First report of Sarocladium kiliense causing brown rot of Hypsizygus marmoreus in China

Hyjpsizygus marmoreus (Peck) H.E. Bigelow is one of the most popular and widely cultivated edible mushrooms worldwide. In June 2021, an epidemic of H. marmoreus fruiting bodies infected with brown rot occurred at a cultivation facility in Yan’an (Shaanxi province), China, which resulted in a 90% economic loss. The fruiting body surface was covered with white-to-gray velvet-like mycelia, which gradually spread to the pileus, eventually covering the whole fruiting body (Fig. 1A). Brown rot, which is the most important factor limiting H. marmoreus fruiting body yield and quality, is responsible for severe economic losses in northern Shaanxi province. To identify the causal agent of this disease, small pieces of diseased tissue were collected from fruiting bodies, disinfected with 70% ethanol, and rinsed three times with sterile distilled water. They were then placed on potato dextrose agar (PDA) medium in plates and incubated at 26 °C. The colonies on the PDA medium after a 14-day incubation at 26 °C were 40–45 mm in diameter, orange–white on the surface (Fig. 1B), pale orange on the underside (Fig. 1C), slightly wrinkled or cerebriform, and glabrous or fasciculate. Vegetative hyphae were septate, hyaline, smooth, and thin-walled. The unicellular conidia were cylindrical with rounded ends (3.5 to 4.0 × 1.0 to 1.5 μm; n = 30). The cultural and morphological characteristics of the representative isolate MG1 were consistent with those of Sarocladium kiliense (Grütz) Summerbell (Giraldo et al. 2015). For the molecular identification, DNA was extracted from MG1. The internal transcribed spacer (ITS) region, a gene encoding the second largest RNA polymerase II subunit (RPB2), a β-tubulin gene (TUB2), and an actin gene (ACT) were amplified by PCR using primers ITS1/ITS4, fRPB2-5F/fRPB2-7cR, Bt2a/Bt2b, and ACT-512F/ACT-783R, respectively. The resulting ITS (MZ818340), RPB2 (MZ833454), TUB2 (MZ833455), and ACT (MZ833456) sequences from MG1 were 99.82%, 99.19%, 99.69%, and 99.22% identical to the corresponding sequences in S. kiliense isolate CBS 400.52 (ITS: KM231849, RPB2: KM232425, TUB2: KC479789, and ACT1: KM231258). On the basis of the morphological and molecular features, MG1 was identified as S. kiliense (Summerbell et al. 2011; Lombard et al. 2015; Giraldo et al. 2015). Pathogenicity tests, which were repeated three times, were conducted using conidial suspensions (approximately 1 × 105 spores/mL) prepared in sterile distilled water. The surface of 30 healthy H. marmoreus fruiting bodies maintained in a plastic box was sprayed with the MG1 conidial suspensions. Control H. marmoreus fruiting bodies were sprayed with sterile distilled water. The inoculated fruiting bodies were maintained in darkness at 25 °C and 95% relative humidity. The disease symptoms that developed in 3 days included the presence of gray mycelia on the fruiting body surface. Additionally, S. kiliense was reisolated from symptomatic pilei at 6 days post-inoculation. Disease symptoms were undetectable on the negative control. To the best of our knowledge, this is the first report of H. marmoreus infected with brown rot caused by S. kiliense in China.

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First Report of Cladobotryum protrusum causing Cobweb Disease on the Edible Mushroom Coprinus comatus

Plant Disease ◽

10.1094/pdis-07-14-0757-pdn ◽

2015 ◽

Vol 99 (2) ◽

pp. 287-287 ◽

Cited By ~ 6

Author(s):

G. Z. Wang ◽

M. P. Guo ◽

Y. B. Bian

Keyword(s):

Fruiting Body ◽

Morphological Characteristics ◽

Edible Mushroom ◽

Its2 Region ◽

Pathogenicity Test ◽

Distilled Water ◽

Fruiting Bodies ◽

Coprinus Comatus ◽

First Report ◽

Medicinal Value

Coprinus comatus is one of the most commercially important mushrooms in China. Its fruiting body possesses rich nutritional and medicinal value. In November 2013, unusual symptoms were observed on C. comatus on a mushroom farm in Wuhan, Hubei, China. At first, fruiting bodies were covered by white and cobweb-like mycelia. Later, the cap and stipe turned brown or dark before rotting and cracking. The pathogen was isolated from infected tissue of C. comatus. Colonies of the pathogen on potato dextrose agar (PDA) medium first appeared yellowish, followed by an obvious ochraceous or pinkish color. Aerial mycelia grew along the plate wall, cottony, 1 to 4 mm high. Conidiophores were borne on the tops of hyphae, had two to four branches, and were cylindrical, long clavate, or fusiform. Conidia were borne on the tops of the branches of conidiophores, had one to two separates, and were long and clavate. The spores ranged from 15.3 to 22.1 μm long and were 5.1 to 8.3 μm wide, which was consistent with the characteristics of Cladobotryum protrusum (1). The species was identified by ribosomal internal transcribed spacer sequencing. The ribosomal ITS1-5.8S-ITS2 region was amplified from the isolated strain using primers ITS1 and ITS4. A BLAST search in GenBank revealed the highest similarity (99%) to C. protrusum (GenBank Accession Nos. FN859408.1 and FN859413.1). The pathogen was grown on PDA at 25°C for 3 days, and the inoculation suspension was prepared by flooding the agar surface with sterilized double-distilled water for spore suspension (1 × 105 conidia/ml). In one treatment, the suspension was sprayed on casing soil (106 conidia/m2) and mixed thoroughly with it, then cased with treated soil for 2 to 3 cm thickness on the surface of compost in cultivation pots (35 × 25× 12 cm), with sterile distilled water as a control (2). Eight biological replicates were included in this treatment. In the second treatment, mycelia plugs (0.3 × 0.3 cm) without spore production were added to 20 fruiting bodies. Mushrooms treated with blank agar plugs (0.3 × 0.3 cm) were used as a control. The plugs were covered with sterilized cotton balls to avoid loss of moisture. Tested cultivation pots were maintained at 18°C and 85 to 95% relative humidity. In the samples where casing soil was sprayed with conidia suspension, white mildew developed on the pileus, and a young fruiting body grew out from the casing soil. Eventually, the surface of the mushroom was overwhelmed by the mycelia of the pathogen and the pileus turned brown or black. For the other group inoculated with mycelia plugs, only the stipe and pileus inoculated with mycelia turned brown or dark; it rotted and cracked 2 to 3 days later. The symptoms were similar to those observed on the C. comatus cultivation farm. Pathogens re-isolated from pathogenic fruiting bodies were confirmed to be C. protrusum based on morphological characteristics and ITS sequence. To our knowledge, this is the first report of the occurrence of C. protrusum on the edible mushroom C. comatus (3). Based on the pathogenicity test results, C. protrusum has the ability to severely infect the fruiting body of C. comatus. References: (1) K. Põldmaa. Stud. Mycol. 68:1, 2011. (2) F. J. Gea et al. Plant Dis. 96:1067, 2012. (3) W. H. Dong et al. Plant Dis. 97:1507, 2013.

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First report of Coniella castaneicola causing leaf blight on blueberry (Vaccinium virgatum) in China

Plant Disease ◽

10.1094/pdis-05-21-1122-pdn ◽

2021 ◽

Author(s):

Jiahao Lai ◽

Guihong Xiong ◽

Bing Liu ◽

Weigang Kuang ◽

Shuilin Song

Keyword(s):

Molecular Identification ◽

Morphological Characteristics ◽

Leaf Blight ◽

Yield Potential ◽

Effective Control ◽

Economic Losses ◽

Distilled Water ◽

First Report ◽

Fungal Isolates ◽

Blight Disease

Blueberry (Vaccinium virgatum), an economically important small fruit crop, is characterized by its highly nutritive compounds and high content and wide diversity of bioactive compounds (Miller et al. 2019). In September 2020, an unknown leaf blight disease was observed on Rabbiteye blueberry at the Agricultural Science and Technology Park of Jiangxi Agricultural University in Nanchang, China (28°45'51"N, 115°50'52"E). Disease surveys were conducted at that time, the results showed that disease incidence was 90% from a sampled population of 100 plants in the field, and this disease had not been found at other cultivation fields in Nanchang. Leaf blight disease on blueberry caused the leaves to shrivel and curl, or even fall off, which hindered floral bud development and subsequent yield potential. Symptoms of the disease initially appeared as irregular brown spots (1 to 7 mm in diameter) on the leaves, subsequently coalescing to form large irregular taupe lesions (4 to 15 mm in diameter) which became curly. As the disease progressed, irregular grey-brown and blighted lesion ran throughout the leaf lamina from leaf tip to entire leaf sheath and finally caused dieback and even shoot blight. To identify the causal agent, 15 small pieces (5 mm2) of symptomatic leaves were excised from the junction of diseased and healthy tissue, surface-sterilized in 75% ethanol solution for 30 sec and 0.1% mercuric chloride solution for 2 min, rinsed three times with sterile distilled water, and then incubated on potato dextrose agar (PDA) at 28°C for 5-7 days in darkness. Five fungal isolates showing similar morphological characteristics were obtained as pure cultures by single-spore isolation. All fungal colonies on PDA were white with sparse creeping hyphae. Pycnidia were spherical, light brown, and produced numerous conidia. Conidia were 10.60 to 20.12 × 1.98 to 3.11 µm (average 15.27 × 2.52 µm, n = 100), fusiform, sickle-shaped, light brown, without septa. Based on morphological characteristics, the fungal isolates were suspected to be Coniella castaneicola (Cui 2015). To further confirm the identity of this putative pathogen, two representative isolates LGZ2 and LGZ3 were selected for molecular identification. The internal transcribed spacer region (ITS) and large subunit (LSU) were amplified and sequenced using primers ITS1/ITS4 (Peever et al. 2004) and LROR/LR7 (Castlebury and Rossman 2002). The sequences of ITS region (GenBank accession nos. MW672530 and MW856809) showed 100% identity with accessions numbers KF564280 (576/576 bp), MW208111 (544/544 bp), MW208112 (544/544 bp) of C. castaneicola. LSU gene sequences (GenBank accession nos. MW856810 to 11) was 99.85% (1324/1326 bp, 1329/1331 bp) identical to the sequences of C. castaneicola (KY473971, KR232683 to 84). Pathogenicity was tested on three blueberry varieties (‘Rabbiteye’, ‘Double Peak’ and ‘Pink Lemonade’), and four healthy young leaves of a potted blueberry of each variety with and without injury were inoculated with 20 μl suspension of prepared spores (106 conidia/mL) derived from 7-day-old cultures of LGZ2, respectively. In addition, four leaves of each variety with and without injury were sprayed with sterile distilled water as a control, respectively. The experiment was repeated three times, and all plants were incubated in a growth chamber (a 12h light and 12h dark period, 25°C, RH greater than 80%). After 4 days, all the inoculated leaves started showing disease symptoms (large irregular grey-brown lesions) as those observed in the field and there was no difference in severity recorded between the blueberry varieties, whereas the control leaves showed no symptoms. The fungus was reisolated from the inoculated leaves and confirmed as C. castaneicola by morphological and molecular identification, fulfilling Koch’s postulates. To our knowledge, this is the first report of C. castaneicola causing leaf blight on blueberries in China. The discovery of this new disease and the identification of the pathogen will provide useful information for developing effective control strategies, reducing economic losses in blueberry production, and promoting the development of the blueberry industry.

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First Report of Downy Mildew Caused by Plasmopara halstedii on Black-eyed Susan (Rudbeckia fulgida cv. ‘Goldsturm’) in Maryland

Plant Disease ◽

10.1094/pdis-12-13-1242-pdn ◽

2014 ◽

Vol 98 (7) ◽

pp. 1005-1005 ◽

Cited By ~ 3

Author(s):

Y. Rivera ◽

K. Rane ◽

J. A. Crouch

Keyword(s):

Downy Mildew ◽

Leaf Surface ◽

Control Plant ◽

Morphological Data ◽

Economic Losses ◽

Morphological Identification ◽

Post Inoculation ◽

Disease Symptoms ◽

Plasmopara Halstedii ◽

First Report

The North American perennial black-eyed Susan (Rudbeckia fulgida cv. Goldsturm) is an important nursery crop, prized by gardeners and landscapers for its persistent bloom and ease of cultivation. In September 2013, disease symptoms characteristic of downy mildew were observed from multiple R. fulgida plants at two commercial nurseries in the Maryland counties of Howard and Anne Arundel. Over 100 R. fulgida were affected by this disease in both nurseries, rendering the plants unmarketable and causing a substantial financial loss. Plants exhibited dark necrotic lesions on the adaxial leaf surface, and sporulating masses of white mycelium on the abaxial leaf surface and on the adaxial in extreme infections. Plants were stunted with a reduced number of blooms. Microscopic visualization showed coenocytic mycelium, hyaline sporangiophores (length 261 to 904 μm; [Formula: see text] = 557 μm; n = 20) that were straight and monopodially branched at right angles with several terminal branchlets. Sporangia were hyaline, ovoid to elliptical with smooth surfaces ([Formula: see text] = 31 × 28 μm; n = 50). Based on morphological data, the organism was identified as Plasmopara halstedii (Farl.) Berl. & De Toni in Sacc (2). Voucher specimens were deposited in the U.S. National Fungus Collections (BPI 892792 to 892794). Molecular identification was conducted by extracting genomic DNA from sporangiophores and mycelium tweezed from the surface of three infected plants, with extractions performed using the QIAGEN Plant DNA kit (QIAGEN, Gaithersburg, MD). The large subunit of the nuclear rDNA was amplified by PCR using primers LROR and LR7 (3) and sequenced bidirectionally. BLASTn searches of NCBI GenBank showed that the resultant rDNA sequences (accessions KF927152 to KF927154) shared 99% nucleotide identity with curated P. halstedii sequences, consistent with morphological identification. To confirm pathogenicity, three 3.78-liter (1 gallon) containerized R. fulgida cv. Goldsturm plants were inoculated with a sporangial suspension of 2.4 × 104 sporangia/ml and sprayed until both the upper and lower surface of the leaves were completely covered. One negative control plant was sprayed with deionized water. Plants were placed in clear plastic bags in a growth chamber (20°C, 12-h photoperiod). Disease symptoms were observed 3 days post inoculation on all plants. The control plant was symptomless. Morphological features of the pathogen on the surface of inoculated plants were identical to those observed from the original infected plants. Although P. halstedii on R. fulgida cv. Goldsturm has been previously reported in Virginia in 2006 and Florida in 2004, to our knowledge, this is the first report on R. fulgida cv. Goldsturm in Maryland (1). Black-eyed Susans are widely distributed throughout Maryland's landscape and are a staple plant for gardeners, nurserymen and landscape professionals. Given the destructive nature of this disease, downy mildew has the potential to cause considerable economic losses to the state's ornamental crop industry. References: (1) D. F. Farr and A. Y. Rossman. Fungal Databases, Syst. Mycol. Microbiol. Lab., ARS, USDA. Retrieved from http://nt.ars-grin.gov/fungaldatabases/ , November 18, 2013. (2) P. A. Saccardo. Syllogue Fungorum 7:242, 1888. (3) R. Vilgalys and M. Hester. J. Bacteriol. 172:4238, 1990.

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First Report of Sooty Blotch and Flyspeck Caused by Species of Dissoconium, Mycosphaerella, and Peltaster on Hawthorn Fruit in China

Plant Disease ◽

10.1094/pdis-93-6-0670a ◽

2009 ◽

Vol 93 (6) ◽

pp. 670-670 ◽

Cited By ~ 3

Author(s):

H. Y. Li ◽

R. Zhang ◽

G. Y. Sun ◽

M. Tang ◽

M. L. Gleason

Keyword(s):

Apple Fruit ◽

Shaanxi Province ◽

Nuclear Ribosomal Dna ◽

Economic Losses ◽

First Report ◽

Sooty Blotch ◽

Putative Species ◽

Sooty Blotch And Flyspeck ◽

Hawthorn Fruit ◽

Reservoir Hosts

Sooty blotch and flyspeck (SBFS), a disease complex comprised of as many as 30 putative species of fungi, occurs on the cuticle of pome fruits in moist production regions worldwide, inciting cosmetic damage that causes significant economic losses (1). Chinese hawthorn (Crataegus pinnatifida Bge.) is an economically important tree species in China. Its fruit are sold fresh or dried and are used as a culinary spice as well as an ingredient in Chinese traditional medicine. In October of 2007, Chinese hawthorn fruit exhibiting SBFS signs were sampled from supermarkets in Yangling, Shaanxi Province and Luoyang, Henan Province, China. Thalli directly from the hawthorn fruit were transferred onto potato dextrose agar (PDA) slants under a dissecting microscope and cultured at 22 ± 1°C in darkness. DNA was extracted from pure isolates and the internal transcribed spacer (ITS) region of the nuclear ribosomal DNA (nrDNA) was amplified and sequenced using primers ITS-1F and ITS4 (3). Phylogenetic analysis of the ITS sequences revealed that the 35 isolates generated in this study included five species in three genera: Dissoconium sp. (18 isolates), Mycosphaerella sp. (5 isolates), and Peltaster sp. 1 (4 isolates), Peltaster sp. 2 (4 isolates), and Peltaster sp. 3 (4 isolates). To fulfill Koch's postulates and verify that these fungi could also infest apple fruit, two representative isolates of each putative species were inoculated onto mature intact hawthorn and apple (cv. Fuji) fruit that had been surface disinfested with 75% ethanol and allowed to dry. Inoculum was prepared by comminuting 1-month-old cultures growing on PDA into a suspension of mycelial fragments and conidia (105 to ~106 CFU/ml) in a blender with sterile deionized water (SDW). Each isolate was inoculated on three hawthorn and three apple fruit by using cotton swabs. As controls, two surface-disinfested hawthorn and apple fruit were swabbed with SDW. After the inoculated hawthorn and apple fruit had been incubated in a moist chamber at 22 ± 1°C for 1 month, all inoculated hawthorn and apple fruit exhibited SBFS signs similar to those of the original colonies on hawthorn fruit, but the controls did not. Reservoir hosts have been inferred to play an important role in SBFS by providing the fungi with overwintering habitat and inoculum for infestations on apple. Many reservoir hosts have been reported in the United States and Japan (2). To our knowledge, this is the first report of fungi in the SBFS complex on hawthorn fruit and the first confirmation that fungi growing on hawthorn fruit can produce SBFS signs on apple fruit. These results identify hawthorn as a potential inoculum source for SBFS in apple orchards. References: (1) J. C. Batzer et al. Mycologia 97:1283, 2005. (2) K. Hemnani et al. Phytopathology 98(suppl):S66, 2008. (3) T. J. White et al. PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

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First Report of Anthracnose of Sunflower Sprouts Caused by Colletotrichum acutatum in New Mexico

Plant Disease ◽

10.1094/pdis-08-12-0805-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 838-838

Author(s):

J. M. French ◽

J. J. Randall ◽

R. A. Stamler ◽

A. C. Segura ◽

N. P. Goldberg

Keyword(s):

New Mexico ◽

Sequence Analysis ◽

The United States ◽

Disease Diagnosis ◽

Colletotrichum Acutatum ◽

Economic Losses ◽

Distilled Water ◽

Koch’S Postulates ◽

First Report ◽

Koch's Postulates

In December 2011, edible sunflower sprouts (Helianthus annus) of two different commercially grown cultivars (Sungrown and Tiensvold) exhibiting stem and cotyledon lesions were submitted to the New Mexico State University Plant Clinic for disease diagnosis. The sample originated from an organic farm in Santa Fe County where the grower utilizes a small indoor growing facility. Stem lesions were elongate, reddish brown, and often constricted, resulting in stem girdling. Lesions on the cotyledons were dark brown with tan centers and round to irregular in shape. In some cases, the entire cotyledon was blighted. Fungal hyphae were observed on some lesions using a dissecting microscope. Colletotrichum acutatum was isolated from stem and cotyledon lesions when symptomatic tissue was plated on water agar. Conidia were fusiform ranging from 6.4 to 18.4 μm long and 2.1 to 5.1 μm wide and averaged 11.9 μm × 3.4 μm. Spores were measured from cream-colored colonies produced on acidified potato dextrose agar. PCR amplification and sequence analysis of 5.8S ribosomal DNA and internal transcribed spacers I and II was performed using primers ITS4 and ITS6 (2). An amplification product of approximately 600 base pairs in size was directly sequenced (GenBank Accession No. JX444690). A BLAST search of the NCBI total nucleotide collection revealed a 99% identity to multiple C. acutatum (syn: C. simmondsii) isolates. Four isolates were identified as C. acutatum based on morphological characteristics and DNA analysis. Koch's postulates were performed using four isolates of the pathogen and the two commercial sunflower cultivars (Sungrown and Tiensvold) originally submitted for disease analysis. Sunflower seeds were imbibed in distilled water for 24 h then sewn into peat plugs. Prior to seed germination, 5 ml of a C. acutatum spore solution (1 × 106/ml) from each isolate was applied to five peat plugs using an atomizer. Control plants were inoculated with distilled water and otherwise treated identically. Both sunflower cultivars were inoculated with each isolate of the pathogen and the test was replicated twice. The sewn peat plugs were incubated for 5 days at 21°C and 50% relative humidity. Symptoms similar to the original samples were present on 100% of the sprouts after 5 days. PCR and sequence analysis performed on cultures obtained from lesions showed a 100% match to the original New Mexico isolates fulfilling Koch's postulates. In an indoor organic facility, such as the one in NM, this disease has the potential to be very difficult to manage and the potential to infect a high percentage of the crop resulting in significant economic losses. To our knowledge, this is the second report of C. acutatum on sunflower sprouts in the United States (1) and the first report in New Mexico. References: (1) S. T. Koike et al. Plant Dis. 93:1351, 2009. (2) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, San Diego, 1990.

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Cladosporium species associated with disease symptoms on Passiflora edulis and other crops in Brazil, with descriptions of two new species

Phytotaxa ◽

10.11646/phytotaxa.409.5.1 ◽

2019 ◽

Vol 409 (5) ◽

pp. 239-260 ◽

Cited By ~ 2

Author(s):

ANDRÉ W. C. ROSADO ◽

FÁBIO A. CUSTÓDIO ◽

DANILO B. PINHO ◽

ANA PAULA S. FERREIRA ◽

OLINTO L. PEREIRA

Keyword(s):

New Species ◽

Phylogenetic Analyses ◽

Plant Diseases ◽

Economic Losses ◽

Passiflora Edulis ◽

Disease Symptoms ◽

First Report ◽

Leaf Spots ◽

Taxonomic Novelties ◽

Postharvest Rot

Fungi belonging to the genus Cladosporium are cosmopolitan occurring in various substrate or hosts. Cladosporium spp. are responsible for economic losses in numerous agricultural crops, causing leaf spots, scab, postharvest rots and other disease symptoms. The etiology of many diseases associated with these symptoms is still uncertain. The aim of this research was to determine the identity of Cladosporium isolates associated with passionfruit scab and some postharvest rots on different crops in Brazil, based on phylogenetic and morphological analyses. The phylogenetic analyses indicated that all samples belong to the C. cladosporioides complex. Three previously described Cladosporium species were identified: Cladosporium pseudocladosporioides (on kiwi, passionfruit and taro), C. subuliforme (on passionfruit) and C. tenuissimum (on cashew fruit, papaya and passionfruit). In addition, four putative new species were found: Cladosporium passiflorae sp. nov., C. passifloricola sp. nov., Cladosporium sp. 1 and Cladosporium sp. 2, all occurring on passionfruit. This study is the first report of the presence of seven different species of Cladosporium associated with diseased passionfruit. Moreover, this paper represents the first report of C. pseudocladosporioides associated with postharvest rot on kiwi and taro and C. tenuissimum on cashew fruit in Brazil. This study contributes with several taxonomic novelties for the knowledge about the diversity of Cladosporium cladosporioides complex, especially those associated with plant diseases.

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First Report of Fusarium crookwellense Causing Tip Blight on Cones of Hop

Plant Disease ◽

10.1094/pdis.2001.85.11.1208a ◽

2001 ◽

Vol 85 (11) ◽

pp. 1208-1208 ◽

Cited By ~ 3

Author(s):

S. J. Pethybridge ◽

F. S. Hay ◽

C. R. Wilson ◽

L. J. Sherriff ◽

G. W. Leggett

Keyword(s):

Late Summer ◽

Personal Communication ◽

Distilled Water ◽

Conidial Suspension ◽

Koch’S Postulates ◽

Disease Symptoms ◽

First Report ◽

Fusarium Crookwellense ◽

Koch's Postulates ◽

Sydney Australia

Hop (Humulus lupulus L.) is grown primarily for the alpha and beta acids produced in the strobile (cone) and used for bittering beer. In late summer (March) 2001, necrotic lesions covering the tips of cones of cvs. Agate, Nugget, and Willamette at hop farms in Tasmania, Australia, were observed. The necrotic lesions encompassed the proximal tips and affected between 5 and 60% of the cone; however, all bracts in the whorl were always affected. Diseased cones were observed in all seven gardens included in the survey. The incidence of plants with cone tip blight in ‘Nugget’ ranged from 5 to 30% in three gardens, in ‘Agate’ ranged from 3 to 10% in three gardens, and in the only ‘Willamette’ garden 30% of cones were affected. Pieces of infected hop cones (N = 55) were surface-treated for 1 min in 2% sodium hypochlorite, placed on 2% water agar, and incubated at 22 ± 2°C. Fusarium crookwellense Burgess, Nelson, & Toussoun was isolated from 95% of the cones (1). F. crookwellense was identified on carnation leaf agar by L. Burgess, University of Sydney, Australia. Koch's postulates were fulfilled by inoculating detached mature hop cones of cvs. Nugget and Willamette (N = 20 for each cultivar) with an atomized conidial suspension (3.5 × 105 spores of a single F. crookwellense isolate per milliliter) until runoff and incubated at 20 ± 2°C in a sealed container on plastic mesh over tissue wetted with sterile distilled water. Symptoms first appeared 5 days after inoculation and were identical to those found in the field. No disease symptoms were observed on cones subjected only to sterile distilled water. The pathogen was reisolated from diseased tissue on inoculated cones, completing Koch's postulates. Similar disease symptoms on hop cones have been described in Oregon and were associated with infection by F. sambucinum and F. avenaceum (C. Ocamb, personal communication). To our knowledge, this is the first report of the infection of hop cones by F. crookwellense. Reference: (1) L. W. Burgess et al. Laboratory Manual for Fusarium Research, 3rd ed. University of Sydney, Australia, 1994.

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First Report of Fusarium Root and Stem Rot Caused by Fusarium oxysporum f. sp. radicis-cucumerinum on Greenhouse Cucumbers in Saudi Arabia

Plant Disease ◽

10.1094/pdis-01-21-0122-pdn ◽

2021 ◽

Author(s):

Mahmoud H. El-komy ◽

Riyadh M. Al-Qahtani ◽

Arya Widyawan ◽

younes molan ◽

Ali Almasrahi

Keyword(s):

Saudi Arabia ◽

Fusarium Oxysporum ◽

Sandy Loam ◽

Economic Losses ◽

Peat Moss ◽

Post Inoculation ◽

Pathogenicity Test ◽

Distilled Water ◽

Conidial Suspension ◽

First Report

Cucumber (Cucumis sativus L.) is an important vegetable crop in Saudi Arabia. During May 2018, 45 - 60% of 5-month-old cucumber plants showed symptoms of a previously unknown wilt in commercial greenhouses around Al Kharj area of Riyadh region. Symptoms consisted of crown and root rot, wilting and stem disintegration, along with yellowish brown to brown external discoloration extended throughout the affected tissues. As the disease progressed, a pinkish-orange mycelial growth was often observed at the basis of affected stems while vessels were discolored. Subsequently, the affected plants were collapsed and died. Crown, stem, and root fragments (4 × 4 mm) were cut from symptomatic tissues, surface sterilized in 2.5% NaOCl, cultured on potato dextrose agar (PDA) with 25 mg/liter of streptomycin sulfate, and incubated at 26°C in darkness for 6 days. Single-spored cultures produced white mycelium with pink, white, or purple pigmentation in the center. The mycelium produced sporodochia. Macroconidia were mainly slightly curved with three to five septa. Microconidia were single-celled oval and produced on short lateral phialides. Chlamydospores were single or in short chains. Morphologically, the isolated fungus was characterized as Fusarium oxysporum (Leslie and Summerell 2006). To further confirm the fungus identification, DNA was extracted from a single-spored culture. Three different fungal nuclear regions of internal transcribed spacer (ITS), elongation factor 1-α, (TEF1-α) and the second largest subunit of DNA-directed RNA polymerase II (rpb2) with the following primers: ITS4 and ITS5 (White et al. 2017), EF-1 and EF-2 (O’Donnell et al. 2008), and fRPB2-5F and fRPB2-7cR (Liu et al. 1999), respectively. The ITS, TEF1-α, and rpb2 sequences of the isolate FCKSU17 were submitted to GenBank (MT232918, MW471131, and MW449833 respectively). Phylogenetic analysis based on the alignment of the ITS, TEF1-α, and rpb2 sequences using MEGA7 placed this strain in the F. oxysporum clade. To confirm the forma specialis radicis-cucumerinum, amplification with the specific primers ForcF1/ForcR2 was conducted (Lievens et al. 2007). The amplified fragment (∼ 250-bp) was sent for sequencing, and the sequence was submitted to GenBank (MW471132). BLASTn analysis of the sequences showed 100% identity with F. oxysporum radicis-cucumerinum (KP746408). To fulfill Koch’s postulates, pathogenicity test was conducted on 7-day-old plants of cucumber cultivar Beit Alpha grown into pots filled with soil mix (2:1 sandy loam-peat moss, vol/vol). The plants were inoculated through drenching with 100 ml of conidial suspension in sterile distilled water (106 spores/ml) per pot. Control plants were treated with sterile distilled water. Each treatment included 10 replicates (pots), with two plants per pot. The pathogenicity test was repeated once. Cucumber plants inoculated with the fungus showed early wilting symptoms within the first 2 weeks post inoculation. At the 6th week post inoculation, 90 to 100% of the inoculated plants developed typical symptoms. No symptoms were observed on the control plants. The pathogen was successfully re-isolated from the inoculated wilted plants and identified morphologically. To our knowledge, this is the first report of F. oxysporum f.sp. radicis-cucumerinum on cucumber in Saudi Arabia. It is recommended that preventive management should be considered as this disease may cause significant economic losses on cucumbers in Saudi Arabia.

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First report of brown rot of nectarine caused by Monilia yunnanensis in Tibet

Plant Disease ◽

10.1094/pdis-09-20-1884-pdn ◽

2021 ◽

Author(s):

Shuwu Zhang ◽

Dong Xiang ◽

Tong Li ◽

Bingliang Xu

Keyword(s):

New Species ◽

Phylogenetic Trees ◽

Prunus Persica ◽

Brown Rot ◽

Fruit Production ◽

Economic Losses ◽

Morphological Identification ◽

First Report ◽

Rot Disease ◽

A New Species

Brown rot caused by Monilinia spp. is one of the most important diseases of stone fruits. To date, three species of Monilinia have been found to occur on Prunus species worldwide: Monilinia fructicola (G. Winter) Honey, Monilinia fructigena (Aderhold & Ruhland) Honey, and Monilinia laxa (Aderhold & Ruhland) Honey (Zhu et al. 2005; Hu et al. 2011a). While M. fructicola is widespread in the Americas, and parts of Europe and Asia (CABI, 2010), M. laxa and M. fructigena are the primary species causing brown rot of peach in Europe (Bryde et al. 1977). In China, a new species Monilia yunnanensis was identified in 2011 (Hu et al. 2011b; Zhao et al. 2013; Yin et al. 2015; Yin et al. 2017). However, the species causing brown rot of nectarine (Prunus persica var. nectarina) in Tibet have not been undertaken. In the summer of 2017-2018, brown rot disease of nectarine was observed in Nyingchi, Tibet, and approximately 30% of nectarines were affected annually. Therefore, the brown rot disease of nectarine is one of the main factors that restrict the yield and quality of nectarine fruit production, and causes severe economic losses in Tibet. Thirty-six nectarine fruit with typical brown rot symptoms were collected from Tibet during the summer of 2017-2018. In order to isolate the causal agent, small pieces of pericarp were disinfected with 75% ethanol for 1 min, and then for 1 min in 1% NaOCl, rinsed in sterile distilled water for three times, dried on sterile paper and placed on potato dextrose agar (PDA). Thirty-six single-spore isolates were obtained and all morphologically similar, and three representative isolates 2-1, 2-16 and 2-31 which were from different period and years in 2017-2018 were characterized phylogenetically and morphologically to identify them to species level. Pathogenicity of each representative isolate was confirmed by inoculating five surface-disinfected mature nectarines with mycelial plugs in the wound of the fruit. Nectarine fruit inoculated with sterile PDA plugs served as the negative control. The inoculated nectarines developed brown lesions after 6 days incubation at 22°C, and the pathogen was successfully re-isolated. There were no symptoms on the control nectarine fruit. The isolates 2-1, 2-16 and 2-31 produced gray-green colonies with even margins and concentric rings of sporogenous mycelium after 3 days incubation, and abundant black-colored stromata on the media after 16 days of incubation at 22°C, resembling those described for M. yunnanensis (Hu et al. 2011b). Conidia were one-celled, hyaline, ellipsoid to lemon shape (9.24 to 15.58 μm), and borne in branched monilioid chains. The average daily growth of mycelium on PDA at 22°C was 11.56 mm. Therefore, the isolates 2-1, 2-16 and 2-31 were preliminarily identified as M. yunnanensis based on the morphological investigations (Hu et al. 2011b). Morphological identification was confirmed by phylogenetic analysis based on sequences of glyceraldehyde-3-phosphate dehydrogenase (G3PDH) and β-tubulin (TUB2) genes of 2-1, 2-16 and 2-31 which were amplified using primers Mon-G3pdhF/Mon-G3pdhR and Mon-TubF1/Mon-TubR1 (Hu et al. 2011b). In both G3PDH and TUB2 phylogenetic trees, the isolates 2-1, 2-16 and 2-31 formed monophyletic clades within a derived clade with the M. yunnanensis isolates. Additionally, the three isolates were more closely related to M. yunnanensis (HQ908782.1 and HQ908783.1) than to other Monilinia species. Based on morphological and molecular identification, the isolates 2-1, 2-16 and 2-31 were identified as M. yunnanensis. Previously, M. yunnanensis has been reported as a new species causing brown rot of peach in China (Hu et al, 2011b). To our knowledge, this is the first report of M. yunnanensis causing nectarine fruit brown rot in Tibet. These findings suggest that M. yunnanensis is spreading on its principal host plants and causing substantial economic losses in the Tibet fruit production.

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First Report of Asiatic Brown Rot Caused by Monilinia polystroma on Peach in Italy

Plant Disease ◽

10.1094/pdis-05-14-0551-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1585-1585 ◽

Cited By ~ 13

Author(s):

C. Martini ◽

A. Lantos ◽

A. Di Francesco ◽

M. Guidarelli ◽

S. D'Aquino ◽

...

Keyword(s):

Czech Republic ◽

Brown Rot ◽

Fruit Trees ◽

Economic Losses ◽

Its2 Region ◽

Malt Extract ◽

Conidial Suspension ◽

The Czech Republic ◽

First Report ◽

Plant Pathol

Monilinia spp. are well-known pathogens causing brown rot of fruit trees in many fruit production areas worldwide. In Italy, three Monilinia species are particularly significant with regard to fruit trees, causing blossom and twig blight and brown rot in fruits: Monilinia laxa (Aderhold and Ruhland) Honey, M. fructicola (Winter) Honey, and M. fructigena (Aderhold and Ruhland). In 2009, a new species, M. polystroma, was distinguished from M. fructigena based on morphological and molecular characteristics in Europe (3). M. polystroma is not known to occur in Italy and to date has been reported from the Czech Republic (1), Hungary (3), Poland (4), Serbia (5), and Switzerland (2). In July 2013, during a survey for fungal postharvest pathogens, stored peaches (Prunus persica (L.) Batsch) belonging to different cultivars showing brown rot symptoms were observed in the Emilia Romagna and Sardinia regions of Italy. Typical decay spots were circular and brown, tending toward black, and 5% of peaches presented a large number of yellowish or buff-colored stromata and firm decayed tissues, the symptoms originated by M. polystroma. The pathogen was isolated on V8 agar (V8A) and culture plates were incubated at 25°C in darkness for 5 days. A conidial suspension was spread on malt extract agar (MEA) and single spores were selected. M. polystroma colonies grown on potato dexstrose agar (PDA) were yellowish in color. Irregular black stromatal crusts occurred on the edges of the colonies after 10 to 12 days of incubation and on the margin was present sporogenous tissue slightly elevated above the colony surface, color buff/pale luteous (1). The conidia were one-celled, ovoid or limoniform, smooth and hyaline, and 12 to 20 × 8 to 12 μm in distilled water when grown on V8A at 22°C. The ribosomal ITS1-5.8S-ITS2 region was PCR-amplified from genomic DNA obtained from mycelium using primers ITS1 and ITS4. A BLAST search in GenBank revealed the highest similarity (99%) to M. polystroma sequences (GenBank Accession No. GU067539). Pathogenicity was confirmed using surface-sterilized mature ‘Red Heaven’ peaches. The fruits were wounded (2 × 2 × 2 mm) twice with a sterile needle and inoculated with 2-mm plugs of 7-day-old mycelia from fungal colony margins. The sample unit was represented by 10 fruits. Control fruits were inoculated with PDA. After 7 days of incubation at 20°C in plastic containers with high humidity, typical symptoms of brown rot developed on both the wounds of all inoculated fruits, while control fruits remained symptomless. By the 14th day, all fruits had rotted and the yellowish exogenous stromata appeared on the surface of infected peaches. The fungus isolated from inoculated fruit exhibited the same morphological and molecular features of the original isolates; the molecular analysis performed using the primers by Petroczy (3) confirmed the result of the PCR with ITS1 and ITS4 primers. To our knowledge, this is the first report of M. polystroma on peach in Italy. This is relevant because the new pathogen could spread into other European countries that are main peach producers (such as Spain), causing economic losses. Bringing it to the attention of the scientific community allows the arrangement of research studies for assessing potential resistances with a significant impact on disease control management. Further studies are necessary to determine geographic distribution, prevalence, and economic importance of this organism in Italy. References: (1) EPPO Reporting Service. 2011/134: First reports of Monilinia polystroma in Hungary and the Czech Republic. No. 6, 2011. (2) M. Hilber-Bodmer et al. Plant Dis. 96:146, 2012. (3) M. Petroczy and L. Palkovics. Eur. J. Plant Pathol. 125:343, 2009. (4) A. Poniatowska et al. Eur. J. Plant Pathol. 135:855, 2013. (5) M. Vasic et al. Plant Dis. 97:145, 2013.

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