First Report of Rhizoctonia solani AG4 HG-II Infecting Potato Stems in Idaho

The fungus Rhizoctonia solani is the causal agent of stem canker and black scurf of potato (Solanum tuberosum). R. solani is a species complex consisting of 13 anastomosis groups (AGs) designated AG1 to 13 (2, 3). Stems of potato (cv. Russet Norkotah) with brown lesions were recovered from one field in Kimberley, Idaho, in August 2011. Using previously described methods (3), R. solani was recovered from the symptomatic stems and one representative isolate (J15) was selected for further characterization. Sequencing of the rDNA ITS region of isolate J15 was undertaken as previously described (3) and the resulting rDNA ITS sequence (HE667745) was 99% identical to sequences of other AG4 HG-II isolates in GenBank (AF354072 and AF354074). Pathogenicity of the isolate was determined by conducting the following experiment. Mini-tubers of cv. Santé were planted individually in 1-liter pots containing John Innes Number 3 compost (John Innes Manufacturers Association, Reading, UK). Pots were either inoculated with J15, an isolate of AG3-PT (Rs08), or were not inoculated. Each treatment was replicated four times. Inoculum consisted of five 10-mm-diameter potato dextrose agar plugs, fully colonized by the appropriate isolate, placed in the compost approximately 40 mm above each seed tuber. Pots were held in a controlled environment room at 21°C with 50% relative humidity and watered as required. After 21 days, plants were assessed for disease. No symptoms of the disease were present in non-inoculated plants. In the Rs08 (AG3-PT) inoculated plants, all stems displayed large brown lesions and 20% of the stems had been killed. No stem death was observed in J15 (AG4 HG-II) inoculated plants. However, brown lesions were observed in three of the four J15 (AG4 HG-II) inoculated plants. These lesions were less severe than in plants inoculated with the Rs08(AG3-PT) inoculated plants and were present in 40% of the main stems. In the J15 (AG4 HG-II) inoculated pots, R. solani AG4 HG-II was reisolated from the five symptomatic stems, thereby satisfying Koch's postulates. To our knowledge, this is the first report of AG4 HG-II causing disease on potatoes in Idaho. AG4 has been isolated from potato previously from North Dakota, although the subgroup was not identified (1). The only previous report where AG4 HG-II was specifically determined to cause disease on potato was in Finland, but the isolate could not be maintained and Koch's postulates were not completed (3). The present study shows that AG4 HG-II can cause stem disease in potatoes, although disease does not develop as severely or as consistently as for AG3-PT. However, as demonstrated with isolates of AG2-1 and AG5, even mild stem infection can reduce tuber yield by as much as 12% (4). AG4 HG-II is a pathogen of sugar beet in Idaho, which was grown previously in this field. This history may have contributed to high levels of soilborne inoculum required to produce disease on potato. References: (1) N. C. Gudmestad et al. Page 247 in: J. Vos et al. eds. Effects of Crop Rotation on Potato Production in the Temperate Zones. Kluwer, Dordrecht, Netherlands, 1989. (2) M. J. Lehtonen et al. Agric. Food Sci. 18:223, 2009. (3) J. W. Woodhall et al. Plant Pathol. 56:286, 2007. (4) J. W. Woodhall et al. Plant Pathol. 57:897, 2008.

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First Report of a Binucleate Rhizoctonia (AG-A) from Potato Stems Infecting Potatoes and Sugarbeet in the Pacific Northwest

Plant Disease ◽

10.1094/pdis-03-13-0292-pdn ◽

2013 ◽

Vol 97 (12) ◽

pp. 1657-1657 ◽

Cited By ~ 9

Author(s):

T. D. Miles ◽

J. W. Woodhall ◽

L. A. Miles ◽

P. S. Wharton

Keyword(s):

Root Growth ◽

Rhizoctonia Solani ◽

Seed Tuber ◽

Management Strategies ◽

Its Region ◽

Peat Moss ◽

First Report ◽

Binucleate Rhizoctonia ◽

Plant Pathol ◽

Soil Interface

Rhizoctonia solani causes economically important diseases on potatoes and sugarbeet throughout the world (2). R. solani is a species complex of 13 anastomosis groups (AGs) of which R. solani AG3-PT is most commonly associated with potato and AG2-2 and AG4 with sugarbeet. However, several AGs, including AG2-2 and AG4, have been recorded causing potato diseases (2,3). In summer 2012, plants in potato fields in Idaho were sampled for R. solani. Isolations were attempted from symptomatic plants. DNA extracted from the resulting pure Rhizoctonia cultures was screened using a real-time PCR assay for AG3-PT (3). For the isolates that tested negative for AG3-PT, AG was determined by amplifying and sequencing the rDNA internal transcribed spacer (ITS) region using the primers ITS5 (5′-GGAAGTAAAAGTCGTAACAAGG-3′) and ITS4 (5′-TCCTCCGCTTATTGATATGC-3′). The resulting sequences of two isolates (isolates 204 and 206, GenBank Accession No. KC782951) shared 99% identity with other AG-A isolates (AY927358 and AY927356). Koch's postulates were confirmed for isolate 206 by placing five 10-mm plugs, from 10-day-old potato dextrose agar (PDA) cultures, onto the surface of a soil-less potting mix (composed of peat moss, perlite, and sand) of 1-liter pots, where non-inoculated PDA plugs served as a control. Each pot contained a ‘Rosara’ seed tuber or three ungerminated (BETASEED – BTS 27RR10) sugarbeet seeds (n = 5). Pots were incubated in a glasshouse between 18 and 22°C for 1 month and then assessed for disease. For potatoes, a pigmented necrosis was observed at the soil interface in 88% of the stems and plants were stunted relative to the non-inoculated controls. A significant reduction in root growth was observed in 60% of the germinated sugarbeet plants. Control plants of both potatoes and beets were asymptomatic. For reisolation, 1-cm sections were taken from each potato stem and germinated beet plant, surface sterilized, and placed on alkaline water agar. The reisolated fungi were identified using morphology and a subset was confirmed by sequencing. Isolate 206 was successfully recovered from 84% of the potato stems and from 20% of the sugarbeet seedlings. In a similar experiment, 2-month-old potato and sugarbeet plants were inoculated using 50 g of autoclaved barley grains (inoculated with isolate 206) per 1-liter pot. Between 40 and 60% of inoculated plants appeared stunted in both cases. Pigmented necrosis was observed at the soil interface on 45% of the potato stems and reduced root growth was observed in the 50% of the sugarbeet plants. Control plants were asymptomatic. To our knowledge, this is the first report of the binucleate AG-A causing disease in Idaho on potato stems. BNR species have previously been isolated from potato (4) and sugarbeet plants (1). The binucleate Rhizoctonia AG-A caused disease on potato stems and sugarbeet roots and was readily reisolated. Since sugarbeet is commonly grown in rotation with potato in Idaho, such a rotation could increase the risk of soilborne infection to either crop by AG-A. It is known that AGs can differ in fungicide sensitivity (2), and thus a knowledge of which AGs may be present is important when considering disease management strategies. References: (1) C. A. Strausbaugh et al. Can. J. Plant Pathol. 33:210, 2011. (2) L. Tsror. Biology, Epidemiology and Management of Rhizoctonia solani on Potato 158:649, 2010. (3) J. Woodhall et al. Eur. J. Plant Pathol. 136:273, 2013. (4) Y. G. Yang and X. H. Wu. Plant Dis. 97:1246, 2013.

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First Report of Rhizoctonia solani AG2-2IIIB Infecting Potato Stems and Stolons in the United States

Plant Disease ◽

10.1094/pdis-10-11-0899 ◽

2012 ◽

Vol 96 (3) ◽

pp. 460-460 ◽

Cited By ~ 3

Author(s):

J. W. Woodhall ◽

A. R. Belcher ◽

J. C. Peters ◽

W. W. Kirk ◽

P. S. Wharton

Keyword(s):

United States ◽

New York ◽

Sugar Beet ◽

Rhizoctonia Solani ◽

Its Region ◽

Stem Canker ◽

The United States ◽

Potato Disease ◽

First Report ◽

Plant Pathol

Rhizoctonia solani is an important pathogen of potato (Solanum tuberosum) causing qualitative and quantitative losses. It has been associated with black scurf and stem canker. Isolates of the fungus are assigned to one of 13 known anastomosis groups (AGs), of which AG3 is most commonly associated with potato disease (2,4). In August 2011, diseased potato plants originating from Rupert, ID (cv. Western Russet) and Three Rivers, MI (cv. Russet Norkotah) were received for diagnosis. Both samples displayed stem and stolon lesions typically associated with Rhizoctonia stem canker. The presence of R. solani was confirmed through isolation as previously described (4) and the Idaho and Michigan isolates were designated J11 and J8, respectively. AG was determined by sequencing the rDNA internal transcribed spacer (ITS) region using primers ITS5 and ITS4 (3). The resulting sequences of the rDNA ITS region of isolates J8 and J11 (GenBank Accession Nos. HE608839 and HE608840, respectively) were between 97 and 100% identical to that of other AG2-2IIIB isolates present in sequence databases (GenBank Accession Nos. FJ492075 and FJ492170, respectively). Koch's postulates were confirmed for each isolate by carrying out the following protocol. Each isolate was cultured on potato dextrose agar for 14 days. Five 10-mm agar plugs were then placed on top of seed tubers (cv. Maris Piper) in 1-liter pots containing John Innes Number 3 compost (John Innes Manufacturers Association, Reading, UK). Pots were held in a controlled environment room at 18°C with 50% relative humidity and watered as required. After 21 days, plants were removed and assessed for disease. Typical Rhizoctonia stem lesions were observed and R. solani was successfully reisolated from symptomatic material. To our knowledge, this is the first report of AG2-2IIIB causing disease on potatoes in the United States. In the United States, AGs 2-1, 3, 4, 5, and 9 have all been previously implicated in Rhizoctonia potato disease (2). AG2-2IIIB should now also be considered a potato pathogen in the United States. Knowledge of which AG is present is invaluable when considering a disease management strategy. AG2-2IIIB is a causal agent of sugar beet (Beta vulgaris) root rot in Idaho (1). Sugar beet is commonly grown in crop rotation with potato and such a rotation could increase the risk of soilborne infection to either crop by AG2-2IIIB. References: (1) C. A. Strausbaugh et al. Can. J. Plant Pathol. 33:210, 2011. (2) L. Tsror. J. Phytopatol. 158:649, 2010. (3) T. J. White et al. Page 315 in: PCR Protocols: A Guide to Methods and Applications. M. A. Innis et al., eds. Academic Press, Inc., New York, 1990. (4) J. W.Woodhall et al. Plant Pathol. 56:286, 2007.

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First Report of Potato Stem Canker Caused by Rhizoctonia solani AG4 HGII in Gansu Province, China

Plant Disease ◽

10.1094/pdis-09-12-0896-pdn ◽

2013 ◽

Vol 97 (6) ◽

pp. 840-840

Author(s):

Y. G. Yang ◽

X. H. Wu

Keyword(s):

Rhizoctonia Solani ◽

Solanum Tuberosum L ◽

Its Region ◽

Stem Canker ◽

The United States ◽

Gansu Province ◽

Molecular Characteristics ◽

Potato Seed ◽

First Report ◽

Wheat Seeds

Black scurf and stem canker on potato (Solanum tuberosum L.), caused by Rhizoctonia solani, is an important disease throughout the world. Isolates of R. solani AG3 are the principal cause of these diseases on potato (2). In August 2011, at the tuber bulking growth stage, symptoms typically associated stem canker, including dark brown stem lesions, were observed on 20% of potato plants collected from 23 locations (about 2,000 ha) in Gansu Province, northwest China. Stem pieces (each 5 mm long) taken from the margins of the healthy and diseased tissues were surface-disinfected with 0.5% NaOCl for 2 min, rinsed with sterilized water, dried, then placed on potato dextrose agar (PDA) at 25°C in the dark. Twenty-nine fungal isolates taken from single hyphal tips were identified as R. solani based on morphological traits, including mycelium branched at right angles with a septum near the branch and a slight constriction at the branch base. Hyphal cells were determined to be multinucleate (4 to 10 nuclei/cell) when stained with 4′-6-diamidino-2-phenylindole (DAPI). Anastomosis groups were determined by pairing with reference strains (kindly provided by N. Kondo, Hokkaido University, Japan), and three isolates (designed GS-15, GS-24, and GS-25) anastomosed with isolates of R. solani AG4. The internal transcribed spacer (ITS) region of rDNA was amplified from genomic DNA of each of the three isolates with primers ITS1 and ITS4. The resulting sequences (GenBank Accession Nos. JX843818, JX843819, and JX843820) were 100% identical to those of >10 R. solani AG4 HGII isolates (e.g., HQ629873.1; isolate ND13). Therefore, based on the anastomosis assay and molecular characteristics, the three isolates were identified as R. solani AG4 HGII. To determine pathogenicity of the AG4 HGII isolates, potato seed tubers (cv. Favorita) with 3 to 5 mm long sprouts were inoculated with wheat seeds (sterilized by autoclaving twice at 121°C for 1 h with a 24 h interval between autoclavings) colonized with each isolate (1). One sprouted tuber was planted in a sterilized plastic pot (1 liter) with a single colonized wheat seed placed 10 mm above the uppermost sprout tip in a sand/sawdust mixture (1:2 v/v, with dry heat sterilization at 161°C for 4 h before use). Plants were incubated in a glasshouse maintained at 25 to 27°C. The test was performed on 20 plants for each isolate, and the experiment was repeated. After 3 weeks, control plants inoculated with sterilized wheat seeds remained asymptomatic, and no Rhizoctonia spp. were isolated from these plants, whereas all inoculated plants showed symptoms of stem canker. R. solani AG4 HGII was reisolated consistently from symptomatic stems, and the identity of the reisolates confirmed by the morphological and molecular characteristics mentioned above, fulfilling Koch's postulates. Potato stem canker caused by R. solani AG4 HGII was reported previously in the United States (3). To our knowledge, this is the first report of R. solani AG4 HGII causing stem canker on potato in Gansu Province, the main potato-producing area of China. R. solani AG4 HGII can cause sheath blight on corn in China (4), which is commonly grown in rotation with potato. This rotation could increase the risk of soilborne infection to either crop by R. solani AG4 HGII. References: (1) M. J. Lehtonen et al. Plant Pathol. 57:141, 2008. (2) L. Tsror. J. Phytopathol. 158:649, 2010. (3) J. W. Woodhall et al. Plant Dis. 96:1701, 2012. (4) X. Zhou et al. J. Shenyang Agric. Univ. 43:33, 2012.

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Elephant Hide and Growth Cracking on Potato Tubers Caused by Rhizoctonia solani AG3-PT in South Africa

Plant Disease ◽

10.1094/pdis-08-13-0815-pdn ◽

2014 ◽

Vol 98 (4) ◽

pp. 570-570 ◽

Cited By ~ 11

Author(s):

N. Muzhinji ◽

J. W. Woodhall ◽

M. Truter ◽

J. E. van der Waals

Keyword(s):

South Africa ◽

Rhizoctonia Solani ◽

Black Scurf ◽

Free State ◽

Potato Tubers ◽

Streptomyces Species ◽

Koch’S Postulates ◽

Plant Pathol ◽

Barley Grains ◽

Koch's Postulates

Rhizoctonia solani consists of 13 anastomosis groups (AGs) designated AG1 to 13. AG3-PT is considered the predominant AG in potatoes (4) and is associated with quantitative and qualitative yield losses. Qualitative losses are typically associated with the tuber blemish disease, black scurf. However, atypical tuber blemishes such as elephant hide consisting of corky lesions on the tuber surface (2) have also been attributed to Rhizoctonia. Such atypical blemishes are not considered specific to Rhizoctonia, making direct-cause effect estimates difficult (1). Koch's postulates for the elephant hide symptom and R. solani AG3-PT have not been completed. Recently, growth cracking and scab lesions were observed on potato tubers in South Africa and attributed to a new Streptomyces species (3). These lesions and cracks were similar to elephant hide symptoms attributed to R. solani AG3-PT. Therefore, the cause of the elephant hide symptom in South Africa was investigated further. Symptoms of elephant hide and cracking have been observed on tubers from the Eastern Free State, KwaZulu-Natal, Limpopo, Mpumalanga, North-Eastern Cape, Northern Cape, North West, Sandveld, and Western Free State growing regions. In 2012, three samples of potato tubers (cv. BP1) with elephant hide and cracking were selected for analysis. These samples were collected from Clanwilliam in the Sandveld potato growing region. Tubers were surface sterilized with 1% NaOCl; sections of affected tissue were excised and plated onto potato dextrose agar (PDA). Rhizoctonia-like colonies were identified and after further sub-culturing on PDA, three representative isolates (Rh3, Rh4, and Rh6) of R. solani from each sample were obtained. For each isolate, genomic DNA was extracted and the rDNA ITS region sequenced using ITS1-F and ITS4 (2). The resulting sequences (KF234142, KF234143, and KF234144) were at least 98% identical to other AG3-PT sequences on GenBank (JX27814 and KC157664). To confirm Koch's postulates, pathogenicity tests were conducted with the three isolates. PDA plugs of each isolate were added to 10 g of barley grains which were incubated for 14 days until fully colonized. The barley grains were then used to inoculate disease-free mini-tubers (cv. BP1) in 5l pots containing a sand-clay-pine bark mixture (1:1:1 ratio). Potato plants inoculated with sterile barley grains served as controls. Plants were held for 120 days in a greenhouse at 22°C with light for 12 h a day. Incidence of the elephant hide symptom for isolates Rh3, Rh4, and Rh6 was 58%, 33%, and 37.5%, respectively. Growth cracking and black scurf were also observed with each isolate. R. solani AG3-PT was successfully re-isolated from symptomatic tubers, confirming Koch's postulates. This is the first report of R. solani AG3-PT causing elephant hide in potato tubers in South Africa. Elephant hide caused by R. solani AG3-PT has been reported in tubers from France (2) and the United Kingdom (3), but Koch's postulates were not proven. In this study, Koch's postulates were proven for R. solani AG3-PT causing scab or elephant hide symptom and cracking in potato tubers. R. solani AG3-PT should thus be considered in addition to Streptomyces as a cause of this symptom and control strategies should also consider R. solani AG3-PT. References: (1) G. J. Banville et al. Pages 321-330 in: Rhizoctonia Species: Taxonomy, Molecular Biology, Ecology, Pathology and Disease Control, B. Sneh et al., eds. Kluwer Academic Publishers, Dordrecht, The Netherlands, 1996. (2) M. Fiers et al. Eur. J. Plant. Pathol. 128:353, 2010. (3) R. Gouws and A. McLeod. Plant Dis. 96:1223, 2012. (4) J. W. Woodhall et al. Eur. J. Plant. Pathol. 136:273, 2013.

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First Report of Anthracnose on Hymenocallis littoralis Caused by Colletotrichum siamense in China

Plant Disease ◽

10.1094/pdis-02-21-0405-pdn ◽

2021 ◽

Author(s):

Yong Huang ◽

Yue Qin zhang ◽

Han Hu ◽

Nai Feng

Keyword(s):

Its Region ◽

Leaf Spot Disease ◽

Data Sets ◽

Conidial Suspension ◽

Single Spore ◽

Koch’S Postulates ◽

First Report ◽

Medicinal Value ◽

Sterile Needle ◽

Koch's Postulates

Spider lily (Hymenocallis littoralis (Jacq.) Salisb.) is a widely cultivated horticultural plant worldwide and has ornamental and medicinal value. Spider lily plants were seriously affected by a leaf spot disease in the campus of Guangdong Ocean University and gardens in Zhanjiang city in February 2018 with an incidence of 30 to 100%. Affected leaves usually developed small circular purple spots, which enlarged to oval spots and large irregular spots. The spots were brown at the center, deep purple at the border and surrounded by a yellow halo. Diseased cultivars were collected in Zhanjiang city, Gangzhou city in Guangdong province and and Zhangping city in Fujian province. Symptomatic leaf samples were disinfested with 1% NaOCl, and cultured on sucrose agar (PSA) at 28 °C for one week. Ten single-spore isolates were recovered from PSA medium. Colonies developing on PSA were grayish white with a regular border. Conidia were straight, hyaline with rounded ends, 4.3 to 6.1×12.8 to 32.1μm (n = 50 conidia of each isolate). Fungal mycelia were hyaline, septate, and branched. Conidia were born on a long conidiogenous cell, appressoria were oval, 6.7 to 10.7 × 5.2 to 6.2 μm (n=50). The isolates were morphologically identified as Colletotrichum sp. (Weir et al. 2012). Tests of pathogenicity were performed according to Koch's postulates using three isolates. Fresh wounds were made with a sterile needle on the healthy surface of leaves of H. littoralis at the 4- to 6-leaf stage and each leaf was covered with a piece of cotton drenched with 200 μL of conidial suspension (106 conidia/ml) from each isolate. Control seedlings were inoculated identically except sterile water was used to drench the cotton. Inoculated plants were placed in a moisturizing light incubator at 25℃ and 80% humidity under a 12-h light/dark cycle for 20 days and examined daily to monitor disease symptom development. Small round brown spots were observed at the inoculation sites 3 days after the inoculation. The brown spots developed into large brown lesions 5 days after inoculation. There were no symptoms observed in the water-inoculated plants. A Colletotrichum spp. strain based on morphology was consistently reisolated from leaves lesions fulfilling Koch’s postulates. For molecular identification, the internal transcribed spacer (ITS) region of ribosomal DNA, calmodulin (CAL), Tublin (Tub) and Apmat loci of three isolates were amplified using primer pairs of ITS4/ITS5, CL1C/CL2C, T1/T2 and AM-F/AM-R (Sharma et al. 2015). A phylogenetic tree derived from a neighbor-joining analysis of a concatenated alignment of ITS, CAL, Tub and ApMAT sequences was created. The accession numbers of three isolates GZHLCG, ZJHLCG and FJHLCG used in this study were MW553083, MN540457, MN540458 for ITS, MW553087- MW553089 for CL, MW553090-MW553092 for Tub and MW553084-MW553086 for ApMAT. The sequences of the three isolates were aligned with related species of Colletotrichum (Sharma et al. 2015). Analyses based on concatenated data sets of four genes showed that the sequences had high levels of identity to those of the C. siamense strains. According to both morphological and sequence analyses, the H. littoralis pathogen was identified as C. siamense. There is a report of foliar diseases on H. littoralis caused by Colletotrichum sp. (Tan et al., 2009). To our knowledge, this is the first report of anthracnose on H. littoralis caused by C. siamense in China. Identification of the pathogen provide valuable information for diagnosis and controlling this disease in H. littoralis.

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First Report of Rhizoctonia solani Subgroup AG 1-ID Causing Leaf Blight on Durian in Vietnam

Plant Disease ◽

10.1094/pdis-92-4-0648b ◽

2008 ◽

Vol 92 (4) ◽

pp. 648-648 ◽

Cited By ~ 1

Author(s):

T. T. M. Thuan ◽

N. Tho ◽

B. C. Tuyen

Keyword(s):

Rhizoctonia Solani ◽

Sequence Similarity ◽

Its Region ◽

The Philippines ◽

Leaf Blight ◽

First Report ◽

Rdna Its ◽

Durio Zibethinus ◽

Leaf Spots ◽

Irregular Border

During the rainy season in Vietnam, leaf blight disease caused by Rhizoctonia solani often occurs on 3- to 5-year-old durian (Durio zibethinus). Symptoms appear as large, pale brown, blighted lesions with an irregular border. In excessive moisture conditions, yellowish white hyphae appear on the lesions, and the affected leaves turn dark brown and wilt. There are no reports describing the anastomosis groups (AG) and subgroups of Rhizoctonia solani occurring in durian. In June of 2004, two isolates of R. solani were obtained from leaf blight lesions on durian growing in Binh Duong and Dong Nai provinces. The durian isolates were identified as AG 1 based on hyphal anastomosis. In pathogenicity tests, the durian isolates infected cucumber, mung bean, and leaf mustard seedlings grown on water agar in petri dishes. The rDNA-ITS sequence of the durian isolates was determined (GenBank Accession Nos. EF197797 and EF197798) and aligned with those of AG 1-IA, AG 1-IB, AG 1-IC, and AG 1-ID available in the GenBank database. The sequence similarity of the total rDNA-ITS region (including 5.8S) within the durian isolates was 99.9%. The sequence similarity of the durian isolates and AG 1-ID isolates was 99.1 to 100%, but similarity with other AG 1 subgroups was 89.1 to 94.0%. The results suggest that the two Vietnam durian isolates of R. solani are members of AG 1-ID. AG 1-ID has only been reported causing necrotic leaf spots on coffees in the Philippines (1). To our knowledge, this is the first report of R. solani AG 1-ID on durian and the first report of the presence of R. solani AG 1-ID in Vietnam. Reference: (1) A. Priyatmojo et al. Phytopathology 91:1054, 2001.

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First Report of Aerial Blight of Peanut Caused by Rhizoctonia solani AG1-IA in Arkansas

Plant Disease ◽

10.1094/pdis-04-13-0414-pdn ◽

2013 ◽

Vol 97 (12) ◽

pp. 1658-1658 ◽

Cited By ~ 1

Author(s):

T. R. Faske ◽

T. N. Spurlock

Keyword(s):

Rhizoctonia Solani ◽

Fungal Pathogens ◽

Health Management ◽

Disease Incidence ◽

Its Region ◽

First Report ◽

Circular Pattern ◽

Rdna Its ◽

Randolph County ◽

Humidity Chamber

In early September 2012, symptoms similar to aerial blight were observed on runner peanut (cv. Georgia 09B) in a commercial field in Randolph County, Arkansas (3). Leaves within the canopy closest to the soil had water-soaked, gray to green lesions or tan to brown lesions. Localized areas of matted leaves with mycelium occurred on stems and hyphae extended along stems and newly affected leaves. Dark brown spherical sclerotia (1.5 to 4 mm diam.) were produced on the surface of symptomatic peanut tissue (3). Aerial blight symptoms were observed in two peanut fields (~4 to 6 ha) that were furrow irrigated. Symptomatic plants were localized in a single circular pattern (~20 × 25 m) near the lower end of each field with the final disease incidence of less than 5%. Isolations from surface-disinfected leaves on potato dextrose agar consistently yielded light brown to brown colonies with sclerotia typical of Rhizoctonia solani AG1-IA. The fungus was confirmed to be R. solani AG1 by anastomosis reaction (2) with known cultures of AG1-IA isolated from soybean and rice in Arkansas. Sequencing of the rDNA ITS region 5.8s with primers ITS1 and ITS4 (1) supported the identification of the R. solani isolates as AG1-IA. The BLAST search revealed that the sequence had a 96 to 97% maximum sequence identity to several R. solani AG1-IA isolates collected from rice sheaths in China and Arkansas. Eight-week-old peanut plants (cv. Georgia 09B) growing in pots were sprayed until runoff (2 ml/plant) with a solution containing approximately 1 × 105 hyphal fragments/ml. Five inoculated plants were placed in a humidity chamber within a greenhouse where temperatures ranged from 28 to 33°C. After 14 days, water soaked, gray to green or light brown lesions developed on all inoculated plants along with hyphal strands along inoculated sections of the peanut with dark brown sclerotia. None of the plants inoculated with sterile water expressed symptoms. Rhizoctonia solani was consistently reisolated from symptomatic tissue plated on PDA. Inoculations were repeated on peanut cv. Flavor Runner 458, Florida 07, FloRun 107, and Red River Runner with similar results. Although R. solani AG1-IA is a common pathogen on rice and soybean, causing sheath blight and aerial blight, respectively, to our knowledge this is the first report of aerial blight of peanut in the region. Currently, there is a renewed interest in peanut production in the state. Production practices include furrow irrigation, which can distribute floating sclerotia to peanut vines and the rotation practiced with soybean and, less frequently, rice, could potentially increase inoculum for the subsequent crop. Thus, this may be a significant disease problem in the region or Mid-South where peanut is planted after rice or soybean and furrow irrigated. References: (1) S. Kuninaga et al. Curr. Genet. 32:237, 1997. (2) G. C. MacNish et al. Phytopathology 83:922, 1993. (3) H. A. Melouk and P. A. Backman. Management of soilborne fungal pathogens. Pages 75-85 in: Peanut Health Management. H. A. Melouk and F. M. Stokes, eds. The American Phytopathological Society, St. Paul, MN, 1995.

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First Report of Potato Stem Canker Caused by Rhizoctonia solani AG-5 in China

Plant Disease ◽

10.1094/pdis-04-12-0388-pdn ◽

2012 ◽

Vol 96 (10) ◽

pp. 1579-1579 ◽

Cited By ~ 2

Author(s):

Y. Yang ◽

X. Wu

Keyword(s):

Rhizoctonia Solani ◽

Solanum Tuberosum L ◽

Its Region ◽

Stem Canker ◽

Molecular Characteristics ◽

Potato Seed ◽

Canker Disease ◽

First Report ◽

Agric Food ◽

Wheat Seeds

Potato (Solanum tuberosum L.) is grown worldwide as a major food crop. Potato stem canker is an important disease mainly caused by Rhizoctonia solani AG-3 (4). In 2011, samples of potato stem canker were collected from 26 sites in Heilongjiang Province, northeast China. Stem fragments taken from the margins of the healthy and diseased tissues were surface disinfected with 0.5% NaOCl for 2 min, rinsed with sterile water, then placed on potato dextrose agar (PDA) at 25°C in the dark. Twenty-two fungal isolates taken from single hyphal tips were identified as R. solani based on morphological traits. Colonies were light brown with abundant growth of mycelia and produced brown, irregular sclerotia after 20 days on PDA. Mycelium was branched at right angles with a septum near the branch and a slight constriction at the branch base. Hyphal cells were determined to be multinucleate (five to 13 nuclei per cell) when stained with 4′-6-diamidino-2-phenylindole (DAPI). Anastomosis groups were determined by pairing with reference strains (kindly provided by N. Kondo, Hokkaido University, Japan) (1), and six out of 22 isolates anastomosed with R. solani AG-5. The internal transcribed spacer (ITS) region of rDNA was amplified from genomic DNA of the AG-5 isolates with primers ITS1 and ITS4. The ITS sequences (GenBank Accession Nos. JQ946291 to JQ946296) were 99% identical to R. solani isolate AG-5 ND1 (GenBank Accession No. HQ629863). Therefore, based on molecular characteristics and the anastomosis assay, these six isolates were confirmed to be R. solani AG-5. To determine the pathogenicity of R. solani AG-5 isolates, potato seed tubers (cv. Favorita) with 3- to 5-mm sprouts were inoculated with wheat seeds (sterilized by autoclaving twice at 121°C for 1 h with a 24-h interval) colonized with each isolate (2). Wheat seeds were placed 10 mm above the uppermost sprout tip (one seed per sprout). Plants were incubated in glasshouse conditions maintained at 25 to 27°C. After 3 weeks, all inoculated plants showed symptoms of potato stem canker disease, whereas control plants inoculated with sterilized wheat seeds remained healthy. R. solani AG-5 was consistently reisolated from symptomatic stems, and the identity was confirmed by morphological and molecular characteristics as previously described, fulfilling Koch's postulates. Potato stem canker caused by R. solani AG-5 was previously detected in Australia, South Africa, Finland, and Japan (3). However, to our knowledge, this is the first report of R. solani AG-5 on potato in China. Besides previously reported AGs 1, 3, and 4 implicated in Rhizoctonia disease in China, AG 5 should also be taken into account when designing programs for disease management in potato. References: (1) W. C. Kronland and M. E. Stanghellini. Phytopathology 78:820, 1988. (2) M. J. Lehtonen et al. Plant Pathol. 57:141, 2008. (3) M. J. Lehtonen et al. J. Agric. Food Sci. 18:223, 2009. (4) L. Tsror. J. Phytopathol. 158:649, 2010.

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First report of Rhizoctonia solani Kühn AG 2-2 LP in Zoyzia japonica Steud in Brazil

Summa Phytopathologica ◽

10.1590/0100-5405/221916 ◽

2020 ◽

Vol 46 (4) ◽

pp. 289-298

Author(s):

Maria Aurea Saboya Chiaradia Picarelli ◽

Flavia Rodrigues Alves Patricio ◽

Ricardo Harakava ◽

Eliana Borges Rivas ◽

Addolorata Colariccio

Keyword(s):

Rhizoctonia Solani ◽

Mycelial Growth ◽

Its Region ◽

Anastomosis Group ◽

Large Patch ◽

First Report ◽

Rdna Its ◽

Rdna Its Region ◽

Important Disease

ABSTRACT The use of cultivated grasses in Brazil has grown by 40% between 2010 and 2015, and the species Zoysia japonica Steud, especially the cultivar ‘Esmeralda’, corresponds to 81% of the grass market in the country. The most important disease affecting zoysia grass, known as large patch, is caused by Rhizoctonia solani and occurs in the Brazilian lawns particularly during winter months. The aim of this study was to contribute to the identification and characterization of the anastomosis group of R. solani isolates from lesions typical of large patch collected from ‘Esmeralda’ grass at gardens and golf courses in the states of São Paulo and Bahia, Brazil. All 12 obtained isolates presented dark-brown colonies with aerial mycelial growth, multinucleated hyphae and absence of concentric zonation or sclerotia, and showed their greatest mycelial growth rate at 25°C. In pathogenicity experiments, except three out of R. solani isolates, reduced the growth of zoysia grass. Based on the analysis of sequences of the rDNA-ITS region, the isolates clustered with reference isolates of the anastomosis group AG 2-2 LP. Phylogenetic inference showed that the Brazilian isolates are grouped into two clades that shared the same common ancestral with 96% bootstrap. One of the clades includes only Brazilian isolates while the other one also includes American and Japanese R. solani isolates AG 2-2 LP. This is the first report and characterization of R. solani AG 2-2 LP in zoysiagrass in Brazil.

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Identification of Colletotrichum liriopes as the Causative Agent of Anthracnose in Buckwheat (Fagopyrum esculentum) in China

Plant Disease ◽

10.1094/pdis-04-21-0689-pdn ◽

2021 ◽

Author(s):

Taixiang Chen ◽

Tian Wang ◽

Yidan Gou ◽

Lihua Wang ◽

Chunjie Li

Keyword(s):

Disease Incidence ◽

Its Region ◽

Stem Canker ◽

The United States ◽

Fagopyrum Esculentum ◽

Tween 20 ◽

Molecular Characteristics ◽

Agricultural Commodity ◽

Koch’S Postulates ◽

Koch's Postulates

Buckwheat (Fagopyrum esculentum), belonging to the Polygonaceae family, is one of the most important “functional food” crops in China. In fall 2020, buckwheat plants grown in field exhibiting stem canker symptoms were found in Tongxin county, Ningxia province, China. Symptoms included stem canker, dieback and extensive vascular discoloration. Cankers were bleached, silvery-white to dark gray, slightly sunken, oval to linear with slightly tapered tips, pycnidia formation was also observed within the cankers. Disease incidence was approximately 30% and moderate to high severity across the field. Symptomatic tissues were cut into 1-2 cm pieces, surface sterilized (75% ethanol for 30 s and 0.1% NaClO for 2 min) and washed four times with sterile distilled water, dried in sterile filter paper for 3 times, and placed on potato dextrose agar (PDA) at 25 ℃. Fluffy mycelium was visible for all isolates after 48 h of incubation. Twenty-five single isolates were hyphal-tip purified on PDA. Six representative isolates were used for further study. The fungal colonies on PDA were flat with an entire margin, gray aerial hyphae, light brown pigmentation, appressed slimy mycelium within which numerous brown-black perithecia formed. Colonies on oatmeal agar (OA) were flat, with flocculent mycelium, conidiomata and conidia and the reverse side was black to smoke-grey. Sparse brown-black perithecia were observed within the mycelium. Conidia were hyaline, one-celled, smooth-walled, rarely finely verruculose, aseptate, slightly curved, both sides gradually tapering towards the round to slightly acute apex and truncate base, measured (15.7-23.7) µm (length) × (2.8-5.7) µm (width), (avg. 20.2 µm×4.2 µm, n=100). Genomic DNA was extracted from the same six isolates, the internal transcribed spacer (ITS) region and the genes encoding beta-tubulin (TUB), chitin synthase (CHS), glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and histone H3 (HIS3) were independently amplified with primers V9G/ITS4, T1/Bt-2b, CHS-354R/CHS-79F, GDF1/GDR1 and CYLH3F/CYLH3R, respectively (Damm et al., 2019). Sequences for all six isolates were identical. The sequences of the representative isolate 9J1 were deposited in GenBank (accession nos. MW819604, MW836580, MW836577, MW836578 and MW836579). The results of BLASTn showed that the ITS, TUB, CHS, GAPDH and HIS3 sequences of 9J1 were greater than 98% (555/557bp, 477/486bp, 258/259bp, 242/248bp and 339/345bp, respectively) identical to those of Colletotrichum liriopes (GenBank: MT645674 (ITS), GU228098 (TUB), MT663546 (CHS), MH291255 (GAPDH) and MH292811 (HIS3)). MrBayes phylogenetic analysis using concatenated sequences of ITS, TUB, CHS, GAPDH and HIS3 showed that the isolate clustered monophyletically with strains of C. liriopes. Based on morphological and molecular characteristics, the isolate was identified as C. liriopes. To fulfill Koch’s postulates, spores of the isolate 9J1 grown on OA for 14 days were harvested in 0.01% Tween 20, and the suspension were adjusted to 104 spores/ml. Six one-month-old potted plants of buckwheat were inoculated by spraying the spore suspension until run-off. Plants were kept inside a plastic bag for 3 d to maintain high relative humidity and maintained in the greenhouse. Six control plants were sprayed with sterile deionized water and kept under the same conditions. Two weeks after inoculation, all inoculated plants showed stem canker symptoms as described above, whereas control plants remained healthy. The pathogen was successfully reisolated from leaf and stem symptomatic tissue, and identified as C. liriopes based on morphological features and DNA sequence analysis, thereby fulfilling Koch’s postulates. C. liriopes has been reported causing anthracnose on Eria coronaria (Yang et al., 2011), Liriope spicata (Chen et al., 2019) in China, Liriope muscari in Mexico (Damm et al., 2009), Rohdea japonica in Korea (Kwon and Kim, 2013) and in the United States (Trigiano et al., 2018). To our knowledge, this is the first report of C. liriopes causing anthracnose on buckwheat worldwide. Occurrence of this disease may represent a significant impact for buckwheat production because this crop is the major agricultural commodity in some parts of China. More studies are needed to understand the epidemiology of this disease and foster disease management programs in China.

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