First report of Sclerotium rolfsii (=Athelia rolfsii) associated with root rot and leaf spot on clove basil (Ocimum gratissimum L.) in India

Kiwifruits (Actinidia ssp.), known as “King of vitamin C”, have been wildly cultivated. In August 2020, about 15% of A. deliciosa (cv. Xuxiang) and A. macrosperma (rootstock) plants displayed symptoms typical of root rot at a farm in Hefei (117°25′E, 31°86′N), Anhui Province of China (Fig.1 a-b). Symptoms first appeared at the root and stem junction which were covered by cottony white mycelium during warm and humid summer. Then, the infected tissues were rotted, and subsequently the whole plant withered. Tan to brown sclerotia were observed on the basal stem epidermis and soil surface surrounding the stem (Fig.1 c-d). Infected plant tissues and sclerotia were collected for isolating the fungal pathogen. The samples were surface sterilized in 70% alcohol for 30 s, followed by 2% sodium hypochlorite for 3 min, washed five times with sterile double-distilled water (ddH2O), dried, placed on potato dextrose agar, and incubated at 25 °C in the dark. In total, twelve fungal isolates were obtained. The mycelia of all the isolates were white with a fluffy appearance (Fig.1 e). Sclerotia formed after 7 days were initially white (Fig.1 f) and gradually turned to dark brown (Fig.1 g) measuring 0.67 to 2.03 mm in diameter (mean = 1.367 ± 0.16 mm; n = 30). Hyphae were hyaline, septate. Some cells possessed multiple nuclei (Fig.1 h) and clamp connections (Fig.1 i). No spores were observed. For species-level identification, ITS1/ITS4 and EF1-983F/EF1-2218R primers were used to amplify the internal transcribed spacer regions (ITS) and translation elongation factor-1 alpha regions (TEF-1α), respectively (White et al. 1990; Rehner & Buckley 2005). Based on ITS and TEF-1α sequence analyses, all 12 isolates were categorized into two groups, group one including isolates NC-1 and NC-6~10 and group two containing NC-2~5 and NC-11~12. The length of ITS sequences for NC-1 (MW311079) was 684bp and 99% to 100% similar to Athelia rolfsii (MN610007.1, MN258360.1). Similarly, ITS sequences for NC-2 (MW311080) were 99% to 100% similar to A. rolfsii (MH858139.1; MN872304.1). Also, TEF-1α sequences of NC-1 (MW322687) and NC-2 (MW322688) were 96% to 99% similar to sequences of A. rolfsii (MN702794.1, GU187681.1, MN702789.1). Based on morphology and phylogenetic analyses (Fig.1 j&k), the isolates NC-1 and NC-2 were identified as Athelia rolfsii (anamorph Sclerotium rolfsii) (Mordue. 1974; Punja. 1985). To fulfill Koch’s postulates, ten sclerotia of NC-1 were incorporated into the soil near stems of healthy Xuxiang plants (Fig.2 a). Similar treatments were also used for plants of A. macrosperma or A. arguta (Fig.2 g&m). Each control group had the same number of plants (n=3) for inoculating with ddH2O. The plants were kept in an incubator with a relative humidity of 80% and temperature of 28°C with 16/8 hours light/dark photoperiod. After twenty days, the pathogen-inoculated plants developed similar symptoms of root rot observed in the field (Fig.2 b-d, h-j, n-o). Similarly, four days after inoculation with sclerotia, leaves developed water-soaked lesions (Fig.2 e, k&p). No significant difference in pathogenicity was observed between NC-1 and NC-2. Non-inoculated control plants remained disease-free (Fig.2 f, l&q). The pathogenicity experiments were repeated three times. The pathogen was re-isolated from infected tissues and sclerotia, and isolates were confirmed as A. rolfsii by the ITS sequences. A. rolfsii has been reported to cause root rot in kiwifruit in the USA (Raabe. 1988). To our knowledge, this is the first report A. rolfsii causing root rot on kiwifruits in China.

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First report of Athelia rolfsii (Curzi) causing stem and root rot on stevia (Stevia rebaudiana Bertoni) in Ecuador

Journal of Plant Pathology ◽

10.1007/s42161-021-00819-z ◽

2021 ◽

Author(s):

Jefferson Bertin Vélez-Olmedo ◽

Sergio Vélez-Zambrano ◽

Bianca Samay Angelino Bonfim ◽

Edisson Cuenca Cuenca ◽

Susana García ◽

...

Keyword(s):

Root Rot ◽

Stevia Rebaudiana ◽

First Report ◽

Stevia Rebaudiana Bertoni ◽

Athelia Rolfsii

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First report of Athelia rolfsii (Sclerotium rolfsii Sacc.) causing collar rot disease on sunflower in Turkey

Journal of Plant Pathology ◽

10.1007/s42161-020-00512-7 ◽

2020 ◽

Vol 102 (3) ◽

pp. 931-931

Author(s):

Ceren Cer ◽

Ayşe Uysal Morca

Keyword(s):

Sclerotium Rolfsii ◽

Collar Rot ◽

First Report ◽

Athelia Rolfsii ◽

Rot Disease

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First Report of Leaf Spot of Houttuynia cordata Caused by Alternaria alternata in China

Plant Disease ◽

10.1094/pdis-10-10-0724 ◽

2011 ◽

Vol 95 (3) ◽

pp. 359-359

Author(s):

L. Zheng ◽

R. Lv ◽

Q. Li ◽

J. Huang ◽

Y. Wang ◽

...

Keyword(s):

Alternaria Alternata ◽

Leaf Spot ◽

Southern China ◽

Sclerotium Rolfsii ◽

Tween 20 ◽

Herbaceous Plant ◽

Houttuynia Cordata ◽

First Report ◽

Perennial Herbaceous Plant ◽

Pathogenicity Tests

Houttuynia cordata is a perennial herbaceous plant (family Saururaceae) that is native to southern China, Japan, Korea, and Southeast Asia where it grows well in moist to wet soils. It is commonly used as a Chinese herbal medicine and as a vegetable. In North America and Europe it is also used as an ornamental. From September 2007 to November 2009, symptoms of leaf spot were found on H. cordata leaves in Dangyang County, Hubei, China, with the crop area affected estimated to be over 600 ha per year. Rhizome yield was reduced by 20% on average, with up to 70% yield losses in some fields during the autumn growing season. Lesions were initially small, brown, and oval or circular that developed into dark spots and sometimes formed target spots with white centers. These spots enlarged and overlapped, extending until the leaves withered entirely usually within 2 months. A fungus was consistently recovered from symptomatic leaf samples collected in October 2008 or 2009 with an average 90% isolation rate from ~60 leaf pieces that were surface sterilized with 0.1% mercuric chloride solution. Three isolates, HCDY-2, HCDY-3, and HCDY-4, were used to further evaluate characteristics of the pathogen. On potato dextrose agar, all cultures initially developed white colonies and the centers turned gray or brown after 4 days of incubation. Conidiophores were single or fasciculate, straight or knee curved, gray-brown with regular septa, and 42 to 61 × 4 to 5 μm. Conidia were obclavate or ovate, brown, and 26 to 38 × 12 to 20 μm with three to five transverse and one to three longitudinal or oblique septa. The tops of some conidia developed into secondary conidiophores, which were cylindrical, beige, and 5 to 17 × 3 to 5 μm. The pathogen was identified as Alternaria alternata based on descriptions in Simmons (3). Genomic DNA of HCDY-2 was extracted, and the rDNA-internal transcribed spacer sequence showed 99.6% identity to A. alternata (GenBank No. AY513941). Pathogenicity tests were performed with the three isolates by spraying conidial suspensions (1 × 106 conidia/ml) containing 0.1% Tween 20 onto upper and lower surfaces of leaves of 40-day-old 15-cm high plants. There were 20 leaves from five replicate plants for each isolate. Control plants were treated with sterilized water containing 0.1% Tween 20 only. All plants were incubated with a 16-h photoperiod at 25°C and 90% relative humidity in an artificial climate chamber. Five days after inoculation, typical brown spots were observed on all inoculated leaves but no symptoms were seen on water-treated control plants. Koch's postulates were fulfilled by reisolation of A. alternata from diseased leaves. The pathogenicity tests were carried out twice. A survey of the literature revealed only a few fungal diseases associated with H. cordata (1,2,4), including Phyllosticta houttuyniae, Pseudocercospora houttuyniae, Rhizoctonia solani, and Sclerotium rolfsii. Although A. alternata is a cosmopolitan plant pathogen, it has not been reported on any species in the four genera in Saururaceae (Anemopsis, Gymnotheca, Houttuynia, and Saururus) (3). To our knowledge, this is the first report of A. alternata infecting H. cordata worldwide. References: (1) Y. L. Guo and W. X. Zhao. Acta Mycol. Sin. 8:118, 1989. (2) K. Sawada. Spec. Publ. Taiwan Univ. 8:138, 1959. (3) E. G. Simmons. Alternaria: An Identification Manual. The American Phytopathological Society, St. Paul, MN, 2007. (4) Y. Wu et al. J. Changjiang Vegetables (In Chinese) 2:19, 2007.

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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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Morphology, Prevalence and Pathogenicity of Fungi Associated with Diseased Betel Vine (Piper betle L.) in Bangladesh

European Journal of Biology and Biotechnology ◽

10.24018/ejbio.2020.1.6.124 ◽

2020 ◽

Vol 1 (6) ◽

Author(s):

Md. Zakaria Masud ◽

Md. Rafiqul Islam ◽

Abdullah All Imtiaz ◽

Tahsin Labiba ◽

Md. Raziur Rahman Raihan ◽

...

Keyword(s):

Leaf Spot ◽

Root Rot ◽

Sclerotium Rolfsii ◽

Fungal Diseases ◽

Piper Betle ◽

Phytophthora Parasitica ◽

Survey Period ◽

Severity Of Disease ◽

Rot Disease ◽

Leaf Rot

Three different fungal diseases were found prevalent namely leaf spot, leaf rot, and foot and root rot of betel vine at five different upazillas of five districts in Bangladesh. Phytophthora parasitica causing leaf rot, Colletotrichum piperis causing leaf spot, and Sclerotium rolfsii causing foot and root rot have been found. The highest incidence (41.60 per cent) and severity (21.86 per cent) of leaf rot disease were recorded at Mohanpur upazilla during the period of August. Minimum incidence (4.24 per cent) of leaf rot was recorded at Kaligong upazilla while minimum severity (2.83 per cent) was recorded at Gouronadi upazilla. The highest incidence of disease (57.44 per cent) and severity of disease (28.32 per cent) of betel vine leaf spot were recorded at same locations and same period of time as per leaf rot disease. Minimum incidence (8.32 per cent) and severity (2.72 per cent) of disease were recorded at Sitakundo upazilla during the period of May. In August at Gouranadi upazilla, highest incidence of disease (27.80 per cent) was filed in case of betel vine foot and root rot while the lowest incidence (6.00 per cent) of disease was reported at Sitakundo upazilla. Lesion sizes were varied in ranging 1.4-2.3 cm in diameter while isolates collected from Mohanpur showed highest pathogenicity caused by Phytophthora parasitica produced lesion 2.3 cm and lowest pathogenicity was recorded by Sclerotium rolfsii produced lesion 1.4 cm isolates collected from Mirpur and Mohanpur. In respects of locations and survey period, it was revealed that betel vine leaf rot and leaf spot were prevalent in Mohanpur upazilla during the month of August under Rajshahi district, and betel vine foot and root rot in Gouronadi upazilla under Barisal district.

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First report of Southern blight, caused by Athelia rolfsii (syn. Sclerotium rolfsii Sacc.), on Hellebores in North America

Plant Disease ◽

10.1094/pdis-09-21-2004-pdn ◽

2021 ◽

Author(s):

Richard Jones ◽

Frances Perez

Keyword(s):

North America ◽

Fungal Pathogens ◽

Large Subunit ◽

Sclerotium Rolfsii ◽

Australasian Plant ◽

Bacterial Disease ◽

First Report ◽

Southern Blight ◽

Plastic Bags ◽

Athelia Rolfsii

Lenten rose (Hellebores hybridus) is an herbaceous perennial grown in landscapes and valued for early spring flowers and high levels of deer resistance. An additional benefit as a landscape plant comes from the high level of disease resistance, with only three fungal pathogens reported in North America. In August of 2021, a Lenten rose plant within a mature landscape in Silver Spring, MD, USA, (lat 39.116629 long 77.043198) was found with a collapsed canopy and brown stems near the soil line. Small clusters of brown sclerotia-like objects were seen along the stem. Samples of the sclerotia and diseased tissue were dipped in 70 percent ethanol for 15 sec, transferred to 5 percent NaClO for 30 sec, immersed in sterile water for one minute, then plated onto Potato Dextrose Agar. Sclerotia-like objects germinated and white mycelia covered the plates within five days of germination. Hyphae emerged from diseased tissue within two days and also grew rapidly. Cultures from sclerotia-like objects and diseased tissue produced white sclerotia which melanized to brown spherical sclerotia ranging in size from two to four mm. Culture samples (1 cm square) were excised from the culture plates and transferred to the base of three two-year old potted hellebore plants. Control plants had blocks of PDA placed at the base of the plants. Plants were placed in plastic bags for two days to maintain humidity, then maintained at room temperature without plastic bags. Petioles turned brown and collapsed within seven days of inoculation. White, fan-like hyphae were present along with maturing sclerotia. Samples from surface sterilized tissue and sclerotia produced the same culture morphology as the originally isolated cultures. Non-inoculated plants remained healthy, and the pathogen was not isolated from non-inoculated plants. Individual DNA samples were prepared from original cultures and the re-isolated cultures. Molecular identification was performed by amplification of the internal rRNA transcribed spacer region (ITS1/4, White et al. 1990 ), the large subunit rRNA (LSU), and the elongation factor-1A (EF1a). Amplification products were cloned into TOPO-TA pcr4 vector and sequenced (Macrogen USA). Sequences were submitted to GenBank for IT1/4 (OK172559) and LSU (OK172560). Homology to ITS1/4 was found with Athelia rolfsii (MN622806), to LSU with Athelia rolfsii (MT225781) and for EF1a with Athelia rolfsii (MW322687). This is the first report of Athelia rolfsii on Hellebores in North America (Farr, D.F & Rossman, A.Y. Fungal Databases, U.S. National Fungus Collections, ARS, USDA. Retrieved September 10, 2021). This report is unique in that few pathogens are known to infect Hellebores(Taylor et al. 2011) and southern blight is not commonly isolated in landscape plantings at Maryland latitudes. 1. White et al. PCR Protocols: A Guide to Methods and Amplifications. Academic Press, San Diego, 1990 2. Taylor, R.K., Romberg, M.K. & Alexander, B.J.R. A bacterial disease of hellebore caused by Pseudomonas viridiflava in New Zealand. Australasian Plant Dis. Notes 6, 28–29, 2011.

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Southern Sclerotium Root Rot Caused byAthelia rolfsiion Table Beet in New York

Plant Health Progress ◽

10.1094/php-07-18-0037-br ◽

2019 ◽

Vol 20 (1) ◽

pp. 4-6

Author(s):

Sarah J. Pethybridge ◽

Sandeep Sharma ◽

Alex Silva ◽

Carol Bowden ◽

Sean Murphy ◽

...

Keyword(s):

New York ◽

Beta Vulgaris ◽

Root Rot ◽

Sclerotium Rolfsii ◽

Specialty Crops ◽

Soilborne Disease ◽

Athelia Rolfsii

Southern Sclerotium root rot caused by Athelia rolfsii (syn. Sclerotium rolfsii) is a damaging soilborne disease of field and specialty crops. In 2015, 2016, and 2017, wilted plants, root rot, and decay in six table beet (Beta vulgaris spp. vulgaris) fields across New York were observed. In these outbreaks, losses ranged between 5 and 25%. White mycelial mats and golden brown sclerotia (1 to 2 mm diameter) were observed on diseased plants and decayed roots. The objective of this study was to identify the fungus associated with these symptoms and assess pathogenicity in table beet.

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