First Report of Brown Spot on White Button Mushroom (Agaricus bisporus) Caused by Cedecea neteri in Iran

In autumn 2018, cap discoloration and browning symptoms (up to 20% incidence) were observed on commercially grown white button mushrooms (Agaricus bisporus) in two distinct farms located in Shiraz and Marvdasht Counties in Southern Iran. Symptomatic caps (13 and six caps from Shiraz and Marvdasht Counties, respectively) were characterized by visible brown discoloration with no blotch symptoms, bacterial sticky mass and cap wilting. Isolation of bacterial strains from infected cap tissues was performed on yeast-extract peptone glucose agar (YPGA) according to Hamidizade et al. (2020). The resulted bacterial colonies were oyster-white in color, non-fluorescent, domed convex circular with smooth margins 1-2 mm in diameter. A total of six bacterial strains (Shiraz: Ir1002, Ir1003, Ir1004, Ir1005, Ir1007 and Marvdasht: Ir1027) were isolated from distinct mushroom samples. Standard biochemical and phenotypic analyses (Schaad et al. 2001) showed that the bacterial strains were Gram and oxidase negative, catalase positive and facultatively anaerobic, while no capsule or endospore was observed. All strains were positive in urease production, arginine dihydrolase, hydrolysis of tween 80, and utilization of sucrose and D-sorbitol, while they were negative in amylase, cellulose, lecithinase, pectinase, and protease production as well as casein hydrolysis. Based on these phenotypic characteristics, the strains were supposed to be members of Enterobacteriaceae. They also did not induce hypersensitive reaction (HR) on tobacco (Nicotiana tabacum cv. Turkish) leaves nor did they produce tolaasin when streaked side-by-side with “Pseudomonas reactans” strains on King B medium (Osdaghi et al. 2019). Pathogenicity of the strains was evaluated (repeated twice) on fresh caps of white button mushroom using cut-cap method (Hamidizade et al. 2020). Reference strains of Pseudomonas tolaasii (CFBP 8707) and Mycetocola spp. (CFBP 8708) were used as positive controls, while sterile distilled water was used as a negative control. Brown discoloration appeared 24-36 hours post inoculation on cap surfaces while control caps remained asymptomatic. Koch’s postulates were accomplished by re-isolation and identification of bacterial strains from the symptomatic caps using colony morphology and Gram staining. For molecular identification, all initial as well as re-isolated strains were subjected to amplification and sequencing of 16S rDNA and gyrB (Yamamoto and Harayama 1995; Hamidizade et al. 2020). Obtained nucleotide sequences were deposited into NCBI GenBank (16S: MZ298620 to MZ298625; gyrB: MZ313184 to MZ313189). BLAST search using the 16S rDNA and gyrB sequences showed that the strains isolated in this study had 97-99% sequence similarity to the reference strains of Cedecea neteri. Phylogenetic analyses also confirmed close relationship of bacterial strains from this study to C. neteri strains. Pure cultures of representative strains Ir1004 (CFBP 8900) and Ir1027 (CFBP 8896) are deposited in CIRM-CFBP culture collection. This is the first report of C. neteri causing brown spot disease on button mushroom in Iran, while the bacterium has previously been reported to cause soft rot on Pholiota nameko (Yan et al. 2018), and yellow sticky disease on Flammulina velutipes (Yan et al. 2019) in China. Further comprehensive investigations will shed a light on the economic impact of the brown spot disease on mushroom industry in Iran.

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First report of brown spot disease in Psidium guajava caused by Alternaria tenuissima in China

Journal of Plant Pathology ◽

10.1007/s42161-020-00594-3 ◽

2020 ◽

Vol 102 (4) ◽

pp. 1309-1309

Author(s):

X. B. Song ◽

Y. P. Cui ◽

A. T. Peng ◽

J. F. Ling ◽

X. Chen

Keyword(s):

Psidium Guajava ◽

Brown Spot ◽

Alternaria Tenuissima ◽

First Report ◽

Spot Disease ◽

Brown Spot Disease

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First Report of Alternaria tenuissima Causing Brown Spot Disease of Angelica dahurica in China

Plant Disease ◽

10.1094/pdis-06-21-1240-pdn ◽

2021 ◽

Author(s):

Shipeng Han ◽

Qing Wang ◽

Shuo Zhang ◽

Xi Jin ◽

Zhi Min Hao ◽

...

Keyword(s):

Morphological Characteristics ◽

Brown Spot ◽

Angelica Dahurica ◽

Sterile Water ◽

Single Spore ◽

Transparent Plastic ◽

Alternaria Tenuissima ◽

First Report ◽

Spot Disease ◽

Brown Spot Disease

Angelica dahurica (Fisch. ex Hoffm.) is an abundantly cultivated Chinese herbal medicine plant in China with about 4000 hectares grown, the annual production is up to 24,000 tons. The medicinal part of A. dahurica is its root, and mainly function for treat cold, headache, toothache, rhinitis, diabetes, etc. Besides, A. dahurica is also used as a spice in Asia. In September 2018, brown spot was observed on the leaves of A. dahurica in fields of Anguo City, Hebei Province, China. In the field investigated, the incidence of brown spot disease reached 15%. The infected leaves showed brown spots surrounded with pale yellow edge, resulting in withered of the whole leaf. It seriously endangers the growth of A. dahurica, reducing the yield and quality of medicinal materials, even leading to the death of plants. We isolated the pathogen from 10 leaves with same lesions, the small square leaf pieces of approximately 3 to 5 mm were obtained with the sterile scissors from the junction of infected and healthy tissues, sterilized with sodium hypochlorite (10%) for 1 min followed by washing in sterile water for 3 times, then incubated on potato dextrose agar (PDA) plates at 25°C for 4 days. The culture was transferred to new PDA plates and was cultivated in dark at 25°C for 10 days. A total of 3 species of fungi were isolated, and only one fungus species has been found to be able to cause the original pathological characteristics of A. dahurica leaves through the back-grafting experiment. The mycelium was black and began to sporulate after 8 days on PDA media by single spore separation. Multiple spores joined together to form spores chain. The spores were spindle-shaped, yellow to yellow brown, and size ranged from 45 to 55 × 15 to 20 µm (n=50), with zero to three longitudinal septa and one to five transverse septa. For pathogenicity tests, the spore suspension (3.5×105 spores/mL) were inoculated to healthy plants grown in experimental field, the test was repeated four times, and 10 leaves were inoculated in each repetition, and the sterile water was inoculated as the blank control. Inoculated leaves were covered with transparent plastic bags for 24 h to keep humidity. Nine days later, it was found that there were lesions on the leaves inoculated with the pathogen, and the traits were the same as those in the field, while the controls are healthy. The fungus was consistently isolated from the inoculated leaves. The similar isolates were re-isolated from the inoculated and infected leaves and identified as Alternaria tenuissima by DNA sequencing, fulfilling Koch’s postulates. Fungal genomic DNA was extracted from 7-day-old culture. PCR amplifications were performed using primers ITS1 / ITS4 and TEFF / TEFR respectively (Takahashi et al. 2006, Du 2008). The nucleotide sequence of PCR products, which have been deposited in Genebank under the accession numbers MN153514 and MN735428, showed 99.8%-100% identity with the corresponding sequences of A. tenuissima (MW194297 and MK415954). In order to further identify the pathogen species, we constructed a phylogenetic tree by combining TEF sequence and ITS sequence to distinguish the relationship between the pathogen and other minor species in the genus Alternaria, the isolate was clustered in the Alternaria clade. Therefore, the pathogen was identified as A. tenuissima based on the morphological characteristics and molecular identification. To our knowledge, this is the first report of A. tenuissima causing leaf spot on A. dahurica in China.

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First Report of Reddish-brown Spot Disease on Pitaya Caused by Nigrospora sphaerica in China

Plant Disease ◽

10.1094/pdis-01-16-0063-pdn ◽

2016 ◽

Vol 100 (8) ◽

pp. 1792 ◽

Cited By ~ 3

Author(s):

F. Liu ◽

J.-B. Wu ◽

R.-L. Zhan ◽

X.-C. Ou

Keyword(s):

Brown Spot ◽

First Report ◽

Spot Disease ◽

Brown Spot Disease

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First Report of Myrothecium roridum Causing Brown Spot Disease on Hiemalis begonia in China

Plant Disease ◽

10.1094/pdis-03-15-0337-pdn ◽

2015 ◽

Vol 99 (12) ◽

pp. 1866-1866 ◽

Cited By ~ 1

Author(s):

H.-Y. Ben ◽

H.-Y. Qu ◽

W. Gao

Keyword(s):

Brown Spot ◽

First Report ◽

Spot Disease ◽

Brown Spot Disease ◽

Myrothecium Roridum

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First report of reddish brown spot disease of red-fleshed dragon fruit (Hylocereus polyrhizus) caused by Nigrospora lacticolonia and Nigrospora sphaerica in Malaysia

Crop Protection ◽

10.1016/j.cropro.2019.05.006 ◽

2019 ◽

Vol 122 ◽

pp. 165-170 ◽

Cited By ~ 3

Author(s):

Y.J. Kee ◽

A.B.M. Hafifi ◽

A.R. Huda-Shakirah ◽

K.L. Wong ◽

X.L. Jin ◽

...

Keyword(s):

Brown Spot ◽

First Report ◽

Spot Disease ◽

Brown Spot Disease ◽

Dragon Fruit ◽

Hylocereus Polyrhizus

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First Report of Alternaria tenuissima Causing Brown Spot Disease of Kiwifruit Foliage in China

Plant Disease ◽

10.1094/pdis-07-18-1217-pdn ◽

2019 ◽

Vol 103 (3) ◽

pp. 582-582 ◽

Cited By ~ 4

Author(s):

L. Li ◽

H. Pan ◽

L. Deng ◽

Z. P. Wang ◽

D. W. Li ◽

...

Keyword(s):

Brown Spot ◽

Alternaria Tenuissima ◽

First Report ◽

Spot Disease ◽

Brown Spot Disease

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First Report of Brown Spot Disease Caused by Neoscytalidium dimidiatum on Hylocereus undatus in Guangdong, Chinese Mainland

Plant Disease ◽

10.1094/pdis-07-12-0632-pdn ◽

2012 ◽

Vol 96 (11) ◽

pp. 1702-1702 ◽

Cited By ~ 9

Author(s):

G.-B. Lan ◽

Z.-F. He ◽

P.-G. Xi ◽

Z.-D. Jiang

Keyword(s):

Aerial Mycelium ◽

Chinese Mainland ◽

Brown Spot ◽

Sterile Water ◽

Potato Dextrose Agar Medium ◽

First Report ◽

Spot Disease ◽

Neoscytalidium Dimidiatum ◽

Brown Spot Disease ◽

Hylocereus Undatus

Pitahaya or dragon fruit [Hylocereus undatus (Haw.) Britton & Rose] is one of the most popular tropical fruits in the world. In China, it is widely planted in Guangdong, Guangxi, Hainan, and Taiwan. In July 2011, a new pitahaya disease was found in Conghua City and Yunfu City, Guangdong Province, China, characterized by many small, circular, reddish brown spots over the diseased stems. The spots continuously expanded, and ultimately formed large areas of canker on stems. It is similar to pitahaya stem canker disease caused by Neoscytalidium dimidiatum in Taiwan (1). Pieces of tissues were collected from the lesion margins. After surface disinfestations with 1% sodium hypochloride for 1 min and rinsing in sterile water three times, the diseased tissues were placed on potato dextrose agar medium plates (PDA) and incubated at 28°C for 3 days. A dark, fast-growing fungus was isolated from all samples. For identification, single-spore cultures were grown on PDA in an incubator at 28°C. After 5 days, colonies with dark gray to black aerial mycelium formed. The colonies produced abundant conidia that occurred in arthric chains in aerial mycelium. The conidia were disarticulating, cylindrical-truncate, oblong-obtuse to doliform, dark brown, zero- to one-septate, and averaged 7.56 (5.46 to 10.30) × 6.20 (3.79 to 8.93) μm. The teleomorph was never observed in PDA culture. Based on these characteristics, the fungus was identified as N. dimidiatum (Penz.) Crous & Slippers (2). The internal transcribed spacer (ITS) regions of rDNAs from two isolates were amplified by primers ITS1 and ITS4 (3), and then sequenced. Both sequences were completely identical and 579 bp long (GenBank Accession Nos. JX128103 and JX128104), with 99% identity to that of N. dimidiatum previously deposited (Accession No. HQ439174). To confirm its pathogenicity, six healthy detached stems of pitahaya designed as two replicates were inoculated by injecting 10 μl of conidia suspension (1 × 106 conidia per ml). Three stems were inoculated with sterile water as controls. The inoculated stems were kept in an incubator at 28°C in dark. The stems exhibited the same symptoms as described above after 10 days post inoculation, whereas no symptoms developed on the control stems. The fungus was reisolated from the lesions of the inoculated stem. These results indicated that N. dimidiatum was the pathogen of pitahaya brown spot disease. To our knowledge, this is the first report of brown spot caused by N. dimidiatum on H. undatus on the Chinese mainland. References: (1) M. F. Chuang et al. Plant Dis. 96:906, 2012. (2) P. W. Crous et al. Stud. Mycol. 55:235, 2006. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, New York, 1990.

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