in the original sample, whereas the control plants remained healthy. The pathogenicity tests were conducted three times. The strains of A. alternata were reisolated from the symptomatic inoculated plants, confirming Koch's postulates. To our knowledge, this is the first report of A. alternata causing leaf blight on A. pilosa in China. Identifying the agent responsible for the disease can help with disease control and plant management in the field.

First Report of Black Spot Disease Caused by Alternaria alternata on Persimmon Fruit in China

Sweet persimmon is native to Japan and valued for its fruit, which are high in sugar and vitamins. In October 2021, symptoms were observed on persimmon (Diospyros kaki L. cv. Yangfeng) fruits in cold storage room in Suiping county, Henan Province (32.59 °N, 15 113.37 °E). Initially, small circular dark-brown spots were visible on the fruit rind, turning into irregular sunken dark areas, and eventually rotting 15% of 200 fruits after four weeks of cold storage (10°C, 95% relative humidity). To isolate the causal agent, 10 fruits of symptomatic tissues (4 mm²) were surface-sterilized in 2% sodium hypochlorite (NaOCl) for 1 minute, washed three times in sterile distilled water, then aseptically transferred to potato dextrose agar (PDA) and incubated for 7 days at 25°C. Fungal colonies were isolated from plant tissue, and on three colonies of similar morphology, single-spore isolation was performed. On PDA, the isolates produced circular colonies of fluffy aerial mycelia, gray-brown in the center with gray-white margins. Conidia were dark brown, obclavate or pyriform, with 0 to 3 longitudinal septa and 1 to 5 transverse septa, and a size range of 19.2 - 35.1 × 7.9 - 14.6 μm (n=100). Conidiophores were olivaceous, septate, straight, or bent, with a length of 18 - 60 × 1 - 3 μm (n=100). These morphological characteristics identify the isolates as Alternaria alternata (Simmons. 2007). Genomic DNA was extracted from a representative isolate YX and re-isolated strain Re-YX by cetyltrimethylammonium bromide (CTAB). The primers of ITS1/4, Alt-F/R, GPD-F/R, EF1/2, EPG-F/R (Chen et al. 2022), RPB2-5F/7cR (Liu et al. 1999), and H3-1a/1b (Lousie et al. 1995) were used to amplify the partial internal transcribed spacer (ITS) region, Alternaria major allergen (Alt a1), Glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-alpha (TEF), endo-polygalacturonase (endoPG), RNA polymerase second largest subunit (RPB2) and Histone 3 (His3), respectively. GenBank accession No of ITS, Alt a1, GAPDH, TEF, endoPG, RPB2, His3 were ON182066, ON160008 to ON160013 for YX and OP559163, OP575313 to OP575318 for Re-YX respectively. Sequence data of Alternaria spp. were downloaded from GenBank and the BLAST analysis showed 99%-100% homology between various A. alternata strains (ITS: MT498268; Alt a1: MF381763; GAPDH: KY814638; TEF: MW981281; endoPG: KJ146866; RPB2: MN649031; His3: MH824346). A phylogenetic analysis based on ITS, Alt a1, GAPDH, TEF, and RPB2 sequences using MEGA7 (Molecular Evolutionary Genetics Analysis) revealed that the isolate YX and Re-YX were clustered in A. alternata clade (Demers M. 2022). For the pathogenicity test, seven-day-old cultures were used to create spores suspensions (5.0 × 105 spores/mL) of each of the three isolates. Ten µL aliquots from each isolate were inoculated onto ten needle-wounded persimmon fruits; ten additional fruits were inoculated with water only to serve as controls. The pathogenicity test was three replications. Fruits were deposited in a climate box at 25°C, 95% relative humidity. Seven days post-inoculation, the wounded fruit treated with spore suspensions displayed black spot symptoms similar to the symptoms on the original fruit. There were no symptoms on the control fruits. The strain Re-YX was re-isolated from the symptomatic tissue of inoculated fruits and its identity confirmed using the morphological and molecular methods previously mentioned, fulfilling Koch's postulates. The persimmon fruit rot caused by A. alternata had been reported in Turkey and Spain (Kurt et al., 2010, Palou et al., 2012). According to our knowledge, this is the first report of black spot disease on persimmon fruits caused by A. alternata in China. The disease could infect persimmon fruits during cold storage, so more control methods should be developed to prevent postharvest disease of persimmon in the future.

First Report of Alternaria alternata Causing White Leaf Spot on Allium tuberosum in China

Puding County is the major Allium tuberosum growing area in Guizhou Province of China. In 2019, white leaf spots were observed on Allium tuberosum in Puding County (26.31°N, 105.64°E). The white spots, ranging from elliptic to irregular in shape, first appeared on leaf tips. With disease aggravation, spots gradually coalesced, forming necrotic patches with yellow margins causing leaf necrosis; sometimes there was gray mold on dead leaves. The incidence of the diseased leaf rate was estimated to be 27-48%. To identify the pathogenic agent, 150 leaf tissues (5 mm × 5 mm) were obtained from disease-healthy junctions of 50 diseased leaves. Leaf tissues were disinfected in 75% ethanol for 30 s, soaked in 0.5% sodium hypochlorite for 5 min, and flushed three times with sterile water, before being placed on potato dextrose agar (PDA) in the dark at 25 °C. When colonies appeared, the mycelial tips were picked and placed on new PDA. Purified fungus was obtained after repeating this last step several times. The colonies were grayish-green with white round margins. Conidiophores (2.7-4.5 μm × 27-81 μm) were brown, straight, or flexuous with branches and septa. Conidia (8-34 µm × 5-16 µm) were brown, with 0-5 transverse septa and 0-4 longitudinal septa. The 18S nuclear ribosomal DNA (nrDNA; SSU), 28S nrDNA (LSU), RNA polymerase II second largest subunit (RPB2), internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and translation elongation factor 1-alpha (TEF-α) (Woudenberg et al. 2013) were amplified and sequenced. The sequences were deposited in GenBank (ITS: OP703616, LSU: OP860684, SSU: OP860685, GAPDH: OP902372, RPB2: OP902373, TEF1-α: OP902374). According to BLAST analysis, the ITS, LSU, GAPDH, RPB2, SSU, and TEF1-α of the straishowed 100% (689 of 731 base pairs; bp), 100% (916 of 938 bp), 100% (579 of 600 bp), 100% (946 of 985 bp), 100% (1093 of 1134 bp), and 100% (240 of 240 bp) sequence identity to those of Alternaria alternata (ITS: LC440581.1, LSU: KX609781.1, GAPDH: MT109295.1, RPB2: MK605900.1, SSU: ON055699.1 and TEF1-α: OM220081.1). A phylogenetic tree was constructed using PAUP4 and the maximum parsimony method with 1000 replicas of bootstrapping for all datasets. According to morphological characteristics and phylogenetic analysis, FJ-1 was identified as Alternaria alternata (Simmons 2007, Woudenberg et al. 2015). The strain was preserved in the Agricultural Culture Collection of China (preservation number: ACC39969). To determine the pathogenicity of Alternaria alternata against Allium tuberosum, wounded healthy leaves were inoculated with a conidial suspension (106 conidial/mL) and round mycelial plugs (4mm). Sterile agar PDA plugs with no mycelium or sterile water were inoculated as negative controls. Three days later, white spots appeared on the wounded leaves inoculated with mycelial plugs or conidial suspension. However, the symptoms caused by conidial suspensions were weaker than those caused by mycelial plugs. No symptoms were observed in the control group. The experimental symptoms were consistent with the phenomena observed in the field. The same fungus was reisolated from necrotic lesions and identified as Alternaria alternata using the method described above. To our knowledge, this is the first report of Alternaria alternata causing white leaf spots on Allium tuberosum in China, a disease seriously affected the yield and quality of Allium tuberosum and caused economic losses to farmers. Reference: Simmons EG (2007) Alternaria: an identification manual. CBS Fungal Biodiversity Centre, Utrecht, the Netherlands. Woudenberg JHC, Groenewald JZ, Binder M, Crous PW ( 2013) Alternaria redefined. Stud Mycol, 75: 171-212. https://doi.org/10.3114/sim0015. Woudenberg JHC, Seidl MF, Groenewald JZ, Vries M de, Stielow JB, Thomma BPHJ, Crous PW (2015) Alternaria section Alternaria: Species, formae speciales or pathotypes? Stud Mycol, 82:1-21. https://doi.org/10.1016/j.simyco.2015.07.001.

First report of Alternaria alternata causing leaf blight on Trollius chinensis in China

Trollius chinensis is widely distributed in east Asian countries that include China, Siberia, and Japan, with antibacterial, antiviral, anti-inflammatory and analgesic activity for medical applications. In August 2021, leaf blight was observed on nearly 80~95% of T. chinensis plants growing in Daxinganling (51.43°N, 126.39°E) from Heilongjiang Province, China. Initial symptoms were gray-black necrosis, wilting progressing from the leaf margin, and eventual defoliation. Six T. chinensis plants with typical symptoms were randomly collected, and three fresh leaf samples were collected from each plant. Diseased leaf pieces that measured 5 mm square were disinfected in 75% ethyl alcohol for 30 s and 7% NaClO for 60 s, rinsed three times in sterile distilled water, and placed on potato dextrose agar (PDA). Twelve fungal isolates, obtained by single-spore isolations, were selected for further. These isolates produced colonies that measured 63 to 73 mm in diameter after 7 days growth on PDA. Colonies were black to brown in color with gray-white aerial hyphae on their surfaces, neat edges, olive green on the back. The isolates produced conidia that were ovate to pear-shaped, brown to black in color, with 1 to 4 transverse septa and 0 to 1 oblique septa, smooth surfaced, parietal cells extending into the beak, and measured 12.5 to 37.5 × 5.0 to 12.5 μm(n=150). Conidiophores were dark, erect or curved, branched, with pronounced spore marks, and measured 35.0 to 50.0 × 4.0 to 5.0 μm(n=150). All twelve fungal isolates were morphologically similar to Alternaria alternata (Simmons 2007). Two representative isolates jlh01 and jlh02 were used for molecular identification. The internal transcribed spacer (ITS) region, RNA polymerase second largest subunit (RPB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-alpha (TEF1), and Alternaria major allergen (Alt a 1) were amplified with the primers ITS4/ITS5, RPB2-5F2/RPB2-7CR (Khodaei and Arzanlou 2013), gpd1/gpd2, EF1-728F/EF1-986R (Nishikawa and Nakashima 2020) and Alt-for/Alt-rev (Woudenberg et al.2015). The resulting sequences were deposited in GenBank (ITS, OM095427, OM108099; RPB2, OM131213, OM131214; GAPDH, OM201165, OM201166; TEF1, OM131211, OM131212; Alta1, OM201167, OM201168). Phylogenetic tree results showed 100% similarity between jlh01, jlh02 and the type strain CBS 118812. Morphological and molecular analysis results confirmed the identity of the fungus as A. alternata. Pathogenicity tests were done by spraying water-spore suspensions containing 106 spores per ml of A. alternata isolates jlh01 and jlh02 on leaves of six healthy T. chinensis plants, separately. Six control plants were sprayed with distilled water and both sets of plants covered with plastic bags and placed in a greenhouse maintained at 25⁰ C. Plastic bags were removed from all plants after 48 h. Black brown lesions and concentric rings developed on spore-inoculated plants after 15 days and control plants remained symptomless. The pathogenicity tests were conducted three times. A. alternata was reisolated and identified based on morphological and molecular traits, thus fulfilling Koch's postulates. To our knowledge, this is the first report of A. alternata causing leaf blight on T. chinensis in China. Based on the plant's medicinal value, this report provides the basis for further research and control of T. chinensis leaf blight.

First Report of Alternaria Leaf Blight Caused by Alternaria alternata on Convallaria majalis in China

Convallaria majalis is native to temperate zones in the northern hemisphere, Europe, Asia, North America and China, and has excellent ornamental properties and medicinal value. In July 2021, leaf blight was observed on nearly 70~90% of C. majalis plants growing in Heilongjiang University of Chinese Medicine campus (45.72°N, 126.68°E) from Harbin City, China. The typical symptom on the leaves is irregular dark brown lesions. As the brown lesions expanded and eventually coalesce, they form large necrotic areas, with chlorosis, curling, and wilting at the apical edge of the diseased leaf. Ten symptomatic leaves were randomly collected from twenty different plants at the site. Several fragments of diseased tissues (5×5mm) were disinfected in 75% ethyl alcohol for 30 s and 7% NaOCl for 60 s, rinsed three times in sterile distilled water, plated on potato dextrose agar (PDA), and incubated at 25 °C in the dark for 7 days. Twenty purified fungal isolates were obtained by single spore isolation. The morphology of all the twenty isolates was similar, and two isolates were randomly selected (LL, LL01) for further study. Colonies of these isolates on PDA were off-white to black with abundant cotton-like aerial hyphae, and the diameter of the colony is 72 to 85 mm. On potato carrot agar (PCA) medium, these isolates produced light brown and solitary conidiophore with septum. Conidia were ovate to pear-shaped, brown to black in color, with 1-4 transverse septa and 0-2 longitudinal septa, and measured 20.5 to 38.5 × 7 to 13.5 µm (n=100). The isolates were identified as Alternaria alternata according to their morphological characteristics (Simmons 2007). Two representative isolates LL and LL01 were used for molecular identification. The internal transcribed spacer (ITS) region, RNA polymerase second largest subunit (RPB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-alpha (TEF1), and Alternaria major allergen (Alt a 1) were amplified with the primers ITS4/ITS5(White et al. 1990), RPB2-5F2/RPB2-7CR (Khodaei and Arzanlou 2013), gpd1/gpd2, EF1-728F/EF1-986R (Nishikawa and Nawashima 2020) and Alt-for/Alt-rev (Woudenberg et al. 2015). The resulting sequences were deposited in GenBank (ITS, OM319508, OP799847; RPB2, OM649830, OP830846; GAPDH, OM296234, OP830845; TEF1, OM393717, OP830844; Alta1, OM171258, OP830847). Phylogenetic analyses showed 100% identity between LL and LL01 and the type strain CBS 118815. Thus, the fungus was identified as A. alternata based on morphology and molecular analysis. Pathogenicity tests were done by spraying conidial suspensions containing 106 conidia/ml of A. alternata isolates LL and LL01 on leaves of six healthy C. majalis plants, separately. Another six plants were sprayed with sterile distilled water as control and both sets of plants covered with plastic bags and placed in a greenhouse maintained at 25⁰ C. Plastic bags were removed from plants after 48 h. After 15 days inoculation, the similar symptoms were observed on the inoculated plants, whereas control plants remained healthy. The pathogenicity tests were conducted three times. A. alternata was reisolated and identified based on morphological and molecular traits, thus fulfilling Koch's postulates. To our knowledge, this is the first report of A. alternata causing leaf blight on C. majalis in China and worldwide. The result will serve as the foundation for management leaf blight of C. majalis.

First Report of Leaf Blight Caused by Alternaria alternata on Leonurus japonicus in China

Leonurus japonicus is cultivated throughout China and is commonly used for medicinal, cosmetic, ornamental and culinary purposes. A leaf blight on L. japonicus was first observed in September 2021 in a field at a research and development farm in Liupu Town, Zhuji City (120.23°N, 29.72°E), Zhejiang Province, China. Disease incidence was more than 90% across the 30 ha. Symptoms included nearly round black to brown spots on the leaf margins that gradually enlarged causing leaves to wither. To isolate and identify the causal organism, 12 L. japonicus leaves from four different plants with typical symptoms were collected, and 5×5 mm tissues were excised at the junction of the diseased and healthy tissue. Samples were surface-sterilized in 75% ethanol for 30s, followed by 7% NaOCl for 1 min, and rinsed three times with sterile distilled water (Sun et al. 2022), and placed on potato dextrose agar (PDA) at 25℃. After 7 d, single-spore isolations were conducted. (Zhu et al. 1992) After 8 d, the colonies on PDA were 75 to 86 mm diam, dark brown, with an irregular shape. A total of 150 conidia on PDA were an inverted rod shape or oval, dark brown, 20 to 45 × 7.5 to 11.3 μm, with a short beak and no septa; or columnar or conical, 2.5 to 20 × 2.5 to 5 μm, with 0 to 6 transverse septa, 0 to 3 longitudinal or oblique septa. The conidiophores were dark or branched, with multiple conidial scars, 15 to 62.5 × 3.0 to 5.0 μm. According to morphological characteristics observation, the 12 isolates were most similar to A. alternata (Simmons 2007). To further identify the fungal species, internal transcribed spacer (ITS) rDNA regions, and the following genes: glyceraldehyde-3-phosphate dehydrogenase (GAPDH), Alternaria major allergen (Alt a 1), RNA polymerase second largest subunit (RPB2) and translation elongation factor 1-alpha (TEF) were amplified and sequenced using the primers ITS4/ITS5, RPB2-5F/RPB2-7CR, gpd1/gpd2, EF1-728F/EF1-986R, and Alt-for/Alt-rev (Woudenberg et al. 2015). Sequences were uploaded (ITS: OM095432, OM095433; RPB2: OM275409, OM275410; GAPDH: OM275411, OM275412; TEF1: OM160771, OM160772; Alta1: OM160773, OM160774). The similarity of YMCLZL, YMCLZL01 and the type strain CBS 59593 T (KP124320, KP124175, KP125096, KP124788, JQ646399) on the phylogenetic tree was 97%. To evaluate pathogenicity, a conidial suspension (106 conidia/ml) of isolates YMCLZL or YMCLZL01 was sprayed on the leaves of six 15-day old healthy plants. The same number of plants were also sprayed with only distilled water as non-inoculated controls. Plants were covered with plastic bags at 25℃ for 48 h. After 8 d, inoculated plants had round, gray and black spots on leaves, while the control plants did not. The experiment was repeated three times. The fungus was reisolated from all diseased leaves fulfilling Koch's postulates. To our knowledge, this is the first report of L. japonicus leaf blight caused by A. alternata on L. japonicus worldwide. The occurrence of leaf blight will be challenging for the commercial production of L. japonicus.

First Report of Alternaria Leaf Blight Caused by Alternaria alternata on Phedimus aizoon in China

Phedimus aizoon is native to east Asian countries that including China, Siberia, Korea, Mongolia, and Japan. In China, the plant is highly valued for use in folk medicine, for detoxification and analgesia, blood pressure, hemostasis, and used as an ornamental. In August 2021, a leaf spot and blight disease were observed on P. aizoon in a 120-ha field in Pizhou, Jiangsu Province, China where disease incidence reached 90%, and almost every leaf was withered. Early symptoms appeared as dark brown lesions on leaf margins that enlarged and coalesced to form large necrotic areas. In efforts to determine the cause of the disease, ten symptomatic leaves were randomly collected from ten different plants at the site. Diseased leaf pieces that measured 5 mm2 were disinfected in 75% ethyl alcohol for 30 s and 7% NaOCl for 60 s, rinsed three times in sterile distilled water, and placed on potato dextrose agar (PDA). Ten fungal isolates obtained by single-spore isolations were selected for further study. These isolates produced colonies that measured 70 to 82 mm in diameter after 7 days growth on PDA. Colonies were black to brown in color with gray-white aerial hyphae on their surfaces. The isolates produced conidia that were ovate to pear-shaped, brown to black in color, with 1 to 4 transverse septa and 0 to 1 oblique septa, smooth surfaced, parietal cells extending into the beak, and measured 10 to 35.5 × 5.0 to 12.5 μm. Conidiophores were brown, erect or curved, branched, with pronounced spore marks, and measured 7.5 to 37.5 × 2.5 to 5.0 μm. All ten fungal isolates were morphologically similar to Alternaria alternata (Simmons 2007). Two representative isolates FC01 and FC02 were used for molecular identification. The internal transcribed spacer (ITS) region, RNA polymerase second largest subunit (RPB2), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-alpha (TEF1), and Alternaria major allergen (Alt a 1) were amplified with the primers ITS4/ITS5, RPB2-5F2/RPB2-7CR (Khodaei and Arzanlou 2013), gpd1/gpd2, EF1-728F/EF1-986R (Nishikawa and Nakashima 2020) and Alt-for/Alt-rev (Woudenberg et al. 2015). The resulting sequences were deposited in GenBank (ITS, ON584560, ON564492; RPB2, ON729984, ON703241; GAPDH, ON652866, ON652867; TEF1, ON652868, ON652869; Alta1, ON652870, ON652871). Phylogenetic analyses showed 100% identity between FC01 and FC02 and the type strain CBS 916.96. Thus, the fungus was identified as A. alternata based on morphology and molecular analysis. Pathogenicity tests were done by spraying conidial suspensions containing 106 conidia per ml of A. alternata isolates FC01 and FC02 on leaves of five healthy P. aizoon plants, separately. Five control plants were sprayed with distilled water and both sets of plants covered with plastic bags and placed in a greenhouse maintained at 25⁰ C. Plastic bags were removed from plants after 48 h. Dark brown lesions developed on inoculated plants after 16 days and control plants remained symptomless. The pathogenicity tests were conducted three times. A. alternata was reisolated and identified based on morphological and molecular traits, thus fulfilling Koch's postulates. To our knowledge, this is the first report of A. alternata causing leaf blight on P. aizoon in China and worldwide. Based on the plant's medicinal value, further studies should be directed toward control of this disease.

First report of Alternaria alternata causing leaf spot of Cynanchum atratum Bunge in China

Cynanchum atratum Bunge belongs to Asclepiadaceae, and is distributed in North Korea, Japan and China. Its roots and rhizomes have antibacterial, antiviral, anti-inflammatory and anti-tumor effects. In July 2021, a leaf spot was observed in a 1.3 ha plantation of C. atratum in Harbin, Heilongjiang Province in China. The incidence was more than 85%. Initial symptoms were yellowing leaves with circular, or ellipsoid brown spots forming on leaf apexes or leaf margins. Small spots expanded and coalesced to form large circular or irregular, pale to light brown lesions, and leaves finally withered. Thirty, 5 × 5 mm, leaf pieces excised from the junction of symptomatic and healthy tissues were collected from different leaves with typical symptoms on ten plants, sterilized in 75% ethanol for 30s, then in 2% NaClO for 30s, rinsed in sterile water three times, placed on potato dextrose agar (PDA) plates, incubated for 5 days at 28°C in the dark, further purified by single spore method and transferred to new PDA and potato carrot agar (PCA) plates. Finally, 12 fungal isolates, most with similar morphology, were selected. After a 7-day incubation in the dark, colonies on PDA were 53 to 70 mm in diameter, circular and grayish brown. A total of 150 conidia were evaluated for morphology. Conidia were single or in chains, ovoid to inverted pear-shaped, with 2 to 6 transverse septa, 0 to 4 longitudinal or oblique septa, and measured 16.5 to 56.5μm × 9.0 to 16.5 μm. Beaks and supposititious beaks were mostly columnar, rarely conical, 0 to 22.5 μm × 2.5 to 4.0 μm. Conidiophores were solitary or clustered, pale brown, erect or bent, branched or unbranched, separated, 53.5 to 120.5 μm × 2.5 to 6.0 μm (Fig 1). Based on morphological characteristics, the fungus was identified as Alternaria alternata (Simmons 2007). Two representative isolates (BW and BW2) were used for molecular identification. Internal transcribed spacer rDNA regions (ITS), RNA polymerase II second largest subunit (RPB2), Alternaria major allergen (Alt a 1), translation elongation factor 1-alpha (TEF-1 α) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) gene were amplified and sequenced with the primers ITS1/ITS4 (White, et al. 1990), RPB2-5F2/RPB2-7CR (Khodaei and Arzanlou. 2013), Alt-F /Alt-R (Hong et al. 2005), TEF-F/TEF-R (Carbone and Kohn. 1999) and GDF/GDR (Templeton et al. 1992). The sequences obtained were deposited in GenBank (ITS: OM317915, ON534349; RPB2: OM296253, ON550475; Alt a 1: OM171248, O550474; TEF: OM238096, O550473; GAPDH: OM296217, ON550472). The phylogenetic analysis of maximum likelihood tree by MEGA 7 showed that the two isolates had 98% similarity with A. alternata CBS 916.96 (Fig 2). To test pathogenicity, 40-day-old plants were sprayed with spore suspensions (1×106 spores /mL) from 7-day-old cultures of BW and BW2. Each isolate was inoculated onto 3 leaves on 3 separate plants. Three other plants were sprayed with sterile distilled water as a control. The plants were incubated in the greenhouse (natural light, T: 25℃, H: 50%). After 15 days, the leaves turned yellow and irregular grayish spots appeared. The fungi reisolated from the inoculated leaves shared the same morphological and molecular features as A. alternata, fulfilling Koch's postulates. No fungi were isolated from the control group. This is the first time to report A. alternata causing leaf spot on C. atratum. Leaf spot can reduce the yields of C. atratum and this study provides a basis for the prevention and control of the disease.

First report of leaf spot on Clematis brevicaudata DC. caused by Alternaria alternata in China

Clematis brevicaudata DC. is distributed in China, Korea, Mongolia, Russia and Japan. This plant is both ornamental and medical, used in the treatment of nervous disease, dyskinesia and other diseases. In September, 2019, a leaf spot on C. brevicaudata was first found in a 5 ha C. brevicaudata plantation in Harbin, Heilongjiang Province, China. The incidence was about 80%. The symptoms were elliptical, circular, or irregular brown to black necrotic lesions in leaf apex and leaf margin. Ten fresh sample leaves with typical symptoms were collected from ten C. brevicaudata plants. The tissues (5mm×5mm) between symptomatic and healthy junction were cut and surface disinfected in 75% ethanol, and with 7% NaClO for 1 min, then rinsed three times with sterilized water, 30s each time. The sterilized tissues were inoculated on potato dextrose agar (PDA) plates for 7 days at 25℃. The colonies were obtained and transferred onto new PDA and potato carrot agar (PCA) plates by single spore method to further purify. After 7 days, the colonies on PDA were 50 to 63 mm in diameter, circular, grayish brown, with white aerial hyphae. A total of 150 conidia on PCA were single or in chains, ovoid, inverted pear, 2 to 7 transverse septa, 0 to 3 longitudinal or oblique septa, 17.5 to 57.5 × 7.5 to 17.5 μm. Beaks and supposititious beaks were mostly columnar, rarely conical, 2.5 to 6.0 × 2.0 to 3.0 μm. Conidiophores were solitary or clustered, pale brown, erect or bent, branched or unbranched, separated, 112.0 to 151.0 × 5.1 to 14.7 μm. Ten isolates purified on PDA were obtained. Morphological identification showed the ten isolates were similar and appeared to be Alternaria alternata (Simmons, 2007). Two strains from ten isolates were selected for molecular identification. Genomic DNA was extracted from mycelia of two isolates (LD2020520 and LD2020521) on PDA using a modified CTAB method. Internal transcribed spacer rDNA regions (ITS), RNA polymerase II second largest subunit gene (RPB2), Alternaria major allergen (Alt a 1), endopolygalacturonase (endoPG) and glyceraldehyde 3-phosphate dehydrogenase (gpd) were amplified and sequenced using two directional sequencing with the primers ITS1/ITS4, RPB2-F/RPB2-R, Alt-F/Alt-R, end-F/end-R and gpd-F/gpd-R (Woudenberg et al. 2015). The sequences obtained were deposited in GenBank (ITS: MT501762, OK571395; RPB2: MT506027, OK631891; Alt a 1: MT506026, OK631890; endoPG: ON054189, ON054188; gpd: ON054191, ON054190). The phylogenetic analysis of maximum-likelihood tree by MEGA 7 software showed that the two isolates had 99% identity with the A. alternata CBS 916.96. For pathogenicity testing, eighteen leaves of six 5-week-old plants were sprayed with spore suspensions (1×106 spores /mL) of the 7 days-old isolates LD2020521 and LD2020520 (Each isolate infected three plants and each infected three leaves). Three plants were sprayed with sterile distilled water as a control group. The plants were incubated at 25℃. After 15 days, taupe irregular spots appeared on the leaves. The pathogenicity test was repeated three times. The same fungi were re-isolated from the inoculated leaves and with the same morphological and molecular characteristics as LD2020520 and LD 2020521, fulfilling Koch's postulates. No fungi were isolated from the control group. This is the first report of leaf spot on C. brevicaudata caused by A. alternata. Leaf spot can reduce the yields of C. brevicaudata. This study provides a reference for the prevention and treatment to the leaf spot of C. brevicaudata.

First report of leaf blight on Ligusticum jeholense (Nakai et Kitagawa) Nakai et Kitagawa caused by Alternaria alternata in China

Ligusticum jeholense (Nakai et Kitagawa) Nakai et Kitagawa is one of the sources of Chinese herb "Gao-Ben". It is widely distributed in the Northeastern China. L. jeholense has antipyretic, antibacterial and anti-inflammatory effects (Zhang et al. 2021). In September 2021, a serious leaf blight was found in a 1.2 ha plantation of L. jeholense in Harbin, Heilongjiang Province, and the incidence was about 85%. The foliar symptoms were grayish-brown lesions, surrounded by a yellow margin at the edge of the leaf. In serious cases, the lesions extended into the middle of the leaf, and finally the whole leaf withered. A total of 12 samples (5×5mm) from symptomatic and healthy junction of 12 infected leaves from 6 different plants of L. jeholense with typical symptoms were cut and surface disinfected in 75% ethanol, and with 7% NaClO for 1 min, then rinsed three times with sterilized water. These tissues were placed onto Potato dextrose agar (PDA) plates at 28℃ in the dark. The colonies cultured for 7 days were obtained and transferred onto new PDA and potato carrot agar (PCA) plates by single spore method to further purify. After 7 days, the colonies on PDA were 63 to 75 mm in diameter, circular, grayish, with white aerial hyphae on the edge, the back of the colonies were grayish green. A total of 150 conidia on PCA were single or in chains, ovoid, inverted pear, 2 to 6 transverse septa, 0 to 3 longitudinal or oblique septa, 16.5 to 67.5 × 8.5 to 20.5 μm. The beaks were conical or cylindrical, 2.5 to 25.3 × 2.0 to 3.0 μm. Conidiophores were grayish brown, erect or bent, separated, 57.0 to 137.0 × 5.1 to 13.7 μm. Morphological characteristic showed the 12 isolates were the same fungus and similar to Alternaria sp. (Simmons 2007). Two typical strains (LGB and LGB2) from twelve isolates were randomly selected for molecular identification. Genomic DNA was extracted from mycelia of two isolates on PDA by modified CTAB method, and internal transcribed spacer rDNA regions (ITS), RNA polymerase II second largest subunit (RPB2) and Alternaria major allergen (Alt a 1), translation elongation factor 1-alpha (TEF) and glyceraldehyde-3-phosphate dehydrogenase (gpd) gene were amplified and sequenced with the primers ITS1/ITS4, RPB2-5F2/RPB2-7CR, Alt-F /Alt-R, TEF-F/TEF-R and gpd-F/gpd-R (Woudenberg et al. 2015). The obtained sequences were deposited in GenBank (ITS: OM319506, OM943431; RPB2: OM393721, OM984854; Alt a 1: OM649816, OM984853; TEF: OM238108, OM984852; gpd: OM296228, OM984851). The phylogenetic analysis of maximum-likelihood tree by MEGA7 showed the LGB and LGB2 had 100% identity with A. alternata CBS 916.96. For pathogenicity test, conidial suspension (1 × 106 spores/mL) of the strain LGB and LGB2 was sprayed on 10 healthy 40-day-old L. jenholense plants and five plants with sterile water as control. The plants were incubated at 25℃. After 28 days, grayish withering appeared on the leaves. The test was repeated three times. The same fungi were re-isolated from the inoculated leaves and with the same morphological and molecular characteristics as A. alternata, fulfill the Koch's postulates. No symptoms and fungi were found in the control group. This is the first report of leaf blight on L. jenholense caused by A. alternata. Leaf blight could reduce the yields of L. jenholense. This study provides a reference for the prevention and treatment to the leaf blight of L. jenholense.

First Report of Alternaria alternata Inciting Leaf Spot of Dangshen (Codonopsis pilosula) in China

As a commonly traditional Chinese medicine, the perennial herb Dangshen (Codonopsis pilosula) has superior curative effects including regulating immunity, strengthening the spleen, and tonifying lungs (Bai et al. 2020). To imitate natural ecological conditions, plants were grown on hillside fields with stems prostrate on the ground, tangle-up with each other. In August 2020, leaf spots were observed on C. pilosula in Wutai county, Shanxi province, China, and indicated a high disease incidence (70%-80%) in investigated fields (6.67 ha). Small brown necrotic spots, occasionally enclosed by chlorotic halos, were observed on leaves, stems, and sepals. For identification of the pathogen, 15 small pieces (5×5 mm) of symptomatic tissues from 5 randomly-collected diseased plants were surface sterilized, placed on potato dextrose agar plates, and incubated for 4 d in darkness at 25 °C to obtain the colonies. Cultures were purified by single spore isolation from these colonies. A total of 15 isolates named as Dcp-3, and Dcp-5~Dcp-18 were recovered. They produced ovoid or obclavate spores with 15.9-57.5×9.1-20.1 μm in size, 1-6 transverse septa, and 0-4 longitudinal septa. The conidial chains with 4 to 6 spores had numerous secondary and occasionally tertiary chains on potato carrot agar plates. Because all isolates had identical morphological traits, five genes from the representative isolate Dcp-3, actin (ACT), Alternaria major allergen (Alt a1), plasma membrane ATPase (ATP), histone 3 (H3), and rDNA ITS, were amplified with primer pairs ACTDF1/ACTDR1, Alt-for/Alt-rev, ATPDF1/ATPDR1, H3-1a/H3-1b, and ITS1/ITS4, respectively (Hong et al. 2005; Lawrence et al. 2013; Ma et al. 2020). BLASTn searches indicated species of Dcp-3 could not be accurately confirmed by rDNA ITS, ATP, ACT, and Alt a1 (GenBank accession nos. OM334894, OM362504, OM326344, OM362500). Phylogenetic analysis showed it was most closely related to Alternaria alternata, A. arborescens, and A. tenuissima based on concatenated sequences of above four genes. The H3 sequence (OM362508) shared 100% homology with that of A. alternata (MN481948). The phylogenetic tree using H3 also confirmed Dcp-3 as A. alternata. Heathly, two-year-old C. pilosula were transplanted to a greenhouse. A surface-sterilized leaf was sprayed with 50 μL spore suspension (106 conidia/mL) of Dcp-3. A leaf sprayed with isometric sterile water was used as controls. Each treatment used six plants (five leaves per plant). Plants were covered with sterilized plastic bags and incubated at 22 ℃. The test was repeated twice. A week later, control leaves were healthy, but brown necrotic spots similar to field symptoms emerged on treated leaves. The A. alternata isolates were re-isolated from the border of lesions, and confirmed by morphological and molecular characteristics mentioned above, fulfilling Koch's postulates. Leaf spot of C. pilosula caused by Septoria codonopsidis has been reported in China (Wang et al. 2011). However, to our knowledge, this is the first report of A. alternata inciting leaf spot of C. pilosula in China. Our report would promote growers to enhance the field management and consider associated strategies on controlling Alternaria leaf spot of C. pilosula.

First Report of Alternaria alternata Causing Leaf Spot of Tartary Buckwheat (Fagopyrum tataricum) in China

Buckwheat (Fagopyrum tataricum) is recognized as a healthy food with abundant nutrients and high levels of rutin. In April and May of 2020, an unknown tartary buckwheat leaf spot distinct from Nigrospora leaf spot (Shen et al. 2020) was observed in Xiangxiang, Hunan, China (27°49'54″N, 112°span style="font-family:'Times New Roman'; color:#0000ff">18'48″E.). Disease incidence was 60-70% within three fields (totally 7, 000 m2). The disease occurred after plants emerged. Initial symptoms began as circular, or ellipsoid, chlorotic, water-soaked spots, mostly on leaf apexes or leaf margins. The small spots gradually enlarged and often coalesced to form large circular or irregular, pale to light brown lesions, and the infected leaves eventually withered and fell off. Thirty 2 × 2 mm infected tissue pieces collected from five locations were sterilized in 70% ethanol for 10 S, in 2% NaClO for 30 S, rinsed in sterile water for three times, dried, and placed on PDA with lactic acid (3 ml/L). After 3-5 days at 28°C in the dark, 17 fungal isolates were purified using single-spore isolation method. Almost all fungal isolates had similar morphology. Colonies were initially olive green with white margin and later turned dark olive or black with profuse sporulation. Conidia were borne in long chains, tawny to brownish green, with 1-3 longitudinal and 1-7 transverse septa, pyriform, and measured 9.5-39.6 µm long, and 5.1-12.6 µm wide (n=50). Based on morphological characteristics, the fungus was identified as Alternaria alternata (Simmons 2007). Partial internal transcribed spacer (ITS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-α(TEF) and Alternaria major allergen (Alt a1) genes of isolate BLS-1 were amplified using ITS1/ITS4 (Mills et al. 1992), EF1-728F/EF1-986R (Carbone and Kohn 1999), Gpd1/Gpd2 and Alt-4for/Alt-4rev (Lawrence et al. 2013), respectively. Sequences were deposited into GenBank with acc. nos MW453091 (ITS), MW480219 (GAPDH), MW480218 (TEF), and MW480220 (Alt a1). BLASTn analysis showed 99.8% (ITS, MH854758.1), 100% (GAPDH, KP124155.1), 99.8% (TEF, KP125073.1) and 100% (Alt a1, KP123847.1) identity with reference strain CBS 106.24 of A. alternata, confirming isolate BSL-1 to be A. alternata. A neighbor-joining phylogenetic tree constructed by MEGA7.0 based on concatenated sequences of the four genes indicated that BSL-1 formed a distinct clade with A. alternata CBS 106.24 with 100% bootstrap values. Pathogenicity test was triplicately performed on healthy leaves. Twenty leaves of five 20-day-old plants (cv. Pinku1) were sprayed with conidial suspension (1×106 conidia/ml) collected from PDA cultures with 0.05% Tween 20. An equal number of control leaves were sprayed with sterile water to serve as the controls. Treated plants were kept in a greenhouse at 28±3 °C with relative humidity of 80±5% for 24 h and transferred to natural conditions (22-30°C, RH 50-60%). After 4 to 6 days, all inoculated leaves developed symptoms similar to those observed in the fields, while the control leaves remained healthy. A. alternata was re-isolated from all infected leaves. Occasionally-isolated Diaporthe isolates were not pathogenic. A. alternata causes leaf spot of oat (Zhao et al. 2020) and leaf blight of F. esculentum (Lu et al. 2019). To our knowledge, this is the first report of A. alternata causing leaf spot on F. tataricum in China and the world. Effective strategies should be developed to manage the disease.