• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.4
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• pp.254-258
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• 1998

Distribution and occurrence of weedy rice in Kyonggi region were surveyed in 1996. Weedy rice was observed in 1368 fields (54.9%) of total 2490 fields. Almost two thirds of paddy fields in northern mountainous region were contaminated by weedy rice and more severe contamination, three forths of paddy fields, was observed in suburban regions. In those regions, occurrence of weedy rice was greater than those in north-eastern inland and south-western plain regions. The occurrence of weedy rice was higher in water seeding cultivation (66.7%) than other cultivation methods. The number of weedy rice per 10a was 756.7 plants in direct seeding on dry paddy and 379.4 plants in water seeding. The occurrence of weedy rice was higher in fields planted by farmer's seeds than that of paddy fields cultivated by certified seeds, and the longer the farmer's seeds being used, the more weedy rice occurred in paddy field.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.42 no.3
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• pp.352-356
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• 1997

In order to trace the survival route of weedy rice in Korean farmer's field, occurrence rate and position of weedy rice, number of weedy rice plants per $m^2$, in transplanted and direct seeded field were investigated. The highest occurrence rate of weedy rice in transplanted field was 5.5％. Number of weedy rice plants in direct seeded field was higher than that in transplanted field. In transplanted field, most of the weedy rice were grown within hills of cultivated rice and only a few was grown between hills of the cultivated rice, however in direct seeded field the number of weedy rice occurred between hills or rows of cultivated rice was higher than that occurred within hills or rows. Weedy rice occurrence rate in the field of .non-recommended rice variety was higher than that in the field of recommended variety. The main survival route of weedy rice in transplanted field was supposed to be mixture of weedy rice seeds with cultivated rice, and that in direct seeded field to be natural survival.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.4
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• pp.232-236
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• 2000

To obtain a basic information on the development of effective control strategies for weedy rice in direct seeding rice cultivation, occurrence patterns of weedy rice as influenced by different cultural practices such as cultivation method, water management, seeding time, and tillage were investigated in field or pot experiments. High occurrence of weedy rice was observed in a continuous direct seeding paddy field as compared to machine transplanted one. Based on the percent of weedy rice panicle over three years trial, high ridged dry seeding was highest with 36.9%, followed by wet seeding with 30.9%, water seeding with 14.6% and machine transplanting rice with 0.8%, indicating 97.8% reduction in weedy rice occurrence by machine transplanting rice as compared with high ridged dry seeding. Germination of weedy rice was promoted to 83-94 % when rice panicle was flooded from September 30 to October 10 for 6 days and 74-88% for 9 days on October 20. Weedy rice occurrence was also substantially reduced by delayed seeding on June 10 and intensive tillage. The results suggest that machine transplanting rice be more effective cultural practice than flooding treatment, delayed seeding and intensive tillage when weedy rice problem occurs in direct seeded paddy field.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.43 no.2
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• pp.124-127
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• 1998

Since weedy rice problems have emerged with the recent advent of direct seeding cultivation in Korea, the establishment of effective control strategies for weedy rice is considered to be one of the urgent issues to be solved for widely practiced direct seeding rice cultivation. A three year experiment was conducted to investigate the occurrence pattern of weedy rice in four different rice cultivation practices: high ridged dry seeding, wet drill seeding, water seeding, and machine transplanting. The highest weedy rice occurrence of 11.0% was observed in high ridged dry seeding practice followed by 9.6% in wet drill seeding, 6.4% in water seeding practice, and 0.2% in machine transplanting practice, respectively. The same trend was observed when we examine the occurrence of contamination of panicle and rice grain by weedy rice. More contamination was observed in high ridged dry seeding than any other practices. It was also found that the possible emergence depths from the soil surface was deeper in both in ridged dry seeding and wet drill seeding practice (0-5 cm from the soil surface) than those in water seeding (0-4 cm), and machine transplanting practice (0-3 cm). The highest yield reduction of 19.5% was observed in high ridged dry seeding practice followed by 13.0% in wet drill seeding, 6.3% in water seeding practice. The reduction may have occurred to the competition between weedy rice and cultivated rice, These findings suggest that among the four cultural practices examined, the machine transplanting practice is the most effective method to control and reduce the weedy rice occurrence and weedy rice seed in soil.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.63 no.3
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• pp.219-228
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• 2018

Weedy rice (Oryza sativa) is a semi-wild rice grown in paddy fields and is more adapted to the environment than cultivated rice. Therefore, it is expected that the seeds of weedy rice might contain some chemicals related to its environmental adaptation, such as antioxidants, which may be useful for nutritional and medicinal purposes. This study was carried out to investigate the antioxidant activities of weedy rice compared to a Korean-bred rice cultivar, Sindongjin (SDJ), and to screen lines that show higher antioxidant activity in 199 accessions of weedy rice germplasm collected in Korea. DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging activity ranged from 31.0 to 91.7%, with an average of 82.5%, and 19 accessions that showed more than 91% antioxidant activity were selected. The 19 accessions were re-screened against non-germinated brown rice (BR) and germinated brown rice (GBR) using four assays, total phenol determination, DPPH radical scavenging, ABTS radical scavenging, and reducing power activities. The results showed that accession 'WD3' had the highest antioxidant capacity in both BR and GBR, suggesting that WD3 is a promising potential source of antioxidants and could be developed as a potentially functional substance material.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.45 no.3
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• pp.195-198
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• 2000

Weedy rice has typical characters such as easy shattering, dormancy, and longevity. These characters let it undergo the winter and occur year by year, It is very difficult to control weedy rice once the field have contaminated with its seeds. Therefore, the control method for weedy rice was focused on the no-tillage direct seeding in this experiment. The germination ability of seeds shattered on the soil surface in the next spring was 92.7% in weedy rice, and 4.3% in cultivated rice. The possible depth of weedy rice emergence were 1.5cm, 3.0cm and 6.8cm in no-tillage, wet seeding and dry seeding paddy field, respectively. The paddy field contaminated with weedy rice was maintained as no-tillage, and then irrigated in early spring (April 15). We could induce weedy rice on the soil to emerge with irrigation, and then kill by using non-selective herbicide, paraquat. Weedy rice was controled 92.2% of total emerged by this method. After seedling establishment of cultivated rice, molinate, thiobencarb, oxadiazon, dithiopyr, butachlor were soil-applied to suppress the emergence of weedy rice seeds buried in the soil. Oxadiazon was the most effective to repress the weedy rice among soil-applied herbicides tested. The highest control value was 96.4% as the result of combination of paraquat and oxadiazon.

• Weed & Turfgrass Science
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• v.2 no.1
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• pp.15-22
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• 2013

The phenotypic traits of herbicide-tolerant transgenic rice were compared with those of wild type (Dongjin) as well as two accessions (Hwaseong-aengmi 1 and Gwangyang-aengmi 12) of weedy rice. This study was conducted to investigate whether unintentional alterations in phenotypic characteristics occurred in the transgenic rice and whether the altered traits were similar to those in the two weedy rices. All qualitative traits studied were similar in the transgenic or wild-type rice. On the other hand, awn presence, flag leaf attitude and grain color differed considerably between herbicide-tolerant transgenic rice and weedy rice. As for quantitative traits, plant height, the number of tillers per plant and shoot dry weight were significantly greater for weedy rice than transgenic or wild-type rice. Grain weight per plant and 1000-grain weight of transgenic (or wild-type) rice were significantly greater than those of weedy rice. Transgenic rice shattered less than the other rices. Amylose and protein contents in embryos of transgenic rice were significantly different from those of weedy rice. The potential for weediness of the transgenic rice may be assessed using phenotype comparison between transgenic and weedy rice as shown in this study.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.35 no.3
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• pp.233-238
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• 1990

Weedy rice(red rice) collected in Korea were crossed with the Japonica, Javanica and Indica tester cultivars, and also crossed among those collected lines. Their seed fertility was counted and refered to their cross affinities. Some tester cultivars such as, Suweongjo, Malagkit Sinaguing and wx 817 which were regarded as belong to the Japonica, Javanica and Indica respectively, showed the typical tendencies of hybrid sterility when they were crossed each other. But, other testers such as Kwanak, Tapaiko, Belle Patna and Tarichaosun showed some differencies from those typical patterns, implying some varigations within a ecotype. The hybrids of weedy rice crossed to the Japonica testers showed higher fertility with a few semisterilities. While the crosses of weedy rice to the Javanicas or Indicas showed high sterility implying closer affinity relationships of weedy rice to the Japonicas. Even those weedy rice lines such as Samsanmyeon 8 and Sanchungaengmi B which showed semi-sterility when they were crossed to the Japonica testers showed high sterility when they were crossed to both Javanicas and Indicas. The hybrids among weedy rice lines showed high fertility raning 69% to 96%. Even those weedy rice lines which showed semi-sterility in the crosses with Japonica testers, showed high-fertility when they were crossed with those weedy rice lines. Though the amylose content, Alkali Digestive Value, Phenol reaction and grain shapes of theose weedy rice lines showed divers variations, the cross affinities of them showed closer phylogenie relationship to the Japonicas than to Japvanicas or Indicas. But the genetic influinces of Indicas to those weedy rices were not ignorable.

• Proceedings of the Korean Society of Crop Science Conference
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• 2017.06a
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• pp.278-278
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• 2017

Brown rice grains are increasingly attended by consumers due to their potential health benefits of antioxidant capacity. Therefore, this research was carried out to evaluate the antioxidant activity of brown rice in Korea-native weedy rice germplasm. Two hundred and twenty one accessions of weedy rice used in this study were received from the National Agrobiodiversity Center of RDA, and were regenerated in the experimental field of Chonbuk National University. The sampled seeds were extracted using methanol and the extracts were analyzed using the 1, 1-dipheny-2-picrylhydrasyl (DPPH) free radical scavenging assay for antioxidant capacity determination. Among the all germplasm, the samples of seed coat in red colour, white colour, red -white mixing colour and brown colour were 171 (81%), 26 (12%), 12 (6%) and 2 (1%), respectively. The antioxidant activity values of all samples were varied in the range from 22.31% to 95.53 % and mean value was 82.09%. Depend on the seed coat colour, the average antioxidant activity of the extract of weedy rice seeds indicated that the following order in seed coat colour: red colour (89.11%) > the red-white mixing colour (70.67%) > brown colour (53.16%) > white colour (45.99%). The antioxidant activity of red coloured weedy rice were significantly higher than those of the others. It is suggested that Korea-native weedy rice accessions with high antioxidant activity could be developed as a potential functional food material by further research of component analysis.

• Weed & Turfgrass Science
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• v.2 no.3
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• pp.322-326
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• 2013

This study was tried to control the weedy rice using minimum tillage direct seeding of rice on dry paddy. Minimum tillage direct seeding on dry paddy is tilled with 4 cm in width at 27 cm intervals by 1-shaped rotary blade. Using this cultivation method can control weedy rice effectively by minimizing the soil disturbance. In this study, weedy rice was firstly emerged at April 28 in 2012. After 11 days emergence rate of weedy rice at May 9 was 61.9%. At this time rice was sown and then herbicides was treated at 10 and 15 days after sowing. When herbicides was treated at 10 days after sowing the control effect was 89-96%, and when treated at 15 days the control effect was 97-99%. However emergence of weedy rice differ according to the year and year. It was thought to be affected by April average temperature and total precipitation. So, for effective weedy rice control and stable rice yield, it was considered that irrigation at April 15-20 to induce the emergence of weedy rice is required.