Plant viruses and viroids in Japan

An increasing number of plant viruses and viroids have been reported from all over the world due largely to metavirogenomics approaches with technological innovation. Herein, the official changes of virus taxonomy, including the establishment of megataxonomy and amendments of the codes of virus classification and nomenclature, recently made by the International Committee on Taxonomy of Viruses were summarized. The continued efforts of the plant virology community of Japan to index all plant viruses and viroids occurring in Japan, which represent 407 viruses, including 303 virus species and 104 unclassified viruses, and 25 viroids, including 20 species and 5 unclassified viroids, as of October 2021, were also introduced. These viruses and viroids are collectively classified into 81 genera within 26 families of 3 kingdoms (Shotokuvirae, Orthornavirae, Pararnavirae) across 2 realms (Monodnaviria and Riboviria). This review also overviewed how Japan’s plant virus/viroid studies have contributed to advance virus/viroid taxonomy

Efficacy of a Simple Formulation Composed of Nematode-Trapping Fungi and Bidens pilosa var. radiata Scherff Aqueous Extracts (BPE) for Controlling the Southern Root-Knot Nematode

We tested a formulation composed of a mixture of Bidens pilosa var. radiata extract (BPE) and nematode-trapping fungi for its effects on Meloidogyne incognita. In earlier evaluations of the effects of plant extracts on the hyphal growth of 5 species of nematode-trapping fungi with different capture organs (traps), the growth of all species was slightly inhibited. However, an investigation on the number of capture organs and nematode-trapping rates revealed that Arthrobotrys dactyloides formed significantly more rings and nematode traps than those of the control. An evaluation of simple mixed formulations prepared using sodium alginate showed that nematodes were captured with all formulations tested. The simple mixed formulation showed a particularly high capture rate. Furthermore, in a pot test, although the effects of a single formulation made from the fungus or plant extract were acceptable, the efficacy of the simple mixed formulation against M. incognita root-knot formation was particularly high

Prospect of the plant pathological study for local agriculture promotion in Okinawa.

With the renewal of staff of the Plant Pathology Laboratory of the University of the Ryukyus, Okinawa, Japan in 2016, plant protection in Okinawa entered a new era. Before then, fungi, oomycete, bacteria, and nematodes were the target pathogens of our research. Since 2016, virus has been added to the list of the research targets. The diagnostic ability of the laboratory has substantially improved with the availability of new molecular biological facilities and a greenhouse that is maintained for the cultivation of tropical crops. As a result, when new diseases emerged in Okinawa, their causal agents were rapidly identified in a few years’ time. Crop protection is one of the most important factors in the promotion of local agriculture in Okinawa. Now, we can contribute to governmental plant protection organizations in Okinawa by identifying new pathogens and educating young plant pathologists, especially in the diagnosis of plant diseases. Additionally, collaboration with governmental organizations and local commercial companies related to plant protection would provide educational benefits to the students of the University of the Ryukyus. Here, we introduce the current status of the Plant Pathology Laboratory in the University of the Ryukyus and discuss its prospects in becoming the center of the Okinawa plant protection community.2016年に新体制となった琉球大学の植物病理学研究室における，2018年までの3年間に行った研究環境の拡充と，それによって得られた成果を紹介する．また植物防疫における産学官連携の重要性とそれによってもたらされる教育的効果を考察し，地域農業振興の推進に資する沖縄作物保護ネットワーク形成に向けた展望について述べる

Combined DECS Analysis and Next-Generation Sequencing Enable Efficient Detection of Novel Plant RNA Viruses

The presence of high molecular weight double-stranded RNA (dsRNA) within plant cells is an indicator of infection with RNA viruses as these possess genomic or replicative dsRNA. DECS (dsRNA isolation, exhaustive amplification, cloning, and sequencing) analysis has been shown to be capable of detecting unknown viruses. We postulated that a combination of DECS analysis and next-generation sequencing (NGS) would improve detection efficiency and usability of the technique. Here, we describe a model case in which we efficiently detected the presumed genome sequence of Blueberry shoestring virus (BSSV), a member of the genus Sobemovirus, which has not so far been reported. dsRNAs were isolated from BSSV-infected blueberry plants using the dsRNA-binding protein, reverse-transcribed, amplified, and sequenced using NGS. A contig of 4,020 nucleotides (nt) that shared similarities with sequences from other Sobemovirus species was obtained as a candidate of the BSSV genomic sequence. Reverse transcription (RT)-PCR primer sets based on sequences from this contig enabled the detection of BSSV in all BSSV-infected plants tested but not in healthy controls. A recombinant protein encoded by the putative coat protein gene was bound by the BSSV-antibody, indicating that the candidate sequence was that of BSSV itself. Our results suggest that a combination of DECS analysis and NGS, designated here as “DECS-C,” is a powerful method for detecting novel plant viruses

マツ葉微生物に及ぼすアワユキセンダングサ抽出液の影響

Extract of Bidens pilosa var. radiata distributed in Okinawa are known to have high insecticidal and repellent activity against plant parasitic nematodes, agricultural pests, and pine wilt disease-related organisms. The effects of this plant extract on crops and soil microorganisms have been studied, but the effects on microorganisms of pine needles have not been investigated. Therefore, we surveyed the influence of the plant extract on pine seedling (Pinus luchuensis Mayr) and its phyllosphere microbes of pine needle. It became clear that the harmful effect on the pine seedling and phyllosphere microbial flora were not observed. Thus, B. pilosa var. radiata extract is judged to be an environmentally friendly control material from the viewpoint of environmental assessment.沖縄に分布するアワユキセンダングサの抽出液は，植物寄生性線虫，一般農業害虫およびマツ材線虫病関連生物に対して高い殺虫・忌避活性を有することが知られている．農作物や土壌微生物に対する本植物抽出液の影響は調査されているが，マツやマツ葉微生物に対する影響は調査されていない．そこで，リュウキュウマツとマツ葉針微生物に及ぼす影響を調べた結果，悪影響は認められないことが明らかになった．従って，アワユキセンダングサ抽出液は環境評価の観点から，環境に優しい防除資材であると判断された