First Report of Melting Decay of ‘Red Globe’ Grapes in California

Since the late 1990s, a melting decay of ‘Red Globe’ grapes has occasionally been observed in cold storage facilities in California. Symptoms of the decay included a cracking and dissolution of the epidermis followed by the development of sunken decayed areas. In extreme cases, nearly the entire berry liquefied. The affected berries usually were randomly distributed over the cluster but sometimes berry-to-berry spread seemed to have occurred. The disease has not been observed in the field. Initial symptoms are usually observed after 2 weeks of cold storage (-0.5 to 0°C and 90 to 95% relative humidity). In 2003, melting decay developed in ‘Red Globe’ grapes in many cold storage facilities in California and in grapes stored for export. Microscopic examination under the skin at the edges of the decayed lesions revealed numerous yeast and bacterial cells. Bacillus subtilis (Ehrenberg) Cohn, Cryptococcus laurentii (Kufferath) Skinner, and Aureobasidium pullulans (de Bary) Arnaud were consistently isolated on potato dextrose agar (PDA) from samples submitted from two cold storage facilities. Certified diagnostic laboratories identified the bacterium and two yeasts. To fulfill Koch's postulates, we performed the following experiments. ‘Red Globe’ grape berries with the pedicel attached were surface disinfested in a solution of 0.084% sodium hypochlorite, 1.5% ethanol, and 0.005% Tween 20 for 4 min, and washed with sterile deionized water. Grape berries were placed on raised plastic screens in a humid chamber. After the surface of the berries dried, 0.25 ml of a cell suspension (108 cells per ml) of each microorganism was placed on the surface of each berry without wounding. Water (150 to 200 ml) was added to the bottom of the container to create >98% relative humidity (measured with a datalogger), and the containers were incubated at 20°C for 7 days or 0.5°C for 6 weeks. With fruit stored at 20°C, the epidermis of all the berries cracked between 24 and 48 h after inoculation. Severe symptoms of melting decay developed 1 week later. With berries incubated at 0.5°C, melting decay symptoms developed after 6 weeks. Symptoms were most severe on berries inoculated with C. laurentii. However, when inoculated berries were preincubated at 20°C for 14 h prior to storage at 0.5°C, symptoms developed after 3 weeks. In this case, and when berries were incubated at 20°C, symptom expression was similar among the three pathogens. A number (>80%) of the affected berries disintegrated and liquefied in a pattern similar to that observed in berries from commercial cold storage facilities. The pathogen used to inoculate the grapes was consistently isolated in pure culture from subsequent lesions. Therefore, a postharvest disease in ‘Red Globe’ grapes called melting decay can be caused by the bacterium, B. subtilis, or two different yeast species. To our knowledge, this is the first report of B. subtilis or C. laurentii as pathogens of grape berries in the United States and worldwide. A. pullulans has been isolated from Vitis vinifera (1,2), but is reported for the first time as one of the causal agents of melting decay of ‘Red Globe’ grapes. All three organisms also caused symptoms on ‘Crimson Seedless’ grapes, but melting decay has not been reported as a problem in this cultivar. References: (1) P. W. Crous et al. Phytopathogenic Fungi from South Africa. University of Stellenbosch, Department of Plant Pathology Press, Stellenbosch, South Africa, 2000. (2) M. Pantidou. Fungus-Host Index for Greece. Benaki Phytopathological Institute, Athens, 1973.

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First Report of Alternaria tenuissima Causing Postharvest Decay on Apple Fruit from Cold Storage in the United States

Plant Disease ◽

10.1094/pdis-07-13-0802-pdn ◽

2014 ◽

Vol 98 (5) ◽

pp. 690-690 ◽

Cited By ~ 1

Author(s):

L. P. Kou ◽

V. L. Gaskins ◽

Y. G. Luo ◽

W. M. Jurick

Keyword(s):

United States ◽

South Africa ◽

Cold Storage ◽

Fungal Pathogens ◽

The United States ◽

Apple Fruit ◽

Conidial Suspension ◽

Single Spore ◽

Alternaria Tenuissima ◽

First Report

Apples are grown and stored for 9 to 12 months under controlled atmosphere conditions in the United States. During storage, apples are susceptible to various fungal pathogens, including several Alternaria species (2). Alternaria tenuissima (Nees) Wiltshire causes dry core rot (DCR) on apples during storage and has recently occurred in South Africa (1). Losses range widely, but typically occur at 6 to 8% annually due to this disease (2). In February 2013, ‘Nittany’ apples with round, dark-colored, dry, spongy lesions were obtained from wooden bins in a commercial cold storage facility located in Pennsylvania. Symptomatic fruits were transported to the lab, rinsed with sterile water, and the lesions were sprayed with 70% ethanol until runoff and wiped dry. The skin was aseptically removed with a scalpel, and asymptomatic tissue was placed onto potato dextrose agar (PDA) and incubated at 25°C. Two single-spore isolates were propagated on PDA and permanent cultures were maintained as slants and stored at 4°C. The fungus produced a cottony white mycelium that turned olive-green to brown with abundant aerial hyphae and had a dark brown to black reverse on PDA. Isolates were identified as Alternaria based on conidial morphology as the spores were slightly melanized and obclavate to obpyriform catentulate with longitudinal and transverse septa attached in unbranched chains on simple short conidiophores. Conidia ranged from 10 to 70 μm long (mean 27.7 μm) and 5 to 15 μm wide (mean 5.25 μm) (n = 50) with 1 to 6 transverse and 0 to 2 longitudinal septa. Conidial beaks, when present, were short (5 μm or less) and tapered. Mycelial genomic DNA was extracted, and a portion of the histone gene (357 bp) was amplified via gene specific primers (Alt-His3-F/R) using conventional PCR (Jurick II, unpublished). The forward and reverse sequences were assembled into a consensus representing 2× coverage and MegaBLAST analysis showed that both isolates were 100% identical to Alternaria tenuissima isolates including CR27 (GenBank Accession No. AF404622.1) that caused DCR on apple fruit during storage in South Africa. Koch's postulates were conducted using 10 organic ‘Gala’ apple fruit that were surface sterilized with soap and water, sprayed with 70% ethanol, and wiped dry. The fruit were aseptically wounded with a nail to a 3 mm depth, inoculated with 50 μl of a conidial suspension (1 × 104 conidia/ml), and stored at 25°C in 80 count boxes on paper trays for 21 days. Mean lesion diameters on inoculated ‘Gala’ apple fruit were 19.1 mm (±7.4), water only controls (n = 10 fruit) were symptomless, and the experiment was repeated. Symptoms observed on artificially inoculated ‘Gala’ apple fruit were similar to the decay observed on ‘Nittany’ apples from cold storage. Based on our findings, it is possible that A. tenuissima can cause decay that originates from wounded tissue in addition to dry core rot, which has been reported (1). Since A. tenuissima produces potent mycotoxins, even low levels of the pathogen could pose a health problem for contaminated fruit destined for processing and may impact export to other countries. To the best of our knowledge, this is the first report of alternaria rot caused by A. tenuissima on apple fruit from cold storage in the United States. References: (1) J. C. Combrink et al. Decid. Fruit Grow. 34:88, 1984. (2) M. Serdani et al. Mycol. Res. 106:562, 2002. (3) E. E. Stinson et al. J. Agric. Food Chem. 28:960, 1980.

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First Report and Epidemics of Buffelgrass Blight Caused by Pyricularia grisea in South Texas

Plant Disease ◽

10.1094/pdis.1999.83.4.398d ◽

1999 ◽

Vol 83 (4) ◽

pp. 398-398 ◽

Cited By ~ 4

Author(s):

O. Rodriguez ◽

J. Gonzalez-Dominguez ◽

J. P. Krausz ◽

G. N. Odvody ◽

J. P. Wilson ◽

...

Keyword(s):

Drought Stress ◽

Relative Humidity ◽

The United States ◽

South Texas ◽

Pyricularia Grisea ◽

Severe Drought ◽

Commonwealth Mycological Institute ◽

Unique Type ◽

First Report ◽

Initial Symptoms

A blight on buffelgrass, Cenchrus ciliaris L., has been observed for several years in south Texas and Mexico. The disease did not reach epidemic proportions until 1996. The causal agent, identified as Pyricularia grisea (Cooke) Sacc., is a common pathogen of grasses and other cultivated crops. Several Pennisetum spp. have been reported as hosts of Pyricularia spp.; this is the first report of buffelgrass as a host of this pathogen (1,2). Pathogenicity of P. grisea on buffelgrass was confirmed by greenhouse inoculations of 2-month-old buffelgrass plants with conidia washed with distilled water from monoconidial isolations of the pathogen, grown on potato dextrose agar, from infected leaves collected in several locations in south Texas and Mexico. Plants were placed for 8 h every night inside a plastic enclosure with a humidifier, simulating the high relative humidity conditions prevalent during the epidemic. Typical lesions developed after 7 days. The pathogen was re-isolated from the lesions after 10 days, fulfilling Koch's postulates. Conidia harvested from the sporulating samples were hyaline, transversely septate, with one to three septa, most of them having two. Conidia were obpyriform, with hylum often protuberant, measuring 20.6 to 26.3 μm in length and 8.5 to 10.1 μm wide. These measurements are consistent with those given for Pyricularia spp. by Ellis (1). Conidiophores were hyaline, single, slender, and unbranched. Initial symptoms were dark, discolored spots on the leaf that developed into tan, round to elliptical, necrotic lesions with a dark red border and a yellow, chlorotic halo. With increasing severity, lesions can coalesce, killing the entire leaf blade. Under heat and moisture stress, leaves with few lesions and yellow discoloration will wilt completely. Except for the presence of distinct lesions, wilted plants appear to be suffering from severe drought stress or herbicide injury. Losses vary from a few lesions to wilted whole plants and entire pastures. The pathogen also reduces the quantity and quality of seed by infecting involucres of the head. In the absence of the disease, even under severe moisture or drought stress, buffelgrass is able to thrive. Common T-4464 buffelgrass, which is highly susceptible to P. grisea, was introduced into south Texas in the late 1940s and is currently grown on 8 to 10 million acres in south Texas and Mexico. Buffelgrass reproduces by obligate apomixis, in which seeds are formed without sexual fertilization. Consequently, the progeny are genetically identical to the maternal parent. The monoculture of this grass with its unique type of reproduction encompasses millions of acres with genetically identical plants. Interaction of inoculum with weather conditions (nights with 8 to 10 h of more than 75% relative humidity) in 1996, 1997, and the late summer of 1998 produced epidemics of buffelgrass blight throughout south Texas and northern Mexico. P. grisea was also isolated from lesions on grassburr Cenchrus incertus M. A. Curtis collected throughout the area. References: (1) M. B. Ellis 1971. Dematiaceous hyphomycetes. Commonwealth Mycological Institute, Kew, Surrey, England. (2) D. F. Farr et al. 1989. Fungi of Plants and Plant Products in the United States. American Phytopathological Society, St. Paul, MN.

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First Report of Sclerotinia Blight Caused by Sclerotinia sclerotiorum on Spearmint in Northern Italy

Plant Disease ◽

10.1094/pdis-04-13-0398-pdn ◽

2013 ◽

Vol 97 (10) ◽

pp. 1384-1384 ◽

Cited By ~ 1

Author(s):

A. Garibaldi ◽

P. Pensa ◽

D. Bertetti ◽

A. Poli ◽

M. L. Gullino

Keyword(s):

Relative Humidity ◽

Sclerotinia Sclerotiorum ◽

Its Region ◽

Soft Rot ◽

The United States ◽

Northern Italy ◽

Mentha Spicata ◽

First Report ◽

Initial Symptoms ◽

Stem Necrosis

Spearmint (Mentha spicata L.) is an aromatic plant belonging to the family Lamiaceae, grown as well as an ornamental potted plant. During the beginning of 2013, extensive wilting was observed on 4-month-old potted plants of M. spicata ‘Moroccan’ grown in a commercial, unheated, plastic house located near Albenga (Savona, northern Italy). Initial symptoms included stem necrosis and darkening and withering of leaves. Wilting of the plant occurred 2 to 4 days after the appearance of the initial symptoms. Infected plants were characterized by the presence of cottony soft rot. In the presence of high relative humidity, lesions became covered with a whitish mycelium and irregular, dark gray sclerotia (2.0 to 9.0 × 1.8 to 4.0, average 4.0 × 2.6 mm) were produced on the mycelium. Diseased tissue was surface sterilized for 1 min in 1% NaOCl and plated on potato dextrose agar (PDA) amended with 100 mg/l streptomycin sulfate. White colonies developed from infected stem pieces and produced sclerotia, mainly at the peripheries of the plates, measuring 2.0 to 8.0 × 2.0 to 6.0 (average 4.4 × 3.1) mm. The internal transcribed spacer (ITS) region of rDNA was amplified using the primers ITS1F/ITS4 and sequenced. BLAST analysis (1) of the 514-bp segment showed a 99% homology with the sequence of Sclerotinia sclerotiorum (JN012605). The nucleotide sequence has been assigned the GenBank Accession KC848769. The morphological and molecular identification permitted to identify as S. sclerotiorum (Lib.) de Bary (2) the causal agent of the disease observed on M. spicata. Pathogenicity of one isolate obtained from infected plants was confirmed by inoculating three 7-month-old plants cv. Moroccan transplanted in 1 liter pots in a glasshouse in a sphagnum peat/pomix/pine bark/clay (50:20:20:10) mix. Each plant was inoculated by placing 4 g of sterile wheat kernels infested with mycelium and sclerotia in the soil and around the collar. Three non-inoculated plants served as controls. Plants were maintained in a growth chamber at 24 ± 1°C and relative humidity >90%. The inoculation trial was carried out twice. All inoculated plants developed the symptoms, consisting of stem necrosis, 5 days after soil infestation, followed by leaf yellowing. White cottony mycelium and dark sclerotia developed on stems and at the base of all inoculated plants. Eventually, infected plants wilted. Control plants remained symptomless. S. sclerotiorum was reisolated from the stems of inoculated plants. To our knowledge, this is the first report of S. sclerotiorum on M. spicata in Italy as well as worldwide. The disease has been previously reported on M. piperita in the United States (4) and on M. arvensis in India (3). The economic importance of this disease in Italy is at present limited. References: (1) S. F. Altschul et al. Nucleic Acids Res. 25:3389, 1997. (2) N. F. Buchwald. Kongl. Veterisk Landb. Aarssk. 75, 1949. (3) K. Perveen et al. Indian Phytopathol. 62:310, 2009. (4) C. B. Skotland and J. D. Menzies. Plant Dis. Rep. 41:493, 1957.

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First Report of Rhizosis Caused by Ceratocystis radicicola on Date Palms in South Africa

Plant Disease ◽

10.1094/pdis.1999.83.9.880b ◽

1999 ◽

Vol 83 (9) ◽

pp. 880-880 ◽

Cited By ~ 9

Author(s):

C. Linde ◽

W. A. Smit

Keyword(s):

South Africa ◽

Late Summer ◽

Phoenix Dactylifera ◽

The United States ◽

Date Palms ◽

First Report ◽

Agar Plug ◽

Initial Symptoms ◽

Young Leaves ◽

Water Plants

During late summer (February to March) of 1997, a sudden loss of large date palms (Phoenix dactylifera L. ‘Medjool’) and adjacent suckers was observed in the Pofadder area of South Africa. The palms were planted in sandy soil, with flood irrigation from the adjacent Orange River. Initial symptoms included wilting of leaves, chlorosis of young leaves, and root necrosis. Ceratocystis radicicola (D.E. Bliss) C. Moreau (synamorph Ceratostomella radicicola; anamorph Chalara) was consistently isolated from necrotic roots and lower crown portions of diseased palms. Dark colored spores were observed in root sections. Pathogenicity studies were performed in a shadehouse on 5-year-old Medjool clones. Two experiments were conducted in which Medjool plants were inoculated with 2-week-old C. radicicola cultures grown on corn meal agar (CMA). In the first experiment, a 7-mm wound was made at the leaf base of 15 plants and inoculated with an agar plug of C. radicicola culture. The same number of control plants was inoculated with CMA. Wounds were sealed with Parafilm, and lesions were measured after 3 months. In the second experiment, conidial suspensions and pieces of mycelia from five C. radicicola cultures were harvested in 1.5 liters of water, and 100 ml of inoculum was added to each of 15 plants. Control plants (15 total) each received 100 ml of sterile water. Plants were examined after 3 months. In the first experiment, all leaves inoculated at the base with C. radicicola became necrotic at the point of inoculation, wilted rapidly, and died. In the second experiment, roots showed severe necrosis resembling rhizosis observed in the field. In each experiment, only three plants died, and C. radicicola was successfully isolated from all inoculated plants. No symptoms developed on control plants, and C. radicicola could not be isolated from them. Rhizosis of date palms caused by C. radicicola has been described in the United States (1) and differs from the disease of date palm stems, leaves, buds, and inflorescences caused by C. paradoxa (Dade) C. Moreau. This is the first report of rhizosis on date palms in South Africa. Reference: (1) D. E. Bliss. Phytopathology 31:1123, 1941.

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

Plant Disease ◽

10.1094/pdis.2002.86.1.71a ◽

2002 ◽

Vol 86 (1) ◽

pp. 71-71

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

United States ◽

Sclerotinia Sclerotiorum ◽

Ornamental Plants ◽

Soil Surface ◽

The United States ◽

First Report ◽

Potted Plants ◽

Initial Symptoms ◽

Stem Necrosis ◽

Campanula Carpatica

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

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First Report of Anthracnose of Papaya (Carica papaya L.) Caused by Colletotrichum siamense in China

Plant Disease ◽

10.1094/pdis-10-20-2154-pdn ◽

2021 ◽

Author(s):

Yujie Zhang ◽

Wenxiu Sun ◽

Ping Ning ◽

Tangxun Guo ◽

SuiPing Huang ◽

...

Keyword(s):

Carica Papaya ◽

Disease Incidence ◽

Aerial Mycelium ◽

Postharvest Disease ◽

Distilled Water ◽

First Report ◽

Surface Samples ◽

Initial Symptoms ◽

Colletotrichum Siamense ◽

Pathogenicity Tests

Papaya (Carica papaya L.) is a rosaceous plant widely grown in China, which is economically important. Anthracnose caused by Colletotrichum sp. is an important postharvest disease, which severely affects the quality of papaya fruits (Liu et al., 2019). During April 2020, some mature papaya fruits with typical anthracnose symptoms were observed in Fusui, Nanning, Guangxi, China with an average of 30% disease incidence (DI) and over 60% DI in some orchards. Initial symptoms of these papayas appeared as watery lesions, which turned dark brown, sunken, with a conidial mass appearing on the lesions under humid and warm conditions. The disease severity varied among fruits, with some showing tiny light brown spots, and some ripe fruits presenting brownish, rounded, necrotic and depressed lesions over part of their surface. Samples from two papaya plantations (107.54°E, 22.38°N) were collected, and brought to the laboratory. Symptomatic diseased tissues were cut into 5 × 5 mm pieces, surface sterilized with 2% (v/v) sodium hypochlorite for 1 minute, and rinsed three times with sterilized water. The pieces were then placed on potato dextrose agar (PDA). After incubation at 25°C in the dark for one week, colonies with uniform morphology were obtained. The aerial mycelium on PDA was white on top side, and concentric rings of salmon acervuli on the underside. A gelatinous layer of spores was observed on part of PDA plates after 7 days at 28°C. The conidia were elliptical, aseptate and hyaline (Zhang et al., 2020). The length and width of 60 conidia were measured for each of the two representative isolates, MG2-1 and MG3-1, and these averaged 13.10 × 5.11 μm and 14.45 × 5.95 μm. DNA was extracted from mycelia of these two isolates with the DNA secure Plant Kit (TIANGEN, Biotech, China). The internal transcribed spacer (ITS), partial actin (ACT), calmodulin (CAL), chitin synthase (CHS), β-tubulin 2 (TUB2) and glyceraldehyde 3-phosphate dehydrogenase (GAPDH) regions were amplified by PCR and sequenced. The sequences were deposited into GenBank with accessions MT904003, MT904004, and MT898650 to MT898659. BLASTN analyses against the GenBank database showed that they all had over 99% identity to the type strain of Colletotrichum siamense isolate ICMP 18642 (GenBank accession numbers JX010278, GQ856775, JX009709, GQ856730, JX010410, JX010019) (Weir et al., 2012). A phylogenetic tree based on the combined ITS, ACT, CAL, CHS, TUB2 and GAPDH sequences using the Neighbor-joining algorithm also showed that the isolates were C. siamense. Pathogenicity tests were conducted on 24 mature, healthy and surface-sterilized papaya fruits. On 12 papaya fruits, three well separated wounded sites were made for inoculation, and for each wounded site, six adjacent pinhole wounds were made in a 5-mm-diameter circular area using a sterilized needle. A 10 µl aliquot of 1 × 106 conidia/ml suspension of each of the isolates (MG2-1 and MG3-1) was inoculated into each wound. For each isolate, there were six replicate fruits. The control fruits were inoculated with sterile distilled water. The same inoculation was applied to 12 non-wound papaya fruits. Fruits were then placed in boxes which were first washed with 75% alcohol and lined with autoclaved filter paper moistened with sterilized distilled water to maintain high humidity. The boxes were then sealed and incubated at 28°C. After 10 days, all the inoculated fruits showed symptoms, while the fruits that were mock inoculated were without symptoms. Koch's postulates were fulfilled by re-isolation of C. siamense from diseased fruits. To our knowledge, this is the first report of C. siamense causing anthracnose of papaya in China. This finding will enable better control of anthracnose disease caused by C. siamense on papaya.

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First Report of Leaf Rust of Blueberry Caused by Thekopsora minima on Vaccinium corymbosum in the Western Cape, South Africa

Plant Disease ◽

10.1094/pdis-94-4-0478c ◽

2010 ◽

Vol 94 (4) ◽

pp. 478-478 ◽

Cited By ~ 7

Author(s):

L. Mostert ◽

W. Bester ◽

T. Jensen ◽

S. Coertze ◽

A. van Hoorn ◽

...

Keyword(s):

South Africa ◽

South African ◽

Water Solution ◽

Phylogenetic Analyses ◽

The United States ◽

Vaccinium Corymbosum ◽

Tween 20 ◽

Western Cape ◽

The South ◽

First Report

Southern highbush blueberry plants (Vaccinium corymbosum interspecific hybrids) showing rust-like symptoms were observed in July 2006 in Porterville in the Western Cape (WC), South Africa. Diseased plants were also found in Villiersdorp and George in the WC in 2007. In 2008, symptoms were observed in George, and in 2009, in all the previous reported areas. Cvs. Bluecrisp, Emerald, Jewel, Sharpblue, and Star were infected. Reddish-to-brown spots appeared on the adaxial surface of leaves and developed into yellow-to-orange erumpent uredinia with pulverulent urediniospores. Uredinia were hypophyllous, dome shaped, 113 to 750 μm wide, and occasionally coalescing. Urediniospores were broadly obovate, sometimes ellipsoidal or pyriform, with yellowish orange content, and measured 19 to 27 × 12 to 20 μm (average 24 × 15 μm, n = 30). Spore walls were echinulate, hyaline, 1 to 1.5 μm thick, and with obscure germ pores. No telia or teliospores were observed. Voucher specimens were lodged in the South African National Fungus Collection in Pretoria (PREM 60245). The isolate was initially identified as Thekopsora minima P. Syd. & Syd., based primarily on the absence of conspicuous ostiolar cells characteristic of Naohidemyces spp. (3). Genomic DNA was extracted from urediniospores. Approximately 1,400 bp were amplified spanning the 5.8S, ITS2, and 28S large subunit of the ribosomal DNA (1). The sequence (GU355675) shared 96% (907 of 942 bp; GenBank AF522180) and 94% (1,014 of 1,047 bp; GenBank DQ354563) similarities in the 28S portion, respectively, to those of Naohidemyces vaccinii (Wint.) Sato, Katsuya et Y. Hiratsuka and Pucciniastrum geoppertianum (Kuehn) Kleb, two of the three known rust species of blueberry (2). Although no sequences of T. minima were available for direct comparison, phylogenetic analyses of the 28S region strongly supported the South African blueberry rust as congeneric with T. guttata (J. Schröt.) P. Syd. & Syd. (GenBank AF426231) and T. symphyti (Bubák) Berndt (GenBank AF26230) (data not shown). Four 6-month-old cv. Sharpblue plants were inoculated with a suspension (approximate final concentration of 1 × 105 spores per ml) of fresh urediniospores in a water solution with 0.05% Tween 20. After incubation at 20°C for 48 h under continuous fluorescent lighting, the plants were grown in a glasshouse (18/25°C night/day temperatures). Identical uredinia and symptoms developed approximately 3 weeks after inoculation on the inoculated plants, but not on two control plants of cv. Sharpblue sprayed with distilled water and kept at the same conditions. The alternate host hemlock (Tsuga spp.) is not endemic to South Africa and not sold as an ornamental plant according to a large conifer nursery. Hosts of T. minima include Gaylussacia baccata, G. frondosa, Lyonia neziki, Menziesia pilosa, Rhododendron canadense, R. canescens, R. lutescens R. ponticum, R. prunifolium, R. viscosum, V. angustifolium var. laevifolium, V. corumbosum, and V. erythrocarpon (3). Visual inspection of possible hosts in the gardens in close proximity of Vaccinium production areas did not show any rust symptoms. To our knowledge, this is the first report of T. minima on blueberries outside of Asia and the United States (2). References: (1) M. C. Aime. Mycoscience 47:112, 2006. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Systematic Botany and Mycology Laboratory. Online publication. USDA-ARS, 2009. (3) S. Sato et al. Trans. Mycol. Soc. Jpn. 34:47, 1993.

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

Plant Disease ◽

10.1094/pd-89-1241c ◽

2005 ◽

Vol 89 (11) ◽

pp. 1241-1241 ◽

Cited By ~ 4

Author(s):

A. Garibaldi ◽

A. Minuto ◽

M. L. Gullino

Keyword(s):

Relative Humidity ◽

Sclerotinia Sclerotiorum ◽

Severe Disease ◽

Soil Surface ◽

Soft Rot ◽

Sclerotinia Stem Rot ◽

First Report ◽

Initial Symptoms ◽

Stem Necrosis ◽

White Mycelium

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

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

Plant Disease ◽

10.1094/pdis-01-13-0021-pdn ◽

2013 ◽

Vol 97 (8) ◽

pp. 1117-1117 ◽

Cited By ~ 1

Author(s):

S. E. Cho ◽

J. H. Park ◽

S. H. Hong ◽

H. D. Shin

Keyword(s):

Its Region ◽

The United States ◽

Infected Leaf ◽

Invasive Weed ◽

Voucher Specimen ◽

First Report ◽

Leaf Spots ◽

Initial Symptoms ◽

Wide Range ◽

Humulus Japonicus

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

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First Report of 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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