First Report of Cercospora coffeicola Causing Cercospora Leaf Spot of Castor Beans in Brazil

In a coffee (Coffea arabica) farm located in Ervália, Minas Gerais State, Brazil, we observed castor bean (CB; Ricinnus communis) plants growing as weeds. Currently, there is increasing interest in CB as a crop in Brazil because it is an alternative source for biofuel production, but there is little knowledge on CB diseases. According to reports from Costa Rica (2) and Malawi (3), Cercospora coffeicola can cause leaf spots in CB plants. Considering the increasing importance of Cercospora leaf spot on coffee and the expansion of CB plantings in Brazil, in 2008 we evaluated whether CB plants were susceptible to C. coffeicola. Healthy seedlings of an unknown CB cultivar were collected from the experimental coffee area in Ervália, transplanted to pots, and kept under greenhouse conditions. Each of two C. coffeicola isolates from coffee, obtained from the collection of the Departamento de Fitopatologia, was inoculated on two CB plants and three ‘Catuaí Vermelho’ coffee plants, each with four fully expanded leaves. Conidia were produced following a standard protocol (4). A suspension with 1 × 104 conidia ml–1 was sprayed with a DeVilbiss atomizer on both leaf surfaces until runoff, dispensing approximately 3 ml per leaf. As controls, two CB and three coffee plants were sprayed with distilled water. All treated plants were kept in a dew chamber at >90% relative humidity, 25°C, and with 12 h per day of light. After 48 h, the plants were placed in a greenhouse with natural lighting and an average temperature of 25 ± 3°C. Plants were checked at 3-day intervals for disease symptoms. On average, the incubation period (time between inoculation and appearance of the first leaf symptom) was 9 days and the latent period (time between inoculation and visualization of the first leaf sporulating lesion) was 12 days for the disease in CB. Both C. coffeicola isolates were pathogenic to all inoculated CB plants, in which approximately 20 spots developed per leaf. Control plants did not develop any symptoms. Leaf spots in CB plants were similar to those previously described (2): necrotic lesions that were black and purple with a yellowish halo and a pale white center. There was intense sporulation at the lesion center, and the conidia were hyaline, acicular to obclavate, nearly straight with truncate to subtruncate bases and acute tips, multiseptate, 2 to 4 × 40 to 150 μm and were produced in fascicles of conidiophores that were pale to medium brown, septate, and 4 to 6 × 20 to 275 μm (1,4). The pathogen was reisolated from the CB leaf spots, grown on potato dextrose agar medium, and the morphology of the colonies was similar to the colonies of the isolates from the C. coffeicola collection. The reisolated cultures were set to sporulate and reinoculated onto new healthy coffee and CB leaves, on which leaf spots developed. To our knowledge, this is the first report of castor beans as a host of C. coffeicola in Brazil. Considering the expansion of CB crops in Brazil, studies are needed to evaluate the susceptibility of the commercial CB cultivars that are grown in the country, particularly those planted close to coffee-production areas where Cercospora leaf spot is endemic and important. References: (1) C. Chupp. A Monograph of the Fungus Genus Cercospora. Charles Chupp, Ithaca, NY, 1954. (2) E. Echandi. Turrialba 9:54, 1959. (3) M. A. Siddiqi. Trans. Br. Mycol. Soc. 54:415, 1970. (4) A. G. C. Souza et al. J. Phytopathol. 159:6, 2011.

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First Report of Diaphorte terebinthifolii causing leaf spot on Pleoroma fotherghillae in Brazil

Plant Disease ◽

10.1094/pdis-11-20-2508-pdn ◽

2021 ◽

Author(s):

Alexandre Claus ◽

Wagner V. Pereira ◽

Louise Larissa May De Mio

Keyword(s):

Leaf Spot ◽

Economic Value ◽

Aerial Mycelium ◽

Its Region ◽

Botanical Garden ◽

Control Treatment ◽

Transparent Plastic ◽

Potato Dextrose Agar Medium ◽

First Report ◽

Leaf Spots

Pleoroma fotherghillae, also known as “princess flower”, is an ornamental species native to Brazil and naturalized in several countries (Faravani et al. 2007). P. fotherghillae has a high economic value, with an ornamental and landscape application (Nienow et al. 2010). In September 2018, leaf spots were observed in approximately 80% of the 50 P. fotherghillae plants grown in a nursery in the municipality of Curitiba-Paraná, Brazil. The spots were round-shaped, with a necrotic brown center and a reddish-brown halo, ranging from 1 to 4 mm in diameter. High leaf fall was observed among plants presenting a higher severity. Symptomatic leaves fragments were collected and disinfected as described by (Pereira et al. 2019). The fragments were transferred to a potato dextrose agar medium supplemented with streptomycin sulfate and incubated at 24 ± 1ºC with a photoperiod of 12 h for 7 days. Four monosporic cultures were obtained from colonies isolated. The isolates had a grayish-white cottony aerial mycelium and reverse olive-yellow with black dots. The colonies reached approximately 60 mm in diameter, forming globular and conical pycnidia, brown to black in color with white or cream globular conidial mass. Beta conidia were hyaline, smooth, curved to the size of 19 - 25 x 1 – 1.5 μm (n = 50). No alpha nor gamma conidia were observed. The characteristics are similar to the description of Diaporthe terebinthifolli (Gomes et al. 2013). The total genomic DNA of a representative isolate, LEMIDPRPf-19-02, was extracted for amplification and sequencing of the internal transcribed spacer (ITS) region and partial of the Tubby (TUB) and thyrotroph embryonic factor (TEF) genes. The sequences of the ITS (No MN415990.1), TUB (No MW505549), and TEF (No MW505550) genes were deposited in GenBank. BLAST analysis showed similarity above 99% with D. terebinthifolli sequences (KC343219.1, KC344187.1, and KC343945.1). The multigene phylogenetic analysis, based on Bayesian Inference, grouped the isolate in a clade with other sequences of Diaporthe terebinthifolii. Four healthy plants of P. fotherghillae about 5 months old, were used for pathogenicity testing. A suspension containing 105 conidia/ml was sprayed on the surface of the leaves of four plants to the point of runoff. The plants were covered with a transparent plastic bag for 24 hours. The leaves of four other plants received sterile distilled water and served as the control treatment. The plants were kept in a greenhouse at 20±5ºC. Necrotic lesions appeared 10 to 15 days after inoculation. No symptoms were observed in the control plants. The pathogen was reisolated from symptomatic leaves and had the same characteristics as the isolate LEMIDPRPf-19-02. A representative sample (MBM 331603) was deposited at the Museu do Jardim Botânico (Botanical Garden Museum) - Curitiba, Brazil. Diaporthe terebinthifolii was previously reported as endophytic in Brazil and Uruguay, isolated from Schinus terebinthifolius and Pyrus communis, respectively (Gomes et al. 2013; Sessa et al. 2017). To our knowledge, this is the first report of D. terebinthifolii causing leaf spot on P. fotherghillae in Brazil and worldwide.

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First Report of Alternaria Leaf Spot of Banana Caused by Alternaria alternata in the United States

Plant Disease ◽

10.1094/pdis-01-13-0007-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1116-1116 ◽

Cited By ~ 3

Author(s):

V. Parkunan ◽

S. Li ◽

E. G. Fonsah ◽

P. Ji

Keyword(s):

United States ◽

Alternaria Alternata ◽

Leaf Spot ◽

Morphological Characteristics ◽

The United States ◽

Its Sequencing ◽

Single Spore ◽

First Report ◽

Alternaria Leaf Spot ◽

Leaf Spots

Research efforts were initiated in 2003 to identify and introduce banana (Musa spp.) cultivars suitable for production in Georgia (1). Selected cultivars have been evaluated since 2009 in Tifton Banana Garden, Tifton, GA, comprising of cold hardy, short cycle, and ornamental types. In spring and summer of 2012, 7 out of 13 cultivars (African Red, Blue Torres Island, Cacambou, Chinese Cavendish, Novaria, Raja Puri, and Veinte Cohol) showed tiny, oval (0.5 to 1.0 mm long and 0.3 to 0.9 mm wide), light to dark brown spots on the adaxial surface of the leaves. Spots were more concentrated along the midrib than the rest of the leaf and occurred on all except the newly emerged leaves. Leaf spots did not expand much in size, but the numbers approximately doubled during the season. Disease incidences on the seven cultivars ranged from 10 to 63% (10% on Blue Torres Island and 63% on Novaria), with an average of 35% when a total of 52 plants were evaluated. Six cultivars including Belle, Ice Cream, Dwarf Namwah, Kandarian, Praying Hands, and Saba did not show any spots. Tissue from infected leaves of the seven cultivars were surface sterilized with 0.5% NaOCl, plated onto potato dextrose agar (PDA) media and incubated at 25°C in the dark for 5 days. The plates were then incubated at room temperature (23 ± 2°C) under a 12-hour photoperiod for 3 days. Grayish black colonies developed from all the samples, which were further identified as Alternaria spp. based on the dark, brown, obclavate to obpyriform catenulate conidia with longitudinal and transverse septa tapering to a prominent beak attached in chains on a simple and short conidiophore (2). Conidia were 23 to 73 μm long and 15 to 35 μm wide, with a beak length of 5 to 10 μm, and had 3 to 6 transverse and 0 to 5 longitudinal septa. Single spore cultures of four isolates from four different cultivars were obtained and genomic DNA was extracted and the internal transcribed spacer (ITS1-5.8S-ITS2) regions of rDNA (562 bp) were amplified and sequenced with primers ITS1 and ITS4. MegaBLAST analysis of the four sequences showed that they were 100% identical to two Alternaria alternata isolates (GQ916545 and GQ169766). ITS sequence of a representative isolate VCT1FT1 from cv. Veinte Cohol was submitted to GenBank (JX985742). Pathogenicity assay was conducted using 1-month-old banana plants (cv. Veinte Cohol) grown in pots under greenhouse conditions (25 to 27°C). Three plants were spray inoculated with the isolate VCT1FT1 (100 ml suspension per plant containing 105 spores per ml) and incubated under 100% humidity for 2 days and then kept in the greenhouse. Three plants sprayed with water were used as a control. Leaf spots identical to those observed in the field were developed in a week on the inoculated plants but not on the non-inoculated control. The fungus was reisolated from the inoculated plants and the identity was confirmed by morphological characteristics and ITS sequencing. To our knowledge, this is the first report of Alternaria leaf spot caused by A. alternata on banana in the United States. Occurrence of the disease on some banana cultivars in Georgia provides useful information to potential producers, and the cultivars that were observed to be resistant to the disease may be more suitable for production. References: (1) E. G. Fonsah et al. J. Food Distrib. Res. 37:2, 2006. (2) E. G. Simmons. Alternaria: An identification manual. CBS Fungal Biodiversity Center, Utrecht, Netherlands, 2007.

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

Plant Disease ◽

10.1094/pdis-05-12-0436-pdn ◽

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.

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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 a Leaf Spot Caused by Alternaria brassicae on the Invasive Weed Lepidium draba in North America

Plant Disease ◽

10.1094/pdis-93-8-0846a ◽

2009 ◽

Vol 93 (8) ◽

pp. 846-846 ◽

Cited By ~ 1

Author(s):

A. J. Caesar ◽

R. T. Lartey

Keyword(s):

North America ◽

Chinese Cabbage ◽

Leaf Spot ◽

The United States ◽

Alternaria Brassicae ◽

Voucher Specimen ◽

First Report ◽

Leaf Spots ◽

Black Spots ◽

Lepidium Draba

The exotic, rangeland weed Lepidium draba L., a brassicaceous perennial, is widely distributed in the United States. For example, Oregon contains 100,000 ha of land infested with L. draba (2). Because it is capable of aggressive spread and has the potential to reduce the value of wheat-growing land (4), it is the target of biological control research. The application of multiple pathogens has been advocated for control of other brassicaceous weeds, including the simultaneous application of biotrophic and necrotrophic pathogens (3). In pursuit of this approach, in 2007, we discovered the occurrence of leaf spots on approximately 90% of L. draba plants near Shepherd, MT, which were distinct from leaf lesions caused by Cercospora bizzozeriana (1). The lesions were initially tiny, black spots enlarging over time to become circular to irregular and cream-colored around the initial black spots and sometimes with dark brown borders or chlorotic halos. Conidia from the lesions were light brown, elongate and obclavate, produced singly from short conidia, with 8 to 12 transverse septa, and 2 to 6 longitudinal septa. The spore body measured 25 to 35 × 200 to 250 μm with a beak cell 42 to 100 μm long. On the basis of conidial and cultural characteristics, the fungus was identified as Alternaria brassicae (Berk.) Sacc. Leaf tissues bordering lesions were plated on acidified potato dextrose agar. Colonies on V8 and alfalfa seed agar were black with concentric rings, eventually appearing uniformly black after 10 to 14 days. The internal transcribed spacer region of rDNA was amplified using primers ITS1 and ITS4 and sequenced. BLAST analysis of the 575-bp fragment showed a 100% homology with a sequence of A. brassicae Strain B from mustard (GenBank Accession No. DQ156344). The nucleotide sequence has been assigned GenBank Accession No. FJ869872. For pathogenicity tests, aqueous spore suspensions approximately 105/ml were prepared from cultures grown at 20 to 25°C for 10 to 14 days on V8 agar and sprayed on leaves of three L. draba plants. Inoculated plants were enclosed in plastic bags and incubated at 20 to 22°C for 72 to 80 h. In addition, three plants of the following reported hosts of A. brassicae were inoculated: broccoli, canola, Chinese cabbage, collards, broccoli raab, kale, mustard greens, radish, rape kale, and turnip. Within 10 days, leaf spots similar to those described above developed on plants of radish, canola, Chinese cabbage, and turnip and A. brassicae was reisolated and identified. Control plants sprayed with distilled water remained symptomless. These inoculations were repeated and results were the same. To our knowledge, this is the first report of a leaf spot disease caused by A. brassicae on L. draba in North America. A voucher specimen has been deposited with the U.S. National Fungus Collections (BPI No. 878750A). References: (1) A. J. Caesar et al. Plant Dis. 93:108, 2009. (2) G. L. Kiemnec and M. L. McInnis. Weed Technol. 16:231, 2002. (3) A. Maxwell and J. K. Scott. Adv. Bot. Res. 43:143, 2005. (4) G. A. Mulligan and J. N. Findlay. Can. J. Plant Sci. 54:149, 1974.

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First Report of Leaf Spot Disease Caused by Exserohilum rostratum on Pineapple in Hainan Province, China

Plant Disease ◽

10.1094/pdis-11-11-0979 ◽

2012 ◽

Vol 96 (3) ◽

pp. 458-458 ◽

Cited By ~ 4

Author(s):

Z. W. Luo ◽

F. He ◽

H. Y. Fan ◽

X. H. Wang ◽

M. Hua ◽

...

Keyword(s):

Leaf Spot ◽

Leaf Spot Disease ◽

Hainan Province ◽

Conidial Suspension ◽

Potato Dextrose Agar Medium ◽

First Report ◽

Spot Disease ◽

Exserohilum Rostratum ◽

Plant Pathol ◽

Pineapple Leaves

Pineapple (Ananas comosus (L.) Merr.) is an important perennial monocotyledonous plant that serves as an important fruit crop globally and is also produced in the Hainan Province of China where production in 2009 was 296,600 t. In July 2009, atypical symptoms of a leaf spot disease were observed on mature pineapple leaves in Chengmai County; approximately 15% of plants propagated from suckers became symptomatic after 150 to 300 days, eventually causing a 3 to 10% yield loss. In the initial infection stage, grayish white-to-yellowish white spots emerged on the leaf surfaces that ranged from 1.0 to 2.4 × 0.3 to 0.7 cm; black specks were not always present in the spots. Leaf spots also had distinctive light brown-to-reddish brown banding pattern on the edges. Several spots would often merge to form large lesions, 6.5 to 15.4 × 2.5 to 5.6 cm, covering more than 67% of the leaf surface, which can lead to death of the plant. Infected pineapple leaves collected from an orchard of Chengmai County were surface sterilized (75% ethanol for 30 s, 0.1% HgCl2 for 2 min, and rinsed three times in sterile distilled water). Leaf pieces were placed on potato dextrose agar medium and then incubated at 25°C. The emerging fungal colonies were grayish white to brown. Similar strains were obtained from Qionghai City and Wanning City subsequently. Two isolates, ITF0706-1 and ITF0706-2, were used in confirmation of the identity of the pathogen and in pathogenicity tests. Colonies were fast growing (more than 15 mm per day at 25 to 30°C) with dense aerial mycelia. Conidia were fusiform, pyriform to oval or cylindrical, olive brown to dark brown, 3 to 10 septate (typically 5 to 8), 33.2 to 102.5 × 9.0 to 21.3 μm, with a strongly protruding hilum bulged from the basal cell, which were similar to the Type A conidia described by Lin et al. (3). The strains were subjected to PCR amplification of the internal transcribed spacer (ITS)1-5.8S-ITS2 regions with universal primer pair ITS1/ITS4. The ITS sequence comparisons (GenBank Accession Nos. JN711431 and JN711432) shared between 99.60 and 99.83% identity with the isolate CATAS-ER01 (GenBank Accession No. GQ169762). According to morphological and molecular analysis, the two strains were identified as Exserohilum rostratum (Drechs.) Leonard & Suggs. Pathogenicity experiments were conducted five times and carried out by spraying a conidial suspension (105 CFU/ml) on newly matured leaves of healthy pineapple plants; plants sprayed with sterile water served as the negative control. Plants were incubated in the growth chamber at 20 to 25°C. Symptoms of leaf spot developed on test plants 7 days after inoculation while the control plants remained asymptomatic. Koch's postulates were fulfilled with the reisolation of the two fungal strains. Currently, E. rostratum is one of the most common pathogens on Bromeliads in Florida (2) and has been reported on Zea mays (4), Musa paradisiacal (3), and Calathea picturata (1) in China, but to our knowledge, this is the first report of leaf spot disease caused by E. rostratum on pineapple in Hainan Province of P.R. China. References: (1) L. L. Chern et al. Plant Dis. 95:1033, 2011. (2) R. M. Leahy. Plant Pathol. Circ. No. 393. Florida Department of Agriculture and Consumer Services Division of Plant Industry, 1999. (3) S. H. Lin et al. Australas. Plant Pathol. 40:246, 2011. (4) J. N. Tsai et al. Plant Pathol. Bull. 10:181, 2001.

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First Report of Leaf Spot Disease on Walnut Caused by Colletotrichum fioriniae in China

Plant Disease ◽

10.1094/pdis-09-14-0938-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 289-289 ◽

Cited By ~ 9

Author(s):

Y. Z. Zhu ◽

W. J. Liao ◽

D. X. Zou ◽

Y. J. Wu ◽

Y. Zhou

Keyword(s):

Dna Sequences ◽

Leaf Spot ◽

Juglans Regia ◽

Morphological Characteristics ◽

Leaf Spot Disease ◽

Koch’S Postulates ◽

First Report ◽

Spot Disease ◽

Leaf Spots ◽

Koch's Postulates

In May 2014, a severe leaf spot disease was observed on walnut tree (Juglans regia L.) in Hechi, Guangxi, China. Leaf spots were circular to semicircular in shape, water-soaked, later becoming grayish white in the center with a dark brown margin and bordered by a tan halo. Necrotic lesions were approximately 3 to 4 mm in diameter. Diseased leaves were collected from 10 trees in each of five commercial orchards. The diseased leaves were cut into 5 × 5 mm slices, dipped in 75% ethanol for 30 s, washed three times in sterilized water, sterilized with 0.1% (w/v) HgCl2 for 3 min, and then rinsed five times with sterile distilled water. These slices were placed on potato dextrose agar (PDA), followed by incubating at 28°C for about 3 to 4 days. Fungal isolates were obtained from these diseased tissues, transferred onto PDA plates, and incubated at 28°C. These isolates produced gray aerial mycelium and then became pinkish gray with age. Moreover, the reverse of the colony was pink. The growth rate was 8.21 to 8.41 mm per day (average = 8.29 ± 0.11, n = 3) at 28°C. The colonies produced pale orange conidial masses and were fusiform with acute ends, hyaline, sometimes guttulate, 4.02 to 5.25 × 13.71 to 15.72 μm (average = 4.56 ± 0.31 × 14.87 ± 1.14 μm, n = 25). The morphological characteristics and measurements of this fungal isolate matched the previous descriptions of Colletotrichum fioriniae (Marcelino & Gouli) R.G. Shivas & Y.P. Tan (2). Meanwhile, these characterizations were further confirmed by analysis of the partial sequence of five genes: the internal transcribed spacer (ITS) of the ribosomal DNA, beta-tubulin (β-tub) gene, glyceraldehyde 3-phosphate dehydrogenase (GAPDH) gene, chitin synthase 3(CHS-1) gene, and actin (ACT) gene, with universal primers ITS4/ITS5, T1/βt2b, GDF1/GDR1, CHS1-79F/CHS1-354R, and ACT-512F/ACT-783R, respectively (1). BLAST of these DNA sequences using the nucleotide database of GenBank showed a high identify (ITS, 99%; β-tub, 99%; GAPDH, 99%; CHS-1, 99%; and ACT, 100%) with the previously deposited sequences of C. fioriniae (ITS, KF278459.1, NR111747.1; β-tub, AB744079.1, AB690809.1; GAPDH, KF944355.1, KF944354.1; CHS-1, JQ948987.1, JQ949005.1; and ACT, JQ949625.1, JQ949626.1). Koch's postulates were fulfilled by inoculating six healthy 1-year-old walnut trees in July 2014 with maximum and minimum temperatures of 33 and 26°C. The 6-mm mycelial plug, which was cut from the margin of a 5-day-old colony of the fungus on PDA, was placed onto each pin-wounded leaf, ensuring good contact between the mycelium and the wound. Non-colonized PDA plugs were placed onto pin-wounds as negative controls. Following inoculation, both inoculated and control plants were covered with plastic bags. Leaf spots, similar to those on naturally infected plants, were observed on the leaves inoculated with C. fioriniae within 5 days. No symptoms were observed on the negative control leaves. Finally, C. fioriniae was re-isolated from symptomatic leaves; in contrast, no fungus was isolated from the control, which confirmed Koch's postulates. To our knowledge, this is the first report of leaf disease on walnut caused by C. fioriniae. References: (1) L. Cai et al. Fungal Divers. 39:183, 2009. (2) R. G. Shivas and Y. P. Tan. Fungal Divers. 39:111, 2009.

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First Report of Cercospora armoraciae, Causal Agent of Cercospora Leaf Spot, on Horseradish in Serbia

Plant Disease ◽

10.1094/pdis-03-15-0251-pdn ◽

2015 ◽

Vol 99 (11) ◽

pp. 1645-1645

Author(s):

N. Trkulja ◽

A. Milosavljević ◽

M. Mitrović ◽

J. Jović ◽

I. Toševski

Keyword(s):

Leaf Spot ◽

Causal Agent ◽

Cercospora Leaf Spot ◽

First Report

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First Report of Bacterial Leaf Spot of Spinach Caused by a Pseudomonas syringae Pathovar in California

Plant Disease ◽

10.1094/pdis.2002.86.8.921a ◽

2002 ◽

Vol 86 (8) ◽

pp. 921-921 ◽

Cited By ~ 3

Author(s):

S. T. Koike ◽

H. R. Azad ◽

D. C. Cooksey

Keyword(s):

Brassica Oleracea ◽

Beta Vulgaris ◽

Pseudomonas Syringae ◽

Leaf Spot ◽

The United States ◽

Nutrient Broth ◽

Bacterial Leaf Spot ◽

First Report ◽

Leaf Spots ◽

Initial Symptoms

In 2000 and 2001, a new disease was observed on commercial spinach (Spinacia oleracea) in the Salinas Valley, Monterey County, CA. Initial symptoms were water-soaked, irregularly shaped leaf spots (2 to 3 mm diameter). As the disease developed, spots enlarged to as much as 1 to 2 cm, were vein-delimited, and turned dark brown. Faint chlorotic halos sometimes surrounded the spots. Death of large areas of the leaf occurred if spots coalesced. Spots were visible from the adaxial and abaxial sides of leaves, and no fungal structures were observed. The disease occurred on newly expanded and mature foliage. No fungi were isolated from the spots. However, cream-colored bacterial colonies were consistently isolated on sucrose peptone agar, and these strains were nonfluorescent on King's medium B. Strains were positive for levan and negative for oxidase, arginine dihydrolase, and nitrate reductase. Strains did not grow at 36°C, did not rot potato slices, but induced a hypersensitive reaction in tobacco (Nicotiana tabacum cv. Turk). These results suggested the bacterium was similar to Pseudomonas syringae. Fatty acid methyl ester (FAME) analysis (MIS-TSBA 4.10, MIDI Inc., Newark, DE) indicated the strains were highly similar (80.1 to 89.3%) to P. syringae pv. maculicola. However, in contrast to P. syringae pv. maculicola, the spinach strains did not utilize the carbon sources erythritol, L+tartrate, L lactate, and DL-homoserine. Pathogenicity of 10 strains was tested by growing inoculum in nutrient broth shake cultures for 48 h, diluting to 106 CFU/ml, and spraying 4-week-old plants of spinach cv. Bossanova. Control plants were sprayed with sterile nutrient broth. After 5 to 8 days in a greenhouse (24 to 26°C), leaf spots identical to those observed in the field developed on cotyledons and true leaves of inoculated plants. Strains were reisolated from the spots and identified as P. syringae. Control plants remained symptomless. The 10 strains were also inoculated on beet (Beta vulgaris), Swiss chard (Beta vulgaris subsp. cicla), cilantro (Coriandrum sativum), and spinach. Spinach showed leaf spots after 8 days; however, none of the other plants developed symptoms. Two strains were inoculated onto spinach cvs. Califlay, Lion, Nordic IV, Polka, Resistoflay, Rushmore, RZ 11, Spinnaker, Springfield, Viroflay, and Whitney. Leaf spot developed on all cultivars, and the pathogen was reisolated. Because the FAME data indicated a similarity between the spinach pathogen and P. syringae pv. maculicola, we inoculated sets of spinach cv. Bolero, cabbage (Brassica oleracea subsp. capitata cv. Grenedere), and cauliflower (Brassica oleracea subsp. botrytis cv. White Rock) with three P. syringae pv. maculicola and three spinach strains. Cabbage and cauliflower developed leaf spots only when inoculated with P. syringae pv. maculicola; spinach had leaf spots only when inoculated with the spinach strains. All inoculation experiments were done twice, and the results of the two tests were the same. To our knowledge, this is the first report of bacterial leaf spot of spinach in California caused by a nonfluorescent P. syringae, and the first record of this disease in the United States. Biochemical characteristics and limited host range of the pathogen indicate the California strains are likely the same as the P. syringae pv. spinaciae pathogen that was reported in Italy (1) and Japan (2). References: (1) C. Bazzi et al. Phytopathol. Mediterr. 27:103, 1988. (2) K. Ozaki et al. Ann. Phytopathol. Soc. Jpn. 64:264, 1998.

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First Report of Pestalotiopsis clavispora Causing Leaf Spot of Carya illinoensis in Brazil

Plant Disease ◽

10.1094/pdis-07-12-0615-pdn ◽

2012 ◽

Vol 96 (12) ◽

pp. 1826-1826 ◽

Cited By ~ 4

Author(s):

M. Lazarotto ◽

M. F. B. Muniz ◽

T. Poletto ◽

C. B. Dutra ◽

E. Blume ◽

...

Keyword(s):

Leaf Spot ◽

Rio Grande ◽

Morphological Characterization ◽

The State ◽

Morphological Identification ◽

Pathogenicity Test ◽

Rio Grande Do Sul ◽

Carya Illinoensis ◽

Potato Dextrose Agar Medium ◽

First Report

Conspicuous leaf spots in combination with fruit spots were observed for the first time in April and May 2010 on a 30-ha pecan [Carya illinoensis (Wangenh.) K. Koch] orchard in the state of Rio Grande do Sul, Brazil. Initially, tiny grey spots were observed on leaves and, over time, the spots expanded to become gray to light brown circles surrounded by a dark brown border, followed by leaves falling. Eventually, fruits were also attacked, with typical symptoms beginning with tiny water soaked spots which then became necrotic. The disease was also observed in pecan nursery and field seedlings. Isolation of the pathogen from symptomatic leaves and morphological identification by conidia characters (number of cells, color, hyaline terminal cells, number of appendages) revealed Pestalotiopsis sp. (2) as the causal agent of the disease. Conidia constituted of transverse septa with four dark intermediate sections and two hyaline terminal sections. One of the terminal sections presented two or three apical appendages. Conidia averaged 6.88 μm wide × 31.00 μm long, not considering the apical appendages. Primers ITS 1 and ITS 4 were used to amplify the internal transcribes spacer ITS 1-5.8S-ITS 2 region. Nucleotide sequences were 99% similar to Pestalotiopsis clavispora (G.F. Atk.) Steyaert. Conidia produced on potato dextrose agar medium were used to inoculate 8 plants with a spore suspension of 2.0 × 106 conidia/ml. Eight additional plants were used as control (non-inoculated). The inoculation was performed by spraying the suspension onto the leaves of Pecan seedlings and the plants were incubated for 72 h in a humid chamber (1). All inoculated plants showed symptoms 25 days after inoculation and the fungus was reisolated. The pathogenicity test was repeated once. Ten more isolates collected from four different cities in the same state were identified as Pestalotiopsis spp. by morphological characterization and pathogenicity was confirmed. Because this disease causes losses on production of nuts indirectly by reducing photosynthetically active area when the pathogen attacks leaves and directly when attacking fruits, it may restrict the production where the pathogen occurs. On some orchards in the state of Rio Grande do Sul, the attack rate reached 80% of the plants. P. clavispora has been reported causing stem end-rot of avocado in Chile (3), but this note constitutes the first report, to our knowledge, of P. clavispora causing leaf spot on C. illinoensis in Brazil. References: (1) A. C. Alfenas and F. A. Ferreira. Page 117 in: Métodos em Fitopatologia. A. C Alfenas and R. G. Mafia (eds.). Editora: UFV, Viçosa, 2007. (2) S. S. N. Maharachchikumbura et al. Fungal Diversity 50:167, 2011. (3) A. L. Valencia et al. Plant Dis. 95:492, 2011.

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