• Research in Plant Disease
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• v.18 no.3
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• pp.245-249
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• 2012

The small brown planthopper (Laodelphax striatellus) is one of the most important rice pests in Republic of Korea because it damages rice plants not only by sap-sucking but also by transmitting Rice stripe virus (RSV). Outbreaks of RSV are closely related to outbreaks of the small brown planthopper (SBPH). Therefore, it is very important to control SBPH for the management of RSV. Mass-migrating SBPH collected by aerial net traps in June 2011 at Taeanup, Geunheungmyon and Gonammyon in Taeangun were examined for virus carrier status and effects of the pesticide, 'Myungtaja', on the control of RSV. Among 1,217 SBPH trapped, about 7.7% were detected as RSV positive and 4.4% were positive for Rice black streak dwarf virus (RBSDV) by RT-PCR. After the mass migration, pesticide 'Myungtaja' was sprayed once or twice on rice fields and compared to untreated fields. The incidence of RSV was not affected by the frequency of spraying 'Myungtaja' but was influenced by the time of pesticide treatment. Myungtaja' treatment within 5-7 days after mass migration resulted in the most efficient RSV control, resulting in RSV incidence decreased by 87.6% compared to the control. Therefore, we conclude that pesticide spraying for RSV control was most effective when it was done within 5-7 days after mass migration.

• Research in Plant Disease
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• v.19 no.4
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• pp.326-330
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• 2013

During the 2012 growing season, 154 leaf samples were collected from sweet cherry trees in Hwaseong, Pyeongtaek, Gyeongju, Kimcheon, Daegu, Yeongju and Eumseong and tested for the presence of Cherry green ring mottle virus (CGRMV). PCR products of the expected size (807 bp) were obtained from 6 samples. The PCR products were cloned and sequenced. The nucleotide sequences of the clones showed over 88% identities to published coat protein sequences of CGRMV isolates in the GenBank database. The sequences of CGRMV isolates, CGR-KO 1-6 shared 98.8 to 99.8% nucleotide and 99.6 to 100% amino acid similarities. Phylogenetic analysis indicated that the Korean CGRMV isolates belong to the group II of CGRMV coat protein genes. The CGRMV infected sweet cherry trees were also tested for Apple chlorotic leaf spot virus (ACLSV), Apple mosaic virus (ApMV), Cherry necrotic rusty mottle virus (CNRMV), Cherry mottle leaf virus (CMLV), Cherry rasp leaf virus (CRLV), Cherry leafroll virus (CLRV), Cherry virus A (CVA), Little cherry virus 1 (LChV1), Prune dwarf virus (PDV) and Prunus necrotic ringspot virus (PNRSV) by RT-PCR. All of the tested trees were also infected with ACLSV.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.52 no.2
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• pp.129-133
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• 2007

To breed virus resistant rice variety, developing an efficient screening method is the most important. Two screening methods such as field screening and tray screening method have been used, but the efficiency of the field screening method is too low because of environment factors and the that of the tray screening method is good but screening capability is limited with only $200{\sim}300$ lines per year. To overcome those problems, mass screening method using screen house was developed. Barely as host plant of vector insect was grown in screen house in winter season. Then viruliferous insects are spread in the first spring of the initiation year and sustain them annually. Screening of virus resistance was tested two times in a year, the first screening was from April to June and the second from July to September. The virus infected rate of each susceptible varieties was increased to 92% for RSV and 100% for RDV from the second year. Also, this method can evaluate as many as $1,500{\sim}2,000$ pedigree lines in one time compared with the tray screening method. The result indicates that the mass screening method using screen house, which combines the advantages of the field and tray screening methods, is proven to be more efficient and reliable.

• Journal of Sericultural and Entomological Science
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• v.38 no.2
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• pp.93-99
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• 1996

By treatment(dropping) of 0.1~0.4% colchicine solution on the sprouts of winter buds of hard wood cutting slips for 4~5 days, two lines of artificial autotetraploids from Yongchonppong and one line from Yeongbyonppong were bred and the important cultivative characteristics of those new lines were as follows. The greentip sprouting stage of the new bred lines in spring season is later than the parental varieties by two days, but growth speed of the new lines after sprouting was faster than that of the parental varieties reaching the same level development with the parental varieties at the fifth leaf sprouting stage to be mid varieties same as the origins. The leaf shape of the new bred lines was wide round and the petioloes were long and thick. The thickness of leaf was thicker than the parental varieties by 17-33% and single leaf weight was heavy. The leaf area weight increased by 21-31% and the content of chlorophyll was also higher by 11-33%. With all the characteristics, the new breds produced good quality of leaves. The length and number of branches were shorter and less, respectively, than the parental varieties, but the internode length was either same or longer than the parents. Looking at the characteristics, the constitution of shoots was slightly inferior to the parental varieties. The cold hardness expressed by the death top rate of Sawonppong 23 and Sawonppong 24 was same level as that of Yongchonppong, but Sawonppong 25 was stronger than Yeongbyonppong in it with a high infection rate of dwarf disease. The productivity was lower than the parental varieties, but young shoot rate to shoot and branch and the ratio of leaf to young shoot were higher than the parental varieties. The fertility of Sawonppong 23 and Sawonppong 24 was comparatively high with 62% of cross success, but that of Sawonppong 25 was low with 23.9% of cross success.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.1
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• pp.84-90
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• 1986

An experiment was conducted to know the effects of planting dates (March 5, 15, and 25 and April 4) and transparent polyethylene (P.E.) film treatments(tunnel, tunnel slit, and mulch) on air and soil temperatures and growth and yield of a sweet corn variety, Great Bell. Maximum air and soil temperatures and minimum air and soil temperatures were greater at tunnel>tunnel slit>mulch in that order. Differences in maximum air and soil temperatures among the P.E. film treatments were much greater than those in minimum air and soil temperatures. However, when film was opened due to high air temperature over 40$^{\circ}C$ in the tunnel, air temperature was similar but soil temperature was lower com-pared to mulch. High temperature stress could be avoided in tunnel slit without opening film by increase in the number of slits. Cold damage of corn seedlings was avoided by tunnel and reduced by tunnel slit, and frost-damaged seedlings under the mulch were recovered in few days. The number of days from planting to silking was reduced as planting date delayed. At early plantings, tunnel enhanced early growth and silking, but it delayed at late plantings because tunnel was opened during the most of day time due to high temperature. Black streaked dwarf virus(BSDV) disease was more severe at early plantings and it was reduced in tunnel slit at late plantings because plants were grown under the film at the time of infection. The number of marketable ears was similar among all treatments except mulch at March 5 planting where BSDV was severely infected. Gross income was high in tunnel and tunnel slit at March 25 planting which had more larger marketbale ears and tunnel and tunnel slit at March 5 planting which had higher market price.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.54 no.3
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• pp.265-269
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• 2009

Technology development for sufficient dry matter production of Chinese milk vetch (CMV) is most important in CMV-rice cultivation system in order to provide sufficient nutrients to rice plants. However, when the CMV plants are dominated by the weed, especially Alopecurus aequalis, the CMV growth could be reduced due to light and nutrient competition. In addition, A. aequalis is potential host of the rice dwarf virus disease. Therefore, control of A. aequalis is necessary to enhance the biomass production of CMV plants when CMV stands are insufficient. The use of chemical like sethoxydim (20%, ai) showed the highest control rate of 84% at early stage and was reduced as application was delayed. A. aequalis control did not change the CMV seedling stand before and after herbicide treatment and the reseeding stand in fall was rather increased 2.2 to 2.6 times. On the other hand, in untreated control, the CMV stand at May 15 and reseeding stand in fall was significantly reduced as compared with the before herbicide treatment. Control of A. aequalis increased the CMV dry matter production by 164% for 50% CMV coverage rate and 63% for 25% CMV coverage rate. This is equivalent to $12.3{\sim}16.4\;kgN$/10a which is greater than the recommended nitrogen rate of 9kg/10a. The result indicates that the control of A. aequalis is an efficient way to enhance dry matter production in CMV-rice cultivation system especially when CMV stand is poor.

• Research in Plant Disease
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• v.15 no.2
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• pp.57-62
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• 2009

Genetic diagnosis method of Virion Captured (VC)/RT-PCR for Rice stripe virus (RSV) and Rice black-streaked dwarf virus (RBSDV), Korean major rice viruses transmitted by small brown plant hopper, Laodelphax striatellus, was developed. Virion extraction buffer for rice plant was 0.01M potassium phosphate buffer, pH 7.0, containing 0.5% sodium sulfite. However, the extraction buffer for L. striatellus was 0.01M potassium phosphate buffer, pH 7.0, containing 0.5% sodium sulfite and 2% polyvinylpyrrolidone wt 40,000 (PVP-40). Specific primers for detection of RSV and RBSDV were selected for VC/RT-PCR method. The specific primers were used as a duplex primer to detect viruliferous small brown plant hopper collected from Gimpo, Pyeongtaek and Siheung areas in Gyeonggi province. The genetic diagnosis methods of single and duplex VC/RT-PCR for RSV and RBSDV could be used easily and economically, especially on the diagnosis of L. striatellus. The rate of viruliferous insect (RVI) for RSV was compared with ELISA and VC/RT-PCR for L. striatellus collected from fields. RVI by ELISA was same as 9.2% with RVI by VC/RT-PCR. However, there were some different detection results between the methods. It could be suggested that there is a possibility of serological and/or genomic differences among RSV isolates. The portion of RVI detected simultaneously by ELISA and VC/RT-PCR was 71.0%, and the detection rate from VC/RT-PCR was higher as 3.2% than that from ELISA, which had a reason of simultaneous detection ability both RSV and RBSDV of VC/RT-PCR.

• Korean Journal of Breeding Science
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• v.43 no.6
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• pp.576-580
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• 2011

'Keunseom', a new second generation Tongil-type rice variety (Oryza sativa L.), is a mid-maturing ecotype developed by the rice breeding team of Department of Functional Crop, NICS, RDA in 2006. This variety was originated from a cross between 'Dasanbyeo' and 'Namyeongbyeo' in 1996's summer season, which developed by pedigree breeding method. The pedigree of 'Keunseom' was YR18234-B-B-98-3-5-1, and it was designated 'Milyang202' in 2002. 'Keunseom' has tolerance to lodging, because it has short culm length as 77 cm. This variety is resistance to bacterial blight K1 race, rice stripe virus, rice dwarf virus, and leaf blast disease. Milled rice kernel of 'Keunseom' is a clean translucent with non-glutinous endosperm, and has good quality as it was clear in chalkness. The milled rice yield potential of 'Keunseom' was about 719 kg/10a at ordinary fertilizer level of local adaptability test. This cultivar would be adaptable to the mid and southern plain of Republic of Korea.

• Korean Journal of Weed Science
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• v.17 no.4
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• pp.362-367
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• 1997

A field experiment was conducted to determine an optimum control time of water foxtail(Alopecurus aequalis var. amurensis Ohwi), a most troublesome weed, in no-tillage dry seeded rice. Paraquat, a non-selective herbicide, was applied at 1.5 days interval from March 15 to May 15 at a concentration of 3,000ml per hectar and its control efficacy to A. aequalis was recorded before and after seed sowing. In addition. other characters such as decayed injury of A. aequalis to rice seedling, and its influence of seedling stand were also investigated in relation to rice grain yield. Dry weight of A. aequalis was rapidly increased with delay in control time from 42g/$m^2$at March 15 to 237g/$m^2$ at May 15. The amount of its regrowth at seeding time was highest with 68.3g, when paraquat was applied at March 15, then decreased thereafter and it was less than 6.2g when paraquat was applied after April 15 which indicates above 98% control rate. The control rate of A. aequalis, at 30 days after paraquat application way likewise similar to that the seeding time. Rice seedling stands in the plot treated with paraquat before April 15 were not affected by decayed injury of A. aequalis while decayed injury of 3 to 4 degree for those after April 30 application was noted. Dwarf virus disease on rice seedling due to occurrence of A. aequalis was not observed when A. aequalis was controled from March 30 to May 15 while it was occurred in the plot of March 15 application and the untreated control. The control plot of A. aequalis at April 15 had the highest grain yield with 4.79ton/10a. Based on control rate of A. aequalis, seedling stands of rice, virus disease, and rice grain yield, the most suitable control time of A. aequalis in no-tillage dry seeded rice is considered to be about April 15.

• Research in Plant Disease
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• v.10 no.3
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• pp.188-193
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• 2004

The symptom expressions such as yellowish and mosaic spots in overwintering barley have been considered to be a damage by cold or water. However, it had revealed that the symptom expressions were caused by viruses throughout three year nationwide surveys. Barley yellow mosaic virus (BaYMV), Barley mild mosaic virus (BaMMV), and Soil-borne wheat mosaic virus (SBWMV) was detected in 2001-2003 and Barley yellow dwarf virus-MA V (BYDV -MA V) from field samples collected on March in 2003. The results of investigation showed that the incidence of BaYMV was more than 70％ and that of BaMMV and SBWMV was 15.7-37.4％ and 0.7-10.1 ％ in three year surveys, respectively. The incidence of BYDV-MAV was approximately 1 ％ in 2003 only. The distribution of BaYMV was relatively uniform throughout barley fields in Korea, but the incidence of the virus in Gyunggi Province was as low as 19％ compared to 65-85％ in the rest of regions. On the other hand, 70％ of BaMMV was found to be in the west south regions of Korea, Jeonbuk and Jeonnam Provinces. Taken together, both BaYMV and BaMMV were thought to be dominant casual agents in overwintering barley by either single or mixed infections. Previous survey data for BaYMV from 1994 to 1996 indicated that the incidence of the virus was approximately 40％ in Jeonbuk, Jeonnam, and Gyungnam Provinces. Thus, comparing with the results from the recent nationwide survey, the incidence of BaYMV had been rapidly increasing in overwintering barley fields in the southern part of Korea.