• Weed & Turfgrass Science
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• v.5 no.3
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• pp.170-176
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• 2016

Superintendents have used a silicate fertilizer to improve a resistance of turfgrass against several diseases, drought damage and wear stress. This study was conducted to evaluate the effect of liquid fertilizer containing silicate (LFSi) on changes of turfgrass quality and growth by investigating visual quality, chlorophyll content-chlorophyll a, chlorophyll b, and total chlorophyll, root length, shoot length, dry weight of clipping, and nutrient content in leaves tissue. Treatments were designed as follows; control fertilizer (CF), SiF-1 (CF + $1ml\;m^{-2}$ LFSi), SiF-2 (CF + $2ml\;m^{-2}$ LFSi), and SiF-3 (CF + $4ml\;m^{-2}$ LFSi). As compared with CF, soil chemical properties, visual turfgrass quality, chlorophyll content, and dry weight of clipping of LFSi treatments were not significantly. Contrastingly, shoot density, root length, and the content of nitrogen or potassium were increased by application of LFSi. The content of Si in the tissue was positively correlated with potassium content or shoot length, and similarly shoot density positively with chlorophyll content or visual quality, respectively. These results suggested that the application of LFSi improved the turfgrass quality by increasing shoot density or K content in leaf tissue of creeping bentgrass.

• Weed & Turfgrass Science
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• v.5 no.3
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• pp.105-110
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• 2016

This paper provides the current status of weed science and prospects for the development of weed science based on the research trends presented at the 7th International Weed Science Conference in 2016. Approximately 520 researchers from 59 countries, including Korea, participated in the conference and presented 625 papers in nine research areas. Major research topics were herbicide resistance, weed ecology, weed management in agricultural and non-agricultural lands, herbicide spray technology, and non-chemical weed control. Studies on herbicide resistance presented more than 30% of all papers presented. Particularly, resistance to non-selective herbicides, such as glyphosate and glufosinate-ammonium, and non-target sites of resistance mechanisms were the main subjects of the herbicide resistance research area. Moreover, the conference focused on research concerning herbicide resistant weeds of staple crops of the world (corn, wheat, and rice). Arylex was introduced as a new compound which has a mode of herbicidal action similar to synthetic auxin. Three compounds being developed as HPPD inhibitors were studied for ways to reduce their toxicity and tested as mixed with safeners. Additionally, parasitic weeds, which are not native to Korea, are an expanding research subject in the world. Although 45 years have passed since the first report of herbicide resistance in 1970, herbicide resistance remains a serious problem in most intensive cropping systems of the world and will continue to be a major area of study in the future.

• Korean Journal of Weed Science
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• v.31 no.1
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• pp.112-117
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• 2011

A series of experiments was conducted to investigate the herbicidal activity of natural compound chrysophanic acid under the greenhouse condition in 16 weed species. Chrysophanic acid showed non-selective herbicidal activity. While chrysophanic acid exhibited severe injury by foliar treatment, little or no injury was found by the soil treatment. Among the tested weeds, the most effective activity was found in grass and broad leaf weeds, a lower significant difference in herbicidal activity was found in sedge. At early post-emergence, weeds appeared to be very susceptible to chrysophanic acid with $2,000{\mu}g\;mL^{-1}$. The higher the natural compound concentrations, the lower weed growth. At middle post-emergence, weeds appeared to be very effective to chrysophanic acid with $30,000{\mu}g\;mL^{-1}$.

• Weed & Turfgrass Science
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• v.1 no.4
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• pp.57-63
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• 2012

This study was carried our to examine the genetic relationship of 13 commercial turfgrass cultivars using Random Amplified Polymorphic DNA to provide genetic informations more efficient golf course management. Analysis of 56 random hexamer primers generated 13 to 54 polymorphic bands among the 13 cultivars with an average of 30.7 bands per primer. The results of cluster analysis based on RAPDs revealed that three major variety groups: Group I - 'Shadow II', 'Aurora Gold', 'Little Bighorn Blue', 'PennA-1', and 'PennA-4'; Group II - 'Midnight II', 'Prosperity', 'Moon light SLT', 'Bright star SLT', and 'Silver dollar'; and Group III - 'Olympic Gold', 'Silver Star', and 'Tar Heel II'. The genetic similarity coefficients among 13 turfgrass cultivars ranged from 0.039 to 1.0 with highest coefficient in Group III. Studies on morphological characters and the effective molecular markers such as sequence characterized amplified regions are further needed to identify relationships and genetic diversities within species and among species.

• Weed & Turfgrass Science
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• v.1 no.4
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• pp.31-37
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• 2012

This study was conducted to make the rice yield prediction model system as affected by densities of Aneilema keisak and Aeschynomene indica and to determine their economic threshold levels in flooded direct-seeded rice. When the density of A. keisak was 8 plants per $m^2$, the yield of rice reduced to 8% and as the density increased up to 96 plants per $m^2$, the reduced rate of rice yield reached to 45% and in A. indica, the reduced rate of rice yield were 20 and 77%, respectively. The rice yield loss models of A. keisak and A. indica were predicted as Y=553.2 kg (1+0.00913X), $R^2=0.912^{**}$ and Y=567.9 kg/(1+0.04434X), $R^2=0.961^{**}$, respectively. Economic threshold levels calculated using cousens' equation were 3.0 plants per $m^2$ in A. keisak and 0.6 plants per $m^2$ in A. indica.

• Korean Journal of Weed Science
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• v.31 no.4
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• pp.323-329
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• 2011

We investigated photodynamic stress-induced antioxidant responses in transgenic rice overexpressing Bradyrhizobium japonicum 5-aminolevulinic acid synthase (ALA-S) coding sequence lacking plastidal transit sequence. High light of $350{\mu}mol\;m^{-2}\;s^{-1}$ decreased the quantum yield in the transgenic lines, C4 and C5, compared to that of wild-type line. By contrast, non-photochemical quenching (NPQ) levels of C4 and C5 under high light were higher than those of the transgenic lines under low light of $150{\mu}mol\;m^{-2}\;s^{-1}$ as well as wild-type line under low and high light. Greater levels of NPQ in the transgenic lines exposed to high light were in a close correlation with increases in the xanthophyll pigment, zeaxanthin. Under high light, levels of neoxanthin, violaxanthin, lutein, and ${\beta}$-carotene in the transgenic lines were lower than those in wild-type line. Taken together, nonphotochemical energy dissipation and photoprotectant xanthophyll pigments play a critical role to deal with the severe photodynamic damage in the transgenic rice plants, although they could not overcome the photodynamic stress, leading to severe photobleaching symptoms.

• Korean Journal of Weed Science
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• v.31 no.4
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• pp.348-354
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• 2011

This study was conducted to find the levels of reduction in rice yield and to determine economic threshold levels as affected by densities of Scirpus planiculmis and Lindernia dubia in wet seeding rice cultivation. In wet seeding rice cultivation, yield of rice in densities of S. planiculmis (192 per $m^2$) and L. dubia (384 per $m^2$) was reduced by 43 and 22%, respectively. Relationship between rice yield and densities of weeds were predicted with these equations of Y=531.3kg/(1+0.003931x), $r^2$=0.964 for S. planiculmis and Y=547.0kg/(1+0.000792x), $r^2$=0.922 for L. dubia. According to Cousens' method, economic threshold densities of S. planiculmis and L. dubia were calculated by 7.2 and 34.9 per $m^2$, respectively. This result indicated that yield of rice in wet seeding rice cultivation could be reduced by over economic threshold densities of S. planiculmis and L. dubia.

• Weed & Turfgrass Science
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• v.1 no.4
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• pp.64-68
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• 2012

Creeping bentgrass (Agrostis stolonifera L.) is one of the highest maintained turfgrass but often problematic especially for Kentucky bluegrass fairway. Mesotrione is one of selective herbicide that is firstly registered for corn (Zea mays L.) and provides preemergence and postemergence control of broadleaf and annual grassy weeds. Although mesotrione is effective to eradicate area contaminated by creeping bentgrass, protracted time is required to recover damaged area by rhizome extension of Kentucky bluegrass. Overseeding is typically used to fill bare or damaged areas using appropriate turf species to create a uniform turfgrass surface. The objectives of this study were to evaluate mesotrione and seeding rate effects to recover Kentucky bluegrass contaminated by creeping bentgrass. Six treatments consisted of three mesotrione rates and two Kentucky bluegrass seeding rates. The mesotrione rate were 0, 0.05 and 0.10 m $ml^{-2}$. Two seeding rate of to Kentucky bluegrass 'Midnight' were 15 and 30 g $m^{-2}$. Mesotrione application and Kentucky bluegrass overseeding at the same time is helpful to damage creeping bentgrass but not for establishment of Kentucky bluegrass to refill damaged area. To maximize mesotrione effects, temperature above $20^{\circ}C$ would be recommended based on this study.

• Weed & Turfgrass Science
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• v.2 no.2
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• pp.122-130
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• 2013

The object of this study is to review the current states of the characteristics and strategies to control annual bluegrass to apply information to the circumstance of South Korea. Annual bluegrass is one of the most widespread turfgrass species which has great ability to produce seedhead and shoot growth. It also has ability to tolerate low mowing height and to form uniformity of turfgrass when it is established. Annual bluegrass is well-known as weak turfgrass for high and low temperature. High rate of nitrogen and phosphorus improves growth of annual bluegrass. To control annual bluegrass, deep and infrequent irrigation is more effective than light and frequent irrigation. Clipping removal is more effective than clipping return to control annual bluegrass. Prodiamine, bensulide, and dithiopyr are applied as pre-emergence herbicide, and ethofumesate and bisbyribac-sodium are used as post-emergence herbicide. Paclobutrazol and flurprimidol are used as plant growth regulator. Trinexapac which is one of the most popular plant growth regulators (PGRs) in South Korea is not proper to control annual bluegrass because it accelerates improve growth of annual bluegrass in summer. Although chemical control is mainly used in South Korea, combination of cultural and chemical control may be the strategy to maximize effectiveness to control annual bluegrass.

• Weed & Turfgrass Science
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• v.2 no.2
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• pp.131-137
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• 2013

The study was carried out to obtain the basic information on distribution and occurrence of weeds including resistant weeds to sulfonylurea herbicides in paddy fields of Gyeongbuk province. In weed distribution on life cycle, annual weed was occupied by 91.8% and perennials were 8.2%, respectively. In morphological distribution of weeds, broad leaf weeds were 85.7%, sedges was 9.1%, and grass weed was 3.8%, respectively. Sulfonylurea-resistant weeds in paddy fields of twelve regions were widely occurred except for Yecheon region. The six sulfonylurea resistant biotypes occurred in paddy fields of Gyeongbuk province were Lindernia dubia, Eleocharis kuroguwai, Monochoria vaginalis and Ludwigia prostrata. It revealed that occurrence rate and area of sulfonylurea-resistant weeds were about 15.9 % and 22,420 ha in Gyeongbuk province.