Tomato spotted wilt virus (TSWV) is distributed all over Japan and globally, seriously damaging infected plants. A resistance-conferring gene, Tsw, that controls the yellow spotted wilt disease in bell pepper (Capsicum annuum) plants caused by TSWV infection in Japan, is now commercially available. In this study, we isolated for the first time in Japan, a resistance-breaking isolate, TSWV-JRB, from bell pepper plants harboring Tsw. The virus overcame the resistance conferred by Tsw in its heterozygous and homozygous configurations. The host range or virulence of TSWV-JRB and one of the non-resistance breaking isolates from Japan did not differ, except in the plants harboring Tsw. The TSWV-JRB acquisition rates and transmission rates of the thrip pests Frankliniella occidentalis and F. intonsa were 93

A multiplex one-step reverse transcription polymerase chain reaction (multiplex RT-PCR) assay was developed to detect nine important viruses that infect cucumber in Japan: beet pseudoyellows virus watermelon mosaic virus (WMV), watermelon silver mottle virus (WSMoV), and zucchini yellow mosaic virus (ZYMV). We newly designed virus species-specific primer pairs for seven viruses and used previously reported primer pairs for two viruses. Specificity and sensitivity tests by simplex RTPCR using the primer set showed that touch-down RT-PCR effectively reduced non-specific amplification and had high sensitivity (10 - 10(5)-fold dilution). For multiplex RT-PCR, the primer set was first divided into two sets: primer set I was for WMV, CCYV, KGMMV, BPYV, and WSMoV; primer set II was for PRSV, ZYMV, CMV, and MYSV. After optimizing the ratio of nine primer pairs and the number of cycles of the multiplex RT-PCR, all viruses could be detected by the same PCR condition. When the assays were applied to cucumber samples obtained from an open field and greenhouses, viral infections were clearly identified without non-specific amplification. Therefore, the multiplex RT-PCR assay can be used for the routine diagnosis of the nine viruses in field-growing samples.

In 2023, cucumber (Cucumis sativus L.) plants in Kyoto Prefecture, Japan, older leaves developed yellowing, which was suspected to be caused by a virus. To identify the virus species extracted from the yellowing leaves, we sequenced its complete genome. The deduced amino acid sequence of the virus had 93.7–99.3

BACKGROUND:Root-knot nematodes (RKN) are well-known plant parasites that seriously damage crops. Meloidogyne incognita, the most prevalent species, infects many globally important crops, including tomato (Solanum lycopersicum L.). Some jasmonic acid (JA) derivatives enhance tolerance against RKN, but the synthetic JA derivative 'prohydrojasmon' (PDJ) has not been thoroughly studied. This study investigated PDJ's influence on M. incognita infection in tomato, focusing on second-stage juveniles (J2) penetration. RESULTS:We used Jasmomate® SL, a commercial plant growth regulator, for the PDJ treatment. PDJ application to tomato significantly reduced M. incognita penetration, with root application being more effective than shoot application. In a soaking test, PDJ did not exhibit nematicidal activity against M. incognita J2 even at the highest concentration in this study. An inoculation experiment with M. incognita soaked in PDJ solution showed no significant difference among treatments. PDJ application also reduced penetration from a Mi-1-virulent isolate of M. incognita and two other Meloidogyne species. CONCLUSION:This study suggests that PDJ treatment in tomato suppresses RKN infection through inhibitory mechanisms against J2 penetration, possibly by activating JA-related basal defense in the host plant. Future research should demonstrate PDJ's practical effectiveness and clarify the detailed mechanisms affecting RKN infection, positioning PDJ as a new eco-friendly tool for RKN control as a plant activator. © 2025 Society of Chemical Industry.

In April 2024, following the annual International Committee on Taxonomy of Viruses (ICTV) ratification vote on newly proposed taxa, the phylum Negarnaviricota was expanded by 1 new order, 1 new family, 6 new subfamilies, 34 new genera and 270 new species. One class, two orders and six species were renamed. Seven families and 12 genera were moved; ten species were renamed and moved; and nine species were abolished. This article presents the updated taxonomy of Negarnaviricota as currently accepted by the ICTV, providing an essential annual update on the classification of members of this phylum that deepen understandings of their evolution, and supports critical public health measures for virus identification and tracking.

Since its first occurrence in Israel and Jordan in 2014 and 2015, the tomato brown rugose fruit virus (ToBRFV) has become one of the most concerning pathogens affecting tomatoes and other crops worldwide. Its rapid spread is believed to result from the international trade of contaminated seeds and its seed transmissibility, underscoring the critical importance of seed health testing for ToBRFV to prevent further dissemination of the virus. To this end, reverse transcription-quantitative polymerase chain reaction (RT-qPCR) protocols employing TaqMan probe chemistry have been widely adopted. However, the development of RT-qPCR protocols for ToBRFV seed testing using SYBR Green chemistry remains limited. The SYBR Green method offers the advantage of distinguishing ToBRFV from other tobamoviruses through melt curve analysis. In this study, we developed a SYBR Green-based RT-qPCR detection method using newly designed primer sets, which demonstrated high specificity for ToBRFV and sufficient sensitivity. While this protocol requires further optimization and validation for application in routine seed testing, it establishes a foundational approach for SYBR Green-based RT-qPCR seed testing. Additionally, this study raises an important question regarding the relationship between RT-qPCR results in seed tests and the likelihood of virus contamination or transmission via seeds.

タバココナジラミによって媒介されるウイルスの感染で引き起こされるトマト黄化葉巻病やトマト黄化病の発生地域である熊本県の冬春トマトにおいて,捕食性天敵であるタバコカスミカメによる春期のタバココナジラミ密度に対する抑制効果を2020~2021年の作期に検証した。隣接する2つの生産者施設をそれぞれ天敵導入区・対照区とし,天敵導入区では連棟間の天井谷間の天窓で0.4 mm,側窓で0.3 mmの目合いの防虫ネットを展張し,対照区では天窓で1.0 mm,側窓で0.4 mmとした。野外のタバココナジラミの発生量が多い定植初期(9,10月)は,天敵導入区・対照区ともに非選択性殺虫剤とコナジラミ類成虫忌避剤を中心とした慣行防除を行い,10月下旬から天敵導入区にタバコカスミカメおよびバンカー植物を導入した。バンカー植物としてクレオメとバーベナを用いた。その結果,天敵導入区では対照区と比較して5月以降のタバココナジラミ密度の上昇ペースが抑えられ,間接的にTYLCVおよびToCVの感染株率も対照区と同等もしくはそれ以下に抑えられた。これらの結果から,トマト黄化葉巻病およびトマト黄化病の発生地域において,0.3~0.4 mm目合い防虫ネットの組み合わせたタバコカスミカメ利用は,タバココナジラミの防除に有効であることが示された。

In 1929, it was reported that yellowing symptoms caused by a tobacco mosaic virus (TMV) yellow mosaic isolate were suppressed in tobacco plants that were systemically infected with a TMV light green isolate. Similar to vaccination, the phenomenon of cross-protection involves a whole plant being infected with an attenuated virus and involves the same or a closely related virus species. Therefore, attenuated viruses function as biological control agents. In Japan, many studies have been performed on cross-protection. For example, the tomato mosaic virus (ToMV)-L11A strain is an attenuated isolate developed by researchers and shows high control efficiency against wild-type ToMV in commercial tomato crops. Recently, an attenuated isolate of zucchini yellow mosaic virus (ZYMV)-2002 was developed and registered as a biological pesticide to control cucumber mosaic disease. In addition, attenuated isolates of pepper mild mottle virus (PMMoV), cucumber mosaic virus (CMV), tobacco mild green mosaic virus (TMGMV), melon yellow spot virus (MYSV), and watermelon mosaic virus (WMV) have been developed in Japan. These attenuated viruses, sometimes called plant vaccines, can be used not only as single vaccines but also as multiple vaccines. In this review, we provide an overview of studies on attenuated plant viruses developed in Japan. We also discuss the application of the attenuated strains, including the production of vaccinated seedlings.

The complete genome sequence of Orthotospovirus tomatozonae (tomato zonate spot virus, TZSV) isolated in Japan was determined and compared with that of Chinese isolates. The lengths of the S, M, and L segments of the RNA genomes of the Japanese isolate (TZSV-TZ1-3) were 3194, 4675, and 8916 nucleotides, respectively, which were similar to the Chinese isolates. Moreover, the eight motifs on the RNA-dependent RNA polymerase (RdRp) gene were conserved in both TZSV-TZ1-3 and Chinese TZSV isolates (TZSV-Bidens and TZSV-Tomato-YN). The nucleotide identity of the genes among the TZSV isolates was more than 94%, indicating low diversity among viruses. The phylogenetic analysis and the prediction of the cleavage sites in the glycoprotein showed that the TZSV-TZ1-3 isolate was closely related to TZSV-Tomato-YN isolated from China. However, there were unique frameshifts and deletions on the RdRp and glycoprotein genes of the TZSV-Tomato-YN isolate, suggesting that both isolates were genetically distinct. The findings of this study indicate that the TZSV-TZ1-3 isolate originated in China and show the sequence diversity among TZSV isolates.

Since the first report of the tobamovirus tomato brown rugose fruit virus (ToBRFV) in 2014, it has become globally distributed. Its rapid spread has been primarily attributed to seed-borne transmission. Here, the seed-borne nature of ToBRFV transmission was investigated in different cultivars of tomato, bell pepper, and eggplant. In situ hybridization to localize the virus in reproductive organs of ToBRFV-infected tomato plants revealed that the virus was not present in shoot apices, flower buds, or in ovules during flower opening, indicating the virus may be restricted to the outer integument and transported in the vascular bundles during seed development. However, during early fruit development, the virus was present in the integuments in the ovule. Seeds of tomato cultivars with or without tobamovirus resistance gene Tm-2 2 transmitted the virus to the progeny seedlings at rates that reflected the ineffectiveness of the gene against ToBRFV. Seeds of bell peppers transmitted ToBRFV at higher rates than tomato seeds, but a bell pepper cultivar that has resistance gene L 3 was not systemically infected, and its seeds did not harbor the virus. Three eggplant cultivars were systemically infected with ToBRFV but without showing any obvious symptoms, and even though ToBRFV was present in their seeds, the seedlings were not infected. ToBRFV was detected in the seed coats of contaminated tomato and bell pepper seeds, but not in eggplant seed coats. These results indicate mechanistic differences in seed-borne transmission among the three Solanaceae crops.

Squash (Cucurbita maxima) is an essential crop cultivated throughout Japan, and viral diseases such as mosaic disease cause a tremendous loss of squash yield in this region. Although surveying and detection of infectious viruses are essential for controlling viral diseases, currently, no in-depth field surveys have yet been conducted. Here, we conducted a field survey in virus-infected squash fields in Okinawa Prefecture, Japan. A total of 138 samples, including 131 from squash and 7 from weeds, were collected from Ishigaki Island, Miyako Island, and Okinawa Main Island. Nine identified viruses were then investigated by reverse transcription-polymerase chain reaction (RT-PCR). Most samples were found to be infected with zucchini yellow mosaic virus (ZYMV), and a few were infected with papaya ringspot virus (PRSV) or both ZYMV and PRSV. No other cucurbit-infecting viruses were detected among the samples. In addition, ZYMV and PRSV were detected in cucurbitaceous weeds grown near squash fields, suggesting that these weeds may act as an infection source for these viruses.

In April 2023, following the annual International Committee on Taxonomy of Viruses (ICTV) ratification vote on newly proposed taxa, the phylum Negarnaviricota was amended and emended. The phylum was expanded by one new family, 14 new genera, and 140 new species. Two genera and 538 species were renamed. One species was moved, and four were abolished. This article presents the updated taxonomy of Negarnaviricota as now accepted by the ICTV.

海外のトマト等ナス科作物での発生と被害が拡大しているtomato brown rugose fruit virus(ToBRFV)について,日本国内への種子を介した侵入を抑制するための種子消毒技術,および,国内で発生した場合に取り得る防除技術として汚染器具の消毒技術およびトマトモザイクウイルス(ToMV)の弱毒株を用いた防除の効果を評価した.トマト汚染種子の消毒では,5%リン酸三ナトリウムおよび次亜塩素酸ナトリウム溶液での処理がともに高い効果が認められたが,発芽率の観点から前者が優れていた.ただし,消毒により感染性が完全に消失した種子からも,RT-PCRによる検出ではToBRFV陽性と判定されうることが明らかとなった.ToBRFV汚染器具の消毒効果については,5%リン酸三ナトリウムおよび1%消石灰には高い効果が認められた.トマト苗への弱毒ウイルス株ToMV-L11A株の接種は,ToBRFVの感染や発病を抑制する効果は期待できないと判断された.

In 2021 in Kanagawa Prefecture, Japan, green pepper ( Capsicum annuum L.) developed necrotic spots on leaves and necrosis of stems. The nucleotide sequence of the N gene of the virus, isolated through two-rounds of single-lesion isolation, shared 95% identity with that of tomato zonate spot virus (TZSV) reported in China. When green pepper plants were inoculated with the isolated virus, the original symptoms were reproduced, and RT-PCR confirmed the presence of the virus in the inoculated plants. This is the first report of TZSV in Japan.

本研究では，既報のオルソトスポウイルスを識別するマルチプレックスRT-PCR法（Uga and Tsuda, 2005; Kuwabara et al., 2010）を改良し，近年国内で新たに発生したウイルスを含め，現在国内のナス科作物で確認されている全6種［トマト黄化えそウイルス（TSWV），tomato zonate spot virus（TZSV），インパチエンスえそ斑点ウイルス（INSV），キク茎えそウイルス（CSNV），スイカ灰白色斑紋ウイルス（WSMoV）およびトウガラシ退緑ウイルス（CaCV）］を検出するためのマルチプレックスRT-PCR法を開発した．プライマーの設計，RT-PCRの条件検討の結果，最適化した条件で，これらのウイルスが感染したナス科植物からTSWV（831 bp），TZSV（734 bp），INSV（592 bp），CSNV（502 bp），WSMoV（395 bp），およびCaCV（324 bp）由来の種特異的増幅産物が確認された．さらに，本法を用いることで，供試したオルソトスポウイルスのいずれの組合せでも，ウイルスを同時に検出することができた．したがって，本手法は，ナス科作物に感染する6種オルソトスポウイルスの同時検出に有効であると考えられた．

海外のトマト等ナス科作物での発生と被害が拡大しているtomato brown rugose fruit virus(ToBRFV)について,日本への侵入抑制と発生時の早期発見に資する情報を収集するため,特に日本国内で広く栽培されている市販トマト品種を中心に,ピーマン,ナス,ジャガイモ等ナス科作物の各品種や,ウイルス検定に用いられる植物,雑草等を対象として,全身感染性と病徴を調査した.トマトのTm-1およびピーマンのL遺伝子はToBRFVに対し有効で全身感染を阻止したが,トマトのTm-2a型品種では抵抗性が機能せずモザイク等を発症した.ナス科の作物,雑草では,調査した範囲で多くの種・品種で全身感染してモザイク等を発症することが示され,一方でナスのようにほぼ無病徴で全身感染する種も見いだされた.ToBRFVの国内侵入および拡散防止には,ナス科植物の直接被害だけでなく,ナス科雑草等を介した種子伝染による拡散経路にも注意する必要がある.

Characterizing the detailed spatial and temporal dynamics of plant pathogens can provide valuable information for crop protection strategies. However, the epidemiological characteristics and evolutionary trajectories of pathogens can differ markedly from one country to another. The most widespread and important virus of brassica vegetables, turnip mosaic virus (TuMV), causes serious plant diseases in Japan. We collected 317 isolates of TuMV from Raphanus and Brassica plants throughout Japan over nearly five decades. Genomic sequences from these isolates were combined with published sequences. We identified a total of eighty-eight independent recombination events in Japanese TuMV genomes and found eighty-two recombination-type patterns in Japan. We assessed the evolution of TuMV through space and time using whole and partial genome sequences of both nonrecombinants and recombinants. Our results suggest that TuMV was introduced into Japan after the country emerged from its isolationist policy (1639-1854) in the Edo period and then dispersed to other parts of Japan in the 20th century. The results of our analyses reveal the complex structure of the TuMV population in Japan and emphasize the importance of identifying recombination events in the genome. Our study also provides an example of surveying the epidemiology of a virus that is highly recombinogenic.

スイカ灰白色斑紋ウイルス（WSMoV）の弱毒株作出を目的として，WSMoV のゲノムに変異を加えるための亜硝酸ナトリウム処理および熱処理の最適条件を検討した。亜硝酸ナトリウム処理は，WSMoV の野生株（強毒株；WSMoV-WD1）が感染した植物の粗汁液に1～4M およびpH4～7 の条件で添加した。一方，熱処理は，野生株感染植物を28℃，35℃あるいは40℃で，14日間栽培した。各処理を施した感染植物の粗汁液をペチュニアに機械接種したのち，単一病斑分離を行い，合計1006株のWSMoV 分離株を得た。それらのうち，各処理条件から無作為に選抜した52株についてNSs およびN 遺伝子の塩基配列を解析し，野生株と比較した。その結果，1M 亜硝酸ナトリウム（pH=5）処理および4M 亜硝酸ナトリウム （pH= ５および６）処理と35℃で熱処理をしたWSMoV 分離株の塩基配列において最も多くの同義置換および非同義置換が認められた。したがって，それらの条件がWSMoV のゲノムへの変異導入に適していると考えられた。

In March 2022, following the annual International Committee on Taxonomy of Viruses (ICTV) ratification vote on newly proposed taxa, the phylum Negarnaviricota was amended and emended. The phylum was expanded by two new families (bunyaviral Discoviridae and Tulasviridae), 41 new genera, and 98 new species. Three hundred forty-nine species were renamed and/or moved. The accidentally misspelled names of seven species were corrected. This article presents the updated taxonomy of Negarnaviricota as now accepted by the ICTV.