• The Korean Journal of Mycology
• /
• v.48 no.4
• /
• pp.511-518
• /
• 2020

This study was conducted to isolate and identify the fungal pathogen caused unreported post-harvest disease on apples (cv. Fuji) fruit in Korea. The disease symptoms on apples appeared as irregular, light to dark brown, slightly sunken spots. The three fungal strains were isolated from infected tissues of apple fruits and their cultural and morphological characteristics were completely consistent with those of Plenodomus collinsoniae. The phylogenetic analysis using the internal transcribed spacer (ITS) regions, beta-tubulin (TUB), and the second largest subunit of RNA polymerase II (RPB2) sequences revealed the closest relationship of the isolates with Plenodomus collinsoniae at the species level. The pathogenicity test showed the same dark brown spots on Fuji apple cultivar. Therefore, P. collinsoniae is a newly reported fungal agent causing post-harvest disease on apples in Korea.

• The Plant Pathology Journal
• /
• v.39 no.3
• /
• pp.275-289
• /
• 2023

Fungal isolates from infected Chinese quince trees were found to cause black rot in Yeongcheon, Gyeongsangbuk Province, Korea. The quince leaves withered and turned reddish-brown and fruits underwent black mummification. To elucidate the cause of these symptoms, the pathogen was isolated from infected leaf and fruit tissues on potato dextrose agar and Levan media. Several fungal colonies forming a fluffy white or dark gray mycelium and two types of fungi forming an aerial white mycelium, growing widely at the edges, were isolated. Microscopic observations, investigation of fungal growth characteristics on various media, and molecular identification using an internal transcribed spacer, β-tubulin, and translation elongation factor 1-α genes were performed. The fungal pathogens were identified as Diplodia parva and Diplodia crataegicola. Pathogenicity tests revealed that the pathogen-inoculated fruits exhibited a layered pattern, turning brown rotting; leaves showed circular brown necrotic lesions. The developed symptoms were similar to those observed in the field. Fungal pathogens were reisolated to fulfill Koch's postulates. Apples were inoculated with fungal pathogens to investigate the host range. Strong pathogenicity was evident in the fruits, with browning and rotting symptoms 3 days after inoculation. To determine pathogen control, a fungicidal sensitivity test was conducted using four registered fungicides. Thiophanate-methyl, propineb, and tebuconazole inhibited the mycelial growth of pathogens. To the best of our knowledge, this is the first report on the isolation and identification of the fungal pathogens D. parva and D. crataegicola from infected fruits and leaves of Chinese quince, causing black rot disease in Korea.

• Research in Plant Disease
• /
• v.20 no.2
• /
• pp.129-131
• /
• 2014

In February 2014, gray mold rotting symptoms were observed in carrots in cold storage at Gangneung, Gangwon province, Korea. The typical symptom of gray mold rot showed abundant blackish gray mycelia and conidia was observed on the infected root. The pathogen was isolated from infected root and cultured on PDA for further fungal morphological observation and confirming its pathogenicity according to Koch's postulates. Results of morphological data, pathogenicity test and rDNA internal transcribed spacer (ITS 1 and 4) sequence showed that the postharvest gray mold rot of carrot was caused by Botyrtis cinerea. This is the first report of postharvest gray mold rot on carrot in Korea.

• Mycobiology
• /
• v.42 no.4
• /
• pp.409-411
• /
• 2014

In March 2014, a kohlrabi stem rot sample was collected from the cold storage room of Daegwallyong Horticultural Cooperative, Korea. White and fuzzy mycelial growth was observed on the stem, symptomatic of stem rot disease. The pathogen was isolated from the infected stem and cultured on potato dextrose agar for further fungal morphological observation and to confirm its pathogenicity, according to Koch's postulates. Morphological data, pathogenicity test results, and rDNA sequences of internal transcribed spacer regions (ITS 1 and 4) showed that the postharvest stem rot of kohlrabi was caused by Sclerotinia sclerotiorum. This is the first report of postharvest stem rot of kohlrabi in Korea.

• Proceedings of the Korean Society of Plant Pathology Conference
• /
• 2003.10a
• /
• pp.111-111
• /
• 2003

Several fungal isolates were isolated from diseased monochoria(Monochoria vaginalis, weed of paddy field), which has an resistance to sulfonyl urea(S.U.) herbicide, and were evaluated in the laboratory and greenhouse as potential mycoherbicide. Eight fungi, Alternaria sp., Colletotrichum sp., Curvularia sp., Paenicillium sp and etc. were observed in the isolates. Pathogenicity testing were done on the monochorias in the greenhouse. Monochorias were inoculated with suspensions containing conidia of each isolate at the rates of 1.0 ${\times}$ 10$\^$5/ conidia/ml and 0.1％ Tween 80 with hand-gun sprayer. Curvularia sp. and an unidentified fungal isolate caused 90-95％ mortality on the monochorias 15∼20 days after inoculation. However the other isolates induced slight symptom of disease on the monochorias. In the early stage of disease development sun-burn appearance was shown at the infected site and the last infected leaves and stems were withered to death. Subsequently the pathogenicity on the rice was evaluated with above two effective isolates. From the test an unidentified isolate showed pathogenicity on the rice but Curvularia sp., named as DBB2003, didn't. Now the mass production and formulation using Curvularia sp. DBB2003 are in progress and the field test will be followed. Combination product with Curvularia sp. DBB2003 and chemical herbicide will be more effect to control the monochoria resisted on S.U. herbicide and need to be further tested.

• Research in Plant Disease
• /
• v.15 no.2
• /
• pp.88-93
• /
• 2009

In 2008, leaf rot and blight on pepper seeding ("Dokya-chungchung") occurred in a pepper farm at Hwaseong-si, Gyeonggi-do, Korea. The typical symptom is water-soaking and dark brown leaf blight at edges and tips of leaves. The fungal colonies isolated from infected tissues were pinkish at first and turned gradually to gray. Conidia were fusiform, non-septum, and $8.1-17.0{\times}2.0-3.8{\mu}m$ in size. Several specific PCR primers derived from the sequence of the internal transcribed spacer (ITS) region of the rDNA, such as CaINT, CgINT and CcINT were used for the identification of the fungal pathogen. The C. acutatum-specific primer CaINT was amplified single fragment of 496 bp that discriminated C. acutatum from the other species. The pathogenicity test was performed on seedlings and fruits of red pepper. On the basis of the morphological, molecular characteristics and pathogenicity test, we identified as Colletotrichum acutatum. This is the first report on leaf rot and blight on pepper seedling caused by C. acutatum in Korea.

• Research in Plant Disease
• /
• v.29 no.4
• /
• pp.377-383
• /
• 2023

In 2020 and 2021, we surveyed diseases of three-leaf ladybell (Adenophora triphylla) plants grown in fields at two locations in Korea. During the disease surveys, severe leaf rot symptoms were observed on the young plants in Hongseong, and stem rot symptoms on the adult plants in Cheolwon. The incidence of leaf rot was 5-60%, and that of stem rot 1-10%. We obtained 6 fungal isolates each from the leaf rot lesions and the stem rot lesions. All the isolates were morphologically identified as Rhizoctonia solani. Anastomosis test and investigation of cultural features of the fungal isolates revealed that the isolates from the leaf rot lesions corresponded to R. solani AG-1(IB), and those from the stem rot lesions to R. solani AG-2-2(IIIB). Two isolates each of R. solani AG-1(IB) and AG-2-2(IIIB) were used for DNA sequence analysis and pathogenicity test to three-leaf ladybell plants through artificial inoculation. The anastomosis groups and cultural types of the R. solani isolates were confirmed by the sequence analysis. The pathogenicity tests revealed that the isolates of R. solani AG-1(IB) caused only leaf rot symptoms on the inoculated plants, and those of R. solani AG-2-2(IIIB) leaf rot and stem rot symptoms. The induced symptoms were similar to those observed in the fields investigated. Leaf and stem rot of three-leaf ladybell caused by the two anastomosis groups and cultural types of R. solani is first reported in this study.

• Mycobiology
• /
• v.51 no.3
• /
• pp.186-194
• /
• 2023

In July 2021, wilting symptoms were observed in adult and seedling hemp (Cannabis sativa L. cv. Cherry Blossom) plants grown in a greenhouse. As the disease progressed, yellowing and wilting symptoms on the leaves developed, resulting in whole plant death. In seedling plants, typical damping-off symptoms were observed. To identify the pathogen, the roots of diseased plants were sampled, surface sterilized, and cultured on potato dextrose agar (PDA) media. From the culture, 4 different fungal isolates were recovered and purely cultured. Each fungal isolate showed distinct growth shapes and color development on malt extract agar, oatmeal agar, sabouraud dextrose agar, and PDA media. Microscopic observation and molecular identification using ribosomal DNA internal transcribed spacer sequencing identified them as 3 Fusarium spp. and 1 Thielaviopsis paradoxa. Additional sequencing of elongation factor 1-alpha and b-tubulin regions of 3 Fusarium spp. revealed that 2 of them are Fusarium solani, and the other one is Fusarium proliferatum. To examine which isolate can act as a causal agent of wilt disease of hemp, each isolate was tested for their pathogenicity. In the pathogenicity test, F. solani AMCF1 and AMCF2, and F. proliferatum AMCF3, but not T. paradoxa AMCF4, were able to cause wilting disease in hemp seedlings. Therefore, we report that F. solani AMCF1 and AMCF2, and F. proliferatum AMCF3 as causal agents of Fusarium wilt of hemp plants. To our knowledge, this is the first report of the wilt disease of C. sativa L. caused by Fusarium spp. in Korea.

• The Korean Journal of Mycology
• /
• v.50 no.3
• /
• pp.249-254
• /
• 2022

In June 2021, foot rot symptoms were observed in wasabi (Eutrema japonicum) plants growing in vinyl greenhouses of the Alpine Agricultural Experiment Station, Wild Vegetable Research Institute, in Taebaek, Gangwon Province, Korea. Diseased plants displayed black soft rot of crowns and petioles at the soil line and wilted. The incidence of diseased plants was 2-10% in four out of five vinyl greenhouses investigated. Eight fungal isolates were obtained from diseased plants. All the isolates were identified as Phytophthora pseudocrytogea based on their morphological characteristics and phylogenetic analysis. Three isolates of P. pseudocrytogea were used for pathogenicity test on wasabi plants via artificial inoculation. The pathogenicity of the isolates was confirmed in the inoculated wasabi plants. The symptoms shown by the inoculated plants were similar to those observed in plants from the investigated vinyl greenhouses. This is the first report of P. pseudocryptogea causing Phytophthora foot rot in wasabi.

• The Korean Journal of Mycology
• /
• v.34 no.1
• /
• pp.59-61
• /
• 2006

Gray mold caused by Botrytis cinerea on Agastache rugosa was occurred at a field of Jinju from 2003 to 2005. The disease symptoms started with water-soaked lesions in the leaves and stem, then these infected lesions became withered, discolored, rotten and died eventually. The fungal pathogen was isolated from the lesions. The fungal conidia were one-celled and mostly ellipsoid or ovoid in shape and light gray in color and $4{\sim}20{\times}4{\sim}13\;{\mu}m$ in size. The fungal conidiophores were $14{\sim}28\;{\mu}m$ in width. The Pathogen formed sclerotia abundantly on PDA. The optimum temperature for mycelial growth and sclerotia formation was $20^{\circ}C$. Pathogenicity of the causal organism was proved according to Koch's postulates. On the basis of symptom, mycological characteristics and pathogenicity test, the fungus was identified as Botrytis cinerea. This is the first report on gray mold of Agastache rugosa caused by B. cinerea in Korea.