First Report of a Leaf Spot Caused by Cladosporium oxysporum on Greenhouse Tomato

In a commercial greenhouse in upstate New York, dark brown, angular lesions were first observed in April on lower, older leaves of 4-month-old tomato plants (Lycopersicon esculentum Mill. ‘Jumbo’). Chlorosis frequently developed around the lesions. Removal of the infected leaves reduced the rate of epidemic development. However, by July, lesions were present throughout the plant canopy, up to 2 m. The irregularly shaped lesions varied in size from 1 to 5 mm, frequently with tan-colored centers initially. Conidia developed in the center of the lesions, primarily on the outer, or adaxial side of the leaf, but were infrequent on the abax-ial surface. This contrasts with Cladosporium leaf mold caused by Fulvia fulva, in which the conidia develop as a velvety brown patch in lesions on the abaxial, or underside of the leaf, accompanied by chlorosis on the upper side of the leaf (1). The conidia ranged in shape from oval or li-moniform (5 to 6 μm in diameter) to cylindrical (5 to 6 μm wide, 7 to 20 μm long). The fungus was identified as Cladosporium oxysporum Berk. & M. A. Curtis (3) by C. J. K. Wang and J. M. McKemy of the State University of New York College of Environmental Science and Forestry in Syracuse, NY. Koch's postulates were fulfilled with a tuft of mycelium and conidia grown on potato dextrose agar as inoculum on fully expanded leaves of 5-week-old tomato plants, cv. Jumbo. Two weeks later, characteristic sporulating lesions developed on inoculated plants, about 1 cm from the inoculation site. Within 3 weeks, in the research greenhouse, the disease spread to healthy tomato plants in the vicinity, confirming the highly infectious nature observed in the commercial greenhouse. The fungus was reisolated from inoculated leaves and also from the adjacent naturally infected plants. C. oxysporum was previously reported as the causal agent of a leaf spot disease of pepper (2) and also a storage disease of ripe tomato fruit (4). To the best of our knowledge this is the first report of C. oxysporum causing disease on tomato foliage. References: (1) E. E. Chamberlain. N.Z. J. Agric. 45:136, 1932. (2) A. M. Hammouda. Plant Dis. 76:536, 1992. (3) J. M. McKemy and G. Morgan-Jones. Mycotaxon 41:397, 1991. (4) S. Singh et al. Indian J. Microbiol. 23:133, 1983.

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First Report of Embellisia hyacinthi Causing a Leaf Spot and Bulb Skin Spot Disease on Scilla peruviana in California

Plant Disease ◽

10.1094/pdis-11-10-0845 ◽

2011 ◽

Vol 95 (3) ◽

pp. 356-356

Author(s):

S. Rooney-Latham ◽

C. L. Blomquist ◽

D. G. Fogle ◽

E. G. Simmons

Keyword(s):

Leaf Spot ◽

Apical Cell ◽

Leaf Spot Disease ◽

Adaxial Side ◽

Internal Transcribed Spacer Region ◽

California Department ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Food And Agriculture

The genus Scilla (Hyacinthaceae) includes more than 50 species of perennial, flowering bulbs grown in landscapes worldwide. In December 2000 and May 2009, an unknown leaf spot disease on Scilla peruviana was submitted to the California Department of Food and Agriculture Plant Pest Diagnostic Lab. Samples were collected during routine phytosanitary inspections of production fields in Santa Cruz County in 2000 and Monterey County in 2009. The disease was detected before plants flowered in one field at each location each year and appeared to have a scattered distribution. Foliar spots were large, elliptical to oblong with grayish black centers and brown margins. Yellow halos surrounded many of the spots. Examination of the bulb material revealed small necrotic patches on the outer bulb scales. A rapidly growing fungus was isolated on one-half-strength acidified potato dextrose agar (APDA) from the sporulating leaf spots and necrotic patches on the bulbs. The colonies were greenish gray and became dark olivaceous with age. Dictyospores, which formed on simple to branched, geniculate conidiophores, were oblong, fusiform or obclavate and usually had a triangular apical cell. They were initially hyaline, turning olivaceous brown with age. Conidia measured 14 to 39 × 8 to 13 μm (average 24.6 × 9.9 μm) typically with two to four (but up to seven) thick, transverse septa and one to two longitudinal septa. Morphologically, the fungus matched the description of Embellisia hyacinthi de Hoog & Miller (1,3). To confirm pathogenicity, four leaves of four S. peruviana plants were inoculated by taking colonized mycelial plugs from 2-week-old cultures and placing them in a plastic screw-cap lid filled with sterile water. The water plus mycelial plug suspension in the lid was then clipped to the adaxial side of a pushpin-wounded leaf (4). Plants were placed in a dark dew chamber at 20°C for 48 h and then moved to a growth chamber at 20°C with a 12-h photoperiod. After 48 h, the clips, caps, and plugs were removed. An equal number of control plants were wounded and mock inoculated with noncolonized APDA agar plugs and the experiment was repeated. Leaf lesions were visible 3 days after clip removal and expanded to an average of 26 × 10 mm, 14 days after inoculation. Sporulation was observed in the lesions after 5 to 7 days and the fungus was isolated from all inoculated leaves. No symptoms developed on the control leaves. DNA sequencing of the internal transcribed spacer region of the isolate (GenBank Accession No. HQ425562) using primers ITS1 and ITS4 matched the identity of E. hyacinthi (2,4). E. hyacinthi has been reported as a foliar and bulb pathogen on Hyacinthus, Freesia, and Scilla in Japan and Europe including Great Britain. Bulbs infected with E. hyacinthi are generally less sound and less valuable than noninfected bulbs (1). To our knowledge, this is the first report of the disease on S. peruviana in California. References: (1) G. S. de Hoog and P. J. Muller. Neth. J. Plant Pathol. 79:85, 1973. (2) B. Pryor and D. M. Bigelow. Mycologia 95:1141, 2003. (3) E. Simmons. Mycotaxon 17:216, 1983. (4) L. E. Yakabe et al. Plant Dis. 93:883, 2009.

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First report of Acidovorax citrulli causing a leaf spot disease on tomato plants in Greece

Journal of Plant Pathology ◽

10.1007/s42161-020-00677-1 ◽

2020 ◽

Author(s):

Dimitris Malliarakis ◽

Evaggelia Mpalantinaki ◽

Marianthi G. Pagoulatou ◽

Konstantina Lorenzou ◽

Dimitrios E. Goumas

Keyword(s):

Leaf Spot ◽

Leaf Spot Disease ◽

Tomato Plants ◽

First Report ◽

Spot Disease ◽

Acidovorax Citrulli

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First Report of a Leaf Spot on Greenhouse Tomato Caused by Cladosporium oxysporum in China

Plant Disease ◽

10.1094/pdis-11-12-1032-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 845-845 ◽

Cited By ~ 2

Author(s):

X.-Y. Huang ◽

Z.-H. Liu ◽

J. Li ◽

P. Ji

Keyword(s):

Leaf Spot ◽

Morphological Characteristics ◽

Its Region ◽

Liaoning Province ◽

Leaf Spot Disease ◽

Tomato Plants ◽

First Report ◽

Greenhouse Tomato ◽

Passalora Fulva ◽

Northern Regions

Tomato (Lycopersicon esculentum Mill.) is an important vegetable crop grown in Liaoning Province, China. In May 2012, dark brown, angular lesions were observed on lower, older leaves of 5-month-old tomato plants of cv. Bi Jiao in commercial greenhouses in Dawa County, which is administered by Panjin City in Liaoning Province. The irregularly shaped lesions varied in size from 1 to 7 mm in diameter. The necrotic lesions were usually surrounded by a yellow halo. Sporulation was rarely seen on the leaf surfaces. This contrasts with tomato leaf mold caused by Passalora fulva, in which the conidia develop as a velvety brown patch in lesions. By July 2012, the same disease was found in research greenhouses of Shenyang Agriculture University and Liaoning Academy of Agricultural Sciences. The incidence of symptoms was 30 to 40%. To identify the pathogen, leaf pieces (3 to 5 mm) with both infected and healthy portions were taken at the edge of lesions and surface-disinfected by placing them in 75% ethanol for 5 s, then transferred to a 0.1% aqueous mercuric chloride solution for 30 s and rinsed with sterilized water three times. The sections were placed on potato dextrose agar (PDA) at 25°C in the dark. Ten pure fungal cultures were obtained from single spores. For studies of microscopic morphology, isolates were grown on synthetic nutrient agar (SNA) in slide cultures. Conidia ranged in shape from subglobose or ovoid (2 to 4 × 2 to 3 μm) to subcylindrical (4.5 to 17.8 × 2.4 to 4.5 μm). Conidiophores were straight to slightly flexuous with typical nodes. The internal transcribed spacer (ITS) region from isolate PJ12-36 was amplified using primers ITS1 and ITS4 and sequenced (GenBank Accession No. KC137278). The 560-bp amplicons had 99% identity to C. oxysporum (JQ775499). On the basis of morphological characteristics (1) and nucleotide homology, the isolate was identified as C. oxysporum. Koch's postulates were fulfilled in the laboratory on fully expanded leaves of 5-week-old tomato plants ‘Moneymaker’ inoculated with C. oxysporum conidial suspensions (107 conidia ml–1). Eight seedlings were incubated in an illuminated incubator at 25°C for 8 to 10 days with 85% relative humidity. Characteristic lesions that developed on inoculated leaves were similar in appearance to those observed on diseased tomato plants in the greenhouse. C. oxysporum was reisolated from lesions and its identity was confirmed by morphological characteristics. C. oxysporum was previously reported as the causal agent of a leaf spot disease of pepper (2) and greenhouse tomato (4). To our knowledge, this is the first report of C. oxysporum causing disease on tomato foliage in China. It is noteworthy that C. oxysporum has led to a decline in pepper yield in northern regions of China (3). In addition, pathogenicity tests showed that the isolate W10-02 from pepper and the isolate PJ12-36 from tomato could each cause damage to the opposite host, producing symptoms similar to those observed on the host of origin. Studies are needed on strategies to manage C. oxysporum in crops, because its prevalence may cause yield loss both on tomato and pepper in northern regions of China. References: (1) K. Bensch et al. Stud. Mycol. 67:1, 2010. (2) A. M. Hammouda. Plant Dis. 76:536, 1992. (3) X. Y. Huang et al. Plant Dis. 96:1072, 2012. (4) J. S. Lamboy and H. R. Dillard. Plant Dis. 81:228, 1997.

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TWO NEW SEVERE LEAF SPOT DISEASE ON FOREST TREES OF JALGAON (MAHARASTRA) INDIA

FLORA AND FAUNA ◽

10.33451/florafauna.v23i2pp288-290 ◽

2017 ◽

Vol 23 (2) ◽

Author(s):

S. A. FIRDOUSI

Keyword(s):

Leaf Spot ◽

Fungal Disease ◽

Leaf Spot Disease ◽

Forest Trees ◽

First Report ◽

Spot Disease ◽

Severe Leaf

During the survey of the forest fungal disease, of Jalgaon district, two severe leaf spot diseases on Lannae coromandelica and ( Ougenia dalbergioides (Papilionaceae) were observed in Jalgaon, forest during July to September 2016-17. The casual organism was identified as Stigmina lanneae and Phomopsis sp. respectively1-4,7. These are first report from Jalgaon and Maharashtra state.

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First report of chick peach (Prunus persica L.) leaf spot disease caused by Didymella glomerata in China

Journal of Plant Pathology ◽

10.1007/s42161-021-00834-0 ◽

2021 ◽

Author(s):

Yiping Cui ◽

Aitian Peng ◽

Xiaobing Song ◽

Baoping Cheng ◽

Jinfeng Ling ◽

...

Keyword(s):

Leaf Spot ◽

Prunus Persica ◽

Leaf Spot Disease ◽

First Report ◽

Spot Disease

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First Report of a Leaf Spot on Conyza sumatrensis Caused by Phoma macrostoma in China

Plant Disease ◽

10.1094/pdis-03-11-0228 ◽

2012 ◽

Vol 96 (1) ◽

pp. 148-148 ◽

Cited By ~ 1

Author(s):

J. Liu ◽

H. D. Luo ◽

W. Z. Tan ◽

L. Hu

Keyword(s):

Leaf Spot ◽

Fungal Pathogens ◽

Biological Diversity ◽

Biocontrol Agent ◽

Continuous Light ◽

The United States ◽

Leaf Spot Disease ◽

Pathogenicity Test ◽

Dry Land ◽

First Report

Conyza sumatrensis (Asteraceae), an annual or biennial plant, is native to North and South America. It is an invasive, noxious weed that is widespread in southern and southeastern China. It invades farm land and causes great losses to dry land crops, including wheat, corn, and beans. It also reduces biological diversity by crowding out native plants in the infested areas (3,4). During a search for fungal pathogens that could serve as potential biological control agents of C. sumatrensis, a leaf spot disease was observed in 2010 in Chongqing, China. An isolate (SMBC22) of a highly virulent fungus was obtained from diseased leaves. Pathogenicity tests were performed by placing 6-mm-diameter mycelial disks of 7-day-old potato dextrose agar (PDA) cultures of SMBC22 on leaves of 15 healthy greenhouse-grown plants of C. sumatrensis; the same number of control plants was treated with sterile PDA disks. Treated plants were covered with plastic bags for 24 h and maintained in a growth chamber with daily average temperatures of 24 to 26°C, continuous light (3,100 lux), and high relative humidity (>90%). Lesions similar to those observed in the field were first obvious on the SMBC22-inoculated leaves 3 days after inoculation. Symptoms became severe 7 to 9 days after inoculation. Control plants remained healthy. The fungus was reisolated from inoculated and diseased leaves and it was morphologically the same as SMBC22. The pathogenicity test was conducted three times. A survey of 10 southern and southeastern Chinese provinces revealed that the disease was widespread and it attacked leaves and stems of seedlings and mature plants of C. sumatrensis. Lesions on leaves were initially small, circular, and water soaked. The typical lesion was ovoid or fusiform, dark brown, and surrounded by a yellow halo. The spots coalesced to form large lesions and plants were often completely blighted. Fungal colonies of SMBC22 on PDA plates were initially white and turned dark gray. Colonies were circular with smooth edges with obvious rings of pycnidia on the surface. Aerial hyphae were short and dense. Pycnidia, black and immersed or semi-immersed in the medium, were visible after 12 days of incubation. Pycnidia were 72 to 140 μm in diameter. Conidia were produced in the pycnidia and were hyaline, unicellular, ellipsoidal, and 4.4 to 6.1 × 1.6 to 2.2 μm. To confirm identification of the fungus, genomic DNA was extracted from mycelia of a 7-day-old culture on PDA at 25°C (2). The internal transcribed spacer (ITS) gene of rDNA was amplified using primers ITS4/ITS5. The gene sequence was 524 bp long and registered in NCBI GenBank (No. HQ645974). BLAST analysis showed that the current sequence had 99% homology to an isolate of Phoma macrostoma (DQ 404792) from Cirsium arvense (Canada thistle) in Canada and reported to cause chlorotic symptoms on that host plant (1). To our knowledge, this is the first report of P. macrostoma causing disease on C. sumatrensis in China. P. macrostoma, thought of as a biocontrol agent of broadleaf weeds in Canada, has been patented in the United States. The current isolate of P. macrostoma is considered as a potential biocontrol agent of C. sumatrensis. References: (1) P. R. Graupner et al. J. Nat. Prod. 66:1558, 2004. (2) S. Takamatsu et al. Mycoscience 42:135, 2001. (3) W. Z. Tan et al. Page 177 in: Manual of Emergency Control Technology Invasive Pests in China. G. L. Zhang, ed. Science Press, Beijing, 2010. (4) C. Wang et al. J. Wuhan Bot. Res. 28:90, 2010.

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First report of banana (Musa acuminate L. AAA Cavendish, cv. Formosana) leaf spot disease caused by Curvularia geniculata in China

Plant Disease ◽

10.1094/pdis-09-21-2001-pdn ◽

2021 ◽

Author(s):

Yanxiang Qi ◽

Yanping Fu ◽

Jun Peng ◽

Fanyun Zeng ◽

Yanwei Wang ◽

...

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Morphological Characteristics ◽

Universal Primers ◽

Leaf Spot Disease ◽

Leaf Margin ◽

Conidial Suspension ◽

Tropical Fruit ◽

First Report ◽

Spot Disease

Banana (Musa acuminate L.) is an important tropical fruit in China. During 2019-2020, a new leaf spot disease was observed on banana (M. acuminate L. AAA Cavendish, cv. Formosana) at two orchards of Chengmai county (19°48ʹ41.79″ N, 109°58ʹ44.95″ E), Hainan province, China. In total, the disease incidence was about 5% of banana trees (6 000 trees). The leaf spots occurred sporadically and were mostly confined to the leaf margin, and the percentage of the leaf area covered by lesions was less than 1%. Symptoms on the leaves were initially reddish brown spots that gradually expanded to ovoid-shaped lesions and eventually become necrotic, dry, and gray with a yellow halo. The conidia obtained from leaf lesions were brown, erect or curved, fusiform or elliptical, 3 to 4 septa with dimensions of 13.75 to 31.39 µm × 5.91 to 13.35 µm (avg. 22.39 × 8.83 µm). The cells of both ends were small and hyaline while the middle cells were larger and darker (Zhang et al. 2010). Morphological characteristics of the conidia matched the description of Curvularia geniculata (Tracy & Earle) Boedijn. To acquire the pathogen, tissue pieces (15 mm2) of symptomatic leaves were surface disinfected in 70% ethanol (10 s) and 0.8% NaClO (2 min), rinsed in sterile water three times, and transferred to potato dextrose agar (PDA) for three days at 28°C. Grayish green fungal colonies appeared, and then turned fluffy with grey and white aerial mycelium with age. Two representative isolates (CATAS-CG01 and CATAS-CG92) of single-spore cultures were selected for molecular identification. Genomic DNA was extracted from the two isolates, the internal transcribed spacer (ITS), large subunit ribosomal DNA (LSU rDNA), glyceraldehyde-3-phosphate dehydrogenase (GAPDH), translation elongation factor 1-alpha (TEF1-α) and RNA polymerase II second largest subunit (RPB2) were amplified and sequenced with universal primers ITS1/ITS4, LROR/LR5, GPD1/GPD2, EF1-983F/EF1-2218R and 5F2/7cR, respectively (Huang et al. 2017; Raza et al. 2019). The sequences were deposited in GenBank (MW186196, MW186197, OK091651, OK721009 and OK491081 for CATAS-CG01; MZ734453, MZ734465, OK091652, OK721100 and OK642748 for CATAS-CG92, respectively). For phylogenetic analysis, MEGA7.0 (Kumar et al. 2016) was used to construct a Maximum Likelihood (ML) tree with 1 000 bootstrap replicates, based on a concatenation alignment of five gene sequences of the two isolates in this study as well as sequences of other Curvularia species obtained from GenBank. The cluster analysis revealed that isolates CATAS-CG01 and CATAS-CG92 were C. geniculata. Pathogenicity assays were conducted on 7-leaf-old banana seedlings. Two leaves from potted plants were stab inoculated by puncturing into 1-mm using a sterilized needle and placing 10 μl conidial suspension (2×106 conidia/ml) on the surface of wounded leaves and equal number of leaves were inoculated with sterile distilled water serving as control (three replicates). Inoculated plants were grown in the greenhouse (12 h/12 h light/dark, 28°C, 90% relative humidity). Necrotic lesions on inoculated leaves appeared seven days after inoculation, whereas control leaves remained healthy. The fungus was recovered from inoculated leaves, and its taxonomy was confirmed morphologically and molecularly, fulfilling Koch’s postulates. C. geniculata has been reported to cause leaf spot on banana in Jamaica (Meredith, 1963). To our knowledge, this is the first report of C. geniculata on banana in China.

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First Report of a Leaf Spot on Snow Lotus Caused by Alternaria carthami in China

Plant Disease ◽

10.1094/pdis-92-2-0318b ◽

2008 ◽

Vol 92 (2) ◽

pp. 318-318

Author(s):

S. Zhao ◽

G. Xie ◽

H. Zhao ◽

H. Li ◽

C. Li

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Leaf Spot Disease ◽

Tianshan Mountain ◽

Causal Organism ◽

Saussurea Involucrata ◽

First Report ◽

Spot Disease ◽

Initial Symptoms ◽

Snow Lotus

Snow lotus (Saussurea involucrata Karel. & Kir. ex Sch. Bip.) is an economically important medicinal herb increasingly grown in China in recent years. In June of 2005, a leaf spot disease on commercially grown plants was found in the QiTai Region, south of the Tianshan Mountain area of Xinjiang, China at 2,100 m above sea level. Disease incidence was approximately 60 to 70% of the plants during the 2006 and 2007 growing seasons. Initial symptoms appeared on older leaves as irregularly shaped, minute, dark brown-to-black spots, with yellow borders on the edge of the leaflet blade by July. As the disease progressed, the lesions expanded, causing the leaflets to turn brown, shrivel, and die. A fungus was consistently isolated from the margins of these lesions on potato dextrose agar. Fifty-eight isolates were obtained that produced abundant conidia in the dark. Conidia were usually solitary, rarely in chains of two, ellipsoid to obclavate, with 6 to 11 transverse and one longitudinal or oblique septum. Conidia measured 60 to 80 × 20 to 30 μm, including a filamentous beak (13 to 47 × 3.5 to 6 μm). According to the morphology, and when compared with the standard reference strains, the causal organism of leaf spot of snow lotus was identified as Alternaria carthami (1,4). Pathogenicity of the strains was tested on snow lotus seedlings at the six-leaf stage. The lower leaves of 20 plants were sprayed until runoff with conidial suspensions of 1 × 104 spores mL–1, and five plants sprayed with sterile distilled water served as controls. All plants were covered with a polyethylene bag, incubated at 25°C for 2 days, and subsequently transferred to a growth chamber at 25°C with a 16-h photoperiod. Light brown lesions developed within 10 days on leaflet margins in all inoculated plants. The pathogen was reisolated from inoculated leaves, and isolates were deposited at the Key Oasis Eco-agriculture Laboratory of Xinjiang Production and Construction Group, Xinjiang and the Institute of Biotechnology, Zhejiang University. No reports of a spot disease caused by A. carthami on snow lotus leaves have been found, although this pathogen has been reported on safflower in western Canada (3), Australia (2), India (1), and China (4). To our knowledge, this is the first report of a leaf spot caused by A. carthami on snow lotus in China. References: (1) S. Chowdhury. J. Indian Bot. Soc. 23:59, 1944. (2) J. A. G. Irwin. Aust. J. Exp. Agric. Anim. Husb. 16:921, 1976. (3) G. A. Petrie. Can. Plant Dis. Surv. 54:155, 1974. (4) T. Y. Zhang. J. Yunnan Agric. Univ.17:320, 2002.

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First Report of a Leaf Spot Disease of Bells-of-Ireland (Moluccella laevis) Caused by Cercospora apii in California

Plant Disease ◽

10.1094/pdis.2003.87.2.203a ◽

2003 ◽

Vol 87 (2) ◽

pp. 203-203

Author(s):

S. T. Koike ◽

S. A. Tjosvold ◽

J. Z. Groenewald ◽

P. W. Crous

Keyword(s):

Leaf Spot ◽

Sequence Data ◽

Disease Incidence ◽

Leaf Spot Disease ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Initial Symptoms

Bells-of-Ireland (Moluccella laevis) (Lamiaceae) is an annual plant that is field planted in coastal California (Santa Cruz County) for commercial cutflower production. In 2001, a new leaf spot disease was found in these commercially grown cutflowers. The disease was most serious in the winter-grown crops in 2001 and 2002, with a few plantings having as much as 100% disease incidence. All other plantings that were surveyed during this time had at least 50% disease. Initial symptoms consisted of gray-green leaf spots. Spots were generally oval in shape, often delimited by the major leaf veins, and later turned tan. Lesions were apparent on both adaxial and abaxial sides of the leaves. A cercosporoid fungus having fasciculate conidiophores, which formed primarily on the abaxial leaf surface, was consistently associated with the spots. Based on morphology and its host, this fungus was initially considered to be Cercospora molucellae Bremer & Petr., which was previously reported on leaves of M. laevis in Turkey (1). However, sequence data obtained from the internal transcribed spacer region (ITS1, ITS2) and the 5.8S gene (STE-U 5110, 5111; GenBank Accession Nos. AY156918 and AY156919) indicated there were no base pair differences between the bells-of-Ireland isolates from California, our own reference isolates of C. apii, as well as GenBank sequences deposited as C. apii. Based on these data, the fungus was subsequently identified as C. apii sensu lato. Pathogenicity was confirmed by spraying a conidial suspension (1.0 × 105 conidia/ml) on leaves of potted bells-of-Ireland plants, incubating the plants in a dew chamber for 24 h, and maintaining them in a greenhouse (23 to 25°C). After 2 weeks, all inoculated plants developed leaf spots that were identical to those observed in the field. C. apii was again associated with all leaf spots. Control plants, which were treated with water, did not develop any symptoms. The test was repeated and the results were similar. To our knowledge this is the first report of C. apii as a pathogen of bells-of-Ireland in California. Reference: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Cornell University Press, Ithaca, New York, 1954.

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First Report of Gray Leaf Spot on St. Augustinegrass in Italy

Plant Disease ◽

10.1094/pdis.2003.87.12.1536a ◽

2003 ◽

Vol 87 (12) ◽

pp. 1536-1536 ◽

Cited By ~ 1

Author(s):

G. Polizzi ◽

I. Castello ◽

A. M. Picco ◽

D. Rodino

Keyword(s):

Leaf Spot ◽

Magnaporthe Grisea ◽

Fungal Spore ◽

Gray Leaf Spot ◽

Blast Disease ◽

Leaf Spot Disease ◽

High Humidity ◽

Conidial Suspension ◽

First Report ◽

Pathogenicity Tests

St. Augustinegrass (Stenotaphrum secundatum (Walt.) Kuntze) is used for lawns in southern Italy because it is much more resistant to biotic and abiotic adversities than other turfgrass species. Because few seeds are viable, this species is established by vegetative propagation. A new disease was noticed during the spring of 2002 and 2003 on cuttings of St. Augustinegrass growing in three greenhouses in eastern Sicily. The disease affected leaves and culms and caused a progressive drying of the plants. The infection was first seen on leaves as gray, necrotic spots that enlarged in high-humidity conditions to form oval, and later, spindle-shaped lesions. In association with the lesions, it was possible to observe fungal spore development and sunken areas with blue-gray centers and slightly irregular, brown margins with yellow halos. Spots were concentrated without specific arrangement along longitudinal veins and the midrib and at the base, tip, and margins of the leaf blade. Symptoms on the culms consisted of brown-to-black blotches that sometimes extended throughout the internodes. From these infected tissues, 20 explants taken from leaves and culms were cut, washed with sterile water, and placed on 1.5% water agar (WA). Later, conidia and conidiophores were obtained from colonies with a sterile glass needle and placed on 4% WA. From these plates, two monoconidial isolates were obtained and transferred to rice meal medium (1). The colonies were identified as Pyricularia grisea Cooke (Sacc.), anamorphic state of Magnaporthe grisea (Hebert) Yeagashi & Udagawa, the cause of rice blast disease and gray leaf spot disease of turfgrasses. The conidia were pyriform to obclavate, narrowed toward the tip, rounded at the base, 2-septate, 21 to 31 μm × 6 to 10 μm (average 25.7 ×8.2 μm). Pathogenicity tests were performed by inoculating leaves and culms of six St. Augustinegrass plants with a conidial suspension of the fungus (1.5 ×105 conidia per ml). The same number of noninoculated plants was used as controls. All plants were incubated in a moist chamber with high humidity at 25°C. After 6 days, all inoculated plants showed typical symptoms of the disease. Koch's postulates were fulfilled by isolating P. grisea from inoculated plants. Gray leaf spot caused by P. grisea has been a chronic problem on St. Augustinegrass since it was first reported in 1957 (2). To our knowledge, this is the first report of P. grisea on St. Augustinegrass in Italy. While it does not appear to be an important disease in the field at this time in Sicily, it could cause losses in greenhouses where vegetative material is propagated for field planting. A preliminary molecular analysis has shown a clear distinction between the tested strain and other strains isolated from rice seeds and plants in northern Italy. References: (1) E. Roumen et al. Eur. J. Plant Pathol. 103:363, 1997. (2) L. P. Tredway et al. Plant Dis. 87:435, 2003.

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