First Report of Sclerotinia Blight on Peanut Caused by Sclerotinia sclerotiorum in Qinghai Province, China

Historically, peanut has not been produced in Qinghai province located in Northwest China because of the high elevation and cold climates. However, since 2020 field studies have been conducted to evaluate peanut cultivars for suitability to field production. In 2020, peanut cultivation was successful for the first time in Haidong city, Qinghai province, China. In August 2020, brown, irregular-shaped lesions were observed on peanut stems from Qinghai province in China. In the early stage, the watersoaked spots were formed on the stems, then lesions expanded rapidly and became brown. In advanced stages of the disease, stems became bleached and eventually died. The inside of the stems was rotten and hollow, and the diseased stem wilted and died. White hyphae and black irregular shaped sclerotia were observed on the infected stems. Finally, local or whole plant rotted and died at the end. Approximately 10% of the plants in a field were infected. Symptomatic stems were cut into small pieces, disinfected with 75% ethanol for 1 minute, 0.5% NaClO for two minutes, and sterile water for three times. Pieces then were plated on potato dextrose agar (PDA) media and incubated at 25°C in darkness. Fungal colonies were initially white, becoming gray, then black sclerotia (2.4 to 6.0 mm in diameter) were appeared at the edge of colonies. Genomic DNA of the pure cultures of an isolate (ZHX7) was extracted and PCR was carried out using glyceraldehydes-3-phosphate dehydrogenase gene (G3PDH) region primers G3PDH-F/G3PDH-R, heat-shock protein 60 gene (HSP60) region primers HSP60-F/HSP60-R, and DNA-dependent RNA polymerase subunit gene (RPB2) region primers RPB2-F/RPB2-R (Staats et al., 2005), respectively. G3PDH region (Accession No. MZ388475) showed 99.44% sequence identity (887 bp out of 909 bp) to Sclerotinia sclerotiorum (Accession No. AJ705044, 887 bp out of 887 bp). HSP60 region (Accession No. MZ388476) showed 99.90% sequence identity (972 bp out of 984bp) to S. sclerotiorum (Accession No. AJ716048, 972 bp out of 980 bp). RPB2 region (Accession No. MZ388477) showed 100.00% sequence identity (1096 bp out of 1129 bp) to S. sclerotiorum (Accession No. AJ745716, 1096 bp out of 1096 bp). Phylogenetic analysis was done using Neighbor-Joining (NJ) analysis based on those gene sequences. The isolate was identified as S. sclerotiorum based on molecular analysis and morphological characteristics. For pathogenicity assay, ten-days-old potted peanut (Luhua No.12) seedlings were inoculated with one mycelial plug (8 mm in diameter ) by placing the inoculum on the base of the stem in a growth chamber (30°C in the day and 25°C at night, a 12-h photoperiod and 80% RH). All inoculated seedlings exhibited typical basal stem rot, and root showed different degrees of damage, and wilted 5 days after inoculation. No symptoms were observed on control plants treated with sterile distilled mycelial plugs, and S. sclerotiorum was consistently re-isolated from symptomatic tissue. S. sclerotiorum has been reported on peanut in Northeastern China (Yan et al., 2005). To our knowledge, this is the first report of S. sclerotiorum causing Sclerotinia Blight on peanut in Qinghai province, China. The peanut planting area in Qinghai has been further expanded this year, and S. sclerotiorum has a broad host range (Boland and Hall, 1994), so Sclerotinia Blight is a potential threat to peanut production, and as a result, it is critical for commercial producers to monitor plants for S. sclerotiorum.

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First Report of Sclerotinia Blight Caused by Sclerotinia sclerotiorum on Peanut in Arkansas

Plant Health Progress ◽

10.1094/php-br-16-0056 ◽

2017 ◽

Vol 18 (1) ◽

pp. 7-8

Author(s):

T. R. Faske ◽

G. Drennan ◽

K. Hurd

Keyword(s):

Sclerotinia Sclerotiorum ◽

Negative Impact ◽

The State ◽

First Report ◽

Sclerotinia Blight ◽

Peanut Production

This is the first report of Sclerotinia blight caused by Sclerotinia sclerotiorum on peanut occurring in Arkansas. There has been renewed interest in commercial peanut production in Arkansas, and this pathogen could have a negative impact on peanut in the state.

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First Report of Stem and Foliage Blight of Chrysanthemum Caused by Phytophthora drechsleri in the United States

Plant Disease ◽

10.1094/pdis-03-21-0631-pdn ◽

2021 ◽

Author(s):

Charles Krasnow ◽

Nancy Rechcigl ◽

Jennifer Olson ◽

Linus Schmitz ◽

Steven N. Jeffers

Keyword(s):

United States ◽

South Carolina ◽

Sequence Similarity ◽

Morphological Characteristics ◽

The United States ◽

Universal Primers ◽

Broad Host Range ◽

Pathogenicity Test ◽

First Report ◽

Foliage Blight

Chrysanthemum (Chrysanthemum × morifolium) plants exhibiting stem and foliage blight were observed in a commercial nursery in eastern Oklahoma in June 2019. Disease symptoms were observed on ~10% of plants during a period of frequent rain and high temperatures (26-36°C). Dark brown lesions girdled the stems of symptomatic plants and leaves were wilted and necrotic. The crown and roots were asymptomatic and not discolored. A species of Phytophthora was consistently isolated from the stems of diseased plants on selective V8 agar (Lamour and Hausbeck 2000). The Phytophthora sp. produced ellipsoid to obpyriform sporangia that were non-papillate and persistent on V8 agar plugs submerged in distilled water for 8 h. Sporangia formed on long sporangiophores and measured 50.5 (45-60) × 29.8 (25-35) µm. Oospores and chlamydospores were not formed by individual isolates. Mycelium growth was present at 35°C. Isolates were tentatively identified as P. drechsleri using morphological characteristics and growth at 35°C (Erwin and Ribeiro 1996). DNA was extracted from mycelium of four isolates, and the internal transcribed spacer (ITS) region was amplified using universal primers ITS 4 and ITS 6. The PCR product was sequenced and a BLASTn search showed 100% sequence similarity to P. drechsleri (GenBank Accession Nos. KJ755118 and GU111625), a common species of Phytophthora that has been observed on ornamental and vegetable crops in the U.S. (Erwin and Ribeiro 1996). The gene sequences for each isolate were deposited in GenBank (accession Nos. MW315961, MW315962, MW315963, and MW315964). These four isolates were paired with known A1 and A2 isolates on super clarified V8 agar (Jeffers 2015), and all four were mating type A1. They also were sensitive to the fungicide mefenoxam at 100 ppm (Olson et al. 2013). To confirm pathogenicity, 4-week-old ‘Brandi Burgundy’ chrysanthemum plants were grown in 10-cm pots containing a peat potting medium. Plants (n = 7) were atomized with 1 ml of zoospore suspension containing 5 × 103 zoospores of each isolate. Control plants received sterile water. Plants were maintained at 100% RH for 24 h and then placed in a protected shade-structure where temperatures ranged from 19-32°C. All plants displayed symptoms of stem and foliage blight in 2-3 days. Symptoms that developed on infected plants were similar to those observed in the nursery. Several inoculated plants died, but stem blight, dieback, and foliar wilt were primarily observed. Disease severity averaged 50-60% on inoculated plants 15 days after inoculation. Control plants did not develop symptoms. The pathogen was consistently isolated from stems of symptomatic plants and verified as P. drechsleri based on morphology. The pathogenicity test was repeated with similar results. P. drechsleri has a broad host range (Erwin and Ribeiro 1996; Farr et al. 2021), including green beans (Phaseolus vulgaris), which are susceptible to seedling blight and pod rot in eastern Oklahoma. Previously, P. drechsleri has been reported on chrysanthemums in Argentina (Frezzi 1950), Pennsylvania (Molnar et al. 2020), and South Carolina (Camacho 2009). Chrysanthemums are widely grown in nurseries in the Midwest and other regions of the USA for local and national markets. This is the first report of P. drechsleri causing stem and foliage blight on chrysanthemum species in the United States. Identifying sources of primary inoculum may be necessary to limit economic loss from P. drechsleri.

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First Report of Leaf Spot Caused by Botrytis cinerea on Cardamine hupingshanensis in China

Plant Disease ◽

10.1094/pdis-04-21-0698-pdn ◽

2021 ◽

Author(s):

Jun Guo ◽

Jin Chen ◽

Zhao Hu ◽

Jie Zhong ◽

Jun Zi Zhu

Keyword(s):

Botrytis Cinerea ◽

Morphological Characteristics ◽

Gray Mold ◽

Hunan Province ◽

Conidial Suspension ◽

Heat Shock Protein 60 ◽

Basal Cells ◽

Single Spore ◽

Internal Transcribed Spacer Region ◽

First Report

Cardamine hupingshanensis is a selenium (Se) and cadmium (Cd) hyperaccumulator plant distributed in wetlands along the Wuling Mountains of China (Zhou et al. 2018). In March of 2020, a disease with symptoms similar to gray mold was observed on leaves of C. hupingshanensis in a nursery located in Changsha, Hunan Province, China. Almost 40% of the C. hupingshanensis (200 plants) were infected. Initially, small spots were scattered across the leaf surface or margin. As disease progressed, small spots enlarged to dark brown lesions, with green-gray, conidia containing mold layer under humid conditions. Small leaf pieces were cut from the lesion margins and were sterilized with 70% ethanol for 10 s, 2% NaOCl for 2 min, rinsed with sterilized distilled water for three times, and then placed on potato dextrose agar (PDA) medium at 22°C in the dark. Seven similar colonies were consistently isolated from seven samples and further purified by single-spore isolation. Strains cultured on PDA were initially white, forming gray-white aerial mycelia, then turned gray and produced sclerotia after incubation for 2 weeks, which were brown to blackish, irregular, 0.8 to 3.0 × 1.2 to 3.5 mm (n=50). Conidia were unicellular, globose or oval, colourless, 7.5 to 12.0 × 5.5 to 8.3 μm (n=50). Conidiophores arose singly or in group, straight or flexuous, septate, brownish to light brown, with enlarged basal cells, 12.5 to 22.1 × 120.7 to 310.3 μm. Based on their morphological characteristics in culture, the isolates were putatively identified as Botrytis cinerea (Ellis 1971). Genomic DNA of four representative isolates, HNSMJ-1 to HNSMJ-4, were extracted by CTAB method. The internal transcribed spacer region (ITS), glyceraldehyde-3-phosphate dehydrogenase gene (G3PDH), heat-shock protein 60 gene (HSP60), ATP-dependent RNA helicaseDBP7 gene (MS547) and DNA-dependent RNA polymerase subunit II gene (RPB2) were amplified and sequenced using the primers described previously (Aktaruzzaman et al. 2018) (MW820311, MW831620, MW831628, MW831623 and MW831629 for HNSMJ-1; MW314722, MW316616, MW316617, MW316618 and MW316619 for HNSMJ-2; MW820519, MW831621, MW831627, MW831624 and MW831631 for HNSMJ-3; MW820601, MW831622, MW831626, MW831625 and MW831630 for HNSMJ-4). BLAST searches showed 99.43 to 99.90% identity to the corresponding sequences of B. cinerea strains, such as HJ-5 (MF426032.1, MN448500.1, MK791187.1, MH727700.1 and KX867998.1). A combined phylogenetic tree using the ITS, G3PDH, HSP60 and RPB2 sequences was constructed by neighbor-joining method in MEGA 6. It revealed that HNSMJ-1 to HNSMJ-4 clustered in the B. cinerea clade. Pathogenicity tests were performed on healthy pot-grown C. hupingshanensis plants. Leaves were surface-sterilized and sprayed with conidial suspension (106 conidia/ mL), with sterile water served as controls. All plants were kept in growth chamber with 85% humidity at 25℃ following a 16 h day-8 h night cycle. The experiment was repeated twice, with each three replications. After 4 to 7 days, symptoms similar to those observed in the field developed on the inoculated leaves, whereas controls remained healthy. The pathogen was reisolated from symptomatic tissues and identified using molecular methods, confirming Koch’s postulates. B. cinerea has already been reported from China on C. lyrate (Zhang 2006), a different species of C. hupingshanensis. To the best of our knowledge, this is the first report of B. cinerea causing gray mold on C. hupingshanensis in China and worldwide. Based on the widespread damage in the nursery, appropriate control strategies should be adopted. This study provides a basis for studying the epidemic and management of the disease.

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First report of Corynespora cassicola causing black spot on Sarcandra glabra in China

Plant Disease ◽

10.1094/pdis-02-21-0273-pdn ◽

2021 ◽

Author(s):

Jiang Ni ◽

B. R. Lin ◽

Lisha Song ◽

Guiyu Tan ◽

Jiang zhan Zhang ◽

...

Keyword(s):

Salvia Miltiorrhiza ◽

Pathogenic Fungus ◽

Morphological Characteristics ◽

Bootstrap Support ◽

Control Group ◽

Broad Host Range ◽

Pathogenicity Test ◽

Guangxi Province ◽

First Report ◽

Fungal Isolates

Sarcandra glabra is an important Chinese medicinal plant, which was widely cultivated under forest in south China. Guangxi province is the main producing areas of this herb. In June 2019, a serious leaf disease was found causing severe defoliation in the S. glabra plantation under bamboo forest in Rongan country, Guangxi province (109°13′N′′E). About 70% of the plants in the plantation (300 ha) showed the similar symptoms. Initially, circular lesions appeared on young leaves as black spots (about 1 to 2 mm). Then, the spots gradually enlarged usually with an obvious yellowish margin (6 to 8 mm). Finally, the lesions coalesced and formed irregular, black, and large necrotic areas, resulting in the leaf abscission. For pathogen isolation, small pieces of tissue (5×5 mm) taken from 25 diseased leaves were sterilized with 75% ethanol for 30 s, subsequently, soaked in 0.1% HgCl2 for 2 min, rinsed three times in sterile distilled water, dried, and then placed aseptically onto the potato dextrose agar (PDA) plates, and incubated at 28 °C (12 h/12 h light/dark). Three days later, the isolates were placed on a new PDA plate for subsequent purification and sporulation. 20 pure fungal isolates were obtained from single spores. Of which, 15 isolates showed similar morphological characteristics.The colonies on PDA were round, dense, gray edge and dark gray in center area. Conidia in culture were appeared light brown, cylindrical in shape, with 0 to 8 septa, and 55 to 165 μm × 5.2 to 13.5 μm in size (mean = 106.2 μm × 8.6 μm, n = 30). These morphological characteristics resemble those of Corynespora sp. (Berk. & M.A. Curtis) C.T. Wei (Ellis et al. 1971). A single-spore isolate (ZD5) was selected from the 15 fungal isolates for a subsequent molecular identification. The genes of internal transcribed spacer (ITS) of ribosomal DNA, β-tublin, and actin were amplified with the primer pairs ITS-1/ITS-4 (White et al. 1990), β-tubulin 2-Bt2a/Bt2b (Glass and Donaldson 1995), ACT-512F/ACT-783R (Carbone and Kohn 1999), respectively. And the ITS, β-tublin, and actin sequences were deposited in the GenBank database with the accession numbers MW362446, MW367029, and MW533122. Blast analysis and neighbor-joining analysis based on ITS, β-tublin, and actin sequences using MEGA 6 revealed that the isolate was placed in the same clade as C. cassicola with 100% bootstrap support. Pathogenicity test was performed on the two-year-old potted S. glabra. Six-mm-diameter mycelial plugs were attached to the healthy leaves of S. glabra for co-culture, while the control group was attached with PDA. All plants were covered with plastic bags for 2 days in order to maintain high humidity and cultured in a greenhouse at 28 °C with a 12-h/12-h light/dark cycle. The symptoms appeared 2 days after co-culture were identical to those observed in the field. The same fungus was re-isolated from the lesions, and further morphological characterization and molecular assays, as described above.The control leaves remained symptomless during the pathogenicity tests. According to the previous literatures, C. cassicola is a plant pathogenic fungus with a broad host range, which can damage diverse tropical plants including Salvia miltiorrhiza (Lu et al. 2019), Solanum americanum (Wagner and Louise 2019), Vitex rotundifolia (Yeh and Kirschner 2017), Cucumis sativus, Lycopersicon esculentum (Hsu et al. 2002), Carica papaya (Tsai et al. 2015),and so on. To our knowledge, this is the first report of C. cassicola causing leaf spot on S. glabra in China.

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First Report of Seedling Stem Rot on Jinxianlian (Anoectochilus roxburghii) Caused by Fusarium oxysporum in China

Plant Disease ◽

10.1094/pdis-09-21-2066-pdn ◽

2021 ◽

Author(s):

Chuan-Qing Zhang ◽

X. Y. Chen ◽

Ya-hui Liu ◽

Dejiang Dai

Keyword(s):

Fusarium Oxysporum ◽

Morphological Characteristics ◽

Aerial Mycelium ◽

Morphological Features ◽

Stem Rot ◽

Broad Host Range ◽

Distilled Water ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Anoectochilus Roxburghii

Anoectochilus roxburghii is an important Chinese herbal medicine plant belonging to Orchidaceae and known as Jinxianlian. This orchid is cultivated and mostly adopted to treat diabetes and hepatitis. About 2 billion artificially cultivated seedlings of Jinxianlian are required each year and approximately $600 million in fresh A. roxburghii seedlings is produced in China. From 2011, sporadic occurrence of stem rot on Jinxianlian have been observed in greenhouses in Jinhua City (N29°05′, E119°38′), Zhejiang Province. In 2018, nearly 30% of seedlings of Jinxianlian grown in greenhouse conditions were affected by stem rot in Jinhua City. Symptoms initially occurred in the stem at the soil line causing dark discoloration lesions, rotted tissues, wilting, and eventually leading to the death of the plants. A total of 23 diseased seedlings collected from seven different greenhouses were surface sterilized with 1.5% sodium hypochlorite for 3 min, then rinsed in water. Pieces of tissues disinfected from each sample were plated on 2% potato dextrose agar (PDA), and incubated at 25°C in the dark for 5 days (Kirk et al. 2008). A total of 19 isolates were recovered. They developed colonies with purple mycelia and beige or orange colors after 7 days of incubation under 25°C on PDA and carnation leaf agar (CLA) media (Kirk et al. 2008; Zhang et al. 2016). Colonies on PDA had an average radial growth rate of 3.1 to 4.0 mm /d at 25°C. Colony surface was pale vinaceous, floccose with abundant aerial mycelium. On CLA, aerial mycelium was sparse with abundant bright orange sporodochia forming on the carnation leaves. Microconidia were hyaline and oval-ellipsoid to cylindrical (3.7 to 9.3 × 1.3 to 2.9 μm) (n=19). Macroconidia were 3 to 5 septate and fusoid-subulate with a pedicellate base (27.4 to 35.6 × 3.2 to 4.2 μm) (n=19). These morphological features were consistent with Fusarium oxysporum (Sun et al. 2008; Lombard et al., 2019). To confirm the identification based on these morphological features, the internal transcribed spacer region (ITS) and translation elongation factor1 (TEF) were amplified from the DNA of 3 out of 19 isolates chosen at random respectively using the set primer ITS1/ITS4 and EF1/ EF2 (Sun, S., et al. 2018; Lombard et al., 2019). BLAST analysis revealed that the ITS sequences (OK147619, OK147620, OK147621) had 99% identity to that of F. oxysporum isolate JJF2 (GenBank MN626452) and TEF sequence (OK155999, OK156000, OK156001) had 100% identity to that of F. oxysporum isolate gss100 (GenBank MH341210). A multilocus phylogenetic analysis by Bayesian inference (BI) and maximum likelihood (ML) trees based on ITS and TEF indicated that the pathogen grouped consistently with F. oxysporum. Three out of 19 isolates chosen at random were selected to evaluate pathogenicity. Uninfected healthy A. roxburghii seedlings about 40 day-old planted in sterilized substrates were sprayed with distilled water containing 2 x 106 conidia per ml suspensions as inoculums, and plants sprayed with distilled water alone served as controls. Plants were then incubated at 25°C and 85% relative humidity. Ten plants were inoculated for each isolate. After 10 days, all plants inoculated developed stem rot symptoms, while control plants remained healthy. Cultures of Fusarium spp. were re-isolated only from inoculated plants with the frequency of 100% and re-identified by morphological characteristics as F. oxysporum, fulfilling Koch’s postulates. To the best of our knowledge, this is the first report of F. oxysporum causing stem rot on A. roxburghii seedlings. As F. oxysporum is a devastating pathogenic fungus with a broad host range, measures should be taken in advance to manage stem rot of A. roxburghii.

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First Report of Powdery Mildew Caused by Golovinomyces sonchicola on Ixeris chinensis in Korea

Plant Disease ◽

10.1094/pdis-11-13-1132-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 999-999 ◽

Cited By ~ 2

Author(s):

J. K. Choi ◽

B. S. Kim ◽

S. H. Hong ◽

S. E. Cho ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Sequence Similarity ◽

Folk Medicine ◽

Morphological Characteristics ◽

Its Region ◽

Width Ratio ◽

Lateral Part ◽

Potential Threat ◽

First Report ◽

Powdery Mildews

Ixeris chinensis (Thunb.) Nakai, known as Chinese ixeris, is distributed from Siberia to Japan, including Korea, Taiwan, and China. The whole plant has been used in folk medicine in Asia (4). In Korea, the plants of Chinese ixeris have been gathered and used as a wild root vegetable. During summer to autumn of 2011, Chinese ixeris leaves were found to be heavily infected with a powdery mildew in several locations of Korea. Symptoms first appeared as thin white colonies, which subsequently developed into abundant hyphal growth on both sides of the leaves, leading to drying of the leaves. The same symptoms on Chinese ixeris leaves were continuously observed in 2012 and 2013. Voucher specimens (n = 10) were deposited at Korea University Herbarium (KUS). Hyphal appressoria were moderately lobed or nipple-shaped. Conidiophores arose from the lateral part of the hyphae, measured 100 to 270 × 10 to 12.5 μm, and produced 2 to 6 immature conidia in chains with a sinuate outline. Basal parts of foot-cells in conidiophores were curved. Conidia were barrel-shaped to ellipsoid, measured 26 to 36 × 13 to 19 μm (length/width ratio = 1.7 to 2.4), lacked fibrosin bodies, and showed reticulate wrinkling of the outer walls. Primary conidia were ovate with conical-obtuse apex and subtruncate base. Germ tubes were produced on the perihilar position of conidia. Chasmothecia were not observed. The morphological characteristics were typical of the Euoidium type anamorph of the genus Golovinomyces, and the fungus measurements and structures were consistent with those of G. sonchicola U. Braun & R.T.A. Cook (1). To confirm the identification, internal transcribed spacer (ITS) region of rDNA sequences from a representative material (KUS-F26212) was amplified using primers ITS5/P3 and sequenced (3). The resulting 416-bp sequence was deposited in GenBank (Accession No. KF819857). A GenBank BLAST search revealed that the isolate showed >99% sequence similarity with those of G. cichoracearum from Sonchus spp. (e.g., AB453762, AF011296, JQ010848, etc.). G. sonchicola is currently confined to G. cichoracearum s. lat. on Sonchus spp., based on molecular sequence analyses (1). Pathogenicity was confirmed through inoculation by gently pressing a diseased leaf onto leaves of five healthy potted Chinese ixeris. Five non-inoculated plants served as controls. Inoculated plants developed symptoms after 6 days, whereas the controls remained symptomless. The fungus present on the inoculated plants was identical morphologically to that originally observed on diseased plants. Powdery mildew infections of I. chinensis associated with Golovinomyces have been known in China (2). To our knowledge, this is the first report of powdery mildew disease caused by G. sonchicola on I. chinensis in Korea. Farming of Chinese ixeris has recently started on a commercial scale in Korea. Though no statistical data are available, we postulate the cultivation area in Korea to be approximately 200 ha, mostly growing without chemical controls. Occurrence of powdery mildews poses a potential threat to safe production of this vegetable, especially in organic farming. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No.11. CBS, Utrecht, 2012. (2) F. L. Tai. Bull. Chinese Bot. Sci. 2:16, 1936. (3) S. Takamatsu et al. Mycol. Res. 113:117, 2009. (4) S. J. Zhang et al. J. Nat. Prod. 69:1425, 2006.

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First report of dragon fruit (Hylocereus undatus) stem rot caused by Diaporthe ueckerae in Taiwan

Plant Disease ◽

10.1094/pdis-09-21-1902-pdn ◽

2021 ◽

Author(s):

Yen-Chieh Wang ◽

Jan-Hong Liu ◽

Chieh-Chen Huang ◽

Cheng-Fang Hong

Keyword(s):

Maximum Likelihood ◽

Phylogenetic Trees ◽

Morphological Characteristics ◽

Stem Rot ◽

Potential Threat ◽

Fungal Isolation ◽

First Report ◽

Fungal Isolates ◽

Dragon Fruit ◽

Necrotic Spots

Dragon fruit (Hylocereus polyrhizus & H. undatus) is a rapidly growing commodity in Taiwan. The production acreage has been tripled since 2011, with an estimation of over 2,800 ha in 2019. From disease survey conducted in July 2020, reddish orange to blackish brown lesions similar to stem canker caused by Neoscytalidium dimidiatum on dragon fruit cladodes (Supplementary Fig. S1, Q) were observed from two orchards in Central Taiwan. Diseased cladodes were brought back to the lab, surface disinfested with 70% ethanol for 15 to 30 sec, and then blotted dried with a paper towel. Small pieces (about 3x3 mm) of necrotic spots were excised, placed on 2% water agar (WA) plates, and incubated with 12 h photoperiod at 28 ± 2 ℃ for 3 days. Among the necrotic spots that were used for fungal isolation, some were detected to have N. dimidiatum accounting for 21 isolates, while three isolates detected in other spots were unknown. Single hyphal tips of the three unknown fungal colonies with similar morphology were transferred on potato dextrose agar (PDA). Brownish- to grayish-white colonies with fluffy aerial mycelium were observed on PDA (Supplementary Fig. S1, A, B, E, F, I and J) after 8 days of incubation. To induce the sporulation, all the fungal isolates were cultivated on autoclaved cowpea pods on 2% WA plates with 12 h photoperiod at 25 ± 2 ℃ for 3 weeks. Black pycnidia embedded in cowpea tissues and creamy yellowish exudates with pycnidiospores extruding from the ostiole were observed (Supplementary Fig. S1, C, G and K). Alpha-conidia were characterized as aseptate, hyaline, smooth, ellipsoidal or fusiform, often bi-guttulate and measured about 6.0 to 6.5 μm × 2.0 to 2.3 μm (n = 50 for each isolate) (Supplementary Fig. S1, D, H and L). Beta-conidia were not observed. Morphological characteristics of these isolates were similar to Diaporthe spp. described by Udayanga et al. (2015). To further identify the fungal isolates, the internal transcribed spacer (ITS), β-tubulin (TUB) and translation elongation factor 1-α (EF1-α) regions were amplified using primer pairs ITS1/ITS4 (White et al. 1990), Bt2a/Bt2b (Glass & Donaldson 1995) and EF1-728F/EF1-986R (Carbone & Kohn 1999), respectively. BLAST analysis of isolates CH0720-010 (ITS: OK067377; TUB: OK149767; EF1-α: OK149764), CH0720-013 (ITS: OK067378; TUB: OK149768; EF1-α: OK149765) and TC0720-016 (ITS: OK067379; TUB: OK149769; EF1-α: OK149766) showed 99.78 to 100% of ITS identity, 98.8 to 99.2% of TUB identity, and 100% of EF1-α identity with Diaporthe ueckerae (ITS: KY565426; TUB: KY569384; EF1-α: KY569388). Phylogenetic trees were constructed using concatenated ITS, TUB, and EF1-α sequences based on maximum likelihood with HKY+G model, maximum parsimony, and Bayesian inference method in MEGA X and Geneious Prime 2020.2.4. All isolates were clustered in D. ueckerae with similar topology based on aforementioned methods, hence the phylogram of maximum likelihood was presented (Supplementary Fig. S2). To confirm the pathogenicity, detached dragon fruit (H. polyrhizus and H. undatus) cladodes (20 to 30 cm in length) were surface disinfested, wounded with sterilized syringe (about 2 mm in depth), and inoculated with mycelial plugs (6 mm in diam.) from 5-day-old colonies on PDA. Each isolate had three mycelial plugs and the PDA plugs without mycelium were inoculated as negative control. Inoculated cladodes were placed in a moisture chamber and incubated at 30 ± 2 ℃ with 12 h photoperiod. Two days after inoculation (DAI), the agar plugs were removed and symptom development on the cladodes was photo recorded every other day. The inoculation experiment was repeated twice. At 6 DAI, round to irregular, dark-brown, and water-soaking lesions were observed on the cladodes of both species inoculated with the three D. ueckerae isolates whereas all negative controls remained asymptomatic (Supplementary Fig. S1, M-P). Morphologically identical fungi were re-isolated from inoculated cladodes, fulfilling Koch’s postulates. Several Diaporthe species have been reported infecting dragon fruit in the southeastern Asian countries such as Thailand, Bangladesh and Malaysia (Udayanga et al. 2012; Karim et al. 2019; Huda-Shakirah et al. 2021). To our knowledge, this is the first report of stem rot caused by D. ueckerae in Taiwan. Since the field symptoms may be easily confused with those caused by N. dimidiatum, the potential threat of Diaporthe species complex on dragon fruit should be aware and may warrant further study.

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First Report of Sclerotinia Blight Caused by Sclerotinia sclerotiorum on Oriental Tobacco in the Yunnan Province of China

Plant Disease ◽

10.1094/pdis-08-19-1701-pdn ◽

2020 ◽

Vol 104 (6) ◽

pp. 1867-1867

Author(s):

C.-H. Lu ◽

J.-Y. Liu ◽

Z.-L. Lin ◽

A.-Z. Zhen ◽

Z.-Y. Xia ◽

...

Keyword(s):

Sclerotinia Sclerotiorum ◽

Yunnan Province ◽

First Report ◽

Sclerotinia Blight

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First Report of Sclerotinia Blight Caused by Sclerotinia sclerotiorum on Pinellia ternata in China

Plant Disease ◽

10.1094/pdis-08-20-1671-pdn ◽

2020 ◽

pp. PDIS-08-20-1671

Author(s):

Fanfan Wang ◽

Tao Tang ◽

Jie Guo ◽

Bin Yuan ◽

Xiaoliang Guo ◽

...

Keyword(s):

Sclerotinia Sclerotiorum ◽

Pinellia Ternata ◽

First Report ◽

Sclerotinia Blight

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First Report of Anthracnose Fruit Rot Caused by Colletotrichum fioriniae on Litchi in China

Plant Disease ◽

10.1094/pdis-07-20-1539-pdn ◽

2020 ◽

Author(s):

Jin-Feng Ling ◽

Aitian Peng ◽

Zide Jiang ◽

Pinggen Xi ◽

Xiaobing Song ◽

...

Keyword(s):

Species Complex ◽

Morphological Characteristics ◽

Morphological Characterization ◽

Fruit Rot ◽

Single Spore ◽

Potential Threat ◽

First Report ◽

Fruit Cracking ◽

Pure Cultures ◽

Colletotrichum Spp

Anthracnose fruit rot of litchi (Litchi chinensis Sonn.), caused by Colletotrichum spp., has been mainly associated with the C. acutatum species complex and C. gloeosporioides species complex (Farr and Rossman 2020). In June 2010, isolates of the C. acutatum species complex were isolated together with the C. gloeosporioides species complex from anthracnose lesions on litchi fruits (cv. Nuomici) obtained from a litchi orchard in Shenzhen (N 22.36°, E 113.58°), China. The symptoms typically appeared as brown lesions up to 25 mm in diameter, causing total fruit rot and sometimes fruit cracking. Based on the number of isolates we collected, the C. acutatum species complex appears less frequently on infected fruit compared to the C. gloeosporioides species complex. Since only the C. gloeosporioides species complex has been reported in China (Qi 2000; Ann et al. 2004), we focused on the C. acutatum species complex in this study. Pure cultures of fungal isolates were obtained by single-spore isolation. The isolate GBLZ10CO-001 was used for morphological characterization, molecular and phylogenetic analysis, and pathogenicity testing. Colonies were cultured on potato dextrose agar (PDA) at 25 ℃ for 7 days, circular, raised, cottony, gray or pale orange, with reverse carmine, and 39.6 to 44.7 mm in diameter. Conidia were 13.5 to 19 × 4 to 6 µm (mean ± SD = 15.9 ± 1.1 × 5.2 ± 0.3 µm, n = 50) in size, hyaline, smooth-walled, aseptate, straight, fusiform to cylindrical with both ends acute. Appressoria were 5.5 to 13.5 × 4.5 to 7.5 µm (mean ± SD = 7.6 ± 1.6 × 6.0 ± 0.7 µm, n = 50) in size, subglobose to elliptical, sometimes clavate or irregular, smooth-walled, with entire edge, sometimes undulate, pale to medium brown. These morphological characteristics were consistent with the descriptions of several Colletotrichum species belonging to the C. acutatum species complex, including C. fioriniae (Shivas and Tan 2009; Damm et al. 2012). For molecular identification, genomic DNA was extracted and the ribosomal internal transcribed spacer (ITS), partial sequences of the β-tubulin (TUB2), actin (ACT), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), chitin synthase 1 (CHS-1), and histone3 (HIS3) genes were amplified and sequenced using the primer pairs ITS4/ITS5, T1/Bt2b, ACT512F/ACT783R, GDF1/GDR1, CHS-79F/CHS-354R, and CYLH3F/CYLH3R, respectively (White et al. 1990; Damm et al. 2012). The resulting sequences were submitted to GenBank (ITS: MN527186, TUB2: MT740310, ACT: MN532321, GAPDH: MN532427, CHS-1: MT740311, HIS3: MT740312). BLAST searches showed 98.70%-100% identity to the sequences of the C. fioriniae ex-holotype culture CBS 128517. The phylogram reconstructed from the combined dataset using MrBayes 3.2.6 (Ronquist et al. 2012) showed that isolate GBLZ10CO-001 clustered with C. fioriniae with high posterior probability. Koch’s postulates were performed in the field to confirm pathogenicity. Isolate GBLZ10CO-001 was grown on PDA (25 ℃ for 7 days) to produce conidia. In June 2014, litchi fruits (cv. Nuomici) were sprayed with conidial suspensions (106 conidia/ml), with sterile water as blank controls, and each treatment inoculated at least 15 fruits. Inoculated fruits were covered by an adhesive-bonded fabric bag until the trial ended. After 31 days, typical symptoms were observed, while control fruits remained asymptomatic. The fungus was re-isolated from diseased fruits and identified as C. fioriniae according to the methods described above. To our knowledge, this is the first report of anthracnose fruit rot on litchi caused by C. fioriniae, one species of the C. acutatum species complex, in China. For the difficulty in distinguishing anthracnose caused by C. fioriniae from the C. gloeosporioides species complex just by the symptoms, and mixed infection usually occurring in the field, further investigations are required to reliably assess the potential threat posed by C. fioriniae for litchi production in China.

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