Search

This study was conducted to evaluate the effects of soil amendments on arsenic (As) bioavailability in As-polluted soils. We determined the subsequent changes in As toxicity toward earthworms (Eisenia fetida) and As uptake by earthworms. We also investigated whether As bioaccumulation could be used as an index to evaluate changes in quality of As-polluted soils. No significant changes in acute toxicity to earthworms were observed, and the observed increases (70-93 mg kg-1) or decreases (27-38 mg kg-1) in bioavailable As in soils at the end of test were not related to the As concentrations in earthworms. The As concentration in earthworms 14 days after exposure was significantly lower in calcium superphosphate (CSP)- and S-treated soils (101.4-112.8 mg kg-1) than in control soil (138.9 mg kg-1), probably owing to reduced earthworm growth due to lower pH in CSP- and S-treated soils (6.3-7.3) relative to control and steel slag-treated soils (7.5-8.4). Comparisons of As toxicity and the effects of soil properties on this toxicity toward various species of earthworms could facilitate the use of earthworms to produce biological indices for evaluating changes in quality of As-polluted soils following amendment treatments.

The nationwide weed survey was conducted in arable land, paddy field, upland, orchard and pasture, over whole country of Korea during 3 years from 2013 to 2015. Also, these survey were conducted in order to determine a change of weed community and to identify a major dominant weed species, and problem weeds. Weeds of arable land were composed of 619 species belonging to 81 families. Weeds occurred in paddy field were 90 species belonging to 28 families, upland weeds were 375 species of 50 families, orchard weeds were 492 species of 63 families and pasture weeds 275 species of 52 families. Among total 81 families, the Asteraceae (15.5%) was the biggest family, followed by Poaceae (13.1%), Fabaceae (5.5%), Cyperaceae (5.2%), Polygonaceae (6.3%), respectively. And these weed species were composed of annual weeds of 209 species (33.8%), winter annual of 102 species (16.4%) and perennial weeds of 308 species (49.8%). Exotic weeds naturalized in Korea were investigated as 166 species. Weed flora in Korean cultivation area have been increased as much as 13 families and 186 species for 10 years compared to 2000~2004 weed survey result of 68 families and 433 species. The increment could be resulted from the change of weed population such as increase of the herbicide-resistant and the difference of investigation method.

Surveys of weed species on upland fields were conducted in Korea to investigate the occurrence of weed flora from April to May 2014 for winter crop fields and from July to August 2014 for summer crop fields. From the nation-wide survey, 375 weed species in 50 families were identified and classified to 162 annuals, 78 biennials and 135 perennials. Based on the occurrence ratio, the most weed species belonged to Compositae (73 species). 44 and 25 weed species belonged to Poaceae and Polygonaceae, respectively, and these 183 weed species in the most five families accounted for 49% of total weed occurrence. While 287 weed species in 45 families occurred in the winter crop fields, 339 weed species in 47 families occurred in summer crop fields. The most dominant weed species in Korean upland fields were Digitaria ciliaris, followed by Portulaca oleracea, Acalypha australis, Chenopodium album, Rorippa palustris etc. 129 weed species in 25 families were considered as exotic weeds. Based on the importance analysis, the highest value was C. album followed by Amaranthus lividus, Conyza canadensis etc. This information could be useful for estimation of future weed occurrence, weed population dynamics and establishment of weed control methods in upland fields of Korea.

The purpose of this study was to establish the optimal growth temperature and to select genetic resources for production of cowpea sprouts. Seowon was treated between 15℃ and 30℃ at intervals of 3℃ to investigate growth temperature. Twelve resources, including Seowon, IT154149, IT154153, Tvu7426, and Tvu7778, were used for cultivating sprouts at a temperature of 27℃. The yield ratio of cowpea sprouts was highest at 27℃ (657%), and was reduced when growth temperature was decreased. The hard seed rate was lower when the growth temperature was increased. Vitamin C content was highest at 24℃ (2.85 ㎎/g), ranged between 2.15 and 2.29 ㎎/g at other growth tem-peratures, and increased with the length of the growth period. The inorganic component content of cowpea sprouts did not vary based on growth temperature, while the amino acid content increased with increasing growth temperature between 15℃ and 24℃, and then subsequently decreased as growth temperature rose from 24℃ to 30℃. IT154153 had the highest yield ratio of cowpea sprouts per genetic resource (647%), followed by Seowon (615%), and Tvu7426 (608%). Genetic resources with a higher yield ratio had smaller seeds, a thinner seed coat, and superior germinability. The inorganic components found at highest concentrations in the cowpea sprouts were potassium, magnesium, calcium, sodium, iron, molybdenum, and zinc (in that order). In comparison to raw seeds, the protein, calcium, zinc, molybdenum, and iron content in the cowpea sprouts was higher, while the content of aluminum and boron was lower.

The purpose of this study was to establish the proper sowing time and planting density of cowpeas for labor-saving cultivation. Experiments were carried out in Naju, Jeonnam Province (Latitude 04` N, Longitude 54` E) during 2012 and 2013. The intermediate-erect type strains used in this study were Jeonnam1 and Jeonnam2. Sowing was performed five times between June 25 and August 5 at approximately 10-day intervals in order to establish proper sowing time, and sowed at 5,000, 10,000, 15,000, and 20,000 plants per 10a to establish proper planting density. The days from sowing to first flowering was shortest (32 days) in plants sowed on July 25 and became longer for plants sowed on or around July 25. The days from sowing to first flowering was longest (41 days) in plants sowed on June 25. The days from first flowering to first maturing was shortest (8 days) in plants sowed on June 25 and, became considerably longer at later sowing dates. The days from first maturing to first harvesting ranged from 8 to 10 days, with little difference among the sowing periods. Plants sowed on August 5 harvested at the same time, and plants sowed between June 25 and July 25 were harvested either three or two times. The yield was highest in plants sowed on July 25: 209 kg/10a was harvested for Jeonnam1 and 221 kg/10a for Jeonnam2. Furthermore, harvested at the same time enabled when the harvesting was delayed for around 15 days because the share of the seeds first harvested was highest (91%). The proper planting density was estimated to be 15,000 plants/10a, showing the highest yields of 199 kg/10a for Jeonnam1 and 224 kg/10a for Jeonnam2.

The purpose of this study was to investigate the effects of sowing time on the bio-active content of major soybean cultivars in a southern region of South Korea. Experiments were carried out in Naju, Jeonnam Province (latitude 35° 04'N, longitude 126° 54'E) from 2008 to 2010. The cultivars grown in summer included Saeol- kong and Tawon-kong and those grown in autumn included Taekwang-kong, Pungsannamul-kong, and Cheongja3, respectively. Sowing dates were May 15 and 30, June 15 and 30, and July 15 of each year. Daidzein content was increased in all the test cultivars grown from later sowing, and the contents of genistein and total isoflavone were increased in all the test cultivars except for Cheongja3. On the other hand, glycitein content showed no significant change in any of the test cultivars across the 5 sowing dates except for Tawon-kong. Cyanidin-3-glucoside (C3G) content was significantly increased in Tawon-kong and Cheongja3, and delphinidin-3-glucoside (D3G) and total anthocyanin contents were significantly increased in Tawon- kong. However, pelargonidin-3-glucoside (Pg3G) and petunidin- 3-glucoside (Pt3G) contents showed no significant difference in plants sown across the 5 dates. Lutein content in Cheongja3 was between 2.7 and 3.0 µg/g based on sowing date and did not vary significantly, while chlorophyll content increased with later sowing and was significantly higher in the cultivars sown on June 30 and July 15. Crude fat content was higher in Taekwang-kong and Cheongja3 when the cultivars were sown earlier; crude fat did not vary in the other test cultivars based on sowing date. Palmitic acid composition was not affected by sowing date in most of the test cultivars. Stearic acid was increased in Saeol-kong, Tawon-kong, and Cheongja3 with later sowing. Oleic acid and linoleic acid were significantly higher in Saeol-kong at an earlier sowing date. The composition of linolenic acid showed significantly increased dates in most of the test cultivars with later sowing. There were no significant differences in carbohydrate and crude protein content across 5 different sowing dates in most of the test cultivars. However, crude protein content was higher in Saeol-kong when sowing occurred earlier, and was higher in Tawon-kong at later sowing dates. Keywords : bio-active substance, sowing time, soybean, variation

Currently, methods for controlling weeds in organically produced crops have not been as effective as conventional methods. This research was carried out to determine the herbicidal effects of leaf, stem, fruit, root extracts of Trichosanthes kirilowii. The extraction methods used were water, boiling water and ethanol. The characteristics of potential herbicidal components among extraction methods were investigated by using the following solvent fractions: hexane, chloroform, ethyl acetate, butanol, and water. Generally, water extracts provided the best on inhibition of germination rate, plant height, and root length in cucumber and barley. Specifically, extractions made from fruit parts of T. kirilowii provided the greatest inhibition effect on plant growth in cucumber and barely. Inhibition of germination rate, plant height, and root length in cucumber and barley in solvent fractions was the best in water fractions, but there were no significant differences among the other fractions. Digitaria siliaris and Solanum nigrum were controlled 80-100% by 5% extractions of water fraction. However, there were no herbicidal effects from foliar treatment in cucumber, barley, black nightshade, and henry crabgrass by 5% extractions of the water fraction. These results show that extractions of T. kirilowii can be used for controlling some weeds in organically produced crops.

Despite the growing body of evidence that ongoing warming modifies the cereal quality of several crop species, little is known about how it interacts with other climate change drivers. Here, we examined how elevated [CO 2 ], warming, and extreme wet events (EWEs) would affect the grain quality of a temperate rice ( Oryza sativa L.). In 2009 and 2010, plants were grown at two levels of [CO 2 ] ( c . 390 and 650 μl l −1 ) and three levels of warming (ambient, +1.2 °C and +2.2/2.4 °C) over the seasons in six independent temperature gradient field chambers (three each for ambient and elevated [CO 2 ]). From 20 days after heading, plants were exposed to EWE with a simulated rainfall of 30 mm a day and cloud cover by shading ( c . 18% of full sunlight) for 10 consecutive days. There were also control plots, which were non-treated (NT) in terms of EWE. We found that warming and EWE, both independently and in their interaction, lead to a significant reduction in the percentages of sound grains, whereas elevated [CO 2 ] does not seem to do so. Not only warming and EWE, but also elevated [CO 2 ] resulted in a significant increase of immature chalky grains (ICGs), which mostly consisted of milky-white chalky grains, degrading the grain quality. In addition, warming interacted positively with elevated [CO 2 ] on ICGs, whereas the warming sensitivity of IGCs was moderated in EWEs: e.g., on average, the % of ICGs in ambient vs. elevated [CO 2 ] were 8.5% vs. 9.4%, 10.7% vs. 18.1% and 17.8% vs. 29.8% at ambient (24.7 °C), +1.2 °C and +2.4 °C, respectively, whereas they in NT vs. EWE were 1.2% vs. 16.6%, 7.7% vs. 21.1% and 19.4% vs. 28.2%. Our results tightly confirmed that elevated [CO 2 ] leads to a significant reduction in rice grain protein content (PC). While warming had little effect on the PC, EWE had a significant positive effect, and the EWE-induced increase in PC was smaller in elevated (+3.3%) than in ambient [CO 2 ] (+10.9%). Given the rice quality predictor of ICGs and PC, our findings imply that expected climate change and weather extremes have a great potential to degrade the quality of rice, in terms of its milling, cooking, eating, and nutritional quality, as well as market value.

The objectives of this study were to investigate the levels of phytotoxicity of rice varieties to HPPD (4-hydroxy phenylpyruvate dioxygenase)-inhibiting herbicides known for their efficiency to control the sulfonylureas-resistant weed species:mestrione, benzobicyclone, and tefuryltrione. The twenty-six rice varieties (8-Japonica × Indica-type varieties and 18-Japonica-type varieties) were grown for 25 days on seedling trays and then transplanted to paddy rice fields followed by herbicide treatment i.e. standard and double doses of there respective herbicides at 5, 10, and 15 days after transplanting. Although mestrione, benzobicyclone and tefuryltrione are all HPPD-inhibiting herbicides, the phytotoxicity symptoms of the different rice varieties based on the timing of application and doses of the herbicides were significantly different. The Japonica × Indica-type varieties showed much more phytotoxicity symptoms than Japonica- type varieties in all applied herbicides. Increasing herbicidal doses of mesotrione, and an earlier application of and increasing herbicidal doses of benzobicyclon caused severe phytotoxicity symptoms. On the other hand, phytotoxicity due to tefuryltrione did not exhibit significant differences between rice varieties in either the timing of application or dose of the herbicide. Regardless of timing of application and dose of the herbicides, Hangangchalbyeo-1, Hyangmibyeo-1 and high-yield rice varieties such as Namcheonbyeo, Dasanbyeo, Areumbyeo, and Hanareumbyeo, which belong to the Japonica × Indica-type varieties, showed 5 to 8 levels of phytotoxicity symptoms including albinism, browning, detached leaf, and necrosis to mesotrione and benzobicyclon whereas only 1 to 3 levels of phytotoxicity symptoms (chlorosis, albinism, and browning) were seen with to tefuryltrione application. The Japonica-type varieties exhibited only slight

Field experiments were conducted to investigate the competition relationships of main paddy weeds with transplanted rice grown in paddy conditions. Data were used to predict crop yield as a function of weed density using a rectangular hyperbola model and determine weed economic threshold (ET) levels. The rectangular hyperbola (equation 2) was fitted to rice yield to estimate weed-free rice yield (Y o ) and weed competitivity (β). Its competitivity for M. vaginalis was 0.0007445, 0.0005713, 0.000988 and 0.0008846 in Daejeon, Suwon, Iksan and Naju, respectively. The competitivity at harvest represented by parameter β ranged from 0.001611 in Naju to 0.002437 in Iksan for S. trifolia. The ET levels of main paddy weeds in machine transplanted rice cultivation were well estimated based on the herbicides applied and its application cost. Therefore, our results can be used to support decision-making on herbicide application for weed management in transplanted rice cultivation.

The fourth leaves (younger leaves) amongst extended 4-upper leaves in 18 squash cultivar were the highest tolerance to the paraquat application, followed by third, the second, and the first leaves (older leaves). The forth leaves in Joongangaehobak showed more than three times higher tolerance to the paraquat application than did the first leaves. When the combining of water extract from the fourth leaves with paraquat were applied to the leaves and stems of maize, the paraquat phytotoxicity in maize was reduced compared to the paraquat application alone. Therefore, this study continued to investigate if the phytotoxicity inhibitor exist in the fourth leaves. The water extract in the fourth leaves were isolated by silica gel column chromatography, Sephadex LH-20 column chromatography, TLC, and HPLC, and the substance in the extract was speculated as a malic acid by identifying through NMR. The mixture malic acid and paraquat were applied to the maize to verify the application effect of malic acid on paraquat toxicity. The 100 µM of paraquat application alone showed 62% of paraquat toxicity to the corn leaves, while the combined application of 100 µM paraquat with malic acid at 0.1, 0.3, 0.5, and 1.0% did not show the symptom.

*ABSTRACT This research has been carried out to find out the highest effect on insecticidal, fungicidal and herbicidal activities in leaves, stem and tuber extracts of yacon (Smallanthus sonchifolius) and extraction methods such as water, boiling water and methanol. Characteristics of potential herbicidal components among extraction methods were investigated by solvent fractions such as hexane, chloroform, ethyl acetate, butanol, and water. Generally, methanol extract was the best on inhibition of germination rate, plant height, and root length in cucumber and barley. On the other hand, the inhibition effect on growth in cucumber and barley was the best in tuber among plant parts of yacon. Inhibition of germination rate, plant height, and root length in cucumber and barley in s olvent fractions was the best in water fraction, but there were no differences in other fractions. Digitaria sanguinalis L. and Solanum nigrum L. by 5 and 10% extractions of yacon tuber were controlled by more than 70～80% and 95～100%, respectively. However, there was no inhibition effect on foliar treatment in cucumber and barley as affected by 5 and 10% extractions of yacon tuber. Mortality of green peach aphid (Myzus persicae Sulzer) was 50% at 3 days after treatment of 5% extracts of yacon leaves. Mortality of brown plant hopper (Nilaparvata lugens Stal) was only 24% in 5% extracts of stems and leaves with midr ib, but was 57% in 5% extracts of leaves without midrib. There was no fungicidal effect on anthracnose (Colletotrichum truncatum), wilt disease (Fusarium oxysporum), verticillium wilt (Verticillium dahliae), bacterial blight (Xanthomonus oryzae) in 5% extracts of yacon leaves.Key words: fungicidal activity; herbicidal activity; insecticidal activity; plant extract; yacon.

The objective of this research was to confirm the difference in physiological responses to environmental stresses such as chilling, high temperature, NaCl, and chemical stress (paraquat) in Protox inhibitor resistant-transgenic rice (MX, PX, and AP37) and its non-transgenic counterpart (WT). Transgenic and non-transgenic rice plants were exposed to a chilling temperature of for 1 day or a high temperature of for 4 days and allowed to recover at for 6 days after the chilling treatment or 8 days after the high temperature treatment. Leaf injury, shoot fresh weight, porphyrin biosynthesis substances, and chlorophyll content were investigated in transgenic and non-transgenic rice at 6 days after 0.5% and 1% NaCl treatments or at 5 days after 0~300 paraquat treatments. No significant difference in leaf injury and shoot fresh weight were observed between transgenic and non-transgenic rice during chilling and recovery. Plant height and shoot fresh weight were also similar between transgenic and non-transgenic rice during the high temperature and recovery period (0~5 days). However, plant height and shoot fresh weight in transgenic rice line MX and PX were lower than in non-transgenic rice at 6 days for recovery. Leaf injury, chlorophyll, and Mg-Proto IX ME contents had no significant difference between transgenic rice and non-transgenic rice after NaCl treatment, but Proto IX content for AP37 and shoot fresh weight for PX and AP37 in 0.5% NaCl treatment were significantly reduced compared with non-transgenic rice. There was no difference in leaf injury and shoot fresh weight when comparing transgenic rice and non-transgenic rice after paraquat treatment. Although transgenic rice and non-transgenic rice showed a little difference at a particular measurement period in certain environmental stresses, there was generally no difference in physiological responses between transgenic rice and non-transgenic rice.

Characteristics related to grain quality and physiochemical components such as mineral, total amino acid, free amino acid, and free sugar composition were investigated in Protox inhibitor resistanttransgenic rice (MX, PX, and AP37) and its nontransgenic counterpart (WT). Head rice, palatability, protein, and whiteness (except for MX and AP37) of milled transgenic rice were high or similar to those of the non-transgenic counterpart. Immature rice, unfilled grain, and cracked kernels (PX and AP37) of milled transgenic rice were lower than those of its non-transgenic counterpart. However, there were no significant differences in damaged grain between the transgenic rice lines and its counterpart. Potassium content in PX and copper contents in PX and AP37 were only low compared with their non-transgenic counterparts, but other mineral contents in transgenic rice lines were high or showed no significant differences compared with non-transgenic counterparts. Contents of most total amino acid composition in transgenic rice lines were high or similar to those in non-transgenic counterparts, but the content of isoleucine in AP37 was only low compared with its non-transgenic counterpart. On the other hand, free amino acid, leucine and tyrosine in PX and AP37, and total free amino acid in PX were low compared with their non-transgenic counterparts. However, the content of free amino acid in other kinds in transgenic rice lines were similar to those in their non-transgenic counterparts. Contents of sucrose in MX and PX were low compared with non-transgenic counterpars, but contents of fructose, glucose, and maltose in transgenic rice lines were high or similar compared with their non-transgenic counterparts. This results indicated that Protox genes had no negative affect on the nutritional composition of rice.

This study was carried out to evaluate genetic variation of early-heading rice (Oryza sativa L. cv. Dongjin 1) lines derived from gamma-ray ( 60 Co, 300 Gy) irradiation. The average heading date of the 5 early-heading lines in M7 and M8 generation was faster than that of untreated control as 11 (line γ-2), 10 (line γ-5), 6 (γ-1 line), 5 (γ-3) and 4 days (line γ-4), respectively. According to ISSR analysis, polymorphic rate of the early-heading lines (from 5.9% to 23.4%) was higher than that of control (4.3%). The result indicates that the gamma-ray promote variation at DNA level. When genetic variations of rps16-trnK region were evaluated by nucleotide analysis, nucleotide length of the rps16-trnK region was 664 bp in all the early-heading lines and control. Out of 5 sites of nucleotide transposition detected in the region, however, 2 sites were appeared only in the early-heading lines.

This study was conducted to predict the rice yield loss and to determine the economic threshold levels for direct-seeding flooded rice cultivation from competition to the most serious weeds, Sagittaria trifolia L. and Bidens frondosa L. The rice yield loss models of S. trifolia and B. frondosa were predicted as Y=497.0/(1+0.003760x), R 2 =0.869 and Y=486.0/(1+0.007612x), R 2 =0.887, respectively. In comparison of the competitiveness represented by parameter β, it was 0.003760 in S. trifolia and 0.007612 in B. frondosa, respectively. Economic thresholds calculated using Cousens' equation was negatively related with the competitiveness of weed. The economic thresholds of S. trifolia and B. frondosa were 7.6 and 3.9 plants per m 2 , respectively.Key words: Bidens frondosa; competitiveness; direct-seeding flooded rice; economic threshold; Sagittaria trifolia. 서 언 최근 들어 실시되고 있는 친환경 벼 재배는 환경보전과 생산비 절감에 대한 중요성이 부각되면서 벼농사의 잡초 관리가 제초제를 이용한 완전방제 개념에서 쌀 생산 경제 비용을 고려한 친환경 잡초관리 기술로 대체되고 있는 실정이다(Kwon 등 2009). 논 잡초는 벼와 양분 및 광, 수분 등 다양한 요소의 경합을 통하여 수량감소를 초래하므로 잡초종류별 발생밀도에 따라 정확한 수량 감수 예측모델을 설정하여 방

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 m2 ) 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 indicat ed that yield of rice in wet seeding rice cultivation could be reduced by over economic threshold densities of S. planiculmis and L. dubia.

*ABSTRACT The objectives of this study were to investigate fitness difference in growth and rice yield in herbicide-transgenic rice overexpressing Myxococcus xanthus and Arabidopsis thaliana protoporphyrinogen oxidase (Protox) genes and non-transgenic rice. We also aimed to determine whether these fitness differences are related to ALA synthesizing capacity, accumulation of terapyrroles, reactive oxygen species, lipid peroxidation, and antioxidative enzymes at different growth stages of rice. Plant height of the transgenic rice overexpressing M. xanthus (MX) and A. thaliana (AP37) Protox genes at 43, 50, and 65 days after transplanting (DAT) was significantly lower than that of WT. Number of tiller of PX as well as MX and AP37 at 50 and 65 DAT was significantly lower than that of WT. At harvest time, culm length and yield of MX, PX and AP37 and rice straw weight of MX and AP37 were significantly low compared with WT. The reduction of yield in MX, PX, and AP37 was caused by spikelets per panicle and 1000 grain weight, ripened grain, spikelets per panicle, 1000 grain weight, and ripened grain, respectively. On the other hand

Weeding effect was investigated based on the leaf stages to several different herbicide treatments for an integrated weed management of herbicide resistant Echinochloa oryzoides to ACCase and ALS inhibitors in a rice field. Efficacy of soil-applied herbicide treatments before resistant E. oryzoides occurred was very effective. Pentaxazon 5% SC showed over 98% of weeding effect although E. oryzoides were emerged 31 days after the treatment. Until the leaf stage of 2.5, five herbicides, azimsulfuron․carfenstole 1.05% GR, bensulfuron-methyl․benzobicyclone․mefenacet 24.52% SC, bensulfuron-methyl․fentrazamide 7% SC, bensulfuron-methyl․mefenacet․oxadiargyl 21.6% SC and mefenacet․pyrazosulfuron-ethyl 3.57% GR showed perfect weeding effect. Benzobicyclone․mefenacet․penoxulam 21.5% SC and mefenacet․pyrazosulfuron-ethyl 3.57% GR were effective at the leaf stage of 3.0. It is very important to select the right herbicides for timing and their systematic application for controlling of E. oryzoides resistant to ACCase- and ALS-inhibitors.Key words: ACCase; ALS; Echinochloa oryzoides; herbicide resistance.

The objective of this research was to find out the weed management techniques in environment-friendly rice paddy fields through the study on herbicidal effects and problems of various organic materials. This experiment was conducted under different conditions of weed species and weed densities in environment-friendly rice paddy fields. There was no difference in weedy efficacy on golden apple snail (GAS), paper mulching (PM), and machine weeding (MW) between low and high weed densities. However, the effect of weed control in rice bran (RB) and effective microorganism (EM) + molasses was higher in high weed density than in low weed density. In general, the effect of weed control as affected by various organic materials was in the order of GAS (97-100%) > PM (93-98%) > RB (15-80%) > EM (7-31%). GAS provided excellent control of all weed species tested except for Persicaria hydropiper. PM gave acceptable control of the weed species except for Echinochloa crus-galli, Ludwigia prostrata, and Eleocharis kuroguwai. However, MW gave fair control (70% biomass reduction) of all weed species tested. BR followed by MW or EM followed by MW treatments had similar effect on weed control compared to each treatment alone. However, BR followed by GAS or EM followed by GAS provided 100% control of weed species tested. The level of rice foliar injury caused by various organic materials was in the order of GAS and MW (10-20%) > RB (10-15%) > PM and EM (5-7%). Typical symptoms of organic materials are wilting, inhibition of growth, missing hill, and reduction of tiller. Cost for weed control of GAS, RB, EM, and PM were 2.1, 3.1, 2.3, and 13.2 times higher than that of the

The objective of this research was to discover the best method for weed management in environment-friendly rice paddy fields through the study on the effect of weed control and injury levels of rice plants as affected by size, input time, and input amount of golden apple snail (GAS). The efficacy of weed control as affected by GAS when applied at 5, 10, and 15 days after transplanting (DAT) was 98, 89, and 58%, respectively. The efficacy of weed control had declined as late the input time of GAS. On the other hand, the efficacy of weed control as affected by rice bran followed by GAS treatment was higher than by GAS treatment alone. Weed species such as Persicaria hydropiper, Echinochloa crus-galli, Scirpus juncoides, and Monochoria vaginalis were not completely controlled by GAS when applied late. Input amount and time of adult GAS (70 days after hatching) for effective weed control were 3 kg 10a -1 at 5 DAT, 6-7 kg 10a -1 at 10 DAT, and 7 kg 10a -1 at 15 DAT. Input time and amount of young GAS (35 days after hatching) for effective weed control were 0 day after harrow (DAH) and 1 kg 10a -1 , respectively. The young GAS when applied 0 DAH at 1 kg 10a -1 provided 100% control of P. hydropiper, E. crus-galli, S. juncoides, M. vaginalis, Ludwigia prostrata, Eleocharis kuroguwai, Sagittaria trifolia and Cyperus difformis. The rice foliar injury caused by adult (3 kg 10a -1 ) and young (1 kg 10a -1 ) GAS were 5-7% and 1% respectively. There was no significant difference in rice injury by size and input amount of GAS on plant height and number of tiller. These data indicate that the young GAS when applied

We investigated the levels of resistance and accumulation of terapyrroles, reactive oxygen species, lipid peroxidation, and antioxidative enzymes for reasons of growth reduction in herbicide-transgenic rice overexpressing Myxococcus xanthus, Arabidopsis thaliana, and human protoporphyrinogen oxidase (Protox) genes. The transgenic rice overexpressing M. xanthus (MX, MX1, PX), A. thaliana (AP31, AP36, AP37), and human (H45, H48, H49) Protox genes showed 43~65, 41~72 and 17~70-fold more resistance to oxyfluorfen, respectively, than the wild type. Among transgenic rice lines overexpressing Protox genes, several lines showed normal growth compared with the wild type, but several lines showed in reduction of plant height and shoot fresh weight under different light conditions. However, reduction of plant height of AP37 was much higher than other lines for the experimental period. On the other hand, the reduction of plant height and shoot fresh weight in the transgenic rice was higher in high light condition than in low light condition. Enhanced levels of Proto IX were observed in transgenic lines AP31, AP37, and H48 at 7 days after seeding (DAS) and transgenic lines PX, AP37, and H48 at 14 DAS relative to wild type. There were no differences in Mg-Proto IX of transgenic lines except for H41 and H48 and Mg-Proto IX monomethyl ester of transgenic lines except for MX, MX1, and PX. Although accumulation of tetrapyrrole intermediates was observed in transgenic lines, their tetrapyrrole accumulation levels were not enough to inhibit growth of transgenic rice. There were no differences in reactive oxygen species, MDA, ALA synthesizing capacity, and chlorophyll between transgenic lines and wild type indicating that accumulated tetrapyrrole intermediate were apparently not high enough to inhibit growth of transgenic rice. Therefore, the growth reduction in certain transgenic lines may not be caused by a single factor such as Proto IX, but by interaction of many other factors.

Field experiments were conducted to investigate rice — Echinochloa crus-galli and rice — Eleocharis kuroguwai competition under transplanted rice cultivation in four major rice production areas; Suwon, Daejeon, Iksan, and Naju in Korea. Rice yield data were used to predict rice yield as a function of plant densities of E. crus-galli and E. kuroguwai using a rectangular hyperbola and to determine economic threshold (ET) levels of the weeds. Both weed species significantly reduced number of tillers at early rice growth stage, resulting in significant reduction in number of spikes, and the other yield components such as number of grains, maturity and 1,000-grain weight at later growth stage. The weed competitivity represented by parameter ranged from 0.0145 to 0.0346 for E. crus-galli and from 0.0037 to 0.0187 for E. kuroguwai, indicating that the competition effect of E. crus-galli on rice yield was slightly greater than that of E. kuroguwai. The ET values of E. crus-galli were between 0.298 and 1.078 plants m−2, while those of E. kuroguwai were between 0.848 and 5.298 plants m−2, depending on weed competitivity and herbicide price. Therefore, our results can be used to support decision-making on herbicide application for E. crus-galli and E. kuroguwai management in transplanted rice cultivation.

This study was conducted to predict the rice yield loss and determine the economic threshold levels for water direct seeded rice from competition of the most serious weeds, Scirpus juncoides Roxb. (bulrush) and Echinochlor crusgalli L. (barnyardgrass) in Daegu of Korea. To predict crop yield as a function of weed density used a rectangular hyperbola, and determine their economic threshold levels used the equation developed by Cousens. The rice yield loss model of S. juncoides was predicted as y

A Cyperus difformis L accession from Chonnam province, Korea was tested for resistance to the sulfonylurea herbicide, imazosulfuron. The accession was confirmed to be resistant (R) and was cross-resistant to other sulfonylurea herbicides, bensulfuron-methyl, cyclosulfamuron and pyrazosulfuron-ethyl, the pyrimidinyl thiobenzoate herbicide, bispyribac-sodium, and the imidazolinone herbicide imazapyr, but not to imazaquin. Multiple resistance was tested using twelve herbicides with target sites other than acetolactate synthase (ALS). The R biotype could be controlled by other herbicides with different modes of action such as butachlor, carfentrazone-ethyl, clomeprop, dithiopyr, esprocarb, mefenacet, oxadiazon, pretilachlor, pyrazolate and thiobencarb, applied to soil at recommended rates. Several sulfonylurea herbicide-based mixtures can control both the R and S biotypes of C difformis, except sulfonylurea plus dimepiperate, molinate or pyriftalid, and pyrazolate plus butachlor. Although mixtures of sulfonylurea herbicides might be more effective, they should be avoided and used only in special cases. In terms of in vitro ALS activity, the R biotype was 1139-, 3583-, 1482-, 416-, 5- and 9-fold more resistant to bensulfuron-methyl, cyclosulfamuron, imazosulfuron, pyrazosulfuron-ethyl, bispyribac-sodium and imazapyr, respectively, than the S biotype. The in vivo ALS activity of the R biotype was also less affected by the sulfonylurea herbicides, imazosulfuron and pyrazosulfuron-ethyl, than the S biotype. Results of in vitro and in vivo ALS assays indicated that the resistance mechanism of C difformis to ALS inhibitor herbicides was primarily due to an alteration in the target enzyme, ALS. Greenhouse experiments showed delayed flowering and reduced seed production of the R biotype, which could possibly result in reduced fitness. This unusual observation needs to be confirmed in field situations.

Sulfonylurea (SU)-resistant monochoria has recently been found in rice paddies in Korea. A quick and accurate means of confirming herbicide resistance is necessary to take timely management decisions. This article describes a rapid and reliable assay to detect SU-resistant biotype of monochoria. The techniques tested include seed germination, in vivo and in vitro acetolactate synthase (ALS; EC 4.1.3.18) activity, leaf, and whole-plant bioassays. In the whole-plant bioassay, shoot dry weight of the resistant (R) biotype was 3,200-fold less affected by imazosulfuron and sevenfold less affected by pyrazosulfuron-ethyl than the susceptible (S) biotype. Although the whole-plant bioassay is reliable, it is expensive, requires a lot of infrastructure, and takes a few months to complete. The germination rate of the R biotype in petri dish bioassays was > 200-fold less inhibited by imazosulfuron and 100-fold less inhibited by pyrazosulfuron-ethyl than that of the S biotype. Seed germination bioassays in p...

Nine Monochoria vaginalis Presl accessions from Chonnam province, Korea were tested for resistance to the sulfonylurea herbicide, imazosulfuron, in whole-plant response bioassay. All accessions were confirmed resistant (R) to imazosulfuron. The GR50 (imazosulfuron concentration that reduced shoot dry weight by 50%) values of R accessions were 1112–3172 (accession #9) times higher than that of the standard susceptible (S) accession. Accession #9 exhibited cross-resistance to other sulfonylurea herbicides, bensulfuron-methyl, cyclosulfamuron and pyrazosulfuron-ethyl, but not to the imidazolinone herbicides, imazapyr and imazaquin. The R biotype could be controlled by other herbicides with different modes of action, such as mefenacet and pyrazolate, applied to soil at recommended rates. Foliar-applied herbicides, 2,4-D and bentazone, also controlled both the R and S biotypes. Sulfonylurea-based mixtures, except ethoxysulfuron plus fentrazamide, did not control resistant M vaginalis. Rice yield was reduced 70% by resistant M vaginalis that escaped pyrazosulfuron-ethyl plus molinate, compared with hand weeding in direct-seeded rice culture. In contrast, rice yield was reduced 44% by resistant M vaginalis that survived the pyrazosulfuron-ethyl plus molinate treatment, compared with pyrazolate plus butachlor in transplanted rice culture. In vitro acetolactate synthase (ALS) activity of the R biotype was 183, 35, 130 and 31 times more resistant to imazosulfuron, bensulfuron-methyl, cyclosulfamuron and pyrazosulfuron-ethyl, respectively, than the S biotype. Imidazolinone herbicides, imazapyr and imazaquin had similar effect on in vitro ALS activity of the R and S biotypes. The in vivo ALS activity of the R biotype was also less affected than the S biotype by the sulfonylurea herbicides imazosulfuron and pyrazosulfuron-ethyl. Results of in vitro and in vivo ALS assays indicate that the resistance mechanism of M vaginalis to sulfonylurea herbicides may be due, in part, to an alteration in the target enzyme, ALS. Since the level of resistance in the enzyme assay was much lower than that in the whole-plant assay, other mechanisms of resistance, such as herbicide metabolism, may be involved. Copyright © 2003 Society of Chemical Industry

A Rotala indica accession from Chonnam province, Korea was tested for resistance to sulfonylurea (SU) herbicide, imazosulfuron. The accession was confirmed to be resistant (R) and was cross-resistant to other SU herbicides, bensulfuron-methyl, cyclosulfamuron, and pyrazosulfuron-ethyl, but not to imidazolinone herbicides, imazapyr, and imazaquin. Multiple resistance was tested using eight herbicides with target sites other than acetolactate synthase (ALS). The R biotype was susceptible to other herbicides with different modes of action, such as fentrazamide and mefenacet. Herbicide mixtures, butachlor + pyrazolate and MCPB + molinate + simetryne can also control R biotype of R. indica . Although mixtures of SU herbicides with other modes of action can control the R biotype, use of these mixtures should be avoided. In vivo ALS activity of the R biotype was 35-, 26-, 278-, and 7-fold more resistant to bensulfuron-methyl, cyclosulfamuron, imazosulfuron, and pyrazosulfuron-ethyl, respectively, than the S biotype. The resistance mechanism of R. indica to imazosulfuron was mainly due to an alteration in the target enzyme, ALS. Since the level of resistance to other SU herbicides in the enzyme assay was much lower than that in the whole-plant assay, other mechanisms of resistance, such as herbicide metabolism, or reduced absorption and translocation may be involved. There was no indication of fitness difference between the R and S biotypes.

The objectives of this research were to quantify resistance levels in different rice biotypes to HPPD-inhibiting herbicides, benzobicyclon, mestrione, and tefuryltrione and determine mechanisms of resistance of benzobicyclon in different rice biotypes. In terms of shoot fresh weight, japonica-type, Ilmibyeo and Baekokchal were 17-and 53-73-fold more resistant to benzobicyclon and mestrione, respectively, than indica x japonica-type, Hyangmibyeo-1 and Dasanbyeo. However, responses of shoot fresh weight in rice cultivars of japonica-type to tefuryltrion were similar to those of indica x japonica-type. Carotenoids and chlorophylls contents of the japonica-type, Iilmibyeo and Baekokchal were also less affected by the benzobicyclon, than the indica x japonica-type, Hyangmibyeo-1 and Dasanbyeo. The levels of MDA and H2O2 in rice cultivars of indica x japonica-type after benzobicyclone treatment were much higher than those of rice cultivars of japonica-type. Thus, the resistance in rice cultivars of japonica-type may be caused by the result of less lipid peroxidation, less H2O2, higher carotenoid and chlorophyll contents when exposed to HPPD-inhibitibg herbicide, benzobicyclon.