• Korean Journal Plant Pathology
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• v.10 no.2
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• pp.136-139
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• 1994

Turnip mosaic virus (TuMV) was isolated from Rorippa islandica showing mild mosaic symptom in growing field of Chinese cabbage and radish. Identification of the virus was based on host range, transmission by aphids, electron micrograph, serological reaction and hybridization detection. The virus systemically infected on Chenopodium quinoa, Nicotiana clevelandii, N. glutinosa, Brassica rapa, B. campestris subsp. pekinensis and Raphanus sativus, whereas showed local infection on C. amaranticolor, Gomphrena globosa and Tetragonia tetragonoides. The virus was transmitted by aphid (Myzus persicae). The virus particle was filamentous with 720$\times$12 nm in length, and reacted positively with an antiserum of TuMV in agar gel double duffusion test. In slot-blot hybridization using the digoxigenin(DIG)-labeled RNA probe, TuMV-RNA could be detected in sap of R. islandica infected with the virus. This is the first report of a natural infection of that virus on R. islandica.

• Microbiology and Biotechnology Letters
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• v.40 no.3
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• pp.261-267
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• 2012

Coastal sand dunes are important for ecosystems due to the variety of rare species that can be found in this kind of habitat, and the beautiful landscapes they create. For environmental remediation, a potential strategy is phytoremediation using the symbiotic relationship of plants and microbes in the rhizosphere, which has proven ecologically sound, safe, and cost effective. Ninety-five colonies were isolated from the rhizosphere soil (RS) or rhizoplane (RP) of Rorippa islandica, Rumex crispus, Artemisia princeps var. orientalis, Lilium sp Stellaria media, and Gramineae. These colonies were then tested for plant growth promoting activities (PGPAs) such as 1-aminocyclopropane-1-carboxylic acid (ACC) deaminase activity, and siderphores synthesis ability. In addition, salt tolerance was evaluated at 4% and 8% salt concentrations. It was observed that amongst the test subjects about 50% of the strains had a high resistance to salinity. Many of them could produce indole-3-acetic acid (IAA) IAA (in RS 13.9% and in RP 7.6%), exhibited ACC deaminase activity (55.8% in RS and 36.6% in RP), and could synthesize siderphores (62.7% in RS and 50% in RP). Correlation coefficient analyses were carried out for the three kinds of plant growth promoting abilities (PGPA) and salt tolerance. A positive correlation was found between an ability to synthesize siderphores and ACC deaminase activity (r=0.605, p<0.037). Similarly, positive correlations were noted between salt tolerance and ACC deaminase activity (r=0.762, p<0.004, r=0.771), and salt tolerance and an ability to synthesize siderphores (r=0.771, p<0.003).

• Korean Journal of Weed Science
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• v.15 no.4
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• pp.313-320
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• 1995

The major weeds observed in soybean(Glycine max(L.) Merr.) culture at the paddy field where transplanted rice was cultivated in previous year were Digitaria spp., Echinochloa spp., Chenopodium ficifolium, Rorippa islandica and Stellaria alsine. C. ficifolium and R. islandica increased as soybean was cultivated for two years in the same field. Weed biomass decreased by 84.8% as the seeding date was delayed from April 26 to May 20. Most of weeds started to emerge from 20 days after seeding(DAS) until 40 DAS, and higher seed yield was obtained by eliminating the weeds emerged until 40 DAS. The development of soybean branches, pods stem diameter was severely injured by weed interference, and thus soybean seed yield was reduced by 70% in comparison with a full season weed free plot. Herbicides such as pendimethalin, metolachlor, metolachlor+prometryn and alachlor controlled very effectively weeds present in soybean culture in rice-soybean rotated paddy field.

• The Korean Journal of Ecology
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• v.18 no.1
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• pp.55-62
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• 1995

This study was conducted to investigate the distribution pattern of plants on streamside of Kyonganchon, which is a tributary of the Han River, and to determine the relationships between plant distribution and environmental factors. Fifteen study sites were selected along the Kyonganchon, and vegetation distribution pattern and soil environmental factors were determined. The most frequently ocurring species in the study sites were Persicaria thunbergii, Persicaria hydropiper, Echinochloa crus-galli and Bidens frondosa, and among them the two Persicaria species were dominants of the community. Many species showed different distribution along the stream:Chenopodium album, Equisetum arvense and Setaria viridies occurred in the upstream region, while Rumex crispus, Leonurus sibiricus and Rorippa islandica occurred in the middle and downstream regions. Analysis of soil properties showed that organic matter and clay content were higher in the upstream region while sand content was higher in the downstream region. The results of DCA ordination showed that axis one was positively correlated with organic matter and clay content and negatively correlated with sand content, indicating that the distribution pattern of vegetation along the Kyonganchon was determined by elevational gradient from upstream to downstream region or gradient of stream width and water level, and by soil organic matter content and soil texture related to these gradients.

• Korean Journal of Weed Science
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• v.17 no.2
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• pp.147-156
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• 1997

The survey of weed population in apple orchard was conducted to investigate basic information on weed flora and its ecology at 27 locations in 1996. The weed species observed include 7 species of grasses, 60 species of broadleaves and 2 species of sedges, and the ratio of annual weed vs perennial weed was 64 : 36. Major dominant weed species by frequence were Chenopodium album, Capsella bursa-pastoris, Digitaria sanguinalis, Rorippa islandica, Alopecurus aequalis and Erigeron canadensis. While, on the basis of dry weight, the most dominant weeds were C. album followed by E. canadensis, A. aequalis, R islandica and R indica. The dominant weed species in middle-north Kyeongbuk region were C. bursa-pastoris, C. album, R indica and R islandica, were E. canadensis, Persicaria hydropiper, A. aequalis and Arenaria serpylliforia in Chungbuk region and were A. aequalis, E. canadenris and R islandica in Honam region.

• Weed & Turfgrass Science
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• v.3 no.4
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• pp.269-275
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• 2014

A survey was conducted to identify the occurrence of problematic weed species on the Dioscorea oppostifolia fields in South Korea. Total 43 sites of the 8 different regions in S. Korea were investigated from May to October, 2014. In yam fields, the identified weeds were distributed in 11 families and 44 species. The exotic plants were identified as 3 families, 10 genera, 10 species. The vegetation of Dioscorea oppostifolia fields was classified into communities of 7 groups by methods of the Zurich-Montpellier school of phytosociology (Xanthium canadense Community, Bidens frondosa Community, Echinochloa oryzoides Community, Eclipta prostrata Community, Portulaca oleracea Community, Centipeda minima Community, Rorippa islandica Community). The weeds occurred in Dioscorea oppostifolia fields were divided into three groups in principal component plot analysis (PCA). Without weed control, yields loss in yam production was reached up to 82% as compared to weed controlled fields.

• The Plant Pathology Journal
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• v.16 no.6
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• pp.297-305
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• 2000

Weeds are widely grown in the field and are infected by many viruses. A survey was conducted to identify viruses infecting weeds in Korea. Virus-infected weed samples including Rorippa indica (L.) Hiern, R. islandica (Oed.) Bord, Crepidiastrum denticulatum (Houtt.) Pak & Kawanno, Achyranthes japonica (Miq.) Nakai, and Chrysanthemum boreale (Makino) Makino were collected in Kyonggi Province. These weeds were grown in the greenhouse and were isolated on 10 test plants. Several virus isolates were isolated fron infected tissues and were further studied by host range assay, serological test, electron microscopy (EM), reverse transcription-polymerase chain reaction (RT-PCR) and sequencing. Each isolated virus strain was mechanically transmitted to weeds and various hosts including Nicotiana spp., Brassica spp., Vigna unguiculata, Capsicum annuum, and Cucumis sativus and showed systemic mosaic, vein clearing, necrosis, mottle, malformation, chlorosis, and/or death of host plants in some cases. Each virus was then purified using infected leaves and observed by EM. From these results three viruses were isolated and identified as Turnip mosaic virus (TuMV), Broad bean wilt virus (BBWV), and Cucumber mosaic virus (CMV). RT-PCR using virus-specific oligonucleotide primers and the cloning were conducted to determine the nucleotide sequences of coat proteins of the three viruses their amino acid sequence were deduced. The amino acid sequence homologies were about 92.7 to 99.7%, 96.2 to 97.7%, and 93.9 to 98.6% to other reported TuMV, BBWV, and CMV strains, respectively. These results suggest that many weeds may serve as primary inoculum source of diseases caused by TuMV, BBWV, CMV and that the management of these viral diseases can be achieved through weed control.

• Korean Journal of Weed Science
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• v.11 no.3
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• pp.178-186
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• 1991

This study was conducted to evaluate the major weeds occurred in direct seeded rice and their compition with rice, and to establish the effective weed control method. The important weeds occurring in dry direct seeded rice were Echinochloa crusgalli, Cyperus amuricus, Rorippa islandica, etc. Among them, Echinochloa crusgalli was the most dominant weed species. In view of the Simpson's dominance index, the maximum number of the weeds was observed at 30 days after seeding, showing 0.26, but decreased as the time passed. In other hand, Simpson's dominance index of weed dry weight increased from 0.09 at 15DAS(days after seeding) to 0.28 at 60DAS indicating that particular weed such as barnyardgrass was dominating the fields. The plant height and the tiller number of rice in the dry direct seeded rice were not greatly affected by the time and duration of competition with weeds, but rice yield was greatly influenced by them. The yield reduction was observed when compition between rice and weeds were initiated at 20 to 40 DAS till the harvesting time. The highest weed control efficacy was observed at the treatment of systematic herbicide application such as soil applied Butachlor followed by Mefenacet/Bensulfuron-methyl/Dymron at 30 DAS after seeding, and soil applied Dimepiperate/Bensulfuron-methyl mixture as a preemergence type gave also an excellent control.

• The Korean Journal of Ecology
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• v.28 no.5
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• pp.271-279
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• 2005

Soil seed banks at ecological preservation areas in Seoul, Jinkwannae-dong, Bangi-dong and Bam-sum, were studied by seedling emergence method from May to October 2004. Total number of species and individuals in seed banks were 42 and 5,190 at Jinkwannae-dong, 39 and 2,290 at Bangi-dong, and 39 and 1,047 at Bamsum. Salix koreensis community at Jinkwannae-dong has the highest number of seedlings among all sites. The most abundant species were Lindernia procumbens in Jinkwannae-dong and Bam-sum and Typha spp. in Bangi-dong. The dominant species of seed banks were different from that of plant communities such as Phragmites communis community, Salix koreensis community, Persicaria thunbergii community, Phragmites japonica community, and Populus tomentiglandulosa community. However the dominant species of seed banks in Typha community was Typha spp. Total 63 species emerged in either the wet or submerged conditions. Fifty six species appeared in the wet condition and 25 in the submerged condition. Eighteen species appeared in both conditions. Numbers of species and individuals were much less in the submerged condition than in the wet condition but free-floating hydrophytes including Rorippa islandica and floating-leaved hydrophytes including Monochoria vaginalis appeared only in the submerged condition. In the investigation of soil seed bank by distance from water edge (Bamsum), water side 3 ($300\sim350m$ from water) edge, where water level is fluctuating frequently, has the highest number of seedlings.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.44 no.3
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• pp.236-242
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• 1999

To examine the seedling stand and growth as affected by early seeding dates of dry direct seeded rice in the Honam plain area of Korea, Dongjinbyeo was seeded at six seeding dates from early March to late April in rice fields of silty loam soil(Jeonbuk series) at the National Honam Agricultural Experiment Station (NHAES) for two years, 1996 and 1998. Seedling stand decreased slightly. with an early seeding date, but it produced more than the optimum seedling number except for the seeding of 25 March in 1996. Days to emergence was significantly longer, as seeding date was earlier, and days to emergence by early seeding was shortened only by 8 days because the mean air temperature was lower in 1996 than average, while in 1998, the reduction effect was nine to twenty five days because the mean air temperature was higher than average. In early seeding, various weeds occurred at the emergence date of rice and dominant weeds were Alopecurus aequailis, Ludwigia prostata and Rorippa islandica. NH$_4$$^{+}$ -N content in the soil at the 5th leaf stage and maximum tillering stage were lower, as the seeding date was earlier when nitrogen was split applied as basal and top dressed in 1996, while it was not significantly different among seeding dates when nitrogen was intensively applied as a top dressing in 1998. Tiller number at the maximum tillering stage and panicle number/m$^2$ were more, as seeding date was earlier in 1996, while it was not different in 1998. Filled grain rate and 1,000 grain weight was not different among the seeding dates. Milled rice yield was significantly decreased in the seeding before the middle of March, but in the seeding after late March, it was not varied when compared with the normal seeding date in 1996, while in 1998, there was no difference among seeding dates. From the above results, in consideration of seedling stand, weed occurance, rice growth and milled rice yield, the critical optimum early seeding time in the southern plain area may lie in early April. But it was suggested that when soil moisture is proper for seeding practices, seeding amount is increased and nitrogen is applied after plumule emergence of rice, milled rice yield may not be reduced in the seeding of middle or late March, compared with the seeding in April.l.