First Report of Choanephora cucurbitarum Causing Leaf Wilt, Flower Rot, and Stem Necrosis on Crotalaria breviflora

Crotalaria breviflora (Fabaceae) is used as green manure crop because of its nitrogen fixation and nematode control (Nascimento et al. 2020). In April 2018, leaf wilting, flower rot, and stem necrosis symptoms were observed on C. breviflora with 100% incidence, in Sorriso (12° 33′ 31″ S, 55º 42′ 51″ W), Santa Carmem (11° 55′ 52″ S, 55º 16′ 47″ W), and Sapezal (12º 59′ 22″ S, 58º 45′ 52″ W) counties in the state of Mato Grosso, Brazil. Three monosporic isolates were isolated from symptomatic leaves, cultivated in potato dextrose agar (PDA) medium, and deposited at the Cultures Collection of the University of Brasilia (codes CCUB 1293, CCUB 1667, CCUB 1668). Colonies on PDA were white and cottony with presence of hyaline and coenocytic hyphae. The mycelia later became pale yellow with abundant reproductive structures. Sporangiophores were hyaline, aseptate, unbranched, and apically dilated to form a clavate vesicle, which produced secondary vesicles bearing sporangiola. Secondary vesicles were clavate, light brown, and 37 to 51 µm in diameter. Sporangia were brown to dark brown, globular to ellipsoid, 115 to 140 µm long, and 96 to 122 µm wide. Sporangiospores (n=30) were brown to reddish-brown, ellipsoid to ovoid, with longitudinal striae, 14 to 19 µm long, and 8 to 12 µm wide. Some with hyaline appendages at both ends. Their morphological characteristics were consistent with the descriptions of Choanephora cucurbitarum (Kirk 1984). To confirm the identity, the DNA of the three isolates was extracted and the sequences of Small Subunit (SSU), Large Subunit (LSU), and complete Internal Transcribed Spacer (ITS) of rDNA were amplified using V9G, ITS3, and LR5 primers (GenBank acc. no: MN897836, MN897837 and MN897838). The sequences were aligned with the MAFFT software. The alignment matrix was subjected to Maximum Likelihood (ML) analysis using RAxML v. 8 and Bayesian Inference performed in MrBayes v.3.1.2. The tree was edited in the FigTree software. The sequences showed 100% identity with the sequences from C. cucurbitarum found on the GenBank. To confirm pathogenicity, a suspension at 5.4 ×106 spores/ml was prepared from a 15-day-old culture grown at 25°C and sprayed on asymptomatic plants of C. breviflora. Sterilized water was sprayed as the control. Plants were kept in a humid chamber at 20°C for 48 h. Initial symptoms were visualized 16 days after inoculation. Complete necrosis of leaves and stems with spore mass on infected tissue was observed 19 days after inoculation. To satisfy the Koch’s postulates, the fungus was successfully reisolated from the infected tissues. No symptoms were observed on the control plants. In Brazil, this pathogen has been reported on Brassica oleracea var. capitata, Capsicum annuum, Crotalaria spectabilis, Cucurbita sp., and Vigna unguiculata (Alfenas et al. 2018; Mendes and Urben, 2019). C. cucurbitarum has been reported to have a wide range of hosts (Farr and Rossman, 2020). It can infect the crops grown in rotation or in succession, including common bean, corn, cotton, quinoa, soybean, and sunflower. Therefore, this pathogen is of epidemiological importance and poses a threat to the croplands where environmental conditions are conducive to the disease to develop and spread. To our knowledge, this is the first report of C. cucurbitarum causing leaf and flower wilt, and stem rot on C. breviflora in the world. Acknowledgment We thank the Environmental Sciences Graduate Program, Federal University of Mato Grosso, University of Brasilia, PROPeq/PROPG-UFMT, EMBRAPA, CODEX/UFMT, Institute of Agricultural and Environmental Sciences (ICAA)/UFMT and CAPES for providing the Master's scholarship. References Alfenas, R. F., et al. 2018. Plant Dis.102:1456. https://doi.org/10.1094/PDIS-10-17-1610-PDN, Google Scholar. Farr, D. F., and Rossman, A. Y. 2020. Fungal Databases, Syst. Mycol. Microbiol. Lab., ARS, USDA. Retrieved May 26, 2020 from https://nt.ars-grin.gov/fungaldatabases/, Google Scholar. Kirk, P. M. 1984. Mycol Paper. 152:1. Google Scholar. Mendes, M. A. S., and Urben, A. F. 2020. Fungos relatados em plantas no Brasil, Retrived May 26, 2020 from http://pragawall.cenargen.embrapa.br/aiqweb/michtml/fgbanco01.asp, Google Scholar. Nascimento, D. D. et al. 2020. Bioscience Journal. 36:713. https://doi.org/10.14393/BJ-v36n3a2020-42248, Google Scholar.

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First Report of Sclerotinia sclerotiorum on Campanula carpatica and Schizanthus × wisetonensis in Italy

Plant Disease ◽

10.1094/pdis.2002.86.1.71a ◽

2002 ◽

Vol 86 (1) ◽

pp. 71-71

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

United States ◽

Sclerotinia Sclerotiorum ◽

Ornamental Plants ◽

Soil Surface ◽

The United States ◽

First Report ◽

Potted Plants ◽

Initial Symptoms ◽

Stem Necrosis ◽

Campanula Carpatica

The production of potted ornamental plants is very important in the Albenga Region of northern Italy, where plants are grown for export to central and northern Europe. During fall 2000 and spring 2001, sudden wilt of tussock bellflower (Campanula carpatica Jacq.) and butterfly flower (Schizanthus × wisetonensis Hort.) was observed on potted plants in a commercial greenhouse. Initial symptoms included stem necrosis at the soil line and yellowing and tan discoloration of the lower leaves. As stem necrosis progressed, infected plants growing in a peat, bark compost, and clay mixture (70-20-10) wilted and died. Necrotic tissues were covered with whitish mycelia that produced dark, spherical (2 to 6 mm diameter) sclerotia. Sclerotinia sclerotiorum was consistently recovered from symptomatic stem pieces of both plants disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar amended with streptomycin sulphate at 100 ppm. Pathogenicity of three isolates obtained from each crop was confirmed by inoculating 45- to 60-day-old C. carpatica and Schizanthus × wisetonensis plants grown in containers (14 cm diameter). Inoculum that consisted of wheat kernels infested with mycelia and sclerotia of each isolate was placed on the soil surface around the base of previously artificially wounded or nonwounded plants. Noninoculated plants served as controls. All plants were maintained outdoors where temperatures ranged between 8 and 15°C. Inoculated plants developed symptoms of leaf yellowing, followed by wilt, within 7 to 10 days, while control plants remained symptomless. White mycelia and sclerotia developed on infected tissues and S. sclerotiorum was reisolated from inoculated plants. To our knowledge, this is the first report of stem blight of C. carpatica and Schizanthus × wisetonensis caused by S. sclerotiorum in Italy. The disease was previously observed on C. carpatica in Great Britain (2) and on Schizanthus sp. in the United States (1). References: (1) D. F. Farr et al. Fungi on Plants and Plant Products in the United States. The American Phytopathological Society, St. Paul, MN, 1989. (2) J. Rees. Welsh J. Agric. 1:188, 1925.

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First Report of Black Stem of Avicennia marina Caused by Fusarium equiseti in China

Plant Disease ◽

10.1094/pdis-08-13-0873-pdn ◽

2014 ◽

Vol 98 (6) ◽

pp. 843-843 ◽

Cited By ~ 6

Author(s):

N.-H. Lu ◽

Q.-Z. Huang ◽

H. He ◽

K.-W. Li ◽

Y.-B. Zhang

Keyword(s):

Morphological Characteristics ◽

Its Region ◽

Avicennia Marina ◽

Optical Microscope ◽

Ethanol Solution ◽

Morphological Observation ◽

Fusarium Equiseti ◽

First Report ◽

Initial Symptoms ◽

Β Tubulin

Avicennia marina is a pioneer species of mangroves, a woody plant community that periodically emerges in the intertidal zone of estuarine regions in tropical and subtropical regions. In February 2013, a new disease that caused the stems of A. marina to blacken and die was found in Techeng Island of Zhanjiang, Guangdong Province, China. Initial symptoms of the disease were water-soaked brown spots on the biennial stems that coalesced so whole stems browned, twigs and branches withered, leaves defoliated, and finally trees died. This disease has the potential to threaten the ecology of the local A. marina community. From February to May 2013, 11 symptomatic trees were collected in three locations on the island and the pathogen was isolated as followed: tissues were surface disinfected with 75% ethanol solution (v/v) for 20 s, soaked in 0.1% mercuric chloride solution for 45 s, rinsed with sterilized water three times, dried, placed on potato dextrose agar (PDA), and incubated for 3 to 5 days at 28°C without light. Five isolates (KW1 to KW5) with different morphological characteristics were obtained, and pathogenic tests were done according Koch's postulates. Fresh wounds were made with a sterile needle on healthy biennial stems of A. marina, and mycelial plugs of each isolate were applied and covered with a piece of wet cotton to maintain moisture. All treated plants were incubated at room temperature. Similar symptoms of black stem were observed only on the stems inoculated the isolate KW5 after 35 days, while the control and all stems inoculated with the other isolates remained symptomless. An isolate similar to KW5 was re-isolated from the affected materials. The pathogenic test was repeated three times with the same conditions and it was confirmed that KW5 was the pathogen causing the black stem of A. marina. Hyphal tips of KW5 were transferred to PDA medium in petri dishes for morphological observation. After 48 to 72 h, white, orange, or brown flocculence patches of KW5 mycelium, 5.0 to 6.0 cm in diameter, grew. Tapering and spindle falciform macroconidia (11 to 17.3 μm long × 1.5 to 2.5 μm wide) with an obviously swelled central cell and narrow strips of apical cells and distinctive foot cells were visible under the optical microscope. The conidiogenous cells were intertwined with mycelia and the chlamydospores were globose and formed in clusters. These morphological characteristics of the isolate KW5 are characteristic of Fusarium equiseti (1). For molecular identification, the ITS of ribosomal DNA, β-tubulin, and EF-1α genes were amplified using the ITS4/ITS5 (5), T1/T2 (2), and EF1/EF2 (3) primer pairs. These sequences were deposited in GenBank (KF515650 for the ITS region; KF747330 for β-tubulin region, and KF747331 for EF-1α region) and showed 98 to 99% identity to F. equiseti strains (HQ332532 for ITS region, JX241676 for β-tubulin gene, and GQ505666 for EF-1α region). According to both morphological and sequences analysis, the pathogen of the black stem of A. marina was identified as F. equiseti. Similar symptoms on absorbing rootlets and trunks of A. marina had been reported in central coastal Queensland, but the pathogen was identified as Phytophthora sp. (4). Therefore, the disease reported in this paper differs from that reported in central coastal Queensland. To our knowledge, this is the first report of black stems of A. marina caused by F. equiseti in China. References: (1) J. F. Leslie and B. A. Summerell. The Fusarium Laboratory Manual, 1st ed. Wiley-Blackwell, Hoboken, NJ, 2006. (2) K. O'Donnell and E. Cigelnik. Mol. Phylogenet. Evol. 7:103, 1997. (3) K. O'Donnell et al. Proc. Natl. Acad. Sci. USA. 95:2044, 1998. (4) K. G. Pegg. Aust et al. Plant Pathol. 3:6, 1980. (5) A. W. Zhang et al. Plant Dis. 81:1143, 1997.

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First Report of Sclerotinia Stem Rot and Watery Soft Rot Caused by Sclerotinia sclerotiorum on Sand Rocket (Diplotaxis tenuifolia) in Italy

Plant Disease ◽

10.1094/pd-89-1241c ◽

2005 ◽

Vol 89 (11) ◽

pp. 1241-1241 ◽

Cited By ~ 4

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Relative Humidity ◽

Sclerotinia Sclerotiorum ◽

Severe Disease ◽

Soil Surface ◽

Soft Rot ◽

Sclerotinia Stem Rot ◽

First Report ◽

Initial Symptoms ◽

Stem Necrosis ◽

White Mycelium

Several species of Diplotaxis (D. tenuifolia, D. erucoides, and D. muralis), known as wild or sand rocket, are widely cultivated in Italy. Rocket is used in Mediterranean cuisine as salad, a component of packaged salad products, and as a garnish for food. In winter 2003, a severe disease was observed on D. tenuifolia grown in unheated glasshouses on commercial farms near Albenga in northern Italy. Initial symptoms included stem necrosis at the soil level and darkening of leaves. As stem necrosis progressed, infected plants wilted and died. Wilt, characterized by the presence of soft and watery tissues, occurred within a few days on young plants. The disease was extremely severe in the presence of high relative humidity and mild temperature (15°C). Necrotic tissues became covered with white mycelium that produced dark sclerotia. Diseased stem tissue was disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 ppm streptomycin sulfate. Sclerotinia sclerotiorum (1) was consistently recovered from infected stem pieces. Sclerotia observed on infected plants measured 1.23 to 3.00 × 1.40 to 5.38 mm (average 2.10 × 2.85 mm). Sclerotia produced on PDA measured 1.00 to 4.28 × 1.00 to 6.01 mm (average 2.38 × 3.23 mm). Pathogenicity of three isolates obtained from infected plants was confirmed by inoculating 30-day-old plants of D. tenuifolia grown in 18-cm-diameter pots in a glasshouse. Inoculum, 2 g per pot of wheat kernels infested with mycelium and sclerotia of each isolate, was placed on the soil surface around the base of each plant. Three replicates of five pots each were used per isolate. Noninoculated plants served as controls. The inoculation trial was repeated once. All plants were kept at temperatures ranging between 10 and 26°C (average 15°C) with an average relative humidity of 80% and were watered as needed. Inoculated plants developed symptoms of leaf yellowing within 12 days, soon followed by the appearance of white mycelium and sclerotia, and eventually wilted. Control plants remained symptomless. S. sclerotiorum was reisolated from inoculated plants. To our knowledge, this is the first report of infection of D. tenuifolia by S. sclerotiorum in Italy as well as worldwide. The disease currently has been observed in the Liguria Region but not yet in other areas where sand rocket is cultivated. The economic importance of this disease for the crop can be considered medium at the moment, but is expected to increase in the future. Reference: (1) N. F. Buchwald. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift, 75, 1949.

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First Report of Leaf Spot Caused by Ascochyta marginata on Aralia elata in Korea

Plant Disease ◽

10.1094/pdis-08-11-0658 ◽

2012 ◽

Vol 96 (1) ◽

pp. 147-147

Author(s):

S. H. Lee ◽

C. K. Lee ◽

M. J. Park ◽

H. D. Shin

Keyword(s):

East Asia ◽

Leaf Spot ◽

Morphological Characteristics ◽

Culture Collection ◽

Research Report ◽

Conidial Suspension ◽

First Report ◽

Commercial Cultivation ◽

Aralia Elata ◽

Initial Symptoms

Aralia elata (Miq.) Seem., known as Japanese angelica tree, is a deciduous shrub belonging to the Araliaceae, which is native to East Asia. The young shoots have long been used in various dishes in East Asia. Commercial cultivation of this shrub, especially in polytunnels, is expanding in Korea. Several diseases including Sclerotinia rot have been known to be present on this plant (1,2). In early September 2007, leaf spot symptoms were first observed on several trees in Hongcheon, Korea. Microscopic observations revealed that the leaf spots were associated with an Ascochyta sp. Further surveys of the Ascochyta leaf spot showed the occurrence of the disease in approximately 5 to 10% of the trees in the 3 ha of commercial fields surveyed in Chuncheon, Gapyeong, Inje, and Jinju, Korea. Initial symptoms on leaves were circular to irregular, brown to dark brown, becoming zonate, and finally fading to grayish brown in the center with a yellow halo. Representative samples were deposited in the herbarium of Korea University. Conidiomata on leaf lesions were pycnidial, amphigenous, but mostly epiphyllous, immersed or semi-immersed in host tissue, light brown to olive brown, and 60 to 200 μm in diameter. Ostioles were papillate, 20 to 35 μm wide, and surrounded by a ring of darker cells. Conidia were hyaline, smooth, cylindrical to clavate, straight to mildly curved, slightly constricted at the septa, medianly one-septate, sometimes aseptate, 8 to 16 × 2.5 to 3.5 μm, and contained small oil drops. These morphological characteristics were consistent with the previous reports of Ascochyta marginata J.J. Davis (3,4). A monoconidial isolate was cultured on potato dextrose agar (PDA) plates and accessioned in the Korea Agricultural Culture Collection (Accession KACC43082). The conidia were readily formed on PDA. Inoculum for the pathogenicity tests was prepared by harvesting conidia from 30-day-old cultures of KACC43082 and a conidial suspension (approximately 2 × 106 conidia/ml) was sprayed onto leaves of three healthy seedlings. Three noninoculated seedlings served as controls. Inoculated and noninoculated plants were covered with plastic bags for 48 h in a glasshouse. After 7 days, typical leaf spot symptoms started to develop on the leaves of the inoculated plants. The fungus, A. marginata, was reisolated from those lesions, confirming Koch's postulates. No symptoms were observed on control plants. Previously, the disease was reported in Japan (4) and China (3). To our knowledge, this is the first report of A. marginata on Japanese angelica trees in Korea. According to our field observations in Korea, the Ascochyta leaf spot mostly occurred on plants growing in a humid environment, especially during the rainy season. The seedlings as well as the trees growing in sunny, well-ventilated plots were nearly free from this disease. Therefore, the growing conditions seemed to be the most important factor for the development and severity of the disease. References: (1) C. K. Lee et al. Plant Pathol. J. 26:426, 2010. (2) S. H. Lee et al. Diseases of Japanese Angelica Tree and Their Control. Research Report 08-10. Korea Forest Research Institute. Seoul, Korea, 2008. (3) J. Sun et al. Acta Mycol. Sin. 14:107, 1995. (4) M. Yoshikawa and T. Yokoyama. Mycoscience 36:67, 1995.

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First Report of White Mold Caused by Sclerotinia sclerotiorum on Thymus × citriodorus in Italy

Plant Disease ◽

10.1094/pdis.2004.88.9.1044a ◽

2004 ◽

Vol 88 (9) ◽

pp. 1044-1044

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Sclerotinia Sclerotiorum ◽

Soil Surface ◽

White Mold ◽

First Report ◽

Potted Plants ◽

Inoculation Trial ◽

Initial Symptoms ◽

Commercial Farms ◽

Stem Necrosis ◽

White Mycelium

Thymus × citriodorus is well known for the citrus aroma released by its leaves and is grown as a potted plant in northern Italy. This species is widely used in gardens and landscapes and for culinary purposes. In the Liguria Region alone, 1.5 million plants are grown. In the winter of 2002, extensive chlorosis was observed on potted plants of Thymus × citriodorus cv. Silver Queen grown outdoors on commercial farms near Albenga. Initial symptoms included stem necrosis at the soil level and darkening of leaves. As stem necrosis progressed, infected plants wilted and died. Wilt, characterized by the presence of soft and watery tissues, occurred within a few days on young plants. Necrotic tissues became covered with whitish mycelium that produced dark sclerotia. Sclerotinia sclerotiorum (Lib.) de Bary (1) was consistently recovered from infected stem pieces of Thymus × citriodorus. The diseased stem tissue was disinfested for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 ppm of streptomycin sulfate. Sclerotia produced on PDA were ellipsoid and measured 5.2 to 4.4 × 2.1 to 1.5 mm (average 3.5 × 3.0 mm). Pathogenicity of three isolates obtained from infected plants was confirmed by inoculating 30-day-old plants grown in 14-cm-diameter pots in a screenhouse. Inoculum that consisted of wheat kernels infested with mycelium and sclerotia of each isolate was placed on the soil surface around the base of each of 10 plants. Noninoculated plants served as controls. The inoculation trial was repeated once. All plants were kept at temperatures ranging between 5 and 26°C and watered as needed. Inoculated plants developed symptoms of leaf yellowing within 13 days, soon followed by the appearance of white mycelium, and eventually wilted. Control plants remained symptomless. White mycelium and sclerotia developed on infected tissues and S. sclerotiorum was reisolated from inoculated plants. To our knowledge, this is the first report of white mold of Thymus × citriodorus caused by S. sclerotiorum. The economic importance of this disease for the crop can be considered low. Reference: (1) N. F. Buchwald. Den. Kgl. Veterin.er-og Landbohojskoles Aarsskrift, 1949.

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First Report of Nigrospora Leaf Blight on Sesame Caused by Nigrospora sphaerica in China

Plant Disease ◽

10.1094/pdis-07-13-0684-pdn ◽

2014 ◽

Vol 98 (6) ◽

pp. 842-842 ◽

Cited By ~ 3

Author(s):

H. Zhao ◽

H. Y. Liu ◽

X. S. Yang ◽

Y. X. Liu ◽

Y. X. Ni ◽

...

Keyword(s):

Morphological Characteristics ◽

Leaf Blight ◽

Morphological Data ◽

Its2 Region ◽

Oilseed Crop ◽

Conidial Suspension ◽

First Report ◽

Initial Symptoms ◽

Central Regions ◽

Leaf Pathogen

Sesame (Sesamum indicum L.) is an important oilseed crop widely grown in the central regions of China. A new leaf blight has increasingly been observed in sesame fields in Anhui, Hubei, and Henan provinces since 2010. Approximately 30 to 40% of the plants were symptomatic in the affected fields. Initial symptoms were yellow to brown, irregularly shaped lesions. Lesions later expanded and the affected leaves tuned grayish to dark brown and wilted, with a layer of whitish mycelial growth on the underside. Severe blighting caused the center of lesions to fall out, leaving holes in the leaves. Sections of symptomatic leaf tissues were surface-sterilized in 75% ethanol for 30 s, then in 1% HgCl2 for 30 s, rinsed three times in sterile distilled water, and plated onto potato dextrose agar (PDA). The resulting fungal colonies were initially white, and then became grayish-brown with sporulation. Conidia were single-celled, black, smooth, spherical, 14.2 to 19.8 μm (average 17.1 μm) in diameter, and borne on a hyaline vesicle at the tip of each conidiophore. Morphological characteristics of the isolates were similar to those of Nigrospora sphaerica (1). To verify the identification based on morphological features, the ITS1-5.8S-ITS2 region of the ribosomal RNA was amplified using ITS1 (5′-TCCGTAGGTGAACCTGCGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′) primers (3), and then sequenced and compared to the GenBank database through a BLAST search. Comparison of the sequence revealed 100% similarity to N. sphaerica (GenBank Accession No. JF817271.1). On the basis of morphological data and the ITS rDNA sequence, the isolate was determined to be N. sphaerica. Pathogenicity tests were conducted using fresh and healthy sesame leaves of 10 plants. A conidial suspension (106 conidia/ml) collected from a 7-day-old culture on PDA was used for inoculation. Leaves of 10 plants were spray-inoculated with the spore suspension at the 6-week-old growth stage, and an additional 10 plants were sprayed with sterile water. Inoculated plants were covered with polyethylene bags to maintain high humidity. Plants were kept at 28°C and observed for symptom every day. Ten to 15 days after inoculation, inoculated leaves developed blight symptoms similar to those observed on naturally infected leaves. No symptoms were observed on the control leaves. N. sphaerica was re-isolated from the inoculated leaves, thus fulfilling Koch's postulates. N. sphaerica has been reported as a leaf pathogen on several hosts worldwide (2). To our knowledge, this is the first report of Nigrospora leaf blight on sesame caused by N. sphaerica in China. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ . July 01, 2013. (3) M. A. Innis et al. PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, CA, 1990.

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First Report of Nigrospora Leaf Blight on Tea Caused by Nigrospora sphaerica in India

Plant Disease ◽

10.1094/pdis-05-14-0545-pdn ◽

2015 ◽

Vol 99 (3) ◽

pp. 417-417 ◽

Cited By ~ 11

Author(s):

J. Dutta ◽

S. Gupta ◽

D. Thakur ◽

P. J. Handique

Keyword(s):

Camellia Sinensis ◽

West Bengal ◽

Morphological Characteristics ◽

Its Region ◽

Causative Organism ◽

Distilled Water ◽

Conidial Suspension ◽

Tea Leaves ◽

First Report ◽

Initial Symptoms

Tea [Camellia sinensis (L.) O. Kuntze] is an economically important non-alcoholic caffeine-containing beverage crop widely cultivated for leaves in India, especially in the Darjeeling district of West Bengal. In May 2012, distinct blight symptoms were observed on leaves of popular tea cultivars AV-2, Tukdah 78, Rungli Rungliot 17/144, and Bannockburn 157 in commercial tea estates of the Darjeeling district. This disease reduces yield and quality of the leaves. The initial symptoms were frequently observed on the young leaf margins and apices. Foliar symptoms are characterized by grayish to brown, semicircular or irregular shaped lesions, often surrounded by pale yellow zones up to 9 mm in diameter. The lesions later expand and the affected leaves turn grayish to dark brown and eventually the dried tissue falls, leading to complete defoliation of the plant. The disease causes damage to leaves of all ages and is severe in young leaves. A portion of the symptomatic leaf tissues were surface sterilized in 70% ethanol for 30 s, then in 2% NaClO for 3 min, rinsed three times in sterile distilled water, and plated onto potato dextrose agar (PDA). The fungal colonies were initially white and then became grayish to brown with sporulation. Conidia were spherical to sub spherical, single-celled, black, 19 to 21 μm in diameter, and were borne on a hyaline vesicle at the tip of each conidiophore. Morphological characteristics of the isolates were concurring to those of Nigrospora sphaerica (1). Moreover, the internal transcribed spacer (ITS) region of the ribosomal RNA was amplified by using primers ITS1 and ITS4 and sequenced (GenBank Accession No. KJ767520). The sequence was compared to the GenBank database through nucleotide BLAST search and the isolate showed 100% similarity to N. sphaerica (KC519729.1). On the basis of morphological characteristics and nucleotide homology, the isolate was identified as N. sphaerica. Koch's postulates were fulfilled in the laboratory on tea leaves inoculated with N. sphaerica conidial suspension (106 conidia ml−1) collected from a 7-day-old culture on PDA. Six inoculated 8-month-old seedlings of tea cultivars AV-2 and S.3/3 were incubated in a controlled environment chamber at 25°C and 80 to 85% humidity with a 12-h photoperiod. In addition, three plants of each cultivar were sprayed with sterile distilled water to serve as controls. Twelve to 14 days after inoculation, inoculated leaves developed blight symptoms similar to those observed on naturally infected tea leaves in the field. No symptoms were observed on the control leaves. The pathogen was re-isolated from lesions and its identity was confirmed by morphological characteristics. It was reported that N. sphaerica is frequently encountered as a secondary invader or as a saprophyte on many plant species and also as a causative organism of foliar disease on several hosts worldwide (2,3). To our knowledge, this is first report of N. sphaerica as a foliar pathogen of Camellia sinensis in Darjeeling, West Bengal, India, or worldwide. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (2) D. F. Farr and A. Y. Rossman. Fungal Databases, Syst. Mycol. Microbiol. Lab., ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ July 01, 2013. (3) E. R. Wright et al. Plant Dis. 92:171, 2008.

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First Report of Zonate Leaf Spot Caused by Hinomyces moricola on Japanese Hop in Korea

Plant Disease ◽

10.1094/pdis-01-13-0021-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1117-1117 ◽

Cited By ~ 1

Author(s):

S. E. Cho ◽

J. H. Park ◽

S. H. Hong ◽

H. D. Shin

Keyword(s):

Its Region ◽

The United States ◽

Infected Leaf ◽

Invasive Weed ◽

Voucher Specimen ◽

First Report ◽

Leaf Spots ◽

Initial Symptoms ◽

Wide Range ◽

Humulus Japonicus

Japanese hop (Humulus japonicus Siebold & Zucc. = H. scandens (Lour.) Merr.), native to East Asia, is an annual, climbing or trailing vine. The vines can spread to cover large areas of open ground or low vegetation, eventually blanketing the land and vegetation. Pollen of H. japonicus is allergenic, and this species is considered as one of the important causes of pollinosis in Korea and China. It is a notorious invasive weed in the United States and also in France, Hungary, and Italy (1). In September 2012, zonate leaf spots were observed on Japanese hops growing in wetlands in Yeongdong County of Korea. A voucher specimen was preserved in the Korea University Herbarium (KUS-F26901). Initial symptoms included grayish-green to grayish-brown spots without border lines. As the lesions enlarged, they coalesced, leading to leaf blight. Sporophores on the leaf lesions were dominantly hypophyllous, rarely epiphyllous, solitary, erect, easily detachable, and as long as 700 μm. The upper portion of the sporophores consisted of a pyramidal head was ventricose, 320 to 520 μm long and 110 to 150 μm wide. The fungus was isolated from leaf lesions and maintained on potato dextrose agar (PDA). Sclerotia were produced on PDA after 4 to 5 weeks at 18°C without light, but conidia were not observed in culture. These morphological and cultural characteristics were consistent with those of Hinomyces moricola (I. Hino) Narumi-Saito & Y. Harada (= Cristulariella moricola (I. Hino) Redhead) (3,4). An isolate was preserved in the Korean Agricultural Culture Collection (Accession No. KACC46955). Genomic DNA was extracted using the DNeasy Plant Mini DNA Extraction Kit (Qiagen Inc., Valencia, CA). The complete internal transcribed spacer (ITS) region of rDNA was amplified with the primers ITS1/ITS4 and sequenced. The resulting sequence of 452 bp was deposited in GenBank (Accession No. KC460209). A BLAST search in GenBank revealed that the sequence showed an exact match with those of C. moricola (JQ036181 ex Acer negundo and JQ036182 ex Glycine max). To determine the pathogenicity of the fungus, according to the procedure of Cho et al. (2), sporophores with the pyramidal head were carefully detached from a lesion on the naturally infected leaf using a needle. Each sporophore was transferred individually onto five places of four detached healthy leaves. The leaves were placed in dew chambers and incubated at 16°C. Symptoms were observed after 2 days on all inoculated leaves. A number of sporophores and immature sclerotia which were morphologically identical to the ones observed in the field were formed on the abaxial surface of the leaf 2 weeks after inoculation. The pathogen was reisolated from lesions on the inoculated leaves, confirming Koch's postulates. No symptoms were observed on the control leaves kept in humid chambers for 2 weeks. H. moricola was known to cause zonate leaf spots and defoliation on a wide range of woody and annual plants (3). To the best of our knowledge, this is the first report of Hinomyces infection on Japanese hops in Korea. References: (1) Anonymous. Humulus japonicus (Cannabaceae): Japanese hop. Eur. Medit. Plant Prot. Org. (EPPO). 2012. (2) S. E. Cho et al. Plant Dis. 96:906, 2012. (3) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., Online publication, ARS, USDA, Retrieved December 8, 2012. (4) S. A. Redhead. Can. J. Bot. 53:700, 1975.

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First Report of a Leaf Spot Disease of Tobacco Caused by Pseudomonas cichorii in China

Plant Disease ◽

10.1094/pdis-10-21-2158-pdn ◽

2021 ◽

Author(s):

Dayu Lan ◽

Fangling Shu ◽

Yanhui Lu ◽

Anfa Shou ◽

Wei Lin ◽

...

Keyword(s):

Pseudomonas Syringae ◽

Leaf Spot ◽

Leaf Spot Disease ◽

Pathogenicity Test ◽

Pseudomonas Cichorii ◽

Koch’S Postulates ◽

First Report ◽

Initial Symptoms ◽

Wide Range ◽

Koch's Postulates

Tobacco (Nicotiana tabacum L.), one of the chief commercial crops, is wildly cultivated worldwide. In June 2020 and 2021, an unknown bacterial leaf spot on tobacco was found in Hezhou and Hechi City, Guangxi, China. 30% of the tobacco were affected and the rate of diseased leaves reached about 10% in the field under high temperature and rainstorm. The disease mainly damaged the middle and top leaves of tobacco plants at vigorous growing stage. The initial symptoms were water-soaked spots on the frontal half of a leaf, and then expanded into circular to irregular spots with a yellow halo at the edge. The spots mostly appeared dark brown at high air humidity, while yellow brown at low humidity and exhibited a concentric pattern. In severe cases, the lesions coalesced and the whole leaf was densely covered with lesions, resulting in the loss of baking value. A bacterium was consistently isolated from diseased leaf tissues on nutrient agar (NA). Growth on NA was predominantly grayish white circular bacterial colonies with smooth margins, and the bacterium is rod-shaped, gram-negative and fluorescent on King’s B medium. Seven isolates (ND04A-ND04C and ZSXF02-ZSXF05) were selected for molecular identification and pathogenicity tests. Genomic DNA of the bacterium was extracted and the housekeeping gene of cts (encoding citrate synthase) was amplified with the primers cts-Fs/cts-Rs (forward primer cts-Fs: 5’-CCCGTCGAGCTGCCAATWCTGA-3’; reverse primer cts-Rs: 5’-ATCTCGCACGGSGTRTTGAACATC-3’) (Berge et al. 2014; Sarkar et al. 2004). 409-bp cts gene sequences were deposited in the GenBank database for seven isolates (accession no. OK105110-OK105116). Sequence of seven isolates shared 100% identity with several Pseudomonas cichorii strains within the GenBank database (accession no. KY940268 and KY940271), and the phylogenetic tree of cts genes of the seven isolates clustered with the phylogroup 11 of Pseudomonas syringae (accession no. KJ877799 and KJ878111), which was classified as P.cichorii. To satisfy Koch’s postulates, a pathogenicity test was tested by using a needle to dip a suspension of the bacterium (108 CFU/ml) and pricking three holes in the tobacco leaf. The control plants leaves were needled with sterile water. Each tobacco plant was inoculated with three leaves, and the test was repeated three times. All plants were placed in transparent plastic boxes and incubated in a greenhouse at 25 ± 3°C. The water-soaked spots appeared 24h after inoculation and quickly expanded through leaf veins. Three days after inoculation, all the inoculated leaves showed symptoms similar to those observed in the field. Control plants remained healthy. Only P. cichorii was successfully re-isolated from the lesions, confirming Koch’s postulates. Pseudomonas cichorii can infect eggplant, lettuce, tomatoand other crops, and has a wide range of hosts (Timilsina et al. 2017; Ullah et al. 2015). To our knowledge, this is the first report of P. cichorii causing leaf spot on tobacco in China.

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First Report of Stem and Crown Rot of Garbanzo Caused by Sclerotinia minor in the United States and by Sclerotinia sclerotiorum in Arizona

Plant Disease ◽

10.1094/pdis.2000.84.11.1250a ◽

2000 ◽

Vol 84 (11) ◽

pp. 1250-1250 ◽

Cited By ~ 4

Author(s):

M. E. Matheron ◽

M. Porchas

Keyword(s):

United States ◽

Cicer Arietinum ◽

Soil Surface ◽

The United States ◽

Crown Rot ◽

Sclerotinia Minor ◽

First Report ◽

Initial Symptoms ◽

Stem Necrosis ◽

White Mycelium

In March 2000, plants began to die within two garbanzo (Cicer arietinum L.) fields about 48 km apart in southwestern Arizona. Initial symptoms included wilting of leaves and stem necrosis on individual branches, followed by entire plant necrosis and death. White mycelium was present on plant stems near the soil surface. In one field, small black irregularly shaped sclerotia (1 mm in diameter) were present on the infected stem surface along with the white mycelia, whereas in the other field the associated sclerotia were of similar shape but larger (5 to 6 mm in diameter). Isolation from diseased garbanzo stem tissue from the respective fields yielded Sclerotinia minor, which produced small sclerotia when cultured on potato-dextrose agar and S. sclerotiorum, which produced the typical larger sclerotia of this species. To fulfill Koch's postulates, healthy plants and associated soil from a garbanzo field with no evidence of infection by Sclerotinia were removed with a shovel and transferred into a series of 8-liter plastic pots. After transporting back to the laboratory, some of the plants were inoculated by wounding stems with a 5-mm-diameter cork borer, placing an agar disk containing either S. minor or S. sclerotiorum onto each wound, securing the agar disk to the stem with plastic tape, then incubating the plants at 25°C for 7 days. Control plants were treated similarly except that agar disks did not contain Sclerotinia. Stems inoculated with S. minor or S. sclerotiorum developed symptoms of wilt and necrosis, including the appearance of white mycelium and sclerotia on the stem surface, whereas control plants remained healthy. S. minor or S. sclerotiorum were recovered from garbanzo stems inoculated with the respective species of the pathogen. Sclerotinia leaf drop, which can be caused by S. minor or S. sclerotiorum on lettuce in Arizona, had been observed in both fields previously. Garbanzo fields in Arizona usually are watered by furrow irrigation. Disease was most severe in areas of the garbanzo fields that were heavily irrigated with resultant wetting of tops of plant beds. Proper management of irrigation water and avoidance of establishing a garbanzo planting in fields following lettuce could help reduce future losses from these pathogens. S. minor previously had been reported as a pathogen on Cicer arietinum from the island of Sardinia (2); however, this is apparently the first report of the pathogen on garbanzo other than in Sardinia. S. sclerotiorum has been reported as a pathogen on this host in several countries including the United States (California) (1) but not previously in the state of Arizona. References: (1) I. W. Buddenhagen, F. Workneh, and N. A. Bosque-Perez. Int. Chickpea Newsl. 19:9–10, 1988. (2) F. Marras. Rev. Appl. Mycol. 43:112, 1964.

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