scholarly journals Occurrence of Leaf Spot of Avena sativa Caused by Canariomyces microsporus in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Jinlong Chen ◽  
Zhaoyu Wang ◽  
Joon-Ho Choi
Keyword(s):  
Relative Humidity ◽  
Avena Sativa ◽  
Leaf Spot ◽  
Morphological Characteristics ◽  
Aerial Mycelium ◽  
Its Region ◽  
Sterile Water ◽  
Disease Survey ◽  
Excised Tissue ◽  
Bearing Part

Oats (Avena sativa) are an important fodder crop in the vast ranges of northern and northwestern China, given the growing demand from livestock. (Yang et al. 2010). In July 2020, diseased leaf samples of cultivar Dingyan-2 were collected from fields near Gonghui Town, Zhangbei County, Zhangjiakou City (41.35° N, 114.55° E). These leaves showed oval to irregular yellowish-brown spots (0.5 to 6 mm in diameter) surrounded by a yellowish halo progressing to form narrowly striped spots fusing into lesions in severe cases. In a disease survey of six fields (about 1.5 ha in total), 35% of the plants were infected with a disease severity ranging from 0 to 20%. To isolate the pathogen, 12 symptomatic leaves (two leaves for each plant) were arbitrarily sampled from different locations across the fields and small pieces (5 mm2) of diseased leaves were excised from the border between diseased and healthy tissue. Excised tissue pieces were surface sterilized by immersion in 75 % ethanol for 30 s, then 1% NaClO solution for 1 min, rinsed in sterilized distilled water three times, and transferred to potato dextrose agar (PDA). Colonies on PDA were 41–46 mm diam in 10 d at 25 °C with surface texture floccose, obverse pale mouse grey to black due to ascomata and aerial mycelium, and reverse pale olivaceous. Asci were ellipsoidal to ovoid, 12–18 × 11–15 μm (av.= 15 ×12 μm; n=30) in spore-bearing part, containing eight irregularly arranged ascospores. Ascospores were 1-celled, dark brown when mature, smooth, ellipsoidal, with attenuated ends, 7.5–8.4 × 4.3–5.5 μm (av.= 8.1 × 5.0 μm; n=50), with an apical or slightly subapical germ pore. These morphological characteristics were consistent with previous descriptions of Canariomyces microsporus (syn. Thielavia microspora, Wang et al. 2019). For molecular identification, genomic DNA (isolate MNK-Y1) was extracted and the internal transcribed spacer (ITS) region and β-tubulin (tub2) were amplified and sequenced by using the primers ITS1 and ITS4 (White et al. 1990) and Btub2Fd and Btub4Rd (Woudenberg et al. 2009). Sequences were deposited in GenBank under accessions MW080329 (ITS) and MW557539 (tub2). Blast search revealed that the ITS and tub2 sequences matched 99.4%, 100% (471 bp out of 474 bp; 648 bp out of 648 bp) with the sequences of the ex-type isolate CBS 276.74 of C. microsporus accession number MH860852.1 and MK926899. Koch’s postulates were proven to confirm the pathogenicity of isolate MNK-Y1. Eight-week-old healthy oat seedlings of cv. Dingyan 2 were grown in the greenhouse, at 15-20 ℃ under 30-40% of relative humidity. Ten oat plants were spray inoculated with a spore suspension (5×105spores/ml; isolate MNK-Y1). Another ten oat plants were sprayed with sterile water as controls. All plants were covered with a transparent glass cover and a black polyethylene bag to maintain relative humidity and dark for two days. After 15 days, all the inoculated plants had developed yellowish-brown spots similar to those observed in the field whereas the control plants sprayed with sterile water remained healthy. The pathogen was reisolated from inoculated plants and identified as C. microsporus based on morphological characteristics and the molecular methods described above. This species has previously been isolated from saline and desert soils as well as from leaves of Thymus (Wang et al. 2019). To our knowledge, this is the first report of leaf spot of oat caused by C. microsporus in China.

scholarly journals First Report of Leaf Spot caused by Bipolaris oryzae on Switchgrass in Tennessee

Plant Disease ◽  
2013 ◽  
Vol 97 (12) ◽  
pp. 1654-1654 ◽  
Author(s):  
A. L. Vu ◽  
M. M. Dee ◽  
J. Zale ◽  
K. D. Gwinn ◽  
B. H. Ownley
Keyword(s):  
Leaf Spot ◽  
Panicum Virgatum ◽  
Morphological Characteristics ◽  
Its Region ◽  
Spore Production ◽  
Post Inoculation ◽  
Sterile Water ◽  
Bipolaris Oryzae ◽  
First Report ◽  
Symptomatic Leaf

Knowledge of pathogens in switchgrass, a potential biofuels crop, is limited. In December 2007, dark brown to black irregularly shaped foliar spots were observed on ‘Alamo’ switchgrass (Panicum virgatum L.) on the campus of the University of Tennessee. Symptomatic leaf samples were surface-sterilized (95% ethanol, 1 min; 20% commercial bleach, 3 min; 95% ethanol, 1 min), rinsed in sterile water, air-dried, and plated on 2% water agar amended with 3.45 mg fenpropathrin/liter (Danitol 2.4 EC, Valent Chemical, Walnut Creek, CA) and 10 mg/liter rifampicin (Sigma-Aldrich, St. Louis, MO). A sparsely sporulating, dematiaceous mitosporic fungus was observed. Fungal plugs were transferred to surface-sterilized detached ‘Alamo’ leaves on sterile filter paper in a moist chamber to increase spore production. Conidia were ovate, oblong, mostly straight to slightly curved, and light to olive-brown with 3 to 10 septa. Conidial dimensions were 12.5 to 17 × 27.5 to 95 (average 14.5 × 72) μm. Conidiophores were light brown, single, multiseptate, and geniculate. Conidial production was polytretic. Morphological characteristics and disease symptoms were similar to those described for Bipolaris oryzae (Breda de Haan) Shoemaker (2). Disease assays were done with 6-week-old ‘Alamo’ switchgrass grown from seed scarified with 60% sulfuric acid and surface-sterilized in 50% bleach. Nine 9 × 9-cm square pots with approximately 20 plants per pot were inoculated with a mycelial slurry (due to low spore production) prepared from cultures grown on potato dextrose agar for 7 days. Cultures were flooded with sterile water and rubbed gently to loosen mycelium. Two additional pots were inoculated with sterile water and subjected to the same conditions to serve as controls. Plants were exposed to high humidity by enclosure in a plastic bag for 72 h. Bags were removed, and plants were incubated at 25/20°C with 50 to 60% relative humidity. During the disease assay, plants were kept in a growth chamber with a 12-h photoperiod of fluorescent and incandescent lighting. Foliar leaf spot symptoms appeared 5 to 14 days post-inoculation for eight of nine replicates. Control plants had no symptoms. Symptomatic leaf tissue was processed and plated as described above. The original fungal isolate and the pathogen recovered in the disease assay were identified using internal transcribed spacer (ITS) region sequences. The ITS region of rDNA was amplified with PCR and primer pairs ITS4 and ITS5 (4). PCR amplicons of 553 bp were sequenced, and sequences from the original isolate and the reisolated pathogen were identical (GenBank Accession No. JQ237248). The sequence had 100% nucleotide identity to B. oryzae from switchgrass in Mississippi (GU222690, GU222691, GU222692, and GU222693) and New York (JF693908). Leaf spot caused by B. oryzae on switchgrass has also been described in North Dakota (1) and was seedborne in Mississippi (3). To our knowledge, this is the first report of B. oryzae from switchgrass in Tennessee. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology and Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/, 28 June 2012. (2) J. M. Krupinsky et al. Can. J. Plant Pathol. 26:371, 2004. (3) M. Tomaso-Peterson and C. J. Balbalian. Plant Dis. 94:643, 2010. (4) T. J. White et al. Pages 315-322 in: PCR Protocols: a Guide to Methods and Applications. M. A. Innis et al. (eds), Acad. Press, San Diego, 1990.

scholarly journals First Report of Neofusicoccum parvum Causing Panicle Blight and Leaf Spot on Vitis heyneana in China

Plant Disease ◽  
2015 ◽  
Vol 99 (3) ◽  
pp. 417-417 ◽  
Author(s):  
D. D. Wu ◽  
G. Fu ◽  
Y. F. Ye ◽  
F. Y. Hu ◽  
H. F. Mou ◽  
...  
Keyword(s):  
Leaf Spot ◽  
Severe Disease ◽  
Morphological Characteristics ◽  
Aerial Mycelium ◽  
Its Region ◽  
Average Diameter ◽  
Wine Production ◽  
Neofusicoccum Parvum ◽  
First Report ◽  
Panicle Blight

The climbing vine, Vitis heyneana Roem. & Schult, is a member of the grape family endemic to Asia. Its fruits are used in wine production, and its roots, stems, and leaves can be used in medicinal materials. This plant is grown in Southwest China, as well as in India, Bhutan, and Nepal. Mulao Autonomous County in Guangxi Province is the only artificial cultivation area in China. During the summer of 2013, a panicle blight and leaf spot were detected on V. heyneana on four farms in Mulao Autonomous County. The symptoms were observed from the onset of florescence through fruit harvest. Brown lesions initially appeared at the base of a panicle and then extended to the whole panicle, finally causing the panicle to die and fruit to drop. When the disease developed on leaves, the symptom initially appeared as small dark brown circular spots, later enlarging into irregular spots (average diameter 6 mm) with a light brown center and dark brown rim. With severe disease, some individual leaves were affected by numerous spots, leading to premature senescence. Small sections of diseased tissue excised from 10 panicle and 10 leaf samples were plated on potato dextrose agar (PDA) and incubated at 28°C. Fungal colonies developed, initially with abundant white aerial mycelium, which turned olivaceous gray after 5 days and formed black pycnidia after 25 days. The conidia were hyaline, ellipsoidal to fusiform, externally smooth, thin-walled, and nonseptate. Thirty conidia were measured; the dimensions were 12.0 to 17.5 × 4.0 to 6.0 μm. Morphological characteristics of the isolates were similar to the descriptions of Neofusicoccum parvum (3). The isolate MPT-1 was selected as a representative for molecular identification. Genomic DNA was extracted and used for PCR to amplify the internal transcribed spacer (ITS) region and partial translation elongation factor 1-alpha (EF1-α) gene, using primers ITS1/ITS4 and EF1-728F/EF1-986R, respectively. The obtained ITS sequence (GenBank Accession No. KJ599627) and EF1-α sequence (KM921768) showed >99% homology with several GenBank sequences of N. parvum. Morphological and molecular results confirmed the isolate as N. parvum. For pathogenicity tests, detached, young healthy panicles and leaves of V. heyneana were surface-sterilized, wounded by sterile needle, and inoculated with mycelial plugs (3 mm in diameter) of four N. parvum isolates. Ten panicles and 10 leaves were used for every isolate. Control panicles and leaves were treated with sterile PDA plugs. All the samples were placed in a humid chamber (RH 90%, 28°C, 12 h of light) for 3 days. Symptoms similar to those observed in the field developed on all panicles and leaves inoculated with N. parvum isolates. N. parvum was reisolated from all inoculated, symptomatic tissues. The controls remained symptomless. N. parvum has been reported to cause trunk canker on V. vinifera (2), dieback on Cupressus funebris (3), and a leaf spot on Myristica fragrans (1). To our knowledge, this is the first report of N. parvum causing panicle blight and leaf spot on V. heyneana in China. Panicle blight caused a large number of fruits to drop and reduced the yield seriously. Some effective measures should be taken to control this disease. References: (1) V. Jayakumar et al. New Dis. Rep. 23:19, 2011. (2) J. Kaliternam et al. Plant Dis. 97:1656, 2013. (3) S. B. Li et al. Plant Dis. 94:641, 2010.

scholarly journals Morphology, Molecular Phylogeny, and Pathogenicity of Neofusicoccum parvum, Associated with Leaf Spot Disease of a New Host, the Japanese Bay Tree (Machilus thunbergii)

Forests ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 440
Author(s):  
Sungyu Choi ◽  
Narayan Chandra Paul ◽  
Kye-Han Lee ◽  
Hyun-Jun Kim ◽  
Hyunkyu Sang
Keyword(s):  
Leaf Spot ◽  
Morphological Characteristics ◽  
Aerial Mycelium ◽  
Its Region ◽  
Leaf Spot Disease ◽  
New Host ◽  
Neofusicoccum Parvum ◽  
Spot Disease ◽  
Leaf Spots ◽  
Machilus Thunbergii

During a survey of diseased plants on Wando Island, Korea from May to June 2020, a severe leaf spot disease was observed in the upper leaves of Japanese bay tree (Machilus thunbergii). Early symptoms were light blackish spots on the leaf surface and enlargement of older spots. Dry leaf spots surrounded with deep black margins were common throughout the plants. Symptomatic leaf samples were collected, and the causal pathogen was isolated on potato dextrose agar (PDA). Three fungal isolates (CMML20-1, CMML20-3, and CMML20-4) were cultured on PDA for morphological characterization at 25 °C in the darkness. Fungal colonies were circular, fast-growing, olivaceous to dark grey, and with abundant aerial mycelium. Sporulation was induced in 14 h-10 h light-dark conditions, and the conidia were single-celled, thin-walled with a smooth surface, ellipsoid with round apices, and measuring 17.5–20.5 (avg. 17.5) μm × 7.5–10.0 (7.9) μm. The morphological characteristics resembled those typical for Neofusicoccum parvum. Molecular identification was confirmed by partially sequencing the internal transcribed spacer (ITS) region and the translation elongation factor 1-α (EF1-α) genes. Pathogenicity tests were conducted on detached leaves and whole plants of M. thunbergii. High disease prevalence was observed, and Koch postulates were fulfilled. This is the first worldwide report of N. parvum causing leaf spots on Machilus thunbergii.

scholarly journals First Report of Leaf Spot Disease in Coconut Seedling Caused by Bipolaris setariae in China

Plant Disease ◽  
2014 ◽  
Vol 98 (12) ◽  
pp. 1742-1742 ◽  
Author(s):  
X.-Q. Niu ◽  
F.-Y. Yu ◽  
H. Zhu ◽  
W.-Q. Qin
Keyword(s):  
Leaf Spot ◽  
Sequence Similarity ◽  
Cocos Nucifera ◽  
Morphological Characteristics ◽  
Aerial Mycelium ◽  
Its Region ◽  
Leaf Spot Disease ◽  
First Report ◽  
Spot Disease ◽  
Cocos Nucifera L

Coconut (Cocos nucifera L.), an important oilseed as well as a multipurpose perennial plantation crop, is distributed and planted in humid tropical areas. In October 2012, a new leaf spot disease was observed on 3-year-old coconut seedlings in Wenchang, Hainan Province, China. The symptom first appeared as spindly or elliptical and brown flecks with water-soaked lesions that became yellow with the progress of the disease. In the later stage of the disease, the lesions merged together, gradually expanding to the leaf apex. In recent years, the disease has been prevalent in all the nursery gardens surveyed. Once young leaves got infected and nearly all the leaves of the tree showed diseased symptoms, the coconut eventually became defoliated. The pathogen was isolated from the lesion margin, surface sterilized with 75% ethanol and 0.1% mercury bichloride, washed by sterile distilled water, and then placed excising pieces of leaves from the leision margin onto potato dextrose agar (PDA). Plates were incubated at 25°C for 4 days. After 7 days, the colony was grayish black and produced black pigment in the medium. Aerial mycelium was fluffy, septate, and branched, the conidiophores were slightly flexuous or straight, 5 to 11 μm thick, and produced curved, spindle-shaped, or fusiform, septate conidia with 4 to 10 septa, measuring 39 to 86 × 9 to 16 μm, with a slightly protuberant hilum, truncated. Based on the symptoms and mycelial and conidial characters above, the fungus was identified as Bipolaris setariae (1). The pathogenicity was established and repeated for six times by following Koch's postulates. Two 1-year-old coconut seedlings were washed with sterilized water and six leaves were wounded with a sterile needle and then inoculated by spraying them with a suspension of conidia of the isolate. The seedlings were kept in two incubators at 25°C for 12 days. Inoculated leaves showed typical symptoms similar to those described above. The pathogen was re-isolated from inoculated leaves. Morphological characteristics were identical to the original isolated fungus. In contrast, the control leaves did not show any symptoms. The genomic DNA of this fungus was extracted, amplification of the internal transcribed spacer (ITS) region was performed with primer ITS1 and ITS4, and the purified PCR product was sequenced (GenBank Accession No. KJ605157). BLASTn analysis revealed 99% sequence similarity with four B. setariae isolates (HE792936.1, JX462256, GU073108.1, and FJ606786.1). Morphologic characters and sequence analysis of the ITS rDNA confirmed that the pathogen was B. setariae. Bipolaris incurvata has been reported causing disease on coconut (2), but B. setariae was not previously reported on coconut. So far, this is the first report of B. setariae caused coconut seedling leaf spot disease in Hainan, China. References: (1) K. C. da Cunha et al. J. Clin. Microbiol. 50:4061, 2012. (2) A. Kamalakannan et al. New Dis. Rep. 12:18, 2005.

scholarly journals First Report of Gray Leaf Spot Caused by Pyricularia oryzae (synonym: Magnaporthe oryzae) in Oat (Avena sativa) in Georgia, USA.

Plant Disease ◽  
2021 ◽  
Author(s):  
Willis Turner Spratling ◽  
Suraj Sapkota ◽  
Brian Christopher Vermeer ◽  
Jason Mallard ◽  
Emran Ali ◽  
...  
Keyword(s):  
Avena Sativa ◽  
Leaf Spot ◽  
Pcr Amplification ◽  
Its Region ◽  
Gray Leaf Spot ◽  
Pyricularia Oryzae ◽  
Spore Suspension ◽  
Sterile Water ◽  
Economic Implications ◽  
First Report

In southeastern U.S., oat (Avena sativa L.) is predominantly grown as a grain or forage crop due to its exceptional palatability (Buntin et al. 2009). In November 2020, leaf spot symptoms were observed in an oat field (cv. Horizon 720) in Screven County, Georgia (GPS: 32°38'57.6"N 81°31'32.178"W). Lesions were oblong, whitish to gray in color, and surrounded by dark brown borders. Symptomatic oat leaves were sampled from the field and cut into 1 cm2 sections that were surface sterilized, plated onto Potato Dextrose Agar (PDA) media and incubated in the dark at 23°C. To obtain pure cultures, fungal hyphal tips were transferred onto fresh PDA plates 3 times. The pathogen was identified as Pyricularia (Magnaporthe) based on typical conidial morphology (Ellis 1971). Conidia were hyaline, pyriform, 2-septate, and displayed a basal hilum. Conidia measured 5.32 to 10.64 μm (average 8.24 μm) wide by 15.96 to 29.26 μm (average 25.40 μm) long. The identification of Pyricularia was further confirmed genetically via PCR amplification followed by sequencing. Genomic DNA was extracted from a 14-day old pure culture using a CTAB method (Doyle and Doyle 1987). The internal transcribed spacer (ITS) region of ribosomal DNA, calmodulin (CaM) gene, and -tubulin (TUB) gene were amplified using ITS5-ITS4 (White et al. 1990), CMD5-CMD6 (Hong et al. 2005), and Bt2a- Bt2b (Glass and Donaldson 1995) primer sets, respectively. Amplicons were Sanger sequenced and blasted against the NCBI database. Results exhibited 100% (ITS), 100% (CaM), and 99.61% (TUB) homology with Pyricularia oryzae Cavara (GenBank accession no. LC554423.1, CP050920.1, and CP050924.1, respectively). The ITS, CaM, and TUB sequences of the isolate were deposited in GenBank as MZ295207, MZ342893, and MZ342894, respectively. In a greenhouse (23°C, 80% RH), Koch’s postulates were carried out by using oat seedlings cv. Horizon 270 grown in Kord sheet pots filled with Sun Gro professional growing mix, and a P. oryzae spore suspension containing 104 conidia ml−1. The spore suspension (10 ml) was sprayed with an air sprayer onto 7 pots of oat seedlings at the two-leaf stage. Seven supplementary pots of oat seedlings of the same cultivar were sprayed with sterile water to act as controls. After inoculation, plants were covered with black plastic bags that had been sprayed with sterile water to maintain high humidity and incubated overnight in the greenhouse. The bags were removed the next day, and plants were evaluated for symptoms in the following days. Seven days after inoculation, plants displayed symptoms similar to those found in the original field sample. Control plants showed no symptoms. Pyricularia oryzae was consistently re-isolated from inoculated symptomatic oat tissues. To our knowledge, this is the first report of gray leaf spot caused by P. oryzae on oat in the state of Georgia and in the continental United States. Pyricularia oryzae can infect several graminaceous plants, including agronomically important crops such as rice (Oryza sativa) and wheat (Triticum spp.) (Chung et al. 2020). Phylogenetic analysis on the ITS region using 6 different host lineages was performed and revealed that this oat isolate was most closely related to the Lolium lineage. This outbreak could have economic implications in oat production.

scholarly journals First Report of Leaf Spot of Sweet Basil Caused by Cercospora guatemalensis in Korea

Plant Disease ◽  
2012 ◽  
Vol 96 (10) ◽  
pp. 1580-1580
Author(s):  
J. H. Park ◽  
K. S. Han ◽  
J. Y. Kim ◽  
H. D. Shin
Keyword(s):  
Leaf Spot ◽  
Morphological Characteristics ◽  
Its Region ◽  
Culture Collection ◽  
Distilled Water ◽  
First Report ◽  
Sweet Basil ◽  
Organic Farm ◽  
Leaf Spots ◽  
Close Phylogenetic Relationship

Sweet basil, Ocimum basilicum L., is a fragrant herb belonging to the family Lamiaceae. Originated in India 5,000 years ago, sweet basil plays a significant role in diverse cuisines across the world, especially in Asian and Italian cooking. In October 2008, hundreds of plants showing symptoms of leaf spot with nearly 100% incidence were found in polyethylene tunnels at an organic farm in Icheon, Korea. Leaf spots were circular to subcircular, water-soaked, dark brown with grayish center, and reached 10 mm or more in diameter. Diseased leaves defoliated prematurely. The damage purportedly due to this disease has reappeared every year with confirmation of the causal agent made again in 2011. A cercosporoid fungus was consistently associated with disease symptoms. Stromata were brown, consisting of brown cells, and 10 to 40 μm in width. Conidiophores were fasciculate (n = 2 to 10), olivaceous brown, paler upwards, straight to mildly curved, not geniculate in shorter ones or one to two times geniculate in longer ones, 40 to 200 μm long, occasionally reaching up to 350 μm long, 3.5 to 6 μm wide, and two- to six-septate. Conidia were hyaline, acicular to cylindric, straight in shorter ones, flexuous to curved in longer ones, truncate to obconically truncate at the base, three- to 16-septate, and 50 to 300 × 3.5 to 4.5 μm. Morphological characteristics of the fungus were consistent with the previous reports of Cercospora guatemalensis A.S. Mull. & Chupp (1,3). Voucher specimens were housed at Korea University herbarium (KUS). An isolate from KUS-F23757 was deposited in the Korean Agricultural Culture Collection (Accession No. KACC43980). Fungal DNA was extracted with DNeasy Plant Mini DNA Extraction Kits (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 548 bp was deposited in GenBank (Accession No. JQ995781). This showed >99% similarity with sequences of many Cercospora species, indicating their close phylogenetic relationship. Isolate of KACC43980 was used in the pathogenicity tests. Hyphal suspensions were prepared by grinding 3-week-old colonies grown on PDA with distilled water using a mortar and pestle. Five plants were inoculated with hyphal suspensions and five plants were sprayed with sterile distilled water. The plants were covered with plastic bags to maintain a relative humidity of 100% for 24 h and then transferred to a 25 ± 2°C greenhouse with a 12-h photoperiod. Typical symptoms of necrotic spots appeared on the inoculated leaves 6 days after inoculation, and were identical to the ones observed in the field. C. guatemalensis was reisolated from symptomatic leaf tissues, confirming Koch's postulates. No symptoms were observed on control plants. Previously, the disease was reported in Malawi, India, China, and Japan (2,3), but not in Korea. To our knowledge, this is the first report of C. guatemalensis on sweet basil in Korea. Since farming of sweet basil has recently started on a commercial scale in Korea, the disease poses a serious threat to safe production of this herb, especially in organic farming. References: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Ithaca, NY, 1953. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Mycology & Microbiology Laboratory, ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , May 5, 2012. (3) J. Nishikawa et al. J. Gen. Plant Pathol. 68:46, 2002.

scholarly journals First Report of Leaf Spot Caused by Corynespora cassiicola on Kiwifruit (Actinidia chinensis) in China

Plant Disease ◽  
2014 ◽  
Vol 98 (11) ◽  
pp. 1586-1586 ◽  
Author(s):  
G. Q. Yuan ◽  
Y. L. Xie ◽  
D. C. Tan ◽  
Q. Q. Li ◽  
W. Lin
Keyword(s):  
Leaf Spot ◽  
Morphological Characteristics ◽  
Its Region ◽  
Corynespora Cassiicola ◽  
Detached Leaf Assay ◽  
Detached Leaf ◽  
Concentric Pattern ◽  
Pathogenicity Tests ◽  
Petri Dishes ◽  
Whole Plants

Kiwifruit (Actinidia) is a common fruit cultivated in many countries. Actinidia deliciosa and A. chinensis are two commercially important kiwifruit species. Over 70,000 ha are grown annually in China. In 2012, a leaf spot disease of A. chinensis was observed in several orchards in Leye County (106°34′ E, 24°47′ N), Guangxi Zhuang Autonomous Region, China. The disease mainly damaged the leaves during the fruit development stage through to the maturity stage. Initially reddish-brown small lesions appeared on the leaves; later, typical symptoms were tan to taupe lesions surrounded by purple brown margins, nearly circular to irregular, 2 to 10 × 2.2 to 15.5 mm in diameter. Some lesions exhibited a concentric pattern. The lesions eventually coalesced, causing extensive leaf necrosis and defoliation. The fungus that sporulated from lesions had the following morphological characteristics: light brown conidiophores with slightly swollen apexes, light brown conidia formed singly or in acropetal chains, straight or curved, cylindrical to oblavate, 52.9 to 240.5 μm long (avg. 138.9 μm) and 5.3 to 13.6 μm wide (avg. 8.4 μm), 5 to 12 distoseptate, with a flat, darkened, and thickened hilum. These morphological characteristics corresponded with that of Corynespora cassiicola (Berk. & Curt.) Wei (1). To isolate the pathogen of the disease, small pieces of symptomatic foliar tissues, including young lesions, typical older lesions, and atypical older lesions with concentric pattern were surface sterilized with 75% ethanol for 30 to 60 s, disinfected in 0.1% HgCl2 for 1 min followed by washing with sterile water, plated on PDA, and incubated at 28°C for 7 to 10 days. Gray to dark gray colonies and conidia of C. cassiicola were observed. To validate the identity of the fungus, the sequence of the ITS region of one of the purified strains, LYCc-1, was determined. DNA was extracted from the isolate that was grown on PDA at 28°C for 4 days, and the ITS region was amplified using the universal primer pair ITS4/ITS5 (2). The double strand consensus sequence was submitted to GenBank (KJ747095) and had 99% nt identity with published sequences of C. cassiicola in GenBank (JN853778, FJ852574, and FJ852587). Pathogenicity tests were carried out on detached leaves in petri dishes in an incubator at 28°C and on whole plants in a glasshouse at 25 ± 3°C. The isolations did not produce enough conidia in pure culture, so mycelial discs were used in pathogenicity tests. For both assays, 60-day-old healthy kiwifruit leaves were inoculated with a 5-mm mycelial disc obtained from the periphery of a 5-day-old C. cassiicola strain (LYCc-1) grown on PDA. The PDA discs were placed on the leaf surface with their mycelial surface down and secured with sterile wet cotton. Controls consisted of leaves that were inoculated with sterile PDA discs. For the detached leaf assay, the leaves were placed on filter paper reaching water saturation in petri dishes, and for the whole plant assays the inoculated leaves were kept moist with intermittent water sprays for 48 h. Four leaves of each plant were inoculated with the isolate in both assays, and experiment was repeated twice. Eight inoculated leaves of the detached leaf assay all showed the first water soaked lesions 36 h after inoculation, followed by extensive leaf rot 72 h after inoculation, and yielded abundant conidia of C. cassiicola. Six out of eight leaves inoculated on whole plants showed the first lesions 5 days after inoculation, whereas control leaves remained healthy. Only C. cassiicola was re-isolated from the lesions in both assays, fulfilling Koch's postulates. This is the first report of leaf spot caused by C. cassiicola on kiwifruit in China. References: (1) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (2) T. J. White et al. In: PCR Protocols: A Guide to Methods and Applications. Academic Press, San Diego, 1990.

scholarly journals First Report of Myrothecium roridum Causing Leaf Spot on Zantedeschia aethiopica in China

Plant Disease ◽  
2014 ◽  
Vol 98 (6) ◽  
pp. 854-854 ◽  
Author(s):  
B.-J. Li ◽  
H.-Y. Ben ◽  
Y.-X. Shi ◽  
X.-W. Xie ◽  
A.-L. Chai
Keyword(s):  
Leaf Spot ◽  
Morphological Characteristics ◽  
Its Region ◽  
First Record ◽  
Conidial Suspension ◽  
Isolation And Identification ◽  
Zantedeschia Aethiopica ◽  
Calla Lily ◽  
Initial Symptoms ◽  
Myrothecium Roridum

Zantedeschia aethiopica (L.) Spreng. (calla lily), belonging to family Araceae, is a popular ornamental plant in China. In the summer of 2010, leaves of calla lily with typical symptoms of necrotic lesions were observed in a commercial glasshouse in Beijing, China (116°20′ E, 39°44′ N). The initial symptoms were circular to subcircular, 1 to 3 mm, and dark brown lesions on the leaf lamina. Under high humidity, lesions expanded rapidly to 5 to 10 mm with distinct concentric zones and produced black sporodochia, especially on the backs of leaves. Later, the infected leaves were developing a combination of leaf lesions, yellowing, and falling off; as a result, the aesthetic value of the plant was significantly impacted. Leaf samples were used in pathogen isolation. Symptomatic leaf tissues were cut into small pieces and surface sterilized with 70% ethanol for 30 s and then in 0.1% mercuric chloride solution for 1 to 3 min. After being washed in sterile distilled water three times, the pieces were plated on potato dextrose agar (PDA) and incubated at 25°C in darkness for 7 days (5). Initial colonies of isolates were white, floccose mycelium and developed dark green to black concentric rings that were sporodochia bearing viscid spore masses after incubating 5 days. Conidiophores branched repeatedly. Conidiogenous cells were hyaline, clavate, and 10.0 to 16.0 × 1.4 to 2.0 μm. Conidia were hyaline, cylindrical, both rounded ends, and 6.0 to 8.2 × 1.9 to 2.4 μm. Morphological characteristics of the fungus were consistent with the description of Myrothecium roridum Tode ex Fr. (3,4). To confirm the pathogenicity, three healthy plants of calla lily were inoculated with a conidial suspension (1 × 106 conidia per ml) brushed from a 7-day-old culture of the fungus. Control plants were sprayed with sterile water. The inoculated plants were individual with clear plastic bags and placed in a glass cabinet at 25°C. After 7 days, all inoculated leaves developed symptoms similar to the original samples, but control plants remained disease free. Re-isolation and identification confirmed Koch's postulates. For molecular identification, genomic DNA of a representative isolate (MTL07081001) was extracted by modified CTAB method (1), and the rDNA-ITS region was amplified by using primers ITS1 (5-TCCGTAGGTGAACCTGCGG-3) and ITS4 (5-TCCTCCGCTTATTGATATGC-3). The 465-bp amplicon (GenBank Accession No. KF761293) was 100% identity to the sequence of M. roridum (JF724158.1) from GenBank. M. roridum has an extensive host range, covering 294 host plants (2). To our knowledge, this is the first record of leaf spot caused by M. roridum on calla lily in China. References: (1) F. M. Ausubel et al. Current Protocols in Molecular Biology. John Wiley & Sons Inc, New York, 1994. (2) D. F. Farr and A. Y. Rossman, Fungal Databases. Syst. Mycol. Microbiol. Lab., ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , October 2013. (3) M. T. Mmbaga et al. Plant Dis. 94:1266, 2010. (4) Y. X. Zhang et al. Plant Dis. 95:1030, 2011. (5) L. Zhu et al. J. Phytopathol. 161:59, 2013.

scholarly journals First Report of Nigrospora osmanthi Causing Leaf Spot on Tartary Buckwheat in China

Plant Disease ◽  
2020 ◽  
Author(s):  
Quan Shen ◽  
Xixu Peng ◽  
Feng He ◽  
Shaoqing Li ◽  
Zuyin Xiao ◽  
...  
Keyword(s):  
Relative Humidity ◽  
Leaf Spot ◽  
Plant Pathogens ◽  
Hunan Province ◽  
Tartary Buckwheat ◽  
Tween 20 ◽  
Pathogenicity Test ◽  
Conidial Suspension ◽  
Sterile Water ◽  
First Report

Buckwheat (Fagopyrum tataricum) is a traditional short-season pseudocereal crop originating in southwest China and is cultivated around the world. Antioxidative substances in buckwheat have been shown to provide many potential cardiovascular health benefits. Between August and November in 2019, a leaf spot was found in several Tartary buckwheat cv. Pinku1 fields in Xiangxiang County, Hunan Province, China. The disease occurred throughout the growth cycle of buckwheat after leaves emerged, and disease incidence was approximately 50 to 60%. Initially infected leaves developed a few round lesions, light yellow to light brown spots. Several days later, lesions began to enlarge with reddish brown borders, and eventually withered and fell off. Thirty lesions (2×2 mm) collected from three locations with ten leaves in each location were sterilized in 70% ethanol for 10 sec, in 2% sodium hypochlorite for 30 sec, rinsed in sterile water for three times, dried on sterilized filter paper, and placed on a potato dextrose PDA with lactic acid (3 ml/L), and incubated at 28°C in the dark for 3 to 5 days. Fungal colonies were initially white and later turned black with the onset ofsporulation. Conidia were single-celled, black, smooth, spherical to subspherical, and measured 9.2 to 15.6 µm long, and 7.1 to 11.6 µm wide (n=30). Each conidium was terminal and borne on a hyaline vesicle at the tip of conidiophores. Morphologically, the fungus was identified as Nigrospora osmanthi (Wang et al. 2017). Identification was confirmed by amplifying and sequencing the ITS region, and translation elongation factor 1-alpha (TEF1-α) and partial beta-tublin (TUB2) genes using primers ITS1/ITS4 (Mills et al. 1992), EF1-728F/EF-2 (Carbone and Kohn 1999; O’Donnell et al. 1998) and Bt-2a/Bt-2b (Glass et al. 1995), respectively. BLAST searches in GenBank indicated the ITS (MT860338), TUB2 (MT882054) and TEF1-α (MT882055) sequences had 99.80%, 99% and 100% similarity to sequences KX986010.1, KY019461.1 and KY019421.1 of Nigrospora osmanthi ex-type strain CGMCC 3.18126, respectively. A neighbor-joining phylogenetic tree constructed using MEGA7.0 with 1,000 bootstraps based on the concatenated nucleotide sequences of the three genes indicated that our isolate was closely related to N. osmanthi. Pathogenicity test was performed using leaves of healthy F. tataricum plants. The conidial suspension (1 × 106 conidia/ml) collected from PDA cultures with 0.05% Tween 20 buffer was used for inoculation by spraying leaves of potted 20-day-old Tartary buckwheat cv. Pinku1. Five leaves of each plant were inoculated with spore suspensions (1 ml per leaf). An equal number of control leaves were sprayed with sterile water to serve as a control. The treated plants were kept in a greenhouse at 28°C and 80% relative humidity for 24 h, and then transferred to natural conditions with temperature ranging from 22 to 30°C and relative humidity ranging from 50 to 60%. Five days later, all N. osmanthi-inoculated leaves developed leaf spot symptoms similar to those observed in the field, whereas control leaves remained healthy. N. osmanthi was re-isolated from twelve infected leaves with frequency of 100%, fulfilling Koch’s postulates. The genus Nigrospora has been regarded by many scholars as plant pathogens (Fukushima et al. 1998) and N. osmanthi is a known leaf blight pathogen for Stenotaphrum secundatum (Mei et al. 2019) and Ficus pandurata (Liu et al. 2019) but has not been reported on F. tataricum. Nigrospora sphaerica was also detected in vegetative buds of healthy Fagopyrum esculentum Moench (Jain et al. 2012). To our knowledge, this is the first report of N. osmanthi causing leaf spot on F. tataricum in China and worldwide. Appropriate strategies should be developed to manage this disease.

scholarly journals First Report of Bipolaris oryzae Causing Leaf Spot on Cultivated Wild Rice (Oryza rufipogon) in China

Plant Disease ◽  
2021 ◽  
Author(s):  
Yue Lian Liu ◽  
Jian Rong Tang ◽  
Ya Li ◽  
Hong Kai Zhou
Keyword(s):  
Leaf Spot ◽  
Wild Rice ◽  
Morphological Characteristics ◽  
Oryza Rufipogon ◽  
Likelihood Method ◽  
Leaf Spot Disease ◽  
Pathogenicity Test ◽  
Sterile Water ◽  
Bipolaris Oryzae ◽  
First Report

Wild rice (Oryza rufipogon) has been widely studied and cultivated in China in recent years due to its antioxidant activities and health-promoting effects. In December 2018, leaf spot disease on wild rice (O. rufipogon cv. Haihong-12) was observed in Zhanjiang (20.93 N, 109.79 E), China. The early symptom was small purple-brown lesions on the leaves. Then, the once-localized lesions coalesced into a larger lesion with a tan to brown necrotic center surrounded by a chlorotic halo. The diseased leaves eventually died. Disease incidence was higher than 30%. Twenty diseased leaves were collected from the fields. The margin of diseased tissues was cut into 2 × 2 mm2 pieces, surface-disinfected with 75% ethanol for 30 s and 2% sodium hypochlorite for 60 s, and then rinsed three times with sterile water before isolation. The tissues were plated on potato dextrose agar (PDA) medium and incubated at 28 °C in the dark for 4 days. Pure cultures were produced by transferring hyphal tips to new PDA plates. Fifteen isolates were obtained. Two isolates (OrL-1 and OrL-2) were subjected to further morphological and molecular studies. The colonies of OrL-1 and OrL-1 on PDA were initially light gray, but it became dark gray with age. Conidiophores were single, straight to flexuous, multiseptate, and brown. Conidia were oblong, slightly curved, and light brown with four to nine septa, and measured 35.2–120.3 µm × 10.3–22.5 µm (n = 30). The morphological characteristics of OrL-1 and OrL-2 were consistent with the description on Bipolaris oryzae (Breda de Haan) Shoemaker (Manamgoda et al. 2014). The ITS region, glyceraldehyde-3-phosphate dehydrogenase (GAPDH), and translation elongation factor (EF-1α) were amplified using primers ITS1/ITS4, GDF1gpp1/GDR1 gdp2 (Berbee et al. 1999), and EF-1α-F/EF-1α-R EF-1/EF-2 (O’Donnell 2000), respectively. Amplicons of OrL-1 and OrL-2 were sequenced and submitted to GenBank (accession nos. MN880261 and MN880262, MT027091 and MT027092, and MT027093 and MT027094). The sequences of the two isolates were 99.83%–100% identical to that of B. oryzae (accession nos. MF490854，MF490831，MF490810) in accordance with BLAST analysis. A phylogenetic tree was generated on the basis of concatenated data from the sequences of ITS, GAPDH, and EF-1α via Maximum Likelihood method, which clustered OrL-1 and OrL-2 with B. oryzae. The two isolates were determined as B. oryzae by combining morphological and molecular characteristics. Pathogenicity test was performed on OrL-1 in a greenhouse at 24 °C to 30 °C with 80% relative humidity. Rice (cv. Haihong-12) with 3 leaves was grown in 10 pots, with approximately 50 plants per pot. Five pots were inoculated by spraying a spore suspension (105 spores/mL) onto leaves until runoff occurred, and five pots were sprayed with sterile water and used as controls. The test was conducted three times. Disease symptoms were observed on leaves after 10 days, but the controls remained healthy. The morphological characteristics and ITS sequences of the fungal isolates re-isolated from the diseased leaves were identical to those of B. oryzae. B. oryzae has been confirmed to cause leaf spot on Oryza sativa (Barnwal et al. 2013), but as an endophyte has been reported in O. rufipogon (Wang et al. 2015).. Thus, this study is the first report of B. oryzae causing leaf spot in O. rufipogon in China. This disease has become a risk for cultivated wild rice with the expansion of cultivation areas. Thus, vigilance is required.

Sign in / Sign up

Export Citation Format

Share Document