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

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 Tomato Gray Leaf Spot Disease Caused by Stemphylium solani in Malaysia

Plant Disease ◽

10.1094/pdis-03-12-0223-pdn ◽

2012 ◽

Vol 96 (8) ◽

pp. 1226-1226

Author(s):

A. Nasehi ◽

J. B. Kadir ◽

M. A. Zainal Abidin ◽

M. Y. Wong ◽

F. Mahmodi

Keyword(s):

Leaf Spot ◽

Disease Incidence ◽

Gray Leaf Spot ◽

Leaf Spot Disease ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Spot Disease ◽

Pcr Product ◽

Morphological Criteria

In June 2011, tomatoes (Solanum lycopersicum) in major growing areas of the Cameron Highlands and the Johor state in Malaysia were affected by a leaf spot disease. Disease incidence exceeded 80% in some severely infected regions. Symptoms on 50 observed plants initially appeared on leaves as small, brownish black specks, which later became grayish brown, angular lesions surrounded by a yellow border. As the lesions matured, the affected leaves dried up and became brittle and later developed cracks in the center of the lesions. A survey was performed in these growing areas and 27 isolates of the pathogen were isolated from the tomato leaves on potato carrot agar (PCA). The isolates were purified by the single spore technique and were transferred onto PCA and V8 agar media for conidiophore and conidia production under alternating light (8 hours per day) and darkness (16 hours per day) (4). Colonies on PCA and V8 agar exhibited grey mycelium and numerous conidia were formed at the terminal end of conidiophores. The conidiophores were up to 240 μm long. Conidia were oblong with 2 to 11 transverse and 1 to 6 longitudinal septa and were 24 to 69.6 μm long × 9.6 to 14.4 μm wide. The pathogen was identified as Stemphylium solani on the basis of morphological criteria (2). In addition, DNA was extracted and the internal transcribed spacer region (ITS) was amplified by universal primers ITS5 and ITS4 (1). The PCR product was purified by the commercial PCR purification kit and the purified PCR product sequenced. The resulting sequences were 100% identical to published S. solani sequences (GenBank Accestion Nos. AF203451 and HQ840713). The amplified ITS region was deposited with NCBI GenBank under Accession No. JQ657726. A representative isolate of the pathogen was inoculated on detached 45-day-old tomato leaves of Malaysian cultivar 152177-A for pathogenicity testing. One wounded and two nonwounded leaflets per leaf were used in this experiment. The leaves were wounded by applying pressure to leaf blades with the serrated edge of a forceps. A 20-μl drop of conidial suspension containing 105 conidia/ml was used to inoculate these leaves (3). The inoculated leaves were placed on moist filter paper in petri dishes and incubated for 48 h at 25°C. Control leaves were inoculated with sterilized distilled water. After 7 days, typical symptoms for S. solani similar to those observed in the farmers' fields developed on both wounded and nonwounded inoculated leaves, but not on noninoculated controls, and S. solani was consistently reisolated. To our knowledge, this is the first report of S. solani causing gray leaf spot of tomato in Malaysia. References: (1) M. P. S. Camara et al. Mycologia 94:660, 2002. (2) B. S. Kim et al. Plant Pathol. J. 15:348, 1999. (3) B. M. Pryor and T. J. Michailides. Phytopathology 92:406, 2002. (4) E. G. Simmons. CBS Biodiversity Series 6:775, 2007.

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First Report of Leaf Spot Disease of Peony Caused by Seimatosporium botan in China

Plant Disease ◽

10.1094/pdis-10-10-0735 ◽

2011 ◽

Vol 95 (2) ◽

pp. 226-226

Author(s):

Y. B. Duan ◽

Z. Z. Yu ◽

Y. B. Kang

Keyword(s):

Basal Cell ◽

Leaf Spot ◽

Apical Cell ◽

Leaf Spot Disease ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

Humid Atmosphere ◽

First Report ◽

Spot Disease ◽

Initial Symptoms

Tree peony (Paeonia suffruticosa Andrews), a perennial ligneous deciduous shrub in the Paeoniaceae family, is known for its beautiful and charming flowers. It is regarded as the flower symbol of China and is cultivated throughout the country. In August 2008, a previously unknown leaf spot was observed on peony cultivated in the Mountain Peony Garden located in the Luoyang area of Henan Province, China. In 2009, the leaf spot disease was observed in some gardens in the city of Luoyang, China. Initial symptoms appeared as small, round or irregular, brown, necrotic lesions in the middle of leaves. These lesions gradually enlarged up to 1 cm in diameter and were circular or irregular, brown to dark brown, and brown on the margins. In a humid atmosphere, black, sessile, discoid acervuli developed on the lesions, and the lesions sometimes became waxy-like, eventually coalesced, and nearly covered the entire leaf. Conidia produced in acervuli had two morphologically different types. One type had a single basal appendage, ellipsoid to fusiform, transversely three septate, 16 to 20 × 5 to 7 μm, smooth, basal cell obconic with a truncate base, subhyaline, 3 to 5 μm long; two central cells subcylindrical to dolioform, brown to dark brown, 8 to 10 μm long, apical cell conical with rounded apex, concolorous with the central cells, 4 to 5 μm long, basal appendage filiform, unbranched, excentric, 4 to 8 μm long. The other type had a single appendage at both ends, fusiform to subcylindrical, transversely three septate, 16 to 20 × 4 to 5 μm, smooth; basal cell obconic with a truncate base, subhyaline, 4 to 5 μm long; two central cells subcylindrical to dolioform, pale brown, 8 to 11 μm long; apical cell conical with an acute apex, hyaline to subhyaline, 4 to 5 μm long; basal appendage filiform, unbranched, excentric, 4 to 8 μm long; apical appendage filiform, unbranched, 4 to 8 μm long. Single conidial isolates of both types of conidia yielded identical colonies, which produced both types of conidia on potato dextrose agar (PDA), thus showing that both types of conidia belonged to the same fungus. Colonies on PDA were slimy in appearance, yellow to villous with an irregular taupe margin; reverse brown to grayish brown. Cultural and conidial characteristics of the isolates were similar to those of Seimatosporium botan (1). The DNA sequence for the fungus showed internal transcribed spacer region (ITS1-5.8S-ITS2) sequences (GenBank Accession No. HM067840) with 93% sequence identity to S. discosioides (Accession Nos. EF600970.1 and EF600969.1). This is the first submission of a S. botan sequence to GenBank. To determine pathogenicity, 20 healthy leaves of P. suffruticosa were inoculated by spraying a conidial suspension of S. botan onto the foliage. Ten leaves were sprayed with sterile water and served as controls. Plants were covered with plastic for 24 h to maintain high relative humidity. After 15 days, the symptoms described above were observed on leaves in all inoculated plants, whereas symptoms did not develop on the control plants. The pathogen was reisolated from inoculated leaves, fulfilling Koch's postulates. On the basis of morphology and ITS region sequences, we conclude that S. botan is the causal agent of leaf spots of P. suffruticosa. There is a report of S. botan on P. suffruticosa stems in Japan (1), but to our knowledge, this is the first report of leaf spot disease of peony caused by S. botan in China. References: (1) S. Hatakeyama et al. Mycoscience 45:106, 2004.

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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 Leaf Spot Disease Caused by Epicoccum nigrum on Lablab purpureus in India

Plant Disease ◽

10.1094/pdis-07-13-0798-pdn ◽

2014 ◽

Vol 98 (2) ◽

pp. 284-284 ◽

Cited By ~ 12

Author(s):

S. Mahadevakumar ◽

K. M. Jayaramaiah ◽

G. R. Janardhana

Keyword(s):

Leaf Spot ◽

Leaf Surface ◽

Disease Incidence ◽

Leaf Spot Disease ◽

Post Inoculation ◽

Conidial Suspension ◽

Lablab Purpureus ◽

First Report ◽

Spot Disease ◽

Epicoccum Nigrum

Lablab purpureus (L.) Sweet (Indian bean) is an important pulse crop grown in arid and semi-arid regions of India. It is one of the most widely cultivated legume species and has multiple uses. During a September 2010 survey, we recorded a new leaf spot disease on L. purpureus in and around Mysore district (Karnataka state) with 40 to 80% disease incidence in 130 ha of field crop studied, which accounted for 20 to 35% estimated yield loss. The symptoms appeared as small necrotic spots on the upper leaf surface. The leaf spots were persistent under mild infection throughout the season with production of conidia in clusters on abaxial leaf surface. A Dueteromyceteous fungus was isolated from affected leaf tissues that were surface sterilized with 2% NaOCl2 solution then washed thrice, dried, inoculated on potato dextrose agar (PDA) medium, and incubated at 28 ± 2°C at 12 h alternate light and dark period for 7 days. The fungal colony with aerial mycelia interspersed with dark cushion-shaped sporodochia consists of short, compact conidiophores bearing large isodiametric, solitary, muricate, brown, globular to pear shaped conidia (29.43 to 23.92 μm). Fungal isolate was identified as Epicoccum sp. based on micro-morphological and cultural features (1). Further authenticity of the fungus was confirmed by PCR amplification of the internal transcribed spacer (ITS) region using ITS1/ITS4 universal primer. The amplified PCR product was purified, sequenced directly, and BLASTn search revealed 100% homology to Epicoccum nigrum Link. (DQ093668.1 and JX914480.1). A representative sequence of E. nigrum was deposited in GenBank (Accession No. KC568289.1). The isolated fungus was further tested for its pathogenicity on 30-day-old healthy L. purpureus plants under greenhouse conditions. A conidial suspension (106 conidia/ml) was applied as foliar spray (three replicates of 15 plants each) along with suitable controls. The plants were kept under high humidity (80%) for 5 days and at ambient temperature (28 ± 2°C). The appearance of leaf spot symptoms were observed after 25 days post inoculation. Further, the pathogen was re-isolated and confirmed by micro-morphological characteristics. E. nigrum has been reported to cause post-harvest decay of cantaloupe in Oklahoma (2). It has also been reported as an endophyte (3). Occurrence as a pathogen on lablab bean has not been previously reported. To our knowledge, this is the first report of the occurrence of E. nigrum on L. purpureus in India causing leaf spot disease. References: (1) H. L. Barnet and B. B. Hunter. Page 150 in: Illustrated Genera of Imperfect Fungi, 1972. (2) B. D. Bruten et al. Plant Dis. 77:1060, 1993. (3) L. C. Fávaro et al. PLoS One 7(6):e36826, 2012.

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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 Bipolaris yamadae leaf spot disease on Guinea grass (Panicum maximum) in Florida.

Plant Disease ◽

10.1094/pdis-07-20-1486-pdn ◽

2020 ◽

Author(s):

Ashish Adhikari ◽

Xuechun Wang ◽

Brett Lane ◽

Philip F Harmon ◽

Erica Goss

Keyword(s):

Leaf Spot ◽

Phylogenetic Trees ◽

Leaf Spot Disease ◽

Panicum Maximum ◽

Conidial Suspension ◽

Internal Transcribed Spacer Region ◽

First Report ◽

Leaf Spots ◽

Guinea Grass ◽

Symptomatic Leaf

Guinea grass is an invasive perennial C4 grass and is a common weed around agricultural crops in Louisiana, Texas, and Hawaii, USA (Overholt and Franck 2019). In November 2018, leaf spots were observed on Guinea grass occurring in an organic garden located in Gainesville, Florida, USA. Lesions were oblong to irregular, dark grey to brownish center with pale-yellow to brownish black margin. Lesions had coalesced, forming necrotic margins that spread from the leaf tip, resulting in leaf blight and collapse of the canopy. Pieces of symptomatic leaf blades (5 sq cm) were surface sterilized (1 min), washed with sterile distilled water and plated onto water agar media plates. Plates were incubated at 27°C under 12-h light/dark for 3 to 5 days. Grey to black cottony mycelium was consistent on all plates and produced conidia characteristic of Bipolaris spp. Conidia were transferred to potato dextrose agar (PDA) plates with a 0.5 mm diameter sterile needle. Three isolates GG1, GG2 and GG3 were successfully grown on PDA. Conidia were black to brown colored, distoseptate with 3 to 8 septa and measured from (60.6- )70-105(-139.8) × (16.0-)17-23(-25.9) μm (avg: 93.3 μm, n=35, SD = 20.6; avg = 21.3 μm, n = 35, SD = 2.89). Conidiophores were in groups or single, brown, smooth and straight, septate and swollen at upper tip. Sigma Extract-N-Amp was used for genomic DNA extraction. Primers ITS1/ITS4 and GPD1/GPD2 (Berbee et al. 1999) were used to amplify and sequence the internal transcribed spacer region (ITS) and partial glyceraldehyde-3-phosphate dehydrogenase (GPDH) gene, respectively. Sequences were aligned using MUSCLE and alignment was trimmed for length. Maximum likelihood phylogenetic trees were constructed with 1,000 bootstrap samples based on the K2+G substitution model, selected by BIC for these two loci using Mega X (Kumar et al. 2018). The ITS and GPDH sequences of GG1, GG2 and GG3 (Genbank accessions MT514518-20, MT576654-56), grouped with B. yamadae isolates CPC_28807 and CBS_202.29 in phylogenetic trees (Marin-Felix et al. 2017). All three isolates from Guinea grass were inoculated on Sach’s agar (Luttrell 1958) at 27°C under 12-h light/dark for a week, but no sexual morph was observed, and consistent for two repeated inoculations. To fulfill Koch’s postulates, one isolate, GG1, was used. Conidia were harvested from a one-week-old colony grown on PDA incubated at 27°C and 12-h light/dark cycle. The concentration of the conidial suspension was adjusted to 105 conidia/ml using a hemocytometer. Using a Passche H-202S airbrush sprayer, five-week-old seedlings of Guinea grass were sprayed until runoff with the conidia suspension or 0.5% tween water only. Each treatment included four replicates and the experiment was repeated. Leaf spot symptoms were observed on the seedlings inoculated with conidia, whereas seedlings sprayed with water were asymptomatic. Cultures with the expected morphology were isolated from symptomatic leaf blades and absent from control plants. To our knowledge, this is the first report of leaf spot on Guinea grass caused by B. yamadae in Florida, USA. B. yamadae was previously reported from Guinea grass in India, and from other Panicum species in the northern USA (Farr and Rossman 2019). B. yamadae was also isolated from sugarcane in Cuba and China, and corn in Japan (Manamgoda et al. 2014, Raza et al. 2019), which suggests that it has the potential to impact agronomic crops in Florida, such as sugarcane and corn.

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First Report of Gray Leaf Spot of Mango (Mangifera indica) Caused by Pestalotiopsis mangiferae in Taiwan

Plant Disease ◽

10.1094/pdis-91-12-1684b ◽

2007 ◽

Vol 91 (12) ◽

pp. 1684-1684 ◽

Cited By ~ 6

Author(s):

Y. Ko ◽

K. S. Yao ◽

C. Y. Chen ◽

C. H. Lin

Keyword(s):

Leaf Spot ◽

Mangifera Indica ◽

Gray Leaf Spot ◽

Leaf Spot Disease ◽

Continuous Exposure ◽

Conidial Suspension ◽

Tropical Fruit ◽

First Report ◽

Spot Disease ◽

Initial Symptoms

Mango (Mangifera indica L.; family Anacardiaceae) is one of the world's most important fruit crops and is widely grown in tropical and subtropical regions. Since 2001, a leaf spot disease was found in mango orchards of Taiwan. Now, the disease was observed throughout (approximately 21,000 ha) Taiwan in moderate to severe form, thus affecting the general health of mango trees and orchards. Initial symptoms were small, yellow-to-brown spots on leaves. Later, the irregularly shaped spots, ranging from a few millimeters to a few centimeters in diameter, turned white to gray and coalesced to form larger gray patches. Lesions had slightly raised dark margins. On mature lesions, numerous black acervuli, measuring 290 to 328 μm in diameter, developed on the gray necrotic areas. Single conidial isolates of the fungus were identified morphologically as Pestalotiopsis mangiferae (Henn.) Steyaert (2,3) and were consistently isolated from the diseased mango leaves on acidified (0.06% lactic acid) potato dextrose agar (PDA) medium incubated at 25 ± 1°C. Initially, the fungus grew (3 mm per day) on PDA as a white, chalky colony that subsequently turned gray after 2 weeks. Acervuli developed in culture after continuous exposure to light for 9 to 12 days at 20 to 30°C. Abundant conidia oozed from the acervulus as a creamy mass. The conidia (17.6 to 25.4 μm long and 4.8 to 7.1 μm wide) were fusiform and usually straight to slightly curved with four septa. Three median cells were olivaceous and larger than the hyaline apical and basal cells. The apical cells bore three (rarely four) cylindrical appendages. Pathogenicity tests were conducted with either 3-day-old mycelial discs or conidial suspension (105 conidia per ml) obtained from 8- to 10-day-old cultures. Four leaves on each of 10 trees were inoculated. Before inoculation, the leaves were washed with a mild detergent, rinsed with tap water, and then surface sterilized with 70% ethanol. Leaves were wounded with a needle and exposed to either a 5-mm mycelial disc or 0.2 ml of the spore suspension. The inoculated areas were wrapped with cotton pads saturated with sterile water and the leaves were covered with polyethylene bags for 3 days to maintain high relative humidity. Wounded leaves inoculated with PDA discs alone served as controls. The symptoms described above were observed on all inoculated leaves, whereas uninoculated leaves remained completely free from symptoms. Reisolation from the inoculated leaves consistently yielded P. mangiferae, thus fulfilling Koch's postulates. Gray leaf spot is a common disease of mangos in the tropics and is widely distributed in Africa and Asia (1–3); however, to our knowledge, this is the first report of gray leaf spot disease affecting mango in Taiwan. References: (1) T. K. Lim and K. C. Khoo. Diseases and Disorders of Mango in Malaysia. Tropical Press. Malaysia, 1985. (2) J. E. M. Mordue. No. 676 in: CMI Descriptions of Pathogenic Fungi and Bacteria. Surrey, England, 1980. (3) R. C. Ploetz et al. Compendium of Tropical Fruit Diseases. The American Phytopathological Society. St. Paul, MN, 1994.

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First Report of Leaf Spot Caused by Corynespora cassiicola on Viburnum odoratissimum Ker-Gawl. var. awabuki (K. Koch) Zabel ex Rumpl. (sweet viburnum) in China

Plant Disease ◽

10.1094/pdis-04-21-0849-pdn ◽

2021 ◽

Author(s):

Tianning Zhang ◽

Huanhuan Liu ◽

Qingni Song ◽

Jun Liu ◽

Qingpei Yang ◽

...

Keyword(s):

Leaf Spot ◽

Leaf Spot Disease ◽

Conidial Suspension ◽

Puncture Wound ◽

First Report ◽

Leaf Spots ◽

Fungal Isolates ◽

Initial Symptoms ◽

Viburnum Odoratissimum ◽

Sweet Viburnum

Sweet viburnum [Viburnum odoratissimum Ker-Gawl. var. awabuki (K. Koch) Zabel ex Rumpl.] belonging to the family Adoxaceae, is a medical and landscape plant, native to Korea (Jeju Island), Taiwan, and Japan (Edita 1988). In June and September 2019, leaf spots were observed on approximately 65% to 80% of sweet viburnum plants in a hedgerow located in Fenghe Xincheng District (28°41'52.9"N 115°52'14.3"E) in Nanchang, China. Initial symptoms of disease appeared as dark brown spots surrounded by red halos (Figure 1 A), which expanded irregularly. Finally, the center of the lesions desiccated and became light-brown, surrounded by a deep-red halos (Figure 1 B). Ten leaf samples with typical symptoms were collected and washed with tap water for about 15 min. The tissue between the healthy and necrotic area (ca. 4 mm × 4 mm) was cut with a sterile scalpel and surface sterilized with 70% alcohol for 45 s, 2% NaClO for 2 min, washed in sterile deionized water three times, dried on sterilized filter paper, then placed in Petri dishes and incubated at 25℃ in the dark. After 3 to 5 days, the hyphal tips from the edges of growing colonies were transferred to fresh PDA dishes. Eventually, 54 fungal isolates were obtained and, of these, 39 isolates were identical in their morphological characteristics. Morphological analysis was performed according with Ellis (1971). The isolate S18, chosen as representative, formed a gray to grayish brown colony with concentric circleson PDA, and a diameter of 8.5 to 9 cm after 7 days incubation at 25℃ (Figure 1 G). Conidia were hyaline, straight or slightly curved, needle shaped, truncate at the base, and acuminate at the tip, with 2 to 6 pseudosepta, 18.90 to 38.38 µm (avg. = 27.51 µm) × 1.64 to 4.50 µm (avg. = 2.60 µm) (n = 36) (Figure 1 H). The genes of fungal isolates (i.e., ITS, tub2 and ACT) were amplified with ITS4/ITS5 for ITS (White, Bruns et al. 1990), Bt2a/Bt2b for tub2 (Glass and Donaldson 1995) and ACT783R/ACT512F for ACT (Carbone and Kohn 1999) and sequenced. The sequences were deposited in GenBank (MW165772 for ITS, MW175900 for ACT and MW168659 for tub2), which showing greater than 99.1% similarity to multiple C. cassiicola accessions, respectively. Pathogenicity tests were performed on healthy leaves in field by inoculating surface-sterilized mature leaves with puncture wound (Figure C) and non-wounded young leaves with 20 µL of a conidial suspension (105 conidia ml-1) (Figure F and G) at 26℃. After 4 to 7 days, all inoculated leaves reproduced similar symptoms as observed initially in the field (Figure 1 C, E and F). To fulfill Koch’s postulates, the fungus was isolated on PDA from the margins of leaf spots on inoculated leaves and confirmed as C. cassiicola by morphological characters and ITS gene sequencing. Previously, C. cassiicola was reported as an endophyte on Viburnum spp. and Viburnum odoratissimum (Alfieri et al. 1994). More recently, C. cassiicola has been reported as a pathogen of many plant species in China, such as kiwifruit (Cui, Gong et al. 2015), American sweetgum (Mao, Zheng et al. 2021), castor bean (Tang, Liu et al. 2020), and holly mangrove (Xie, He et al. 2020). To our knowledge, this is the first report of leaf spot disease on sweet viburnum caused by C. cassiicola in China and the precise identification of the causal agent will be useful for its management.

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First Report of Leaf Spot of Phoenix theophrasti Caused by Paraconiothyrium variabile in Greece

Plant Disease ◽

10.1094/pdis-01-13-0114-pdn ◽

2013 ◽

Vol 97 (9) ◽

pp. 1250-1250

Author(s):

E. K. Ligoxigakis ◽

I. A. Papaioannou ◽

E. A. Markakis ◽

M. A. Typas

Keyword(s):

Leaf Spot ◽

Rrna Genes ◽

Leaf Spot Disease ◽

28S Rrna ◽

Conidial Suspension ◽

First Report ◽

Spot Disease ◽

Initial Symptoms ◽

Palm Species ◽

Paraconiothyrium Variabile

In the spring of 2011, a severe leaf spot disease of Phoenix theophrasti was observed in the vicinity of Heraklion (Crete), Greece. Initial symptoms were small, round-ovoid spots of varying shades of brown on the leaves, later being transformed into oblong streaks (average dimensions 7.3 ± 1.0 × 3.3 ± 0.5 mm), surrounded by dark brown rings. As the disease progressed, the expanding streaks often coalesced to form enlarged necrotic lesions. Similar symptoms were also detected on petioles and leaf bases. Extended spotting and blighting occasionally resulted in leaf death. A filamentous fungus was consistently isolated onto potato dextrose agar plates from the periphery of the characteristic lesions, with cultures invariably producing brick to cinnamon colonies with sparse aerial mycelium, subglobose and dark brown superficial pycnidial conidiomata on pine needles, 1- to 3-celled hyaline conidiophores, and hyaline, subcylindrical to ellipsoidal, 1-celled, smooth- and thin-walled conidia, with average dimensions of 3.5 ± 0.6 × 1.7 ± 0.4 μm (n = 100). Total DNA of two isolates was extracted and used for PCR amplification and sequencing of the ITS1-5.8S-ITS2 region, together with parts of the flanking 18S and 28S rRNA genes (4). Both sequences (GenBank Accession Nos. JX456476 and JX456477) were 100% identical to deposited Paraconiothyrium variabile ITS sequences (EU295640 to 48, JN983440 and 41, and JF934920), and were clustered together as a single group with these sequences with good support by phylogenetic analysis that included representatives of the relative P. brasiliense and P. africanum species. Based on the morphological, molecular, and phylogenetic analyses, the pathogen was identified as P. variabile Riccioni, Damm, Verkley & Crous (2). To prove pathogenicity, 10 P. theophrasti 2-year-old seedlings were sprayed with a conidial suspension of the fungus (107 conidia ml–1, 10 ml per plant), while five additional control plants were treated with sterile distilled water. All plants were maintained in the greenhouse at 15 ± 5°C, with 90% humidity. Characteristic leaf spots were evident 4 weeks post inoculation on the older leaves, and P. variabile was consistently reisolated from all inoculated plants. No symptoms were observed on control plants. Paraconiothyrium variabile has been isolated from various woody host plants such as Prunus persica, P. salicina, and Malus sp. in South Africa (1,2), Actinidia chinensis and A. deliciosa in Italy (2), Laurus nobilis in Turkey (2), and Salix matsudana in China (3). To our knowledge, this is the first report of P. variabile naturally infecting and causing a leaf spot disease on a palm species. Palms are extensively used as ornamentals throughout Greece and the occurrence of P. variabile can potentially result in economic loss to the local ornamental industry. References: (1) M. Cloete et al. Phytopathol. Mediterr. 50:S176, 2011. (2) U. Damm et al. Persoonia 20:9, 2008. (3) H. Gao et al. Afr. J. Biotechnol. 10:4166, 2011. (4) M. P. Pantou et al. Mycol. Res. 109:889, 2005.

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