Seog-Won Chang

Genetic Relationships among Typhula ishikariensis Varieties from Wisconsin

Typhula ishikariensis Imai is a causal agent of Typhula snow mold, one of the most important turfgrass diseases in northern regions of the United States. Within Wisconsin isolates, there are three district groups clustered with known isolates of T. ishikariensis var. ishikariensis, var. canadensis and var. idahoensis as identified by RAPD markers. To further investigate the genetic relationship among these groups (varieties), monokaryon-monokaryon and dikaryon-monokaryon mating experiments were conducted. Mating types from var. ishikariensis, var. canadensis and var. idahoensis isolates were paired in all possible combinations. Pairings between var. canadensis and var. idahoensis were highly compatible, while no compatibility was detected between var. ishikariensis and either var. canadensis or var. idahoensis. These results indicate that var. ishikariensis is genetically separated from var. canadensis and var. idahoensis, whereas var. canadensis and var. idahoensis appeared to be genetically related to each other as a taxonomic unit. In the genetic relationship with the known biological species, var. ishikariensis and var. canadensis were genetically related to biological species I and II, respectively. However, var. idahoensis was not compatible with any of the biological species, suggesting that the pathogen may be in the process of biological speciation from var. canadensis.

Control Effect on Dollar Spot Disease Caused by Sclerotinia homoeocarpa under Different Application Rates and Intervals with Two Mixed Fungicides

Dollar spot caused by Sclerotinia homoeocarpa F.T. Benn. is a common and economically important turfgrass disease in South Korea. Fungicides mixture (propiconazole 25% + boscalid 47%) treatments, showing synergistic interaction, with three application rates (low: 50.3 ml 10a -1 and 97.5 g 10a -1 , intermediate: 67.0 ml 10a -1 and 130.0 g 10a -1 , and high: 100.5 ml 10a -1 and 195.0 g 10a -1 ) and two application intervals (10 and 15 days) were evaluated for control of dollar spot in creeping bentgrass golf course putting green. In both nontreated plots of field A and B, the disease has severed as 48.3 and 60.0% after the pathogen inoculation. Two fungicide mixture treatments showed significantly higher the disease control effect than a single fungicide treatment (propiconazole). Field A which showed more the disease severity but the fungicide still showed acceptable level of the disease efficacy (89.0%), significant differences in control value were not detected among treatments. The results suggest that the lower application rate of two fungicides mixture treatments may reduce the dollar spot disease severity in creeping bentgrass golf course putting green.

First Report of Curvularia Leaf Blight Caused by Curvularia trifolii on Creeping Bentgrass in Korea

Curvularia leaf blight of creeping bentgrass (Agrostis stolonifera) putting green by caused Curvularia trifolii was observed in Hapcheon, Korea. In July to September 2014, curvularia leaf blight developed on leaf blades of creeping bentgrass as small water-soaked lesions that subsequently turned into dark-colored, necrotic spots. The spots were expanded and became gray, grayish-brown, or light brown, circular to oblong lesions with purple to dark brown borders that often were surrounded by a yellow halo. The necrotic lesions coalesced, became irregular in shape and caused tip or complete blighting of the leaves. Blighted leaf blades appeared grayish-white to tan. The fungus was identified by morphological characters and 16S rDNA sequencing as C. trifolii. Conidia of the pathogen were short, with predominantly 3-septa, straight or often curved, with end cells frequently paler than intermediate cells. Size of the 3-septate conidia in culture are 26~28×11~12 μm. Pathogenicity of the fungus was proved by artificial inoculation on the host. This is the first report of C. trifolii causing leaf blight on creeping bentgrass in Korea.

Survey of Current Status of the Graveyard Lawn Maintenance in Korea

본 연구에서는 우리나라의 지역별 묘지 잔디 관리 실태를 조사하였다. 인터넷 포털 사이트에 등록된 묘지 관리 대행 업체, 산림조합중앙회, 농협(단위 농협)으로부터 묘지관리에 대한 정보를 직접 받거나 설문을 통해 자료를 얻은 다음 정리, 분석하였다. 조사한 모든 지역에서 개인 및 가족 묘지는

Suppression Effect of Clubroot Disease by Reduced Irrigation Times after Planting in Chinese Cabbage

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Determination of Several Phenolic Compounds in Cultivars of Grape in Korea

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Determination of Major Phenolic Compounds of Grape Juice and Wine of Different Geographic Origins

Clubroot of Chinese cabbage, caused by Plasmodiophora brassicae, is one of the most serious plant diseases in the world. The objectives of this study were to investigate the effect of the irrigation times on the development of club root after planting and to evaluate the effect of clubroot disease on yield of chinese cabbage in pot and field. The clubroot disease gradually increased with increasing irrigation frequency after planting. The growth characters and yield of chinese cabbage by irrigation times varied according to soil moisture and clubroot disease severity. Based on marketable yield and control value, an ideal irrigation point was at the soil matric potential of 0.06 MPa. These results suggest that the suppression on clubroot disease development could be achieved by initially reduced irrigation times after planting. Future studies on irrigation times using fungicide treatment and resistant cultivar under natural field conditions are required to improve the control effect of clubroot.