Sclerotium Rot Research Articles

Biological management of Sclerotium rot of chilli

Sclerotium rot of chilli caused by Sclerotium rolfsii is one of the most devastating soil-borne diseases whichposes a problem for the successful cultivation of the crop. The present field investigation was carried out forthe biological management of Sclerotium rot of chilli during rabi seasons of 2019-20 and 2020-21. It was foundthat all the modules were effective to reduce the incidence of the disease. Among the biological modules, seedtreatment with T. viride + P. fluorescens @ 10.0 g/kg of seed and soil application of T. viride and P. fluorescens @2.5kg/ha and soil application of neem cake @ 5 q/ha + drenching with T. viride and P. fluorescens @10 g/l of watereach twice at 10 days interval starting from 30 DAT was most effective in reducing the incidence of the diseaseby 56.2% and increasing the fruit yield by 66.7% in comparison to untreated control. The treatment also improvedsoil microbial status and achieved the highest plant growth promotion in terms of plant height and leaf numberand maximum B:C ratio of 2.26.

A Rhizobacterium, Streptomyces albulus Z1-04-02, Displays Antifungal Activity against Sclerotium Rot in Mungbean.

Sclerotium rot causes damping-off and stem rot in seedlings and mature mungbeans, which negatively impacts cultivation. The use of a rhizobacterium to control soil-borne diseases is an alternative method to the excess use of synthetic fungicides; therefore, this study aims to screen rhizosphere actinobacteria with fungicidal activities against Sclerotium rolfsii, the pathogen that causes sclerotium rot in mungbeans. Primary screening showed that the Streptomyces sp. isolate Z1-04-02 displayed the highest effectiveness against S. rolfsii in dual culture plates, with a percentage inhibition of 74.28%. An assay containing enzymes that degrade cell walls, of the cell-free culture filtrate (CF) of Z1-04-02, showed that the activities of chitinase and β-1,3-glucanase were 0.0209 and 1.0210 U/mL, respectively, which was significantly higher than that of the control (media alone). The cell-free CF of Z1-04-02, incubated at 37 °C and 100 °C, using agar well diffusion, effectively inhibited the growth of S. rolfsii with inhibition percentages of 37.78% and 27.78%, respectively. Solid-phase microextraction (SPME) was applied to trap volatiles released from Z1-04-02 and gas chromatography–mass spectrometry (GC/MS); volatile antifungal compounds were tentatively identified as bicyclic monoterpene (1R)-(-)-myrtenal. The application of the cell-free CF, and the spore suspension of Z1-04-02, showed disease severity indexes (DSIs) of 12.5% and 8.25%, respectively, which were significantly lower than those showing inoculation by S. rolfsii alone. The identification of this strain by morphology, biochemistry tests, and 16s rDNA sequences revealed that Z1-04-02 was Streptomyces albulus. This finding revealed that S. albulus Z1-04-02 displayed diverse fungicidal activities against S. rolfsii, and it has the potential to act as a biological control agent in terms of inhibiting sclerotium rot in mungbeans.

First report of sclerotium rot in sword bean caused by Athelia rolfsii

In 2018, sclerotium rot was observed in sword beans (Canavalia gladiata DC.) grown in a field at Gyeongsangnam-do Agricultural Research and Extension Services. The disease mainly affected the stems and pods of sword beans that touched the ground. The stems that touched the ground were water-soaked at the start of the infection and rotted, slowly withered, and eventually died. White mycelia spread across the lesions, and numerous sclerotia formed on the petiole near the soil line. The sclerotia were globoid, 1–3 mm in diameter, and white to brown in color. Hyphae on PDA were 4–8 μm wide, and clamp connections were observed. Pathogenicity of isolated fungus on sword beans was confirmed according to Koch’s postulates. For molecular identification, we sequenced the entire ITS rDNA sequence of the causative fungus and analyzed its phylogenetic relationships. The fungi isolated from sword beans were in a clade r-1 containing the reference strains of A. rolfsii and S. delphinii. The 540-bp PCR amplicons corresponding to A. rolfsii-specific amplification were produced in all three isolates. Mycological characteristics, ITS rDNA sequencing, the species-specific PCR analysis, and pathogenicity in the host plant identified this fungus as Athelia rolfsii (Curzi) C.C. Tu & Kimbr. This is the first report of sclerotium rot on sword bean caused by A. rolfsii.

Vermicompost in combination with Trichoderma asperellum isolate T13 as bioagent to control sclerotium rot disease on vegetable soybean seedlings

Vermicompost in combination with Trichoderma asperellum isolate T13 as bioagent to control sclerotium rot disease on vegetable soybean seedlings

Incidence and severity of major fungal diseases on tomato in three districts within the forest and forest-savannah agro-ecological zones of Ghana

This study was initiated to determine the incidence and severity of fungal diseases of tomatoes and document farmers’ knowledge of these diseases and their control measures in Offinso North, Techiman North and Asante Akim North Districts within the forest and forest-savannah agro-ecological zones of Ghana. A survey was conducted in three selected communities in each district to document the incidence and severity of fungal diseases of tomato and also farmers’ knowledge of fungal diseases of tomato and control practices adopted on their farms using a well-structured questionnaire. Early blight, Septoria leaf spot, Fusarium wilt, Crown rot and Sclerotium rot were the major fungal diseases identified in the study. The mean incidence of diseases recorded for the districts was low with the exception of early blight with an incidence of 63.9% at Asante Akim North District. Though the mean fungal disease severities in the three districts were also low, the highest score was recorded by early blight and fusarium wilt in the Asante Akim North District and fusarium wilt and sclerotium rot in the Offinso North District. In general, farmers had perceived knowledge of the tomato diseases because of losses that these diseases caused, but their knowledge on control was poor.

Antifungal effect of some plant extracts and their combination with Moncut fungicide on sugar beet root rot

Sugar beet (Beta vulgaris L. Chenopodiaceae) has become the first Egyptian crop for sugar production because it contributed with 59.5% of total sugar production. Sclerotium rolfsii is a soil-borne plant pathogenic fungi incident of southern sclerotium rot in sugar beet. The aim of the present study was to investigate the effect of some plant extracts in different solvents as inhibitory control agents against the growth plant pathogen S. rolfsii. Five plant extracts; Roselle, pomegranate, rosemary, black pepper and chamomile were evaluated as inhibitors for Sclerotium rolfsii of sugar beet root rot under laboratory and greenhouse conditions during 2016/2017 growing season at Gemmeiza Agricultural Research Station, (ARC). The results indicated that all tested plant extracts caused remarkable growth inhibition of S. rolfsii compared with control. However, black pepper extract was the most effective against S. rolfsii (recorded 93.33% inhibition). On the other hand, Pomegranate extract in methanol solvent showed also high inhibition percentage (93.30%). All plant extracts mixed with Moncut fungicides demonstrated an antagonistic effect. The pomegranate and black pepper treatments showed the lowest disease severity compared with control. Furthermore, the pomegranate and black paper treatments recorded the highest root weight, root yield/plot, total soluble solids percentage and sucrose content. Also, pomegranate and black pepper treatments reflected the highest amount of total phenols, free phenols, and conjugated phenols. Additionally, the interaction of pomegranate and black pepper treatments with S. rolfsii pathogen, showed the highest activity of oxidative enzymes peroxidase and polyphenol oxidase. This study recommends the application of pomegranate and black pepper as natural alternative fungicides against Sclerotium rolfsii plant infection.

Economical important phytopathogenic diseases in Vanilla planifolia: A review paper.

The vanilla orchid is one of the high value and most favorite culinary crops in the world. The aroma or flavor of vanillin make the plant as an important economic crop in the food and beverage industry. Nevertheless, the production of vanilla is hindering by two main factors which are the propagation and diseases. Devastating disease has cause losses in bean production as it can infect the vines at any times and at all stages of the plant growth. As a result, it is cause the losses of quality and quantity of pod production. Some of important diseases associated with fungal and viral on vanilla such as Fusarium root and stem rot, anthracnose, black rot, sclerotium rot, rust, mosaic and stem necrosis are discussed in this review paper.

PERAN AGEN HAYATI ASAL RIZOSFER DAN ENDOFIT MENEKAN PENYAKIT BUSUK SKLEROTIUM ROLFSII BAWANG DAUN DI MEDIA GAMBUT (Role of Rhizosphere and Endophytes Biological Agents to Supress Sclerotium rolfsii Rot Disease on Scallions in the Peat Media)

ABSTRACTThe Sclerotium Rot Disease is highly destructive to the scallions cultivation in the peat soil. Theantagonistic fungi isolated from the rhizosphere and the endophytes of healthy plants, have beenproven to be able to reduce Sclerotium rolfsii. The aim of this study was to evaluate thecharacteristics of antagonistic fungi from rhizosphere and endophytes of Scallions to S. rolfsii in- vitro in the laboratory. The purpose of this study was also to perform the suppression test on theintensity of Sclerotium rolfsiiRot Disease in planta in the peat media in the screen house. Thisresearch it was shown that genus Fusarium, Penicillium, Aspergillusas antagonistic fungi, wereidentified from the endophytes, meanwhile genus Trichoderma, Penicillium dan Aspergillus sp. were identified from the rhizosphere. Trichoderma Rz-1 and Trichoderma Rz-3 isolated from therhizosphere was shown to have the highest antagonistic activity by 94,4 %, followed by AspergillusEd-2, which was isolated from the endophytes by 83,8%. In planta on peat media, TrichodermaRz-1 was capable to demonstrate 82,19% of antagonistic effect and it could suppress SclerotiumRot Diseasehence it produced the fresh weight of the plant highest to 19gcluster-1. Taken together,the result of this study showed that Trichoderma Rz-1 isolated from rhizosphere has been proven tobe the most beneficial to reduce the Sclerotium rolfsii on Scallions as a biological control agent,especially in peat soils.Keywords: biocontrol, rhizosphere,endophyte, scallions, Sclerotium rolfsii

Https://doi.org/10.36873/agp.v20

ABSTRACTThis study aims to determine effective management patterns to control Sclerotium rot and to improvepeat soil fertility with the application of the Trichoderma sp + Aspergillus sp consortium.as biologicalagents and P solvents, combined with spacing arrangements in the cultivation of scallion in peatlands.The study used a factorial randomized block design consisting of two factors with four replications.Factor I Application of biological agents consists of: A0 = No biological agents; A1 = Consortium ofTrichoderma sp. + Aspergillus sp; Factor II Plant spacing, consisting of J1 = 20x25 cm; J2 = 25x25cm and J3 = 30x25 cm. The results showed that the interaction treatment of Trichoderma sp. +Aspergillus sp. and spacing of 25x25 cm effectively suppresses the incidence of white rot disease(Sclerotium cepivorum Berk) up to 34.02%, while at a spacing of 20x25 cm with the application ofTrichoderma sp. + Aspergillus sp. produced the highest fresh plant weight of 8.80 kg plot-1 or 24.44tons hectares-1. Increasing the number of leaves is only influenced by a single factor of biologicalagents (23.29%) and spacing of 25x25 cm (19.7%). Application of Trichoderma sp. + Aspergillus sp.can increase the nutrient content of N, P (total and available), K and peat soil organic matter.Consortium of biological agents Trichoderma sp. and Aspergillus sp. indigenous have the potential tobe developed as biological agents and biofertilizers, with optimum spacing can be applied to themanagement of scallion cultivation in peatlands.Key words: Sclerotium cepivorum Berk, scallion, Trichoderma sp. and Aspergillus sp., spacing

Oxalis purpurea sclerotium rot caused by Athelia rolfsii

Over a 3-year period (2015–2017), sclerotium rot was observed on purple wood sorrel (Oxalis purpurea) in the exhibition field of Gyeongsangnam-do Agricultural Research and Extension Services, Jinju, South Korea. Infected plants exhibited blight and rot symptoms. White mycelial mats spread over lesions, and numerous sclerotia formed on the petiole near the soil line. Sclerotia were globoid in shape, 1–3 mm in size, and white to brown in color. The optimum temperature for mycelial growth and sclerotium formation on potato dextrose agar (PDA) was 30 °C and the hyphal width was 4–8 μm. Typical clamp connections were observed in the hyphae of fungi grown on PDA. Molecular identification was conducted by sequencing and analysis of the complete internal transcribed spacer (ITS) rDNA sequence of the causal fungus. On the basis of mycological characteristics, molecular identification, and pathogenicity to host plants, this fungus was identified as Athelia rolfsii. This is the first report of sclerotium rot on purple wood sorrel caused by A. rolfsii.

Morphological and Molecular Characterization of Sclerotium rolfsii(Teleomorph Athelia rolfsii) Associated with Sclerotium Rot of Cucumis melo L. var. makuwa Makino

In the present study, a severe outbreak of Sclerotium rot on Korean melon(Cucumis melo L. var. makuwa Makino) observed in Jinju, Korea in August of 2014 and 2015 is reported. The fruit rot disease on the surface of Korean melon fruit appeared as water soaked lesion followed by the development of large rotten areas with abundant white mycelial growth. Abundant white mycelial mats with globoid and white to brown sclerotia(1-3 mm) were also developed on stems near the soil line, and infected plants withered. The fungal pathogen was isolated on potato dextrose agar(PDA) and formed white colonies with numerous sclerotia on PDA. The sclerotia were globoid in shape, 1-3 mm in size, and white to brown in color. The mycelium formed typical clamp connection. These measurements and taxonomic characteristics were most similar to those of Sclerotium. DNA sequencing and phylogenetic analysis of the complete internal transcribed spacer rRNA gene region confirmed that the fungal isolates were Sclerotium rolfsii Saccardo. Koch’s postulates were supported by pathogenicity tests conducted on fruit. Based on mycological characteristics, pathogenicity tests, and molecular identification, the fungus was identified as Sclerotium rolfsii. To the best of our knowledge, this is the first report of a Sclerotium rot caused by S. rolfsii on Korean melon in Korea.

First report of southern blight on Vesicularia vesicularis caused by Sclerotium rolfsii in Florida

Vesicularia vesicularis, also known as vesicularia moss, belongs to the family Hypnaceae. Vesicularia moss thrives in a riparian habitat and is very common throughout the Everglades in south Florida. It is also grown in the ornamental plant trade where it is widely used in landscapes to accent rock gardens and waterfalls. During August 2015, a local nursery submitted a sample of V. vesicularis to the Florida Extension Plant Diagnostic Clinic in Homestead, Florida. The leaves and stem were covered with a white mat of mycelium and some sclerotia (Fig. 1). Symptomatic tissues were plated on acidified potato dextrose medium (APDA) and grown at 25°C. White mycelium and light to dark brown sclerotia of 1 to 2 mm diameter were observed in APDA (Fig. 2). Microscopic examination of the morphological characteristics revealed the presence of clamp connections. The fungus was identified as Sclerotium rolfsii and identification of the fungus was confirmed by the amplification of the complete internal transcribed spacer (ITS) region of rDNA with the primers ITS1 and ITS4 (White et al., 4). The PCR product was sequenced and the resulting sequence was deposited in GenBank (Accession No. KX594831). A BLAST search in GenBank showed 98% nucleotide identity with an isolate of S. rolfsii (teleomorph Athelia rolfsii; KJ944396) causing sclerotium rot of Vinca rosea in South Korea. To further support identification, phylogenetic analysis by the Maximum Likelihood method (Tamura 3-parameter model) was performed (MEGA 7.07). In this phylogenetic analysis, the ITS sequences from S. rolfsii and S. delphinii strains formed three clusters. Cluster r-1 consisted of strains from both S. delphinii and S. rolfsii, cluster r-2 included only S. rolfsii strains, and cluster r-3 contained S. delphinii strains (Okabe & Matsumoto, 3). The S. rolfsii isolate from this study grouped in cluster r-1 with other S. delphinii and S. rolfsii strains (94% bootstrap values, 1000 replicates) (Fig. 3). Pathogenicity experiments were conducted using V. vesicularis distributed in five 10-cm diameter pots each inoculated on the surface with a mycelial plug of 2 mm taken from a seven-day-old APDA culture of S. rolfsii. The same treatment was performed using two non-inoculated controls and the experiment was repeated. The experiments were conducted in a shade house where the temperature ranged from 25 to 32°C. Five days post inoculation the moss developed chlorotic spots around the inoculated area. The spots enlarged within days and were covered with the white fanlike mycelia of S. rolfsii. No symptoms developed on the non-inoculated controls. To our knowledge, this is the first report of S. rolfsii causing southern blight of V. vesicularis in Florida. Sclerotium rolfsii is an economically important pathogen causing southern blight affecting a wide host range of ornamental plants including orchids and tropical foliage (Alfieri et al., 1, Cating et al., 2). The authors would like to thank George Butler of Butler's Foliage for first bringing this disease to our attention and providing moss specimens for research.

Preventive and curative control of sclerotium rot disease of cocoyam cormel (Colocasia esculenta [L., Scott]) using plant extracts and Trichoderma koningii

ABSTRACT: Air-dried aqueous leaf extracts of Carica papaya, Chromolaena odorata and Azadirachta indica were screened for antifungal properties against Sclerotium rolfsii, causing cormel rot disease in cocoyam at 50, 70, and 100% concentrations and Trichoderma koningii (4.9x106spores/ml) in vivo. Dithane M45 (mancozeb) at 2% concentration was also used as positive control for better comparison. The aqueous extracts and T. koningii were applied as preventive and curative control measures against Sclerotium rolfsii. Spraying fresh and healthy cormels inoculated with Sclerotium rolfsii at 3.75x105spores/ml indicates that the plant extracts, Mancozeb and T. koningii had significant preventive and curative effects on disease severity and percentage weight loss on diseased cocoyam cormels. Preventive and curative application of T. koningii significantly reduced disease severity, though the later was not significantly different from the other control methods. Specifically, highest disease severity was observed in C. papaya at 50% concentration. The plant extracts and dithane M45 (fungicide) were more effective as curative, while T. koningii was more effective in the preventive method. On percentage weight loss, C. odorata at 70% concentration gave the highest (49.61%), followed by C. papaya (50%) with 47.85% and the least (23.77%) was observed in A. indica at 70% concentration. Therefore, the curative method revealed the effects of the different management methods on the percentage weight of cormels affected by rot. However, C. odorata and A. indica 50 at 100% concentration respectively, significantly reduced weight loss in cormels, while C. odorata (100% concentration) and the control gave the highest percentage weight loss in the curative treatment. From these findings, we conclude that the plant extracts and T. koningii were more effective in controlling cocoyam cormel rot and reduce weight loss than the synthetic fungicide Mancozeb.

Sclerotium rolfsii에 의한 동부 흰비단병

Sclerotium rot disease on cowpea (Vigna sinensis King) was observed in the exhibition field of Gyeongsangnam-do Agricultural Research and Extension Services in September 2015. Lesions were covered by white mycelial mats, and numerous sclerotia were formed on the stem near the soil line. The sclerotia were globoid in shape, 1~3 mm in size and white to brown in color. The optimum temperature for mycelial growth and sclerotia formation on potato dextrose agar (PDA) was 30oC, with the hyphal width of 4~8 μm. For molecular identification, the complete internal transcribed spacer (ITS) rDNA region of the causal fungus was sequenced and analyzed. Based on the mycological characteristics, ITS rDNA sequence analysis, and pathogenicity test, this fungus was identified as Sclerotium rolfsii. This is the first report of sclerotium rot on cowpea caused by S. rolfsii in Korea.

The occurrence of sclerotium rot on Momordica charantia caused by Sclerotium rolfsii in Korea

Sclerotium rolfsii is one of the most destructive pathogens and thought to affect a broad range of plant hosts. In July 2014, an occurrence of sclerotium rot was observed on bitter melon (Momordica charantia L.) in Jinju, South Korea. The rot symptoms were most developed on stems and fruit near the soil line, and infected bitter melon plants withered and eventually died. White mycelial mats with numerous sclerotia were produced on diseased stems and fruit near the soil surface. Based on the morphological characteristics, pathogenicity tests, and DNA sequencing and phylogenetic analysis of the internal transcribed spacer (ITS) ribosomal RNA (rRNA) gene region, the causal fungus was identified as S. rolfsii Saccardo. This is the first report of sclerotium rot caused by S. rolfsii on bitter melon in Korea. The recent occurrence of sclerotium rot on bitter melon poses a potential threat to its production in Korea.

A Strong Antifungal-producing Bacteria from Bamboo Powder for Biocontrol of Sclerotium rolfsii in Melon (Cucumis melo var. amanta)

Bamboo (Bambusa edulis Munro) rhizosphere has been known for its potency to reduce plant pathogen because it contains diverse beneficial microbes, thus bamboo plant itself might be a potential source for bio-control agent discovery. Sclerotium rot, caused by Sclerotium rolfsii Sacc, is one of the most devastating non-specific diseases of plant, including melon (Cucumis melo var. amanta). The aim of this study was to screen and characterise novel bacteria isolates from bamboo powder that have beneficial application for crop protection. Bacillus subtilis BMB26 produced an extracellular metabolite that effective against a wide range of pathogenic fungi, including S. rolfsii, and resistant to heat and protease. Furthermore, to evaluate the application of cell-free filtrates BMB26 on melon plants, a cotyledon test was done under greenhouse condition. A significant decrease was observed in disease incidence (up to 77%) occurred in BMB26-treated melon leaves inoculated with S. rolfsii after 4 days post-inoculation. This result showed that Bacillus subtilis BMB26 has a potential application as a bio-control agent against phytopathogenic fungi.

First Report of Fruit Rot of Ridge Gourd (Luffa acutangula) Caused by Sclerotium rolfsii

Ridge gourd is a specialty cucurbit vegetable cultivated in the United States on a small scale for select markets. We report the infection of ridge gourd fruit by Sclerotium rolfsii (teleomorph: Athelia rolfsii). This appears to be the first report of Sclerotium rot of ridge gourd. In fields with history of S. rolfsii, the gourds should be grown on trellis to prevent fruit contact with wet soil. Several fungicides are available to manage S. rolfsii and may have to be applied if and when needed. Accepted for publication 12 January 2016. Published 14 January 2016.

파프리카 병원균들에 대한 길항미생물, Burkholderia cepacia strain YJK2의 분리 및 특성

【Although several adverse effects have been increased in recent years, synthetic agro-chemicals have been widely used to control diseases on paprika. This research was conducted to isolate and to characterize the antagonistic microorganism to control major paprika diseases, gray mold rot, fruit and stem rot, phytophthora blight, sclerotium rot, and wilt disease. Analysis of the fatty acid and analysis of the 16S rDNA gene sequence revealed that isolated in this research belongs to a group of Burkholderia cepacia. Specially, 16S rDNA gene sequence of showed 99% of sequence similarity with cepacia. Observation through the optical microscope revealed that was effective on suppression of the spore germination and the hyphal growth of pathogens. treatment on pathogens induced marked morphological changes like hyphal swelling and degradation of cell wall. In the case of phytophthora blight, the zoosporangium formation was restrained. On the basis of the results of this study, we propose that an antagonistic microorganism, cepacia, found in this study naming as B. cepacia strain YKJ2 and has great potential as one of biological control agents against major diseases of paprika.】

First Report of Sclerotium Rot Caused by Sclerotium rolfsii on Yacón in South Korea.

Yacón, or ground apple (Smallanthus sonchifolius), is a perennial plant grown in the northern and central Andes from Colombia to northern Argentina for its crisp, sweet, and tuberous roots. In 2012, yacóns cultivated in the research field of the Gyeongsangnam-do Agriculture and Extension Services, Jinju, South Korea, suddenly died. The characteristic symptoms consisted of rotting, wilting, and blighting. Initial symptoms included water-soaked lesions on lower stem tissue near the soil line. Infected plants gradually withered, and white mycelial mats and sclerotia appeared on the surface of roots and stems at the soil line. The sclerotia were collected and disinfested by immersion in 1% sodium hypochlorite solution for 30 s and in sterilized distilled water for 1 min. Then, the sclerotia were placed on potato dextrose agar (PDA) and incubated at 30°C. Numerous globoid sclerotia were formed on PDA after 18 days of growth. The sclerotia (1 to 3 mm in diameter) were white at first and then gradually turned dark brown. Aerial mycelia usually formed many narrow hyphal strands 4 to 9 μm wide. The white mycelium formed a typical clamp connection after 5 days of growth. To fulfill Koch's postulates, 50-day-old healthy seedlings were transplanted individually into pots (10 × 10 × 9 cm) containing autoclaved soil. After 7 days, five seedlings were inoculated with colonized agar discs (6 mm in diameter) directly on the base of the plant, and five yacón seedlings were inoculated similarly with PDA discs as the control treatment. The inoculated and non-inoculated plants were incubated in a humid growth chamber at 28°C for 24 h and then maintained in a greenhouse. Eight days after inoculation, the yacón seedlings inoculated with the fungus died, whereas those treated with PDA discs were symptomless. The fungus was re-isolated from the artificially inoculated plants. To confirm the identity of the causal fungus, the complete internal transcribed spacer (ITS) rDNA region of the fungus was amplified using the primers ITS1 (5'-TCCGTAGGTGAACCTGCGG-3') and ITS4 (5'-TCCTCCGCTTATTGATATGC-3') (2), and the PCR amplicons were cloned into the pGEM-T Easy vector. The resulting plasmid (pOR119) was sequenced in both directions with the primers M13F and M13R. The resulting 684 bp of ITS rDNA sequence was deposited in GenBank (Accession No. KJ944395). A DNA analysis revealed that it was 100% identical to Sclerotium rolfsii (HM355751). Cultures of S. rolfsii have been deposited with the Korean Agricultural Culture Collection (KACC 47750), National Academy of Agricultural Science, Suwon, South Korea. On the basis of symptoms, fungal colonies, the ITS sequence, and pathogenicity to the host, this fungus was identified as S. rolfsii Saccardo (1). This is the first report of sclerotium rot on yacón caused by S. rolfsii in South Korea.

Asian Foxtail (Uraria crinita), a New Host for Sclerotium rolfsii from Taiwan.

Asian foxtail (Uraria crinita (L.) Desv. ex DC.) is an herb cultivated for the use of roots and stems in Taiwanese cuisine. In September 2013, symptoms of leaf blight and basal rot were observed on U. crinita in a commercial field in Longjing District, Taichung, Taiwan, at an incidence of approximately 20%. White mycelia and brown sclerotia formed on the surfaces of the basal stems. The infected plant gradually wilted and eventually died. Diseased lower stem tissues were surface sterilized in 0.6% NaOCl, rinsed with sterile distilled water, and transferred to potato dextrose agar plates. The cultures were incubated at 25°C in the dark. The radial mycelial growth was 9.0 mm/day during the first 4 days, and the diameter of mature sclerotia was 1.76 mm following 3 weeks of incubation. The internal transcribed spacer (ITS) sequence of the isolate was amplified by PCR using the primers ITS5 and ITS4 (2). The amplicon was cloned, sequenced, and deposited in GenBank (Accession No. KJ677121). The sequence similarity was 99% compared with that of Sclerotium rolfsii Sacc. from Spain (GU080230) (1). Based on the characteristics, the fungus was identified as S. rolfsii. The fungal isolate (BCRC FU30230) was deposited in the Bioresource Collection and Research Center, Hsinchu, Taiwan. Pathogenicity tests were conducted on six 2-month-old potted U. crinita plants in a greenhouse. Prior to infesting the plant, fungal inoculum of S. rolfsii BCRC FU30230 was prepared by inoculating the isolate on autoclaved rice (rice/water/dextrose = 50:50:1) in a flask. After 20 days incubation at room temperature, rice colonized by S. rolfsii was placed near the base of the plants (approximately 30 g/plant) in the greenhouse. Sterile rice applied to an equal number of plants served as negative controls. All inoculated plants developed blight symptoms with mycelia and sclerotia produced near the bases of each seedling 1 week after inoculation at an average temperature of 26°C. The control plants remained healthy. The pathogen re-isolated from the inoculated plants was morphologically identical to the original isolate. The pathogenicity test was repeated by inoculated healthy plants with reduced inoculum (five granules/plant). A delay of symptom development was observed and similar results were obtained. To our knowledge, this is the first report of Sclerotium rot on U. crinita in Taiwan, and the first report on U. crinita as a host for S. rolfsii.