• Korean Journal of Plant Taxonomy
• /
• v.41 no.1
• /
• pp.47-50
• /
• 2011

Monochoria vaginalis var. angustifolia (Pontederiaceae) was newly found in a furrow in Imha-ri, Boeun-gun, Chungcheongbuk-do for the first time in Korea. This taxon is distinguished from the other species of the genus Monochoria in Korea by having the smallest plant height, very narrow lanceolate leaves, a cuneate leaf base, and raceme with 1 to 2 flowers. A local name was newly given, 'Ga-neun-moul-dal-ge-bi' for the species. The morphological characteristics and illustrations of the taxon as well as photographs at the habitat are provided with a taxonomic key to the species of Monochoria in Korea.

• Agrochemical news magazine
• /
• v.25 no.3 s.196
• /
• pp.18-21
• /
• 2004

• The Korean Journal of Pesticide Science
• /
• v.8 no.1
• /
• pp.63-70
• /
• 2004

Sulfonylurea(SU)-resistant Monochoria korsakowii has resently been found in rice fields in Korea. A quick, practical and accurate test of confirming herbicide resistance is necessary to take timely management decision. This article describes a rapid reliable assay to detect SU-resistant biotype of Monochoria korsakowii. Up to now, the resistance to SU has been usually checked by application seedlings with herbicide. This application technique is time consuming and not practical. Therefore, we have developed efficient, rapid and practical diagnosis which allow easy detection of the SU-resistant Monochoria korsakowii by survival rate and regenerated plant length to herbicide application after cutting plants $0.5\sim1cm$ from the planted surface. This new rapid diagnosis can determine the SU resistance of the Monochoria korsakowii within 7 days at least. If the resistance of Monochoria korsakowii is identified by the rapid diagnosis, the selection of herbicide according to the stages of plants for the effective control is very important. The resistant biotype which treated with SU herbicide-based mixtures survived from the fields could effectively be controlled by soil application of butachlor+pyrazolate GR or by foliar application of the mixtures of bentazone SL and 2,4-D SL.

• Korean Journal of Environmental Agriculture
• /
• v.17 no.3
• /
• pp.211-214
• /
• 1998

Changes in physico-chemical properties and major nutrient contents were investigated in the soil of paddy fields during fallow period. Weed vegetation change in the fallow paddy fields was also examined. As the fallow period became longer, organic matter content in the paddy soil has gradually increased. Soil pH of the paddy fields has not changed until three years of fallow period and thereafter slightly increased. Cation exchange capacity of the paddy soil, and exchangeable N, K, Ca and Mg contents in the soil tended to decrease until three years of fallow period and then increase with the prolonged fallow period. As the fallow period became longer, available $P_2O_5$ content in the paddy soil has continuously decreased. Available $SiO_2$ content in the paddy soil has not changed until three years of fallow period and thereafter increased. The vegetation in the fallow paddy fields have mostly been occupied by the weeds of the Gramineae, Cyperaceae, and Compositae. As the fallow period became longer, the weeds of the Polygonaceae and Juncaceae have increased, whereas the weeds of the Leguminosae, Commelinaceae, Pontederiaceae, and Onagraceae have gradually disappeared. However, the weeds of the Gramineae and Cyperaceae have always been dominant in the paddy fields during the fallow paddy period.

• The Korean Journal of Pesticide Science
• /
• v.7 no.4
• /
• pp.239-247
• /
• 2003

This experiment was carried out to study the resistant mechanism of sulfonylurea(SU) herbicides to Monochoria korsakowii occurring in the rice fields of Korea. The activity of acetolactate synthase(ALS), absorption and translocation of $[^{14C}]$bensulfuron-methyl, and DNA sequence of ALS genes were studied. The apparent SU resiatance to Monochoria korsakowii was confirmed in greenhouse testes. Fresh weight accumulation$(GR_{50})$ in the resistant biotype was about 5- to 64-fold higher in the presence of six SU herbicides compared to the susceptible biotype. The ALS activity isolated from the resistant biotype to herbicides tested was less sensitive than that of susceptible biotype. The concentration of herbicide required for 50% inhibition of ALS activity$(I_{50})$ was 14- to 76-fold higher as compared to the susceptible biotype. No differences were observed in the rates of $[^{14C}]$bensulfuron uptake and translocation. However, the DNA sequence from the resistant biotype differed from that of the susceptible biotype by single nucleotide substitution at three amino acid each in the middle region excluding the ends of ALS genes. We found three point mutations causing substitution of serine for threonine at amino acid 168, arginine for histidine at amino acid 189, and a aspartic acid for phenylalanine at amino acid 247, respectively, in the resistant biotype.

• Weed & Turfgrass Science
• /
• v.3 no.2
• /
• pp.78-85
• /
• 2014

The survey of weed occurrence was conducted to identify dominant weed species in the paddy field. Total 346 sites of the 12 regions in Chungbuk Province in Korea were investigated in July, 2013. Weed flora was composed of 43 species belonged to 15 families. The compositions of major plant families, Cyperaces, Poaceae, Pontederiaceae and Asteraceae, were 21.5, 17.4, 15.5 and 12.7%, respectively. Based on life cycle, weed species was grouped into annuals of 71.3 and perennials of 28.1%. The most dominant weed species in paddy fields of Chungbuk Province were Monochoria vaginalis (14.5%), followed by Scirpus juncoides (10.5%), Echinochloa oryzoides (9.3%), Eleocharis kuroguwai (7.0%), Aeschynomene indica (6.2%) et al. The similarity of paddy weeds in 12 regions observed through TWINSPAN analysis was distinguished by Persicaria longiseta, Aneilema keisak, Persicaria thunbergii, Fimbristylis millacea, Blyxa japonica, Digitaria ciliaris, Potamogeton distinctus, Cyperus nipponicus. This information could be useful for estimation of future weed occurrence and establishment of weed control methods in chungbuk province in Korea.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.39 no.3
• /
• pp.64-71
• /
• 1997

Floating aquatic plant system using water hyacinth was applied to examine feasibility as a wastewater treatment system for the industrial complex in rural area. The wastewater from the industrial complex does not likely contain toxic pollutants because the industries which generate wastewater with toxic compounds are not allowed to move in. Pilot plant was installed at Baeksuk Nongkong Danzi in Chunahn-City, Chunchungnam - Do , and field study was performed during summer and fall of 1996. Hydraulic loading rate was 0. $0.19m^3/m^2$.day. The effluent concentration of DO was higher than influent, and it implies that 0.6m depth reactor was reaerated enough to increase DO level. The influent concentration of BOD varied significantly from less than 30 to 120mg/${\ell}$ during the study period, however, effluent concentrations were generally lower than the water quality standard and removal efficiency was up to 85%. The influent concentration of COD also showed wide variation from less than 40 to 160mg/${\ell}$ and effluent concentration was higher than water quality standard when influent concentration was over l00mg/${\ell}$. The influent concentrations of T-N and T-P were lower than water quality standard and no further treatment was required, and these compounds were also removed in the system. Although some improvement and refinement are still required, overall* the floating aquatic plant system was proved to be feasible to apply to treat wastewater from industrial complex in rural area.

• Korean Journal of Weed Science
• /
• v.31 no.2
• /
• pp.119-133
• /
• 2011

Sulfonylurea (SU)-resistant weeds include seven annual weeds such as Monochoria vaginalis, Scirpus juncoides and Cyperus difformis, etc., and three perennial weeds of Scirpus planiculmis, Sagittaria pigmaea and Eleocharis acicularis as of 2010 since identification Monochoria korsakowii in the reclaimed rice field in 1998. The Echinochloa oryzoides resistant to acetyl CoA carboxylase (ACCase) and acetolactate synthase (ALS) inhibitors has been confirmed in wet-direct seeding rice field of the southern province, Korea in 2009. In the beginning of occurrence of SU-resistant weeds the M. vaginalis, S. juncoides and C. difformis were rapidly and individually spreaded in different fields, however, theses resistant weeds have been occurring simultaneously in the same filed as time goes by. The resistant biotype by weed species demonstrated about 10- to 1,000-fold resistance, base on $GR_{50}$ (50% growth reduction) values of the SU herbicides tested. And the resistant biotype of E. oryzoides to cyhalofop-butyl, pyriminobac-methyl, and penoxsulam was about 14, 8, and 11 times more resistant than the susceptible biotype base on $GR_{50}$ values. In history of paddy herbicides in Korea, the introduction of SU herbicides including besulfuron-metyl and pyrazosulfuron-ethyl that control many troublesome weeds at low use rates and provide excellent crop safety gave farmers and many workers for herbicide business refreshing jolt. The products and applied area of SU-included herbicides have been rapidly increased, and have accounted for about 69% and 96%, respectively, in Korea. The top ten herbicides by applied area were composed of all SU-included herbicides by 2003. The concentrated and successive treatment of ACCase and ALS inhibitors for control of barnyardgrass in direct-seeded rice led up to the resistance of E. oryzoides. Also, SU-herbicides like pyrazosulfuron-ethyl and imazosulfuron which are effective to barnyardgrass can be bound up with the resistance of E. oryzoides. The ALS activity isolated from the resistant biotype of M. korsakowii to SU-herbicides tested was less sensitive than that of susceptible biotype. The concentration of herbicide required for 50% inhibition of ALS activity ($I_{50}$) of the SU-resistant M. korsakowii was 14- to 76-fold higher as compared to the susceptible biotype. No differences were observed in the rates of [$^{14}C$]bensulfuron uptake and translocation. ALS genes from M. vaginalis resistant and susceptible biotypes against SU-herbicides revealed a single amino acid substitution of proline (CCT), at 197th position based on the M. korsakowii ALS sequence numbering, to serin (TCT) in conserved domain A of the gene. Carfentrazone-ethyl and pyrazolate were used mainly to control SU-resistant M. vaginalis by 2006, the early period, in Korea. However, the alternative herbicides such as benzobicyclone, to be possible to control simultaneously the several resistant weeds, have been developing and using broadly because the several resistant weeds have been occurring simultaneously in the same filed. The top ten herbicides by applied area in Korea have been occupied by products of 3-way mixture type including herbicides with alternative mode of action for the herbicide resistant weeds. Mefenacet, fentrazamide and cafenstrole had excellent controlling effects on the ACCase and ALS inhibitors resistant when they were applied within 2 leaf stage.

• Weed & Turfgrass Science
• /
• v.7 no.1
• /
• pp.15-21
• /
• 2018

Since sulfonylurea (SU) herbicide-resistant Monochoria korsakowii in Seosan reclaimed land in 1998 was reported first, herbicide-resistant weed species and their area of occurrence have been steadily increasing. In recent years, Sagittaria trifolia resistant to SU herbicides has been reported in Gimhae, Gyeongnam province. While collecting S. trifolia for constructing barcode database of major weeds we were suspicious by the continuous variation in the leave morphology of the species. In order to identify the S. trifolia from S. aginash we barcoded the species collected from domestic using ITS and compared the sequence variation with the ITS sequences of S. aginash downloaded from NCBI. As a result, it was found that the plants collected from the domestic did not have any variation among individuals although they showed wide morphological variation. On the other hand, interspecific variation between S. trifolia and S. aginash was 4.6%. Plants that are difficult to identify using morphological characters can be identified quickly and accurately using the barcode technique. Herbicide-resistant weeds may require different management practices depending on the species even in the same genus. Domestic herbicide-resistant weeds are steadily increasing. Therefore, accurate identification of these species must be preceded for effective weed control.