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.

뿌리응애류는 양파, 마늘, 생강, 백합 등의 뿌리를 가해한다. 최근 백합재배지에서는 질경이모자이크바이러 스(Plantago asiatica mosaic virus, PLAMV)에 의한 잎의 괴사 피해가 확산되고 있다. 태안 백합재배지에서 PlAMV 가 감염된 백합을 채집하여 구근을 조사한 결과, 식물체 당 뿌리응애 100개체 이상이 발견되었으며 Rhizoglyphus robini로 동정되었다. 이 종이 PlAMV의 보독여부를 확인하기 위해 채집된 R. robini에서 RNA를 추출하여 RT-PCR로 진단한 결과, 모든 개체에서 PlAMV가 확인되었다. 본 연구는 뿌리응애가 백합 구근 뿌리를 먹으면서 만든 상처를 통해 PlAMV가 전염될 수 있다는 가능성을 제시한다.

진딧물은 감자에 다양한 바이러스병을 옮기는 대표적인 매개충이다. 따라서 감자밭으로 날아오는 진딧물을 방제하는 것은 매우 중요하다. 비래진딧물의 종류, 비래시기와 비래량, 바이러스 보독률 및 진딧물의 겨울철 월동기주를 구명하기 위하여 강원도 고랭지의 씨감자 생산지역 3곳 을 중심으로 진딧물 비래양상을 조사하였고, 비래초기부터 6월 하순까지 날아오는 진딧물의 잎말림바이러스(PLRV) 보독 여부를 조사하였다. 또한 진딧물의 이동방향을 따라 57종의 수목류 가지와 수피를 채집하여 월동중인 진딧물 알의 존재 여부를 조사하였다. 강릉 왕산 지역과 홍천 내 면 지역의 여름기주 비래최성기는 모두 6월 중순이었고 평창 횡계 지역은 5월 하순으로 나타났다. 겨울기주로 날아가는 비래최성기는 3개 지역 모두 10월 상순이었다. 비래진딧물의 2.8%가 PLRV를 갖고 있었으며, 진딧물 종류별 보독률은 복숭아혹진딧물 15.4%, 감자수염진딧물 9.1% 였다. 시기별로는 5월 하순부터 PLRV 보독 진딧물이 비래하였고 6월 중순에 비래한 진딧물의 바이러스 보독률이 10.4%로 가장 높게 나타났다. 고로쇠나무(Acer pictum subsp. mono (Maxim.)), 당단풍나무(Acer pseudosieboldianum (Pax)) 등 17종의 수목류에서 진딧물알이 월동하였다. 월동 진딧물은 복숭아혹진딧물(Myzus persicae), 홉사마귀진딧물(Phorodon humuli) 등 14종으로 동정되었다. 특히 자작나무진딧물(Betula platyphylla var. japonica), 단풍알락진딧물(Yamatocallis hirayamae) 등은 아직까지 감자에서 바이러스를 옮기는지 여부는 알려진 바 없지만, 넓 은 지역에 걸쳐 분포하는 기주식물에서 월동하기 때문에 앞으로 바이러스 매개 능력에 대한 연구가 필요하다.

Vector-borne plant virus transmission is a complex mechanism. Plant viruses modify development and behavior of vectorinsects in a positive, negative, or neutral manner. Bemisia tabaci transmits Tomato yellow leaf curl virus (TYLCV) whichis a virus that seriously damaged tomato cultivars all around the world. We compared several behavioral and physiologicalcharacteristics between non-viruliferous (NV) and TYLCV-viruliferous (V) of whiteflies. When B. tabaci acquired TYLCV,total life span was shorter and fecundity was lower than NV ones. V whiteflies were more susceptible to thermal stressby increasing hsp mRNA levels but higher in mortality by either heat or cold shocks. Further, V whiteflies increasedthe rates of plant sap probing and light attraction behaviors than NV ones. Our results provide insights to understandvector’s role in relation to the acquisition and transmission of plant viruses.

Different types of insect-borne plant viruses can modify their hosts and vectors in distinct manners. Therefore, interactionsbetween two types of viruses co-existing in a field are known to be complex to predict. Obtaining empirical data byconducting field experiments, however, requires numerous biotic and abiotic factors to be controlled, and is therefore hardto execute. Thus, we designed an individual based model to simulate the transmission pattern of two viruses, using potatoes(Solanum tuberosum) for host plant, aphids (Myzus persicae) for virus vector, potato leafroll virus and potato virus Yfor different types of plant viruses. More specifically, we aimed to investigate the effect of the following on the spreadof the plant viruses: dispersal by winged-form aphids, initial number of virus-infected seed potatoes, and indirect interactionsbetween two viruses by affecting life traits of the vectors.

The hepatitis E virus (HEV) is a leading causative agent of acute hepatitis in humans. Zoonotic HEV strains have been isolated from several animal species, including pigs. New HEV variants have been recently isolated from camels in the Middle East. In the present study, fecal samples from fallow deer, formosan deer, alpaca, and guanaco were analyzed for the detection of HEV. One HEV strain was detected from guanaco, a species of camelids. The nucleotide sequence of guanaco HEV was identical to those of deer HEV-3 strains, which implied the cross-species transmission of HEV-3 from deer to guanaco.

The Ixodid ticks has been suspected to be the vector of severe fever with thrombocytopenia syndrome virus (SFTSV) in Korea. In order to confirm transovarial transmission of Ixodid ticks, a total of blood fed 284 ticks were collected from six host animals. They were identified as 3 genera and 4 species, Haemaphysalis longicornis (97.2%), H. flava (0.7%), Ixodes nipponensis (1.8%) and Amblyomma testudinarium (0.4%). Among them, 192 female adults hatched their eggs successfully. Our results showed a high prevalence of SFTSV among collected ticks (3.1%, 6/192 ticks), and we detected SFTSV from their larvae. This result suggests that the parent generation of H. longicornis can transmit SFTSV transovarially into their F1 progeny and H. longicornis might be one of major vectors of SFTSV in Korea.

Ixodid ticks are notorious as the vector of severe fever with thrombocytopenia syndrome virus (SFTSV) in Korea. To confirm the transovarial transmission of SFTSV, we collected blood-fed adult ticks from animals in SFTS case reported area of Jeju island in 2015. A total of 476 ticks were collected from four host animal species, horse (81.3%), dog (9.0%), roe deer (7.1%) and wild boar (2.5%). They were identified as 1 genus and 2 species, Haemaphysalis longicornis (87.8%) and H. flava (12.2%). Among them, 131 adults hatched their eggs successfully. The body weight of females was highly correlated with the number of egg masses laid (P < 0.05). We confirmed that one adult H. flava was infected with SFTSV and its infection rate was 0.77%. The eggs of the SFTSV-infected adults also were infected with SFTSV and its transovarial transmission was confirmed. This result suggests that the parent generation of H. flava could transmit SFTSV transovarially into their F1 progeny and H. flava might be one of major vectors of SFTSV in Korea.

Acquisition of plant viruses has various effects on physiological mechanisms in vector insects. Bemisia tabaci is the only known vector of Tomato yellow leaf curl virus (TYLCV), which is a serious virus affecting tomato cultivars. In this study, the lifespan of Q1 biotype was compared between non-viruliferous (NV) and TYLCV-viruliferous (V) whiteflies. Total lifespan from egg to adult death of NV whiteflies was 62.54 days but 10.64 days shorter in V whiteflies. We investigated the temperature susceptibility of B. tabaciby comparing mortalities as well as heat shock protein (hsp) mRNA levels between NV and V whiteflies. For this, NV and V whiteflies were exposed for either 1 or 3 h at 4, 25, and 35 °C. The mortality of V whiteflies was higher than NV ones following exposure at either 4 or 35 °C, but there was no significant difference at 25 °C. Analysis of the expression level of heat shock protein (hsp) genes using quantitative real-time PCR showed that both cold and heat shock treatments stimulated higher expression of hsps (hsp40, hsp70, and hsp90) at various rates in V whiteflies than NV ones, but there was no difference at 25 °C. All together, our results show that TYLCV acquisition accelerated the developmental rate and increased susceptibility to thermal stress in B. tabaci. Therefore, this modification may result in reduced vector longevity due to increased metabolic energy utilization. Our results provide insights into the complex interaction between vector fitness and thermal stress in relation to the acquisition and transmission of plant viruses.

The sweetpotato whitefly, Bemisia tabaci, acts as a vector of more than 100 plant viruses. B. tabaci is known to harbor a primary endosymbiont (Portiera) and 6 secondary endosymbionts (Arsenophonus, Cardinium, Fritschea, Hamiltonella, Rickettsia and Wolbachia). These endosymbionts play important roles in the acquisition and transmission of plant viruses. Using PCR analysis, we identified endosymbiotic bacteria in various B. tabaci populations collected from different places of Korea. Distribution of endosymbionts was different according to the biotype of B. tabaci. Subsequently, their relative densities of endosymbionts were compared between TYLCV-viruliferous and non-viruliferous populations of the Q biotype using quantitative realtime PCR. We found that the densities of Portiera, Cardinium and Hamiltonella are higher in viruliferous than non-viruliferous whiteflies. Our results suggest the role of endosymbiont for the TYLCV transmission of whiteflies.

The whitefly Bemisia tabaci (Gennadius) (Homoptera: Aleyrodidae) is one of the most important agricultural pests in Japan, that causes retard of plant growth and sooty moulds through excreted honeydew by direct sucking of pholoem sap, and additionally transmits several kinds of plant virus. B. tabaci consists of more than 20 biotypes which possess different ecological or physiological characters but cannot be distinguished from others morphologically. In Japan, exotic B and Q biotypes are the common pests of vegetables, flowers and ornamental plants. B biotype, the silver-leaf whitefly, was first recorded in Aichi Prefecture, Tokai region, in 1989 and expanded its distribution to almost all part of Japan, except for the northern area, within several years. Q biotype was recently found in Hiroshima Prefecture, Chugoku region, in 2004 and is still expanding the distribution in our country. Indigenous B. tabaci biotypes also exist in the southwestern part of Japan: JpL biotype was recorded in Honshu, Shikoku, Kyushu Islands and Nauru biotype was found in Amami and Ryukyu Islands. Although the host plants of these indigenous biotypes include some agricultural crops, these insects are not important as agricultural pests. The most serious problem in vegetable cultivation caused by B. tabaci is an intensive epidemic of the tomato yellow leaf curl disease (TYLCD) which leads to a large yield loss of tomato production in green houses. TYLCD distributes worldwide and it was found in Aich and Sizuoka Prefectures, Tokai region, and Nagasaki Prefecture, Kyushu region, simultaneously in 1996. The distribution of TYLCD expanded mainly in the western part of Japan for several years after its first finding, but recently TYLCD started to occur also in the eastern part of Japan, Kanto and Tohoku regions. Tomato yellow leaf curl virus (TYLCV), a pathogen of TYLCD, is transmitted by B or Q biotype of B. tabaci in a persistent manner. Although an effective control of B. tabaci is essential for decreasing of TYLCD outbreaks in tomato green houses, it is quite difficult to control these whiteflies only by the spraying of chemically synthesized insecticides due to their insecticide resistance. Especially, Q biotype shows a high level of resistance to pyriproxyfen and neonicotinoid insecticides. To avoid the development of insecticide resistance in B. tabaci, we are trying to combine some different control methods, for example, use of a fine mesh screen to prevent the invasion of vector insects, use of the physical-coating or microbial insecticides with the chemically synthesized insecticides to prevent the reproduction of vector insects, closing and steaming of a green house at the end of tomato cultivation to kill vector insects and prevent their escape from there, as an integrated pest management (IPM) system for B. tabaci and TYLCD control. We are also breeding TYLCV resistant varieties of tomato and considering how to use these varieties effectively.

본 연구는 오동나무천구소병 바이러스의 매개충을 구명하기 위하여 착수했으며, 결과는 다음과 같다. 1) 오동나무천구소병의 이병수에 모여드는 흡수성곤충 중에서 가장 발생이 많았던 곤충은 담배장님노린제며 난, 약충, 성충이 8월 중순부터 10월 하순까지 발생하였다. 2) 담배장님노린재가 오동나무천구소병 바이러스의 매개곤충임이 구명되었다. 3) 담배장님노린재에 의하여 오동나무천구소병 바이러스를 접종한 결과 오동나무유식물에서는 접종 후 20일만에 발병을 보았고 접종 40일만에 오통나무천구소병 특유의 병징이 발현되었다. 4) 접종실험을 통해서 확인된 오동나무천구소병 바이러스의 기주식물은 오동나무 이외에 금잔화 및 나팔꽃이며, 일년감당근과꽃 백일흥코스므스대두질경이 등에서는 충접종 후 2개월까지도 뚜렷한 발병을 확인할 수 없었다. 5) 금잔화와 나팔꽃은 발병까지의 잠복기간이 짧고 병징발현이 뚜렷한 점으로 미뤄 오동나무천구소병 바이러스의 유망한 검정식물로 생각된다.

농가를 방문하는 가금관련업체의 관계자 및 차량은 HPAI 질병 확산의 매개체가 된다. 농가들의 가금관련업체 이용 정보를 이용하면 농가간의 연결을 확인할 수 있고 HPAI 확산 가중 네트워크를 구성할 수 있다. 네트워크 분석중 중심성 측정은 질병에 취약하거나 타 농가에 영향력이 큰 역할을 하는 농가를 분석하는 방법으로 HPAI 초기 확산을 통제하는 방법으로 이용된다. 단, HPAI 바이러스는 네트워크의 연결선 가중치에 따라서 확산 경로가 달라질 수 있다.

Soybeans X soybeans mosaic virus (SMV) strains interactions affected plant growth and seed transmission. Strain virulence of SMV depended on host cultivars. Kwangankong and Tawonkong were susceptible to G7H and G5 strains, causing mosaic symptoms. The distribution patterns of two SMV strains in soybean plants inoculated with G7H, G5 and G7H/G5 sets were investigated by RT-PCR/RFLP analysis. In the first treatment, two primary leaves in a single plant were infected with both strains by means of one strain per leaf. The leaves of Kwangankong and Tawonkong at V2, V4 and V6 stage were doubly infected with the two strains and the upper leaves than those had only G7H strain. Secondly, the two soybeans were inoculated with G7H, and 24 h after followed by the other strain inoculation. The leaves of V6 and V8 stages in all infected plants showed mosaic symptoms caused by G7H, and there was no detection of G5 strain. In contrast, the reverse treatment with G5 and G7H induced different results. Pre-inoculated G5 strain detected in every stage besides G7H strain. Host X SMV strain compatibility influenced seed coat mottling, yield, plant height, number of pod per plant. G7H had a seed mottling rate of 98.5% in Kwangankong, while G5 had an incidence of seed mottling of 1.4% in the same cultivar. G5 was more virulent to Kwangankong and had a lower affinity for infecting soybean seed mottling. Additional inoculation of G7H protected soybean yield and growth from G5-inducing loss in Kwangankong.