• The Plant Pathology Journal
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• v.15 no.2
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• pp.112-118
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• 1999

Eleven species of Pythium were isolated from leaf blight symptoms on creeping bentgrass (Agrostis palustirs Huds.), Kentucky bluegrass (Poa pratenisis L.) and zoysiagrasses (Zoysia japonica Steud., and Z. matrella (L.) Merr.) planted on golf courses in Korea. Mycelial growth on potato carrot agar medium under various temperature conditions indicated that Pythium species obtained in this study could be divided into four groups based on their responses to temperature conditions. P. vanterpoolii was found to favor low temperature conditions with the optimum temperature of $25^{\circ}$, whereas P. aphanidermatum and P. myriotylum favored relatively high temperature conditions with the optimum temperature of $35^{\circ}$. Other species including P. arrhenomanes, P. catenulatum, P. graminicola, P. oligandrum, P. rostratum, P. torulosum, and P. ultimum were the intermediate group with the optimum temperature of 25~$35^{\circ}$. P. periplocum was similar to the intermediate group but the minimum temperature for its mycelial growth was $15^{\circ}$, which was approximately $5^{\circ}$ above that for the intermediate Pythium spp.group. In the pathogenicity tests conducted in the lab using potted plants, P. aphanidermatum, P.a arrhenomanes, P. catenulatum, P. graminicola, P. myriotylum, P. periplocum, P. rostratum, P. torulosum, P. ultimum, and P. vanterpoolii were found to be pathogenic to creeping bentgrass and Kentucky bluegrass. P. aphanidermatum, P. catenulatum, and P. graminicola were frequently isolated from leaf blight symptoms of creeping bentgrass and Kentucky bluegrass in golf courses during the warm and humid periods in July-August. On the other hand, P. vanterpoolii and P. torulosum were frequently isolated during the cool and humid periods in March-May, suggesting both species might be the major causes of leaf blight occurring in the spring time. Zoysiagrass was susceptible to P. arrhenomanes and the heterothallic Pythium sp. (Ht-F), showing stem and crown rot of turf-grasses at poorly drained areas under coool and humid or rainy conditions. P. oligandrum and the heterothallic Pythium sp. (Ht-L) isolated from creeping bentgrass were avirulent to all species of turfgrasses tested in this study.

• Asian Journal of Turfgrass Science
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• v.9 no.3
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• pp.235-252
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• 1995

Turfgrass Rhizoctonia blight is a severe disease in golf courses in Korea. Attempts were made in 1989 to 1994 to identify the Rhizoctonia species associated with turfgrass blights and also to examine their epidemiology. A total of 120 Rhizoctonia isolates collected were identified as R. solani AG1, R. solani AG2-2, R. cerealis(AG-D) and R. oryzas from brown patch, large patch, yellow patch and white patch, re-spectively. R. solani AG1 was mostly associated with brown patch of cool-season grasses. and most frequently isolated in June through July and also in September. R. solani AG2-2 was isolated exclusively from zoysiagrasses from April to November, most frequently in June through July and October through November. R. cerealis was isolated frequently from both creeping hentgrass in March through April and in November, and zoysiagrass in April and July. Thermophilic R. oryzae was isolated only from creeping bentgrass in August, although with very low frequency. R. solani AG2-2 was strongly pathogenic specifically to Korean lawngrasses(Zoysia japonica, Z.matrella, Z. tenuifolia), but non-pathogenic to creeping bentgrass(Agrostis palustris), bermudagrass (Cynodon dactylon), Kentucky bluegrass(Poa pratensis), perennial ryegrass(Lolium prenne), and creeping red fescue(Festuca rubra subsp. ruhra L.). R. cerealis was strongly pathogenic to zoysiagrass and bentgrass only, but was isolate-specific i.e., from non-pathogenic to pathogenic, for other turfgrasses. The mycelial growth was optimum at relatively high temperature ranges of 25~30$^{\circ}C$ for R.solani AG1, AG2-2 and R. oryzae, while the mycelial growth of R. cerealis was initiated at $^{\circ}C$ and almost ceased at or above $^{\circ}C$.

• Journal of The Korean Society of Grassland and Forage Science
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• v.26 no.4
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• pp.267-276
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• 2006

To investigate the physiological responses to winter freezing stress naturally occurring, the level of lipid peroxidation and enzymatic antioxidant responses were compared between zoysiagrass and creeping bentgrass during overwintering. Root mortality of creeping bentgrass was significantly higher than zoysiagrass at January. Root growth of creeping bentgrass was nearly parallel with temperature fluctuation, while zoysiagrass showed little changes in root growth until the end of April. Total nonstructural carbohydrate of zoysiauass was 10% higher than creeping bentgrass. Malondialdehyde(MDA) content in creeping bentgrass was 2-fold higher than that of zoysiagrass. The peroxidase(POD) activity of creeping bentgrass in January was 4.2 times higher, while superoxide(SOD) and catalase(CAT) activities lowered 22% and 67%, respectively, compared to zoysiagrass. These results suggest that zoysiagrass roots much properly operate cold tolerance mechanism and: are less susceptible to cold stress in comparison to creeping bentgrass.

• Asian Journal of Turfgrass Science
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• v.26 no.1
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• pp.1-7
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• 2012

Field experiments were conducted to evaluate the morphological characteristics and growth rates of 101 medium-leaf type zoysiagrasses (Zoysia spp.) collected at the major sod production area (Jang Seong Gun) in South Korea. Collected lines with distinctive morphology and visual growth rate were planted in plastic pots and measured morphological characteristics under the plastic house conditions. Variation of leaf width, plant height, leaf angle, length of leaf sheath, trichome, stolon length, and color were measured. Six lines were selected by evaluating growth rates from one hundred one collected lines. Eight standard cultivars and three other superior lines previously collected were compared to 7 selected lines form Jang seong area by checking growth rates and morphological characteristics. Average leaf blade width was 3.4 mm, leaf angle was 45.8 degree, plant height was 21.6 cm, height of lowest leaf was 5.0 cm, and length of leaf blade was 14.1 cm. Ground cover rates of selected lines 'CY6097' and 'CY6069' were 70% and 68.3%, respectively. These are believed to be faster than 60% ground cover rate of zoysiagrass 'Anyang', and also, twice as faster than the 31.7% ground cover rate of Z. matrella. Selected line 'CY6069' showed fast growth rate with shorter internode length (5.1 cm) compared to zoysiagrass 'Anyang'. Based on the results of this study, we could select useful fast growing zoysiagrass breeding lines from the major sod production area (Jang Seong Gun) in Korea.

• Journal of The Korean Society of Grassland and Forage Science
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• v.22 no.2
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• pp.145-152
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• 2002

To compare the Carbon metabolic response to high temperature stress in Zoysiagrass [Zoysia matrella (L.) Merr.] and Creeping bentgrass (Agrostis palustris Huds) with respect to heat tolerance, C metabolites were determined from April to September. Sampling was carried out on an established golf course (Muan Country Club, Chonnam, Korea). Shoot mass(g Dry weight per hole cup) of creeping bentgrass started to decrease from June and recovered from August whereas that of zoysiagrass was less varied. Chlorophyll content in creeping bentgrass was significantly higher than zoysiagrass until July, and then decreased by 43% from July to August. Zoysiagrass contained higher soluble sugar than creeping bentgrass throughout experimental period. Soluble sugar in zoysiagrass increased about 58% from April to May, and less varied until August. Soluble sugar in creeping bentgrass slightly increased until July and sharply decreased at August. Starch concentration in zoysiagrass continuously decreased to September after a significant increase from April to May. A remarkable fluctuation in both starch and fluctuation concentration was observed between June and August showing high accumulation for June to July and high degradation for July to August. These results suggest that through creeping bentgrass suffers much severely from high temperature stress than zoysiagrass especially June to August. An active accumulation and degradation in nonstructural carbohydrate in creeping bentgrass during this period might be associated with heat stress.