First Report of Fusarium culmorum and Microdochium bolleyi Causing Root Rot on Triticale in Kazakhstan

Triticale (×Triticosecale Wittmack) is obtained from wheat × rye crossing. It is positioned between wheat and rye in terms of resistance to soilborne pathogens including Gaeumannomyces graminis var. tritici, Fusarium culmorum, F. avenaceum, and Bipolaris sorokiniana (Arseniuk and Góral 2015). In 2019, seven triticale fields were surveyed in Almaty Province, Kazakhstan to examine soil-borne fungal pathogens. A total of 28 symptomatic plants with stunting, rot or discolored root were collected to identify causal agents. The overall disease incidence was approximately 8 to 10% in the fields. Fungi were isolated from 3-5 mm pieces excised from symptomatic tissues. The pieces were exposed to surface disinfection in 1% sodium hypochlorite solution for 2 min, rinsed three times with sterile distilled water, blotted dry, and plated on 1/5 strength potato dextrose agar (PDA) amended with 0.01% streptomycin. Plates were left in the dark at 23°C for 7 days. A total of 34 fungal colonies were isolated of which nineteen isolates, originally from six fields showed the cultural characteristics of B. sorokiniana. This species was previously reported to cause common root rot on triticale in Kazakhstan (Özer et al. 2020). Ten isolates from four fields produced pale orange and cottony mycelium with red pigmentation on the agar, which is typical of Fusarium-like growth. The remaining isolates (n=5) from two fields produced salmon-colored and scarce aerial mycelium with no soluble pigmentation, similar to Microdochium spp. Fusarium isolates produced thick-walled and curved macroconidia with 3-4 septa (n=50, 25.7 to 37.6 × 4.1 to 7.3 μm in size) and notched basal cell on PDA, but microconidia were absent, which matches the description of F. culmorum (Wm.G. Sm.) Sacc. (Leslie and Summerell 2006). Microdochium isolates produced swollen, brown, and thick-walled chlamydospores and hyaline, one-celled, and thin-walled conidia (n=50, 5.4 to 9.3 × 1.5 to 3.0 μm in size) formed on ampullate and cylindrical conidiogenous cells on oatmeal agar (OA). These morphological features are consistent with previous observations for Microdochium bolleyi (R. Sprague) de Hoog & Herm.-Nijh. (Hong et al. 2008). To confirm morphological preliminary identifications, the portion of the translation elongation factor 1-alpha (EF1-α) gene was amplified with EF1/EF2 primers (O’Donnell et al. 1998) for representative Fusarium isolates (n=4) for each field. Additionally, the internal transcribed spacer (ITS) of ribosomal DNA was amplified with ITS1/ITS4 primers (White et al. 1990) for representative Microdochium isolates (n=2) for each field. BLASTn queries against NCBI GenBank revealed that the EF1-α sequences of Fusarium isolates (MW311081-MW311084) shared 100% identity with F. culmorum strain CBS 110262 (KT008433). The ITS sequences of M. bolleyi isolates (MW301448-MW301449) matched that of M. bolleyi strain CBS 137.64 (AM502264) with 100% sequence similarity. Pathogenicity test was conducted on pregerminated seeds of triticale cv. Balausa. A plastic pot (17 cm height, 9 cm in diam) was filled with a sterile mixture of vermiculite, peat, and soil (1:1:1, v/v/v). Mycelial plugs (1 cm in diam) were cut from the margin of a growing culture of representative isolates (Kaz_Fus123 and Kaz_Mb01) and placed onto the mixture in the pot. A sterile agar plug was employed as a control treatment. One pregerminated seed was put on the plug and covered with the mixture. The pots were transferred to a growth chamber set at 23 ± 2°C and a photoperiod of 14 hours. The experiment was performed twice using 5 replication pots per isolate. Four weeks after inoculation, discoloration of the crown was observed on all the inoculated roots, whereas no symptoms were observed on the control plants. Koch’s postulates were fulfilled by reisolating and identifying the pathogen based on the morphology described above. This is the first report of M. bolleyi and F. culmorum causing root rot on triticale in Kazakhstan. Although B. sorokiniana is the most primary pathogen that may limit yield in the production of triticale in Kazakhstan, F. culmorum and M. bolleyi have been found to be less frequent and less aggressive pathogens, respectively. Further studies are needed to better understand the potential distribution and impact of these pathogens on triticale.

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First Report of Root Rot Caused by Sclerotium rolfsii on Daucus carota var. sativa in Southern Korea

Plant Disease ◽

10.1094/pdis-03-11-0233 ◽

2011 ◽

Vol 95 (12) ◽

pp. 1585-1585

Author(s):

J.-H. Kwon ◽

Y. H. Lee ◽

H.-S. Shim ◽

J. Kim

Keyword(s):

Daucus Carota ◽

Root Rot ◽

Pathogenic Fungus ◽

Sclerotium Rolfsii ◽

Agricultural Science ◽

Control Treatment ◽

Pathogenicity Test ◽

Optimum Temperature ◽

First Report ◽

Causal Fungus

Carrot (Daucus carota var. sativa DC.), an important root vegetable, is cultivated widely because of its dietary fiber and beta carotene. In June 2009 and June 2010, a disease suspected as root rot of carrot caused by Sclerotium rolfsii occurred in a 5-ha field in Jinju, Korea. Early symptoms consisted of water-soaked lesions on root and lower stem tissue near the soil line. Infected plants gradually withered and white mycelial mats appeared on the surface of roots. Numerous sclerotia were often produced on stem and root surfaces in contact with the soil. The heavily infected carrots became rotted and blighted and the whole plant eventually died. The freshly isolated pathogenic fungus was grown on potato dextrose agar (PDA) and examined microscopically. Optimum temperature for mycelia growth or sclerotia formation was 25 to 30°C. Numerous globoid sclerotia formed on the PDA after 18 days of mycelial growth. The sclerotia (1 to 3 mm in diameter) were white at first and then gradually turned dark brown. Aerial mycelia usually formed, consisting of many narrow hyphal strands 3 to 9 μm wide. The white mycelium formed a typical clamp connection after 5 days of growth at optimum temperature. To fulfill Koch's postulates, 10 carrot seedlings were inoculated with colonized agar discs (6 mm in diameter) of the causal fungus directly on the root and incubated in a humid chamber at 25°C for 24 h. Ten carrot seedlings were inoculated similarly with agar discs as the control treatment. After this period, the inoculated and noninoculated plants were maintained in a greenhouse. Eight days after inoculation, the disease symptoms seen in the field were reproduced and the fungus was reisolated from the artificially inoculated plants. To confirm identity of the causal fungus, the complete internal transcribed spacer (ITS) rDNA region of the causal fungus was amplified using the primers ITS1 and ITS4 (2) and sequenced. The resulting sequence of 684 bp was deposited in GenBank (Accession No. JF342557). The sequence was 99% similar to sequences of Athelia rolfsii (Sclerotium rolfsii) in GenBank. Cultures of S. rolfsii have been deposited with the Korean Agricultural Culture Collection (KACC 45154), National Academy of Agricultural Science, Korea. On the basis of symptoms, fungal colonies, the ITS sequence, and the pathogenicity test on the host plant, this fungus was identified as S. rolfsii Saccardo (1). To our knowledge, this is the first report of root rot of carrot caused by S. rolfsii in Korea. This disease is highly dependent upon environmental conditions, including warm weather and high humidity. Recent occurrence of the disease suggests that S. rolfsii could spread widely. References: (1) J. E. M. Mordue. CMI Descriptions of Pathogenic Fungi and Bacteria. No. 410, 1974. (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, Inc., New York, 1990.

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First Report of Leaf Spot Caused by Cladosporium oxysporum on Greenhouse Eggplant in China

Plant Disease ◽

10.1094/pdis-06-13-0606-pdn ◽

2014 ◽

Vol 98 (4) ◽

pp. 566-566 ◽

Cited By ~ 3

Author(s):

C. Zheng ◽

Z.-H. Liu ◽

S.-S. Tang ◽

D. Lu ◽

X.-Y. Huang

Keyword(s):

Leaf Spot ◽

Early Stage ◽

Disease Incidence ◽

Solanum Melongena ◽

Morphological Characteristics ◽

Liaoning Province ◽

Control Treatment ◽

Pathogenicity Test ◽

Potato Dextrose Broth ◽

First Report

Eggplant (Solanum melongena L.) is an important vegetable crop that has significant economic value in northern regions of China, especially in Liaoning Province. In April 2013, a leaf spot was discovered on the eggplant cultivar 706 in ten 1-ha commercial greenhouses in Huludao, Liaoning Province, with 30% of the eggplants infected, resulting in reduced eggplant yield and quality. By July 2013, disease incidence was 35%. Spots were found mainly on the leaves. At the early stage of infection, small, chlorotic spots appeared on leaves and gradually expanded into brown, irregular spots with a diameter of 1 to 7 mm. Dark green mold developed in the spots on both sides of the leaves at high humidity, and the spots led to leaf yellowing and defoliation. Conidiophores in the lesions were straight or slightly flexuous with 1 to 7 septa, brown and smooth, with typical swellings at the junction of septa, and 45 to 670 × 3.0 to 5.3 μm. Conidia were oval or obpyriform with a smooth surface, brown or dark brown, with 0 to 2 septa and 5.5 to 14.8 × 2.5 to 4.0 μm. The pathogen was consistent morphologically with Cladosporium oxysporum (1). To identify the pathogen, leaf pieces (3 to 5 mm2) taken from the edge of lesions so that each leaf section included both infected and healthy leaf tissue, were surface-disinfested in 75% ethanol for 30 s, then transferred to a 0.1% aqueous mercuric chloride solution for 30 to 60 s, and rinsed with sterilized water three times. The sections were cultured on potato dextrose agar (PDA) at 25°C in the dark for 7 days. Three pure cultures were obtained from single spores. The conidia on PDA were oval or obpyriform, and 5.4 to 14.7 × 2.4 to 4.2 μm with 0 to 1 septa, and were smaller than the conidia examined directly from infected eggplant leaves. Two isolates were grown on synthetic nutrient agar (SNA) in slide cultures. The conidiophores on SNA were straight or slightly flexuous with swellings at the junctions of septa. On the grounds of these morphological characteristics, the pathogen was identified as C. oxysporum (1,3). For DNA extraction, cultures were grown in potato dextrose broth and the internal transcribed spacer (ITS) region of ribosomal DNA (rNDA) was amplified using primers ITS1 and ITS4 (2). Sequence analysis showed that the ITS sequences of the two isolates were 99% identical to that of C. oxysporum (GenBank Accession No. EF029816). Two isolates were tested for pathogenicity on eggplant using 1 × 107 conidia/ml in sterilized water atomized onto each of six 7-week-old plants of the cultivar Xi'an Green Eggplant. Sterilized water was applied similarly to another six plants as the control treatment. The plants were incubated at 25°C with 85% relative humidity for 8 to 10 days. After 10 days, light brown, irregular spots were found on inoculated leaves, whereas no symptoms were observed on control plants. The pathogen was re-isolated from lesions on inoculated plants but not from control plants. The re-isolates were confirmed to be C. oxysporum based on morphological characteristics. The pathogenicity test was repeated and the same results obtained. Therefore, the pathogen causing leaf spot on eggplant in these greenhouses was identified as C. oxysporum. This is the first report of C. oxysporum causing leaf spot on greenhouse eggplant in China. C. oxysporum is a known pathogen of pepper and tomato. Additional studies are needed to provide management recommendations for this pathogen on Solanaceae crops. References: (1) K. Bensch et al. Stud. Mycol. 67:1, 2010. (2) Q. Li and G. Wang. Microbiol. Res. 164:233, 2009. (3) W. T. H. Peregrine and K. B. Ahmad. Phytopathol. Pap. 27:1, 1982.

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First Report of Lasiodiplodia crassispora as a Pathogen of Grapevine Trunks in South Africa

Plant Disease ◽

10.1094/pdis-94-8-1063a ◽

2010 ◽

Vol 94 (8) ◽

pp. 1063-1063 ◽

Cited By ~ 10

Author(s):

J. M. van Niekerk ◽

W. Bester ◽

F. Halleen ◽

P. W. Crous ◽

P. H. Fourie

Keyword(s):

South Africa ◽

Control Treatment ◽

Fluorescent Light ◽

Vitis Vinifera L ◽

Ammonium Compound ◽

Pathogenicity Test ◽

Santalum Album ◽

First Report ◽

Agar Plug ◽

Northern Cape

In 2003 and 2004, a survey of grapevine (Vitis vinifera L.) trunk pathogens was conducted in 30 vineyards in the Western and Northern Cape and Limpopo provinces of South Africa. In each vineyard, 20 visually healthy plants were sampled randomly by removing the distal part of one cordon arm. Isolations were made onto potato dextrose agar (PDA) from the internal wood decay symptoms observed in the cordon samples. Seven Botryosphaeriaceae spp. were identified, including Lasiodiplodia crassispora (1). Other Botryosphaeriaceae spp. are known grapevine trunk pathogens (2). Species identity was confirmed by DNA sequence data of the partial translation factor 1-α gene (1) and sequences deposited in GenBank (GU233658 and GU233659). The L. crassispora isolates (CBS 125626 and 125627) were associated with brown internal necrosis, a known symptom of grapevine Botryosphaeriaceae spp. infection (3), in the cordon arms of Ruby Cabernet grapevines occurring in two vineyards in the Northern Cape Province. L. crassispora was described from cankered wood of Santalum album in Western Australia and endophytically from Eucalyptus urophylla in Venezuela (1). Its grapevine pathogen status was determined using both isolates in a repeated pathogenicity test that included three isolates each of Botryosphaeria dothidea and Neofusicoccum australe as positive controls (2), Trichoderma harzianum as a nonpathogen treatment, and an uncolonized agar plug as a negative control. The Botryosphaeriaceae spp. and T. harzianum were plated on PDA and incubated at 25°C for 7 days. Lignified, 6-month-old shoots of grapevine cv. Chardonnay were excised from grapevines with internodes 4 to 6 used for inoculations. Before wounding, shoots were disinfected by submersion for 1 min in a 1 ml/liter solution of a quaternary ammonium compound (Sporekill; ICA International Chemicals (Pty) Ltd, Stellenbosch, South Africa). Twelve shoots were used for each isolate or control treatment. Wounds were made 2 mm deep on the fifth internode of the shoots with a 5-mm flame-sterilized cork borer (2,3). Wounds were inoculated with a pathogen colonized agar plug (5 mm in diameter) or an uncolonized agar plug and then covered with Parafilm (2,3). Inoculated shoots were incubated in the dark in moist chambers for 14 days at 25°C. After incubation, the bark of the shoots was peeled from the area around the wound and the lengths of any resultant lesions were measured under sterile conditions. The inoculum effect was assessed by analysis of variance and Student's t-test. Results showed that significantly (P < 0.0001) longer lesions were caused by L. crassispora (13.36 mm) compared with N. australe (9.27 mm) and B. dothidea (5.28 mm) and also significantly longer than lesions caused by the nonpathogen and negative controls (3.23 and 2.90 mm, respectively). To determine if lesions were caused by inoculated fungi, isolations were made from the tissue at the edges of the lesions by aseptically removing five 0.5 × 1 mm pieces of wood and placing them on PDA dishes amended with 0.04 g/liter of streptomycin sulfate. Dishes were incubated under normal fluorescent light at 25°C for 14 days before identifying isolated fungi based on morphological and cultural characteristics (1). To our knowledge, this is the first report of L. crassispora as a grapevine pathogen. References: (1) T. I. Burgess et al. Mycologia 98:423, 2006. (2) J. M. van Niekerk et al. Mycologia 96:781, 2004. (4) J. M. van Niekerk et al. Phytopathol. Mediterr. 45:S43, 2006.

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First Report of Lasiodiplodia theobromae and L. pseudotheobromae Causing Canker Disease of Sacha Inchi in Hainan, China

Plant Disease ◽

10.1094/pdis-11-20-2507-pdn ◽

2021 ◽

Author(s):

Weiwei Wang ◽

Xiqiang Song

Keyword(s):

Phylogenetic Analysis ◽

Tap Water ◽

Disease Incidence ◽

Gene Bank ◽

Sodium Hypochlorite Solution ◽

Pathogenicity Test ◽

Oilseed Crop ◽

Canker Disease ◽

First Report ◽

Sacha Inchi

Sacha inchi (Plukenetia volubilis L.) belongs to the family Euphorbiaceae. It is a perennial wooden oilseed crop, and also exhibits a good source of polyunsaturated fatty acids, protein and other bioactive compounds, such as tocopherols, carotenes and phytosterols (Chirinos et al. 2013). During 2017-2018 survey, canker disease showing greyish-brown sunken lesions was observed on the branches of sacha inchi in Danzhou campus, Hainan University, China. The disease incidence is less than 5%. However, it can lead to leaf yellowing, wilt, and eventually the whole plant death. In Nov. 2017, twelve branches showing the typical canker symptoms were collected and covered with parafilm at both ends of all samples to prevent desiccation and placed in black plastic bags keeping at 4°C until isolations were made. Samples were rinsed with tap water and dried with paper towels. Fragments, 5mm in length and cut from the junction of diseased and healthy parts of branches, were surface-sterilized with 2% sodium hypochlorite solution for 2 min, rinsed with sterilized distilled water for 5 times, dried by sterilized filter paper, plated on PDA medium amended with 100 μg/mL streptomycin (PDA-str) and incubated in the dark for 4 days at 28°C. Pure cultures of fungal isolates were obtained by transferring mycelial fragments from colony margins onto fresh PDA plates and incubated as described before. The colonies of cultures were initially white, and eventually turned black after 4 days on PDA medium (Fig S1A). The morphology characterization of conidia produced by the isolates was initially hyaline and aseptate (Fig S1B), and a single median septum formed in the mature conidia (Fig S1B). The average size of 50 conidia was 16.39±1.46ⅹ 8.52±0.92μm for J6, and 15.64±1.73ⅹ 8.94±0.86μm for J3. Three genes were used for phylogenetic analysis (Alves et al. 2006). ITS regions and the partial of TUB (β-tubulin gene) were amplified using the primer pairs ITS1 and ITS4 (White et al. 1990), Bt2a and Bt2b (Glass and Donaldson 1995), respectively, and EF1-688F/EF1-1251R for J3 and EF1-728F/EF1-986R for J6 were used to amplify TEF (translation elongation factor 1-alpha) (Alves et al. 2008). The sequences of ITS, TUB and TEF from J3 and J6 were deposited in Gene-Bank (Table S1). The blast searches in Gene-Bank with ITS, TUB and TEF amplified from isolates J3, respectively, revealed 100, 99, and 100% identities with L. pseudotheobromae, and isolate J6 showed 100, 100 and 99% of identity with L. theobromae. The phylogenetic analysis of the combined ITS, TUB and TEF sequences of J3, J6 and 28 reference strains retrieved from Gene-Bank was performed using the program MEGA 6.0 evaluated by 1000 bootstrap replications, and the result was consistent with the conclusion above (Fig S2). With the phylogenic studies supported by morphological characters, J3 was identified as L. pseudotheobromae and J6 was L. theobromae. For the pathogenicity test, J3 and J6 were used to inoculate 4-week-old healthy sacha inchi potted seedlings. One wound about 5 mm in depth per seedling stem was made using a sterile blade. A 5-mm-diameter mycelium plug of each isolate taken from the edge of 4-day-old culture growing on PDA was placed to the freshly wound of each plant stem and the inoculated area was wrapped with Parafilm. Sterile PDA plugs were placed onto the wounds of control seedlings. Nine healthy seedlings were inoculated with each isolate or PDA plugs in a completely randomized design. After inoculation, plants were placed in a greenhouse at room temperature (26 to 30°C, 80% RH) and were irrigated when needed. The experiment was conducted twice. Five days later, black or dark-brown canker lesions formed on the stems of inoculated plants, and expended upward and downward from the inoculation points. Pycnidia produced on the necrotic regions and were used to to observe the morphology of conidia (Fig S3). The fungus L. pseudotheobromae or L. theobromae can be re-isolated from the inoculated plants, but not from the control ones. L. pseudotheobromae was recorded to be collected from dead leaves of P. volubilis in Yunnan Province, China, but did not prove this fungus to be pathogenic (Tennakoon et al. 2016). This is the first report that L. theobromae and L. pseudotheobromae causing stem canker in sacha inchi in Hainan, China. The results pave the way for the development of management strategies for canker disease in sacha inchi.

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First Report of Flyspeck Caused by Zygophiala wisconsinensis on Sweet Persimmon Fruit in Korea

Plant Disease ◽

10.1094/pdis-12-10-0917 ◽

2011 ◽

Vol 95 (5) ◽

pp. 616-616 ◽

Cited By ~ 1

Author(s):

J. Kim ◽

O. Choi ◽

J.-H. Kwon

Keyword(s):

Disease Incidence ◽

Morphological Characteristics ◽

Its Rdna ◽

Control Treatment ◽

Diospyros Kaki ◽

Distilled Water ◽

First Report ◽

Persimmon Fruit ◽

Fungal Isolates ◽

Agar Disc

Sweet persimmon (Diospyros kaki L.), a fruit tree in the Ebenaceae, is cultivated widely in Korea and Japan, the leading producers worldwide (2). Sweet persimmon fruit with flyspeck symptoms were collected from orchards in the Jinju area of Korea in November 2010. The fruit had fungal clusters of black, round to ovoid, sclerotium-like fungal bodies with no visible evidence of a mycelial mat. Orchard inspections revealed that disease incidence ranged from 10 to 20% in the surveyed area (approximately 10 ha) in 2010. Flyspeck symptoms were observed on immature and mature fruit. Sweet persimmon fruit peels with flyspeck symptoms were removed, dried, and individual speck lesions transferred to potato dextrose agar (PDA) and cultured at 22°C in the dark. Fungal isolates were obtained from flyspeck colonies on 10 sweet persimmon fruit harvested from each of three orchards. Fungal isolates that grew from the lesions were identified based on a previous description (1). To confirm identity of the causal fungus, the complete internal transcribed spacer (ITS) rDNA sequence of a representative isolate was amplified and sequenced using primers ITS1 and ITS4 (4). The resulting 552-bp sequence was deposited in GenBank (Accession No. HQ698923). Comparison with ITS rDNA sequences showed 100% similarity with a sequence of Zygophiala wisconsinensis Batzer & Crous (GenBank Accession No. AY598855), which infects apple. To fulfill Koch's postulates, mature, intact sweet persimmon fruit were surface sterilized with 70% ethanol and dried. Three fungal isolates from this study were grown on PDA for 1 month. A colonized agar disc (5 mm in diameter) of each isolate was cut from the advancing margin of a colony with a sterilized cork borer, transferred to a 1.5-ml Eppendorf tube, and ground into a suspension of mycelial fragments and conidia in a blender with 1 ml of sterile, distilled water. The inoculum of each isolate was applied by swabbing a sweet persimmon fruit with the suspension. Three sweet persimmon fruit were inoculated per isolate. Three fruit were inoculated similarly with sterile, distilled water as the control treatment. After 1 month of incubation in a moist chamber at 22°C, the same fungal fruiting symptoms were reproduced as observed in the orchards, and the fungus was reisolated from these symptoms, but not from the control fruit, which were asymptomatic. On the basis of morphological characteristics of the fungal colonies, ITS sequence, and pathogenicity to persimmon fruit, the fungus was identified as Z. wisconsinensis (1). Flyspeck is readily isolated from sweet persimmon fruit in Korea and other sweet persimmon growing regions (3). The exposure of fruit to unusual weather conditions in Korea in recent years, including drought, and low-temperature and low-light situations in late spring, which are favorable for flyspeck, might be associated with an increase in occurrence of flyspeck on sweet persimmon fruit in Korea. To our knowledge, this is the first report of Z. wisconsinensis causing flyspeck on sweet persimmon in Korea. References: (1) J. C. Batzer et al. Mycologia 100:246, 2008. (2) FAOSTAT Database. Retrieved from http://faostat.fao.org/ , 2008. (3) H. Nasu and H. Kunoh. Plant Dis. 71:361, 1987. (4) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, Inc., New York, 1990.

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First report of Anthracnose on Peach Fruit Caused by Colletotrichum siamense in Uruguay

Plant Disease ◽

10.1094/pdis-05-21-0950-pdn ◽

2021 ◽

Author(s):

María Julia Carbone ◽

Victoria Moreira ◽

Pedro Mondino ◽

Sandra Alaniz

Keyword(s):

South Carolina ◽

Prunus Persica ◽

Disease Incidence ◽

Management Strategies ◽

Control Treatment ◽

Fluorescent Light ◽

Peach Fruit ◽

First Report ◽

Anthracnose Disease ◽

Equidistant Points

Peach (Prunus persica L.) is an economically important deciduous fruit crop in Uruguay. Anthracnose caused by species of the genus Colletotrichum is one of the major diseases in peach production, originating significant yield losses in United States (Hu et al. 2015), China (Du et al. 2017), Korea (Lee et al. 2018) and Brazil (Moreira et al. 2020). In February 2017, mature peach fruits cv. Pavia Canario with symptoms resembling anthracnose disease were collected from a commercial orchard located in Rincon del Colorado, Canelones, in the Southern region of Uruguay. Symptoms on peach fruit surface were characterized as circular, sunken, brown to dark-brown lesions ranging from 1 to 5 cm in diameter. Lesions were firm to touch with wrinkled concentric rings. All lesions progressed to the fruit core in a V-shaped pattern. The centers of the lesions were covered by orange conidial masses. Monosporic isolates obtained from the advancing margin of anthracnose lesions were grown on PDA at 25ºC and 12h photoperiod under fluorescent light. The representative isolates DzC1, DzC2 and DzC6 were morphologically and molecularly characterized. Upper surface of colonies varied from white or pale-gray to gray and on the reverse dark-gray with white to pale-gray margins. Conidia were cylindrical, with both ends predominantly rounded or one slightly acute, hyaline and aseptate. The length and width of conidia ranged from 9.5 to 18.9 µm (x ̅=14.1) and from 3.8 to 5.8 µm (x ̅=4.6), respectively. The ACT, βTUB2, GAPDH, APN2, APN2/MAT-IGS, and GAP2-IGS gene regions were amplified and sequenced with primers ACT-512F/ACT-783R (Carbone and Kohn, 1999), BT2Fd/BT4R (Woudenberg et al. 2009), GDF1/GDR1 (Guerber et al. 2003), CgDLR1/ColDLF3, CgDLF6/CgMAT1F2 (Rojas et al. 2010) and GAP1041/GAP-IGS2044 (Vieira et al. 2017) respectively and deposited in the GenBank database (MZ097888 to MZ097905). Multilocus phylogenetic analysis revealed that Uruguayan isolates clustered in a separate and well supported clade with sequences of the ex-type (isolate ICMP 18578) and other C. siamense strains (isolates Coll6, 1092, LF139 and CMM 4248). To confirm pathogenicity, mature and apparently healthy peach fruit cv. Pavia Canario were inoculated with the three representative isolates of C. siamense (six fruit per isolate). Fruit were surface disinfested with 70% ethanol and wounded with a sterile needle at two equidistant points (1 mm diameter x 1 mm deep). Then, fruit were inoculated with 5 µl of a spore suspension (1×106 conidia mL-1) in four inoculation points per fruit (two wounded and two unwounded). Six fruit mock-inoculated with 5 µl sterile water were used as controls. Inoculated fruit were placed in moist chamber and incubated at 25°C during 10 days. Anthracnose lesions appeared at 2 and 4 days after inoculation in wounded and unwounded points, respectively. After 7 days, disease incidence was 100% and 67% for wounded and unwounded fruit, respectively. The control treatment remained symptomless. The pathogens were re-isolated from all lesions and re-identified as C. siamense. C. siamense was previously reported in South Carolina causing anthracnose on peach (Hu et al. 2015). To our knowledge, this is the first report of anthracnose disease on peach caused by C. siamense in Uruguay. Effective management strategies should be implemented to control anthracnose and prevent the spread of this disease to other commercial peach orchards.

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Root and Basal Rot of Leek Caused by Fusarium culmorum in California

Plant Disease ◽

10.1094/pdis.2003.87.5.601c ◽

2003 ◽

Vol 87 (5) ◽

pp. 601-601 ◽

Cited By ~ 3

Author(s):

S. T. Koike ◽

T. R. Gordon ◽

B. J. Aegerter

Keyword(s):

Disease Incidence ◽

Fusarium Species ◽

Fusarium Culmorum ◽

Control Treatment ◽

Fluorescent Light ◽

Allium Porrum ◽

Conidial Suspension ◽

Allium Species ◽

Basal Rot ◽

Field Samples

In 1999 and 2000, greenhouse-grown leek (Allium porrum) transplants produced in coastal California (Monterey County) developed a root and basal rot. Affected roots were initially gray and water soaked in appearance and later became pink, soft, and rotted. Basal plates were also affected, becoming water soaked and rotted. Severely affected transplants grew poorly and had chlorotic older leaves; many of these plants collapsed. Disease incidence varied greatly, though some transplant plantings had more than 50% disease. Similar symptoms were found in commercial, field-planted leek crops in the same region. The problem caused significant economic loss to transplant producers because of the loss of plants and the reduction in quality of surviving infected plants. Isolations from transplant and field samples consistently recovered a Fusarium species from both root and basal plate tissues. Single-spore subcultures were grown on carnation leaf agar and incubated under fluorescent light. All isolates produced abundant macroconidia that were stout, thick walled, and had prominent septa. Foot cells were indistinct to slightly notched. Conidiophores were monophialidic. Microconidia were absent and chlamydospores were present. Colonies on potato dextrose agar produced abundant, dense, white, aerial mycelium. The undersurface of these cultures was carmine red. Based on these features, all isolates were identified as Fusarium culmorum. To confirm the identification, a partial sequence (645 bp) of the translation elongation factor (EF-1α) was obtained for one isolate using primers EF-1 and EF-2 (2). The EF-1α sequence from the leek isolate was identical to that of two F. culmorum isolates in Genbank (Accession Nos. AF212462 and AF212463). The next closest match was F. cerealis, which differed from the leek isolate at six nucleotide positions. To test pathogenicity of the leek isolates of F. culmorum, we prepare inocula of four isolates from transplants and three isolates from field plants. A conidial suspension (1 × 105 conidia/ml) of each isolate was applied to the roots of 3-month-old potted leek (cvs. Autumn Giant, Blauwgroene, and Cisco). For the control treatment, leek plants were treated with water. All plants were maintained in a greenhouse at 25°C. After 1 month, inoculated plants showed foliar and root symptoms similar to those observed on the original samples. F. culmorum was reisolated from these symptomatic plants. Control plants did not develop symptoms. Using the same procedures, the seven isolates were inoculated onto other Allium species, but did not cause any symptoms on shallot (A. cepa var. ascalonicum) or eight cultivars of onion (A. cepa). Two of the seven isolates caused slight root symptoms on garlic (A. sativum). All experiments were conducted two times and the results of both tests were similar. To our knowledge, this is the first report of a root and basal rot of leek in California caused by F. culmorum. The occurrence of this disease on transplants grown in a soilless rooting medium and on raised benches in enclosed greenhouses provides circumstantial evidence that the pathogen could possibly be seedborne. This disease was reported recently in Spain (1). References: (1) J. Armengol et al. Plant Dis. 85:679, 2001. (2) K. O'Donnell et al. Proc. Natl. Acad. Sci. 95:2044, 1998.

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First Report of Phytophthora drechsleri Associated with Stem and Foliar Blight of Gynura bicolor in Taiwan

Plant Disease ◽

10.1094/pdis-12-10-0931 ◽

2011 ◽

Vol 95 (7) ◽

pp. 874-874 ◽

Cited By ~ 1

Author(s):

Y. M. Shen ◽

C. H. Chao ◽

H. L. Liu

Keyword(s):

Disease Incidence ◽

Morphological Characteristics ◽

Hyphal Growth ◽

Pathogenicity Test ◽

Distilled Water ◽

First Report ◽

Foliar Blight ◽

Dual Cultures ◽

Phytophthora Drechsleri ◽

Gynura Bicolor

Gynura bicolor (Roxb. ex Willd.) DC., known as Okinawa spinach or hong-feng-cai, is a commonly consumed vegetable in Asian countries. In May 2010, plants with blight and wilt symptoms were observed in commercial vegetable farms in Changhua, Taiwan. Light brown-to-black blight lesions developed from the top of the stems to the petioles and extended to the base of the leaves. Severely infected plants declined and eventually died. Disease incidence was approximately 20%. Samples of symptomatic tissues were surface sterilized in 0.6% NaOCl and plated on water agar. A Phytophthora sp. was consistently isolated and further plated on 10% unclarified V8 juice agar, with daily radial growths of 7.6, 8.6, 5.7, and 2.4 mm at 25, 30, 35, and 37°C, respectively. Four replicates were measured for each temperature. No hyphal growth was observed at 39°C. Intercalary hyphal swellings and proliferating sporangia were produced in culture plates flooded with sterile distilled water. Sporangia were nonpapillate, obpyriform to ellipsoid, base tapered or rounded, and 43.3 (27.5 to 59.3) × 27.6 (18.5 to 36.3) μm. Clamydospores and oospores were not observed. Oospores were present in dual cultures with an isolate of P. nicotianae (p731) (1) A2 mating type, indicating that the isolate was heterothallic. A portion of the internal transcribed spacer sequence was deposited in GenBank (Accession No. HQ717146). The sequence was 99% identical to that of P. drechsleri SCRP232 (ATCC46724) (3), a type isolate of the species. The pathogen was identified as P. drechsleri Tucker based on temperature growth, morphological characteristics, and ITS sequence homology (3). To evaluate pathogenicity, the isolated P. drechsleri was inoculated on greenhouse-potted G. bicolor plants. Inoculum was obtained by grinding two dishes of the pathogen cultured on potato dextrose agar (PDA) with sterile distilled water in a blender. After filtering through a gauze layer, the filtrate was aliquoted to 240 ml. The inoculum (approximately 180 sporangia/ml) was sprayed on 24 plants of G. bicolor. An equal number of plants treated with sterile PDA processed in the same way served as controls. After 1 week, incubation at an average temperature of 29°C, blight and wilt symptoms similar to those observed in the fields appeared on 12 inoculated plants. The pathogen was reisolated from the lesions of diseased stems and leaves, fulfilling Koch's postulates. The controls remained symptomless. The pathogenicity test was repeated once with similar results. G. bicolor in Taiwan has been recorded to be infected by P. cryptogea (1,2), a species that resembles P. drechsleri. The recorded isolates of P. cryptogea did not have a maximal growth temperature at or above 35°C (1,2), a distinctive characteristic to discriminate between the two species (3). To our knowledge, this is the first report of P. drechsleri being associated with stem and foliar blight of G. bicolor. References: (1) P. J. Ann. Plant Pathol. Bull. 5:146, 1996. (2) H. H. Ho et al. The Genus Phytophthora in Taiwan. Institute of Botany, Academia Sinica, Taipei, 1995. (3) R. Mostowfizadeh-Ghalamfarsa et al. Fungal Biol. 114:325, 2010.

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First Report of Curvularia aeria on Etlingera linguiformis from Nagaland, India

Plant Disease ◽

10.1094/pdis-01-14-0060-pdn ◽

2014 ◽

Vol 98 (11) ◽

pp. 1580-1580 ◽

Cited By ~ 2

Author(s):

C. Kithan ◽

L. Daiho

Keyword(s):

Leaf Surface ◽

Agricultural Research ◽

Disease Incidence ◽

Indian Agricultural Research Institute ◽

Mountain Range ◽

Pathogenicity Test ◽

Distilled Water ◽

Conidial Suspension ◽

First Report ◽

Initial Symptoms

Etlingera linguiformis (Roxb.) R.M.Sm. of Zingiberaceae family is an important indigenous medicinal and aromatic plant of Nagaland, India, that grows well in warm climates with loamy soil rich in humus (1). The plant rhizome has medicinal benefits in treating sore throats, stomachache, rheumatism, and respiratory complaints, while its essential oil is used in perfumery. A severe disease incidence of leaf blight was observed on the foliar portion of E. linguiformis at the Patkai mountain range of northeast India in September 2012. Initial symptoms of the disease are small brown water soaked flecks appearing on the upper leaf surface with diameter ranging from 0.5 to 3 cm, which later coalesced to form dark brown lesions with a well-defined border. Lesions often merged to form large necrotic areas, covering more than 90% of the leaf surface, which contributed to plant death. The disease significantly reduces the number of functional leaves. As disease progresses, stems and rhizomes were also affected, reducing quality and yield. The diseased leaf tissues were surface sterilized with 0.2% sodium hypochlorite for 2 min followed by rinsing in sterile distilled water and transferred into potato dextrose agar (PDA) medium. After 3 days, the growing tips of the mycelium were transferred to PDA slants and incubated at 25 ± 2°C until conidia formation. Fungal colonies on PDA were dark gray to dark brown, usually zonate; stromata regularly and abundantly formed in culture. Conidia were straight to curved, ellipsoidal, 3-septate, rarely 4-septate, middle cells broad and darker than other two end cells, middle septum not median, smooth, 18 to 32 × 8 to 16 μm (mean 25.15 × 12.10 μm). Conidiophores were terminal and lateral on hyphae and stromata, simple or branched, straight or flexuous, often geniculate, septate, pale brown to brown, smooth, and up to 800 μm thick (2,3). Pathogen identification was performed by the Indian Type Culture Collection, Division of Plant Pathology, Indian Agricultural Research Institute, New Delhi (ITCC Accession No. 7895.10). Further molecular identity of the pathogen was confirmed as Curvularia aeria by PCR amplification and sequencing of the internal transcribed spacer (ITS) regions of the ribosomal DNA by using primers ITS4 and ITS5 (4). The sequence was submitted to GenBank (Accession No. MTCC11875). BLAST analysis of the fungal sequence showed 100% nucleotide similarity with Cochliobolus lunatus and Curvularia aeria. Pathogenicity tests were performed by spraying with an aqueous conidial suspension (1 × 106 conidia /ml) on leaves of three healthy Etlingera plants. Three plants sprayed with sterile distilled water served as controls. The first foliar lesions developed on leaves 7 days after inoculation and after 10 to 12 days, 80% of the leaves were severely infected. Control plants remained healthy. The inoculated leaves developed similar blight symptoms to those observed on naturally infected leaves. C. aeria was re-isolated from the inoculated leaves, thus fulfilling Koch's postulates. The pathogenicity test was repeated twice. To our knowledge, this is the first report of the presence of C. aeria on E. linguiformis. References: (1) M. H. Arafat et al. Pharm. J. 16:33, 2013. (2) M. B. Ellis. Dematiaceous Hyphomycetes. CMI, Kew, Surrey, UK, 1971. (3) K. J. Martin and P. T. Rygiewicz. BMC Microbiol. 5:28, 2005. (4) C. V. Suberamanian. Proc. Indian Acad. Sci. 38:27, 1955.

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First Report of Powdery Mildew Caused by Golovinomyces biocellatus on Agastache rugosa in Korea

Plant Disease ◽

10.1094/pdis-03-14-0298-pdn ◽

2014 ◽

Vol 98 (9) ◽

pp. 1278-1278 ◽

Cited By ~ 1

Author(s):

S. E. Cho ◽

J. H. Park ◽

S. H. Hong ◽

I. Y. Choi ◽

H. D. Shin

Keyword(s):

Powdery Mildew ◽

Severe Disease ◽

Morphological Characteristics ◽

Control Measures ◽

Control Treatment ◽

Width Ratio ◽

Korean Isolate ◽

Pathogenicity Test ◽

Agastache Rugosa ◽

First Report

Agastache rugosa (Fisch. & C.A. Mey.) Kuntze, known as Korean mint, is an aromatic plant in the Lamiaceae. It is widely distributed in East Asian countries and is used as a Chinese traditional medicine. In Korea, fresh leaves are commonly added to fish soups and stews (3). In November 2008, several dozen Korean mints plants growing outdoors in Gimhae City, Korea, were found to be severely infected with a powdery mildew. The same symptoms had been observed in Korean mint plots in Busan and Miryang cities from 2008 to 2013. Symptoms first appeared as thin white colonies, which subsequently developed into abundant hyphal growth on stems and both sides of the leaves. Severe disease pressure caused withering and senescence of the leaves. Voucher specimens (n = 5) were deposited in the Korea University Herbarium (KUS). Appressoria on the mycelium were nipple-shaped or nearly absent. Conidiophores were 105 to 188 × 10 to 13 μm and produced 2 to 4 immature conidia in chains with a sinuate outline, followed by 2 to 3 cells. Foot-cells of the conidiophores were straight, cylindrical, slightly constricted at the base, and 37 to 58 μm long. Conidia were hyaline, ellipsoid to barrel-shaped, measured 25 to 40 × 15 to 23 μm (length/width ratio = 1.4 to 2.1), lacked distinct fibrosin bodies, and showed reticulate wrinkling of the outer walls. Primary conidia were obconically rounded at the apex and subtruncate at the base. Germ tubes were produced at the perihilar position of conidia. No chasmothecia were observed. The structures described above were typical of the Oidium subgenus Reticuloidium anamorph of the genus Golovinomyces. The measurements and morphological characteristics were compatible with those of G. biocellatus (Ehrenb.) V.P. Heluta (1). To confirm the identification, molecular analysis of the sequence of the internal transcribed spacer (ITS) region of ribosomal DNA (rDNA) of isolate KUS-F27200 was conducted. The complete ITS rDNA sequence was amplified using primers ITS5 and P3 (4). The resulting 514-bp sequence was deposited in GenBank (Accession No. KJ585415). A GenBank BLAST search of the Korean isolate sequence showed >99% similarity with the ITS sequence of many G. biocellatus isolates on plants in the Lamiaceae (e.g., Accession Nos. AB307669, AB769437, and JQ340358). Pathogenicity was confirmed by gently pressing diseased leaf onto leaves of five healthy, potted Korean mint plants. Five non-inoculated plants served as a control treatment. Inoculated plants developed symptoms after 7 days, whereas the control plants remained symptomless. The fungus present on inoculated plants was identical morphologically to that observed on the original diseased plants. The pathogenicity test was repeated with identical results. A powdery mildew on A. rugosa caused by G. biocellatus was reported from Romania (2). To our knowledge, this is the first report of powdery mildew caused by G. biocellatus on A. rugosa in Korea. The plant is mostly grown using organic farming methods with limited chemical control options. Therefore, alternative control measures should be considered. References: (1) U. Braun and R. T. A. Cook. Taxonomic Manual of the Erysiphales (Powdery Mildews), CBS Biodiversity Series No. 11. CBS, Utrecht, 2012. (2) D. F. Farr and A. Y. Rossman. Fungal Databases. Syst. Mycol. Microbiol. Lab., online publication, USDA ARS, retrieved 17 February 2014. (3) T. H. Kim et al. J. Sci. Food Agric. 81:569, 2001. (4) S. Takamatsu et al. Mycol. Res. 113:117, 2009.

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