The small brown planthopper (SBPH), Laodelphax striatellus, is a major insect pest for the rice plants. SBPH is also a known vector of rice stripe virus (RSV), which causes severe yield losses in rice crops throughout the East Asia. RSV is persistently transmitted by SBPH and can also be transmitted to offspring through transovarial transmission. SBPH is known to migrate from China to the west coast of the Republic of Korea (ROK). The study investigated the impact of temperature on the acquisition and transmission of RSV by SBPH in ROK, which is expected to experience increased migration and emergence of SBPH due to climate change. The results revealed that the acquisition and transmission rates of RSV were higher at 27°C compared to 24°C, with rates of 100% and 78.3%, respectively. However, at 30°C, the acquisition and transmission rates of RSV was decreased. The results suggests that temperature can impact the transmission of RSV by SBPH. To investigate this further, SBPH adults were fed on RSV-infected plants and infection rates were compared across various tissues, including the head, salivary glands, midgut, Malpighian tubules, ovary, and hindgut. Results showed that at 36 hours post-infection, RSV was highly detected in the Malpighian tubules, ovary, and hindgut. At 48 hours post-infection, RSV was also detected in the thorax. These results suggest that the transmission rates of RSV in SBPH increase with temperature between 24-27°C, but decrease at 30°C, indicating that the vectorial capacity of SBPH for RSV decreases above a certain threshold.

The relationship between virus, vector insect and its host plant has been studied in epidemic of virus disease, fitnessof vector insect, symbiosis and phylogenesis of the relationship, etc. The biological association, symbiosis, concept hasbeen suggested on the virus-vector relationship since 2000. We have conducted such a typical study with the Rice stripevirus and the small brown planthopper, Laodelphax striatellus. In addition, it is able to extend our view to ecosystemservice of the relationship. We reviewed the trophic efficiency included with virus factor. Nutrient loss of the host plantby virus is negative effect but terrestrial decomposition by the virus may be positive feedback in ecosystem. Thus, thevirus-vector relationship is able to be understand not only as competition for the host plant’s nutrition but also as indirectmutualism for the efficient utilization of the host plant or fitness to environmental conditions, especially climate change.

Rice stripe virus (RSV) is one of the serious plant pathogenic viruses for rice transmitted by small brown planthopper (SBPH), Laodalphax striatellus. RNA interference (RNAi) was recently suggested as a promising strategy for controlling insect pests, including those that serve as important vectors for plant pathogens. To disturb transmission of the RSV in SBPH using RNAi pathway, we chose nine genes highly expressed in RSV-viruliferous SBPH by transcriptome sequencing. These SBPH-derived dsRNAs were applied to the insects indirectly through xylem of rice leaves by irrigation. qPCR result demonstrated that five out of nine SBPH-derived dsRNAs successfully reduced the replication of RSV in viruliferous SBPH in dose-dependent manner, suggesting that these five dsRNAs could suppress replication of RSV and provide a new tool for RSV control strategy.

애멸구(Laodelphax striatellus)는 rice stripe virus (RSV)의 매개충으로 벼에 큰 피해를 주는 해충이다. 본 연구에서는 애멸구의 장·단시형, 암·수, 약·성충에 대한 RSV 보독률과 이병률을 비교하였다. 애멸구의 장·단시형의 RSV 보독률은 각각 60.7%, 63.1%로 크게 차이는 없었다. 암·수에 대한 RSV 보독률은 각각 61.9%, 52.2%로 암컷의 보독률이 더 높았으나 유의성은 없었다. 약·성충의 보독률을 비교한 결과 각각 51.2%, 58.7%로 역시 크게 차이가 나지는 않았다. RSV에 감염된 애멸구에 노출된 건전한 벼의 이병률은 장시형은 53.3%, 단시형은 48.2%를 보였으며, 약·성충의 이병률은 각각 38.2%, 42.6%를 보여 유의성은 없었다. 반면 암컷은 50.5%의 이병률을 보이고 수컷은 22.3%의 이병률을 보여 암컷이 수컷에 비해 22.3% 이병률이 높아 유의성이 있었다. 또한 벼와 애멸구의 RSV 감염여부에 의한 애멸구의 발육기간은 건전한 벼에 RSV 감염 애멸구를 접종 했을 때 가장 긴 것으로 나타났으며, 건전한 벼에 건전한 애멸구를 접종 했을 때 발육기간이 가장 짧은 것으로 나타났다.

Rice stripe virus (RSV) is one of the serious plant pathogenic viruses for rice transmitted by small brown planthopper, SBPH, Laodalphax striatellus. RNA interference (RNAi) is an universal gene-knockdown mechanism in eukaryotic organisms which includes insects，and has been considered as an alternative strategy to control insect pests. Hence, we applied this technique to interfere the translation of target RNA genes to knockdown the virus gene on RSV-viruliferous L. striatellus. Three out of seven RSV genes, RdRp, NS3, and NCP were used as target genes and each dsRNA targeting the viral genes were delivered to the insects indirectly through the rice leaves by irrigation. As a result, not only the relative expression level of target genes decreased but also those of non-target genes and the replication of RSV genome as well. In summary, leaf-mediated dsRNA feeding methods would be useful in the knockdown of target genes on piercing-sucking insects. The genes used in this experiment can be utilized for the development of pest-resistant transgenic plants based on RNAi.

Rice stripe virus (RSV) is one of the serious plant pathogenic viruses for rice and mediated by small brown planthopper, Laodalphax striatellus. So far, the studies have been mainly focused on the interaction between the host plant and the virus. In this study, for better comprehension of the interactions among Rice stripe virus, rice and small brown planthopper, transcriptomes of the RSV-viruliferous (RVLS) and non-viruliferous L. striatellus (NVLS) were comparatively analysed. For this, non-viruliferous L. striatellus were collected from non-infected rice field and fed RSV-infected rice for 5 days. With the RNAs prepared from the RSV-viruliferous and the non-viruliferous small brown planthoppers, we conducted Illumina RNA sequencing (Hiseq 2000) and then two transcriptome databases were generated from RVLS and NVLS, respectively. The transcriptome of RVLS and NVLS were campared to figure out how the gene expression of the insects affected by Rice Stripe Virus. RSV-dependently regulated genes analysed from this study may have important functions in the transmission and replication of RSV.

Rice stripe virus disease (RSVD), one of the most serious disease of rice is mediated through the sucking by small brown planthopper, Laodalphax striatellus. So far, the studies have been mainly focused on the interaction between the host plant and the virus. In this study, for better comprehension of the interactions among the host plant, vector insect and plant-pathogenic virus, we investigated transcriptome of the vector insect and the differences between viruliferous and naïve L.striatellus. For this, naïve L. striatellus were collected from non-infected rice field and 50 L.striatellus of them were fed RSV-infected rice for 5 days. With the RSV-viruliferous and the naïve insects, we conducted Illumina RNA sequencing (Hiseq 2000) and obtained 175,243,488 and 146,031,348 reads from viruliferous and naïve L.striatellus, respectively. These reads were assembled into contigs and two transcriptome databases were generated. The transcriptome of naïve and RSV-viruliferous L. striatellus were campared to figure out up-regulated or down-regulated genes. These RSV-dependently regulated genes may have important function in the behavior of planthoppers or the transmission of RSV.

Among hemipteran insects which is the most important insect vector of plant viruses, small brown planthopper, Laodelphax striatellus, transmits the rice stripe virus (RSV) causing rice stripe disease. For effective control of RSV, it is important to understand interaction between RSV and L. striatellus. Therefore, in this study, expressed sequence tag (EST) databases were generated based on 454 GS-FLX pyrosequencing for comparative transcriptome analysis between nonviruliferous and RSV-viruliferous L. striatellus. By comparing the two EST libraries, we showed that 108 host genes were significantly up-regulated and 28 host genes were significantly down-regulated in viruliferous insects. Interestingly, genes encoding ribosomal proteins were mainly up-regulated in viruliferous L. striatellus, whereas genes related to translation were concentrated in the downregulated cohort. These RSV-dependently regulated genes may have important function in the behavior of planthopper or the transmission of RSV.

Rice stripe virus (RSV), the type member of the genus Tenuivirus, causes rice stripe disease and the viral transmission is mediated through the sucking by small brown planthopper, Laodelphax striatellus. Considerations have been mainly focused on the protection of rice from RSV and/or the planthopper, rather than the interaction between RSV and the insect. To clarify the interaction, in this work, mRNA was extracted from RSV-viruliferous planthopper with non-viruliferous control, and expressed sequence tag (EST) databases were generated based on 454 GS-FLX pyrosequencing technology for comparative analysis. RSV-viruliferous planthopper had ca. 2500 isotigs, which included genes on biological process (19%), cellular component (13%), molecular function (22%) and no hits (46%) from gene ontology (GO) analysis; this structure was similar to the control. However, in the viruliferous planthopper, 109 isotigs were up-regulated and 660 isotigs were down-regulated, compared to the non-viruliferous control. These RSV-dependently regulated genes may have important function in the behavior of planthopper or the transmission of RSV.

In many cases over the years, we failed to forecast accurately outbreak of Rice stripe virus (RSV) disease using population density of overwintering small brown planthopper (SBPH), Laodelphax striatellus. What is the source of error in this viral disease assessment? For answering the question, spatial distribution of RSV in paddy fields was investigated in relation to the yield of rice grain, and the population density of overwintering SBPH in ridge of paddy fields. Total 14 paddy fields in 5 regions were surveyed in June, 2008. Disease assessment was carried out with each of 30 rice plants in the one of the borders, 5th, 10th line from ridge, and 90 rice plants in diagonal line for conventional method. The ears of rices from 18 plants in the same surveyed line were collected in the late of August for the weights of 100 rice grains. The infection rate of RSV was decreased by the distance from ridge; on the contrary, the increase tendency was shown in the yield of rice grains in the middle of paddy field. It is suggested that the border effect of viral distribution between ridge and paddy field is caused by the spatial distribution of the vector insect. Thus, in this case, the narrow border effect could represent that the SBPH migrated short distance from the ridge to paddy field. The conventional method, observing the disease in middle area of diagonal line, showed no correlation to the population density of overwintering vector generation in ridge. It might cause underestimation of the regional disease rate. The counting of RSV-diseased plant in border line only overestimated it also. However, the RSV infection rate in the near border had highly positive linear relationship (R2=0.91) to the regional average values by regression analysis. Therefore, the near border sampling method can improve the RSV disease risk assessment.

The small brown planthopper (SBPH), Laodelphax striatelleus (Fallén), is a insect vector of Rice stripe virus (RSV) in temperate countries such as Korea, Japan, China, and Taiwan. As SBPH is able to overwinter successfully in these areas, RSV disease in subsequent rice fields has been believed to be endemic. In Korea, however, the RSV disease outbreaks have been observed mainly but not continuously at some western regions since 2001, caused a severe damage to the rice production. Although many efforts are underway to explain the outbreak phenomenon, the exact related factors are not known yet. In the meantime of the study on SBPH population dynamics in 2009, we catched unusually large numbers of SBPH adults by aerial net traps, maximally over 900, in early June at western coastal counties such as Taean, Seocheon, Buan, Sinan, and Jindo in Korea. Age distribution changes of SBPH in winter and post-winter seasons at some selected fields shows that the adults might be not related to overwintering population. The adults of overwintering population emerged from early April. Newly hatched nymphs of first generation were found from mid-May. In late May, just before the unusual catch of adults, the developmental stages of SBPH were mostly below 5th instars. This means that the big adult populations would be results of mass migration of SBPH abroad. We present also spacial distribution and host relationship of overwintering population as well as viruliferous rate changes of immigratory population.

초 록 벼줄무늬잎마름병 바이러스에 대한 혈청학적인 검토결과를 다음과 같이 적요한다. 1. 벼줄무늬잎마름병 바이러스는 항원성을 갖고 있으며 항체와 특이적인 혈청반응을 타나냈다. 2. 가토 정맥주사에 의한 항혈청의 항체가는 아주 낮아 16배에 불과하였다. 3. 벼 품종 사도미노리에 있어서 침강반응혼합법으로 측정한 결과 이병엽의 병징정도에 따라 바이러스 농도에 차이가 인정되는데 병징정도가 심할수록 바이러스농도가 높았다. 4. 동정도의 병징이라도 벼품종에 따라 바이러스농도가 달랐는데 저항성품종인 통일에서는 높았고 이병성인 사도미노리, 팔굉, 만경, 니혼바레에서는 낮았다. 그러나 저항성 품종인 유신에서는 낮았다. 5. 항체감작적혈구 응집반응에 의한 항체가는 아주 높아 512배였으며 보독충의 검정시험에서도 반응이 잘 나타나 라는 보독충율을 나타냈다.

1. 벼줄무늬 잎마름병에 의한 기주범위를 알기위하여 화곡류 사료작물, 잡초등을 대상으로 온실에서 보독충을 접종한 결과 30종의 공시식물중 9종이 발병되지 않았으며 나머지 21종은 발병되었다. 2. 발병된 식물중 화본과에 속하지 않으나 논과 들에 자생하고 있는 방동사니대가리와 넓은 잎개수염 방동사니 등은 새로운 기주이다. 특히 방동사니대가리는 습기있는 포장에서 흔히 볼 수 있는 것으로서 발병율이 높았다. 3. 각종작물에 있어서 애멸구의 서식충수는 대체로 24시간후보다 48시간후에 적은 편이었다.

벼의 줄무늬잎마름병 방제에 보다 능률적이고 완전한 실효를 얻기 위해 우선 본병에 대한 저항성 검정방법을비교검토하고 장려 품종 중에서 저항성품종을 선발하여 장래 저항성품종 육성의 모체를 제공할 목적으로 410품종에 대하여 저항성검정을 실시하였다. (1) 집단접종과 개체접종법을 비교 검토한 결과 발병률은 집단접종법이 다소 높은 경향이 있어 차이가 있음을 알 수 있다. (2) 발병지수에서 Lacrose는 두 방법이 모두 S였고 ZenithSt. No.1St. No. 2는 R, 나머지는 M로 나타나 같은 경향을 보여 주었다. (3) 병징형은 이병성품종에서는 모두 감수성형인 A형이 많고 저항성품종에서는 반대로 저항성병징형인 C형이 많아 두 방법이 같은 경향을 보여 주였다. (4) 410품종의 저항성검정에서 저항성이(12품종) St. No.1St. No. 2 신 2호GulfrosebonnetArkroeSunbonnetZenith이천칠일찰농림 24호오백조계양주밭찰농림나 1호 등이고 남선97호, 이황 , 간척 호 수원 77호농림 22호적나 등은 이병성이며, 중간성이 377품종이었다. (5) 숙기별로 볼 때 큰 차이는 없으나, 만생조생중생종의 순으로 저항성이 컸다. (6) 장려품 중에서는 신 2호 외는 거의 중간성이었다.

This study was conducted to develop the early maturing rice lines with genes conferring resistance to bacterial blight and rice stripe virus to enhance the adaptability in plain area. Unkwang carrying Xa3 was used as a recurrent parent and SR30075 carrying Xa4+xa5+Xa21+Stvb-i was used as a donor parent. RL1(Resistant Line, BC1F7), RL2, RL3, RL4, and RL5(BC2F6) were bred through bio-assay of K3a race inoculation and phenotypic selection of agronomic traits. The presence of introduced genes was confirmed by testing the resistance levels against bacterial blight and rice stripe virus and then double-checked by using DNA marker. RL1 has all target genes, Xa3+xa5+Xa21+Stvb-i. RL2, RL3, and RL5 have Xa3+Xa21+Stvb-i whereas RL4 has only Xa21. Rice lines carrying Stvb-i showed resistance reaction to rice stripe virus. The combinations of bacterial blight resistant genes(Xa3+xa5+Xa21 and Xa3+Xa21) were found to be promising, as the rice lines carrying these genes enhanced a strong resistant reaction against 16 bacterial blight isolates. Also, the inoculation of K3a race did not alter the brown rice yield, ripened grain ratio and kernel quality of brown rice compared to control. Although RL1 containing all the target resistance genes showed excellent resistance performance, it is not suitable to cultivate in plain area due to instability to lodging, 80% yield level than Unkwang, and low grain quality. RL5 backcrossed twice with Unkwang was found to be a promising line due to its effective resistance gene combination, Xa3+Xa21+Stvb-i and good agronomic traits such as stability to lodging, higher yield and quality compared to Unkwang.

본 연구는 벼멸구, 벼흰잎마름병, 벼줄무늬잎마름병에 저항성인 자포니카 복합내병충성 품종을 조기에 확보하고자 약배양을 수행하여 목표 저항성 유전자 조합의 우량 고정계통을 개발하고 육성 과정 중에 발생할 수 있는 문제점을 파악하여 병해충 저항성 육종사업에 반영하고자 수행하였다. 벼흰잎마름병과 벼줄무늬잎마름병에 저항성인 우량 계통 HR26234- 12-1-1과 벼멸구, 벼흰잎마름병, 벼줄무늬잎마름병에 저항성인 SR30071-3-7-23-6-2-1-1을 인공 교배한 F1을 약배양하여 213개 고정계통을 육성하였다. HR26234는 Xa3+xa5, Stvb-i, SR30071은 Bph18, Xa4, Stvb-i를 가지고 있는 것으로 확인되었다. 이들 유래 약배양 계통들은 모두 Stvb-i를 가지고 있었고, Bph18+Xa3, Bph18+Xa4, Bph18+Xa3+xa5, Bph18+Xa4+xa5, bph18+Xa3, bph18+Xa4, bph18+Xa3+ xa5과 bph18+Xa4+xa5의 조합이 확인되었다. 약배양 집단에서 xa5+Bph18(또는 bph18)+Stvb-i 조합이 발생하지 않았고 Bph18 보유 계통이 bph18 보다 적게 발생하는 등 segregation distortion이 발생하였다. Bhp18을 보유하며 벼멸구에 저항성인 계통들이 감수성인 계통들에 비해 간장이 컸다. 선발된 Bph18+Xa4+xa5+Stvb-i 조합의 계통은 단간이면서 벼멸구, 벼흰잎마름병, 벼줄무늬잎마름병에 저항성을 나타내었으나, 낮은 수량성과 일부 불임의 발생, 단간임에도 도복에 안정적이지 못한 특성을 나타냈다. 병해충에 대한 저항성 육종사업에서 약배양을 활용하여 조기에 육종 목표를 달성하고자 할 경우에 segregation distortion이 발생하여 편의 된 변이가 발생할 수 있고, 저항성 유전자 도입 시 linkage drag에 의해 예기치 못한 열악형질 특성이 나타날 수 있음을 고려하여 신중하게 목표에 접근하여야 할 것으로 생각한다.

‘조평’은 고품질 조생종 품종육성을 위하여 2000/2001동계에 국립식량과학원 벼맥류부에서 조생종이면서 내냉성인 HR16683-46-3-1를 모본으로 하고 중만생종으로 줄무늬잎마름병과 흰잎마름병에 저항성인 HR18129-B-16-1-4를 부본으로 인공교배하여 F3이후부터는 계통육종법에 준하여 육성 선발하면서 주요 병해충, 내냉성 및 미질검정 등을 실시하였다. 2006년부터 2007년까지 생산력검정을 실시한 결과 조생종이면서 줄무늬잎마름병과 흰잎마름병에 저항성이고, 직립이면서 숙색이 좋은 ‘HR22799-66-3-2-5-2’ 계통을 선발하여 ‘운봉42호’로 계통명을 부여하고 2008년부터 2010년까지 지역적응시험을 실시한 결과 도열병, 줄무늬잎마름병 및 흰잎마름병에 강한 조생, 고품질 계통으로 우수성이 인정되어 2010년 12월 농촌진흥청의 농작물 직무육성 신품종 선정 심의회에서 특색 있는 품종으로 결정 조생종으로 평야지적응성이 있다는 의미로 ‘조평’으로 명명하여 중북부 평야지, 중산간지 및 남고냉지(경기, 강원, 경북, 충북, 전북)에 적응하는 품종으로 보급하게 되었다. 출수기는 북부평야지 및 중산간지, 남부고냉지, 동북부해안지에서는 평균 출수기가 7월 28일로 ‘오대벼’와 비슷한 조생종이다. 간장은 67 cm로 ‘오대벼’ 보다 약간 작다. 주당수수와 수당립수는 14개와 84개이다. 등숙비율이 94%로 높은 편이며, 현미천립중은 22.6 g으로 중소립종이다. 재배기간 동안에 위조는 나타나지 않았으며 성숙기 하엽노화가 늦다. 불시출수와 수발아는 ‘오대벼’ 보다 약간 잘되는 편이고, 춘천 내냉성 검정 결과 ‘오대벼’에 비해 적고는 비슷하고, 출수지연일수는 짧으나, 임실율은 낮은 편이다. 재배 포장의 도복은 ‘오대벼’와 비슷하다. 도열병, 흰잎마름병(K1 ~ K3)과 줄무늬잎마름병에는 저항성이나 오갈병 및 검은줄오갈병에는 약하며, 벼멸구 및 애멸구에 대한 저항성은 없다. 쌀은 심복백이 없이 맑고 투명하며, 아밀로스 함량은 19.9%로 ‘오대벼’ 보다 낮으나 단백질 함량은 6.5%로 ‘오대벼’ 보다 높다. 도정율과 밥맛은 ‘오대벼’와 거의 비슷하다. 쌀수량성은 9개소의 보통기 보비재배에서 평균 쌀수량이 5.67 MT/ha으로 ‘오대벼’에 비하여 8% 증수되었고, 소득후작재배에서는 평균 쌀수량이 4.88 MT/ha으로 ‘금오벼’에 비하여 25% 증수되었다.

‘중모1008호’는 내냉성이 강한 조생종 품종육성을 위하여 1999/2000 동계에 국립식량과학원 벼맥류부에서 줄무늬잎마름병에 저항성이면서 밥맛이 좋은 ‘익산451호’를 모본으로 하고 조생종이면서 내냉성인 ‘상주21호’를 부본으로 인공교배하여 계통육종법에 따라 육성하였다. ‘중모1008호’는 북부평야지 및 중산간지, 남부고랭지, 동해안 북부해안지 보통기 보비재배에서 평균 출수기가 7월 27일로 ‘오대벼’보다 3일정도 빠른 조생종이다. 간장은 73 cm로 ‘오대벼’보다 약간 크며, 주당수수는 13개이고 수당립수는 ‘오대벼’에 비해 많으며 등숙비율이 91.1%로 높고, 현미천립중은 23.0 g이다. 노화묘 늦심기에서 위조현상이 나타나지 않았으며 성숙기 하엽노화가 늦고 수발아는 ‘오대벼’보다 잘되는 편이다. 유묘기 내냉성은 ‘오대벼’와 비슷하나 임실률은 다소 떨어지는 편이다. ‘중모1008호’는 도열병과 줄무늬잎마름병에 강한 반응을 보이나 흰잎마름병(K1～K3)과 바이러스병에 약하고 벼멸구, 애멸구 등 해충에 대한 저항성은 없었다. ‘중모1008호’의 쌀은 심복백이 거의 없고 투명하며 외관 품위가 양호하고, 쌀수량은 보통기 보비재배에서 5.60 MT/ha로 ‘오대벼’보다 3% 증수되었다.