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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.

A new badnavirus, aucuba ringspot virus (AuRV), was identified in plants of Aucuba japonica showing mild mosaic, vein banding, and yellow ringspot symptoms on the leaves. The complete nucleotide sequence of the AuRV genome was determined and found to be 9,092 nt in length, and the virus was found to have a genome organization typical of members of the genus Badnavirus. ORF3 was predicted to encode a polyprotein containing conserved movement protein, coat protein, aspartic protease, reverse transcriptase (RT), and RNase H domains. Phylogenetic analysis suggested that this virus is most closely related to codonopsis vein clearing virus but belongs to a distinct species, based on only 69.6% nucleotide sequence identity within the part of ORF 3 encoding the RT and RNase H domains. The vector of AuRV is unknown, but based on phylogenetic relationships, it is predicted to be a type of aphid.

A potyvirus with the proposed name ashitaba mosaic virus was detected in ashitaba [Angelica keiskei (Miq.)] plants exhibiting mosaic and vein clearing in Japan. The host range of the virus includes species from three families, Apiaceae, Chenopodiaceae, and Solanaceae. The genome of the virus was determined to comprise 9,651 nucleotides, excluding the poly(A) tail. A phylogenetic analysis based on the polyprotein revealed the virus is closely related to carrot thin leaf virus and potyviruses isolated from Apiales and Apiaceae plant species. Sequence comparisons indicated the nucleotide and polyprotein amino acid identities between the isolated virus and related species are 53.4–60.5% and 49.7–58.7%, respectively. These results suggest this virus is a new species in the genus Potyvirus. Furthermore, the results of a field survey suggest the virus may be widespread on the Izu Islands, with isolates classified into two genotypes.

Rice yellow mottle virus (RYMV) causes severe rice (Oryza sativa L.) yield loss. It has been endemic to sub-Saharan Africa and Madagascar since 1966. Transmission (plant community level) and long-dispersal (regional and continental scale) models have been established but viral spread in farming communities continues, while the conditions causing local disease outbreaks remain unclear. We hypothesized that local outbreaks, comprising inter-plot virus spread and intra-plot disease aggravation, are significantly associated with individual farmers’ attributes and agronomic practices. To test this hypothesis, spatial autoregressive models were constructed using variables collected by visual observation and farmer interviews. Field surveys were conducted during four consecutive cropping seasons from 2011 to 2013 in the Lower Moshi Irrigation Scheme of Kilimanjaro, Tanzania. Our models detected spatial dependence in inter-plot virus spread, but not in intra-plot disease aggravation. The probability of inter-plot virus spread increased with use of the IR64 cultivar (26.9%), but decreased with straw removal (27.8%) and crop rotation (47.7%). The probability of intra-plot disease aggravation decreased with herbicide application (24.3%) and crop rotation (35.4%). A simple cost-benefit analysis suggested that inter-plot virus spread should be mitigated by cultivar replacement and straw removal. When disease severity is critical, intra-plot disease aggravation should be inhibited by herbicide application, and rice should be rotated with other crops. This is the first study to upscale the spatial autoregressive model from the experimental field level to the farming community level, by obtaining variables through easy-to-implement techniques such as visual observation and farmer interview. Our models successfully identified candidate agronomic practices for the control of RYMV. However, as the causal relationships between agronomic practices and RYMV outbreaks remain unknown, field trials are needed to develop robust control measures.

Lima bean (Phaseolus lunatus) plants exhibiting yellow mosaic and stunted growth symptoms, typical of begomovirus infection, were collected in Rampur city Nepal. Symptomatic plants were shown to be infected by a monopartite begomovirus in association with a betasatellite. The two begomovirus isolates associated with the disease showed 98.7% nucleotide sequence identity to previously characterized isolates of the recently identified begomovirus species Pea leaf distortion virus (PLDV) from Nepal. The associated betasatellite isolates showed highest nucleotide sequence identity at 99% to Ludwigia leaf distortion betasatellite (LuLDB) from Nepal. This is the first identification of PLDV and LuLDB infecting the grain legume Phaseolus lunatus.

Cassava mosaic disease (CMD), a serious threat to cassava production, is caused by two begomovirus species in Asia, Indian cassava mosaic virus (ICMV) and Sri Lankan cassava mosaic virus (SLCMV). Cassava mosaic disease has recently spread into Southeast Asia and it is urgent to establish an efficient system to monitor its spread. Cassava fields were surveyed for CMD on the web using a smartphone-based farming support application, AGRIBUDDY, to obtain photos of CMD and their time, location, and contact information posted to the AGRIBUDDY cloud by farmers. To diagnose a pathogen, we designed novel PCR primers for CMD identification. By combining these two techniques, we detected SLCMV occurrence in Kampong Thom, Cambodia.

A new badnavirus, aucuba ringspot virus (AuRV), was identified in plants of Aucuba japonica showing mild mosaic, vein banding, and yellow ringspot symptoms on the leaves. The complete nucleotide sequence of the AuRV genome was determined and found to be 9,092 nt in length, and the virus was found to have a genome organization typical of members of the genus Badnavirus. ORF3 was predicted to encode a polyprotein containing conserved movement protein, coat protein, aspartic protease, reverse transcriptase (RT), and RNase H domains. Phylogenetic analysis suggested that this virus is most closely related to codonopsis vein clearing virus but belongs to a distinct species, based on only 69.6% nucleotide sequence identity within the part of ORF 3 encoding the RT and RNase H domains. The vector of AuRV is unknown, but based on phylogenetic relationships, it is predicted to be a type of aphid.

In 2016, in Miyakojima, Okinawa, Japan, banana plants (Musa × paradisiaca) ‘Shima-banana’ developed yellowing and wilt associated with vascular discoloration of the pseudostems. Fusarium oxysporum, identified based on morphological characters, was frequently isolated from the vascular tissue of the infected plant and reproduced the original symptoms on ‘Shima-banana’ after drench inoculation with a spore suspension. Thereby, we determined that the disease is Panama disease caused by F. oxysporum. This is the first official report of Panama disease (Panama-byo in Japanese) of banana in Japan.

Recently, the widespread occurrence of Sri Lankan cassava mosaic virus (SLCMV), genus Begomovirus, family Geminiviridae, which causes a mosaic disease in cassava (Manihot esculenta Crantz) in South-East Asia have, become a serious economic issue. Since cassava is propagated through vegetative cuttings, a rapid virus diagnostic method is crucial for generating virus-free planting materials. In this study, a loop-mediated isothermal amplification (LAMP) assay using six primers was developed and validated for the rapid detection of SLCMV in cassava leaves. This SLCMV assay had a detection sensitivity that was up to 10,000 times higher than that of the conventional polymerase chain reaction assay and can detect the virus from symptomless stem cutting, which is a potential long-distance spreader of the virus. Furthermore, a practical LAMP protocol using stable dried reagents from a commercial kit was established so that the assay could be performed in the field by incubating the reactions in water at 60-65 °C instead of using a thermal cycler. The primer sequences and the LAMP protocol described here should be useful for the rapid and sensitive on-site detection of SLCMV.

Cucumber (Cucumis sativus L.) is an important vegetable in Indonesia. Cucumber plants showing yellowy green mosaic symptoms on leaves were observed in Klaten, Central Java, Indonesia in August 2008. Total DNAs were extracted from symptomatic leaves, and the putative viral genomes were amplified by PCR with the Deng A and B primers (2). The PCR-amplified viral genomic DNA was sequenced. The remaining part of DNA-A was amplified with two primers sets (ToLCNDV-A1F 5′-ACCAACAGGCCGATGAACA-3′ and ToLCNDV-A1R 5′-TTCCCACTATCTTCCTGTGCA-3′; ToLCNDV-A2F 5′-TCGAGTGTGATRAAGAYTGCA-3′ and ToLCNDV-A2R 5′-ACTAACTAAGCATTGCAGCGTC-3′ [R = A and G, Y = C and T]) and sequenced. The remaining part of DNA-B was amplified with two primers sets (ToLCNDV-B1F 5′-ARGAGTTYMCRYYTGTGGA-3′ and ToLCNDV-B1R 5′-TKCWGTYGGTCATGTCGT-3′; ToLCNDV-B2F 5′-TCYGTCAATCKCATGTCGYGT-3′ and ToLCNDV-B2R 5′-CCTTACGCGTATAYTGTYTRGA-3′ [K = G and T, M = A and C, W = A and T]) and sequenced. Full-length DNA-A (2,739 nt; GenBank Accession No. AB613825) and DNA-B (2,690 nt; GenBank Accession No. AB613826) sequences of a bipartite Tomato leaf curl New Delhi virus (ToLCNDV) from Central Java were obtained and they were most similar to the corresponding sequences of both DNA-A and DNA-B of ToLCNDV-[cucumber:Thailand] (DNA-A, GenBank Accession No. AB330079; DNA-B, GenBank Accession No. AB330080) at 95.5 and 91.0% nucleotide identities, respectively. On the basis of high nucleotide sequence identity with ToLCNDV-[cucumber:Thailand] and the demarcation criteria in species identification (3), the virus isolate from the diseased cucumber in Central Java is considered as a variant of ToLCNDV and was accordingly named ToLCNDV-Indonesia[Indonesia:Java:Cucumber:2008] (ToLCNDV-ID[ID:Jav:Cuc:08]). Although the importance of begomovirus diseases on chili pepper (Solanaceae) is currently highly noticed in Indonesia (1), ToLCNDV was newly isolated from cucumber (Cucurbitaceae) in this study. Therefore, farmers in Indonesia should pay more attention to controlling begomovirus vectors, white flies, on Cucurbitaceae. To our knowledge, this is the first report of the natural occurrence of ToLCNDV in Indonesia. References: (1) P. J. D. Barro et al. Biol. Invas.10:411, 2008. (2) D. Deng et al. Ann. Appl. Biol. 125:327, 1994. (3) C. M. Fauquet et al. Arch. Virol. 153:783, 2008.

Cassava is an important crop, in which root tubers have been known as a staple food in tropical area. Recently, cassava tubers are processed by various methods into numerous products and utilized in various ways. The land area of cassava cultivation has been increasing especially in Southeast Asia. Such a situation is causing an introduction of new cassava diseases and insect pests in the region. In the main part of this chapter, we reviewed the current cassava situation in Vietnam, Cambodia, and Thailand and then illustrated the major cassava diseases and insect pests and their management methods. In addition, we described the international activities developing the cassava agriculture to date, the existing agricultural extension system, and the socioeconomic situation of cassava farmers. Since 2016, we have been conducting SATREPS project to establish a management of invasive cassava diseases and insect pests. At last part chapter, we showed our approach to establish the sustainable agriculture of cassava.

Rice yellow mottle virus (RYMV) is the most important rice virus in Africa. We examined RYMV transmission via soil and water contaminated with RYMV-infected rice plants and by serial cutting with RYMV-contaminated scissors. Transmission of RYMV via dried rice straw kept at 27°C was also examined. The results showed the virus could be transmitted via soil and water, and by scissors. Rice straw that was RYMV-infected was not infective if it was dried and was kept longer than 42 days. By insect transmission experiments and ELISA, long-horned grasshoppers (Conocephalus spp.) were found to be a possible vector of RYMV in Uganda.

Samples of Cucurbita maxima plants with foliar yellowing and curling symptoms were collected in Komae City (Japan) in 2011 and shown by Southern blot hybridization to be associated with a begomovirus. Rolling circle amplification and PCR-mediated amplification with specific primers showed the presence of a begomovirus and an alphasatellite, but neither a DNA-B component or a betasatellite. Sequence analysis of full-length clones showed the virus to be an isolate of the Israel strain of Tomato yellow leaf curl virus and the alphasatellite Sida yellow vein China alphasatellite. This is the first identification of these components in a cucurbit in Japan.

Samples were collected in 2011 from tomato plants exhibiting typical tomato leaf curl disease symptoms in the vicinity of Komae, Japan. PCR mediated amplification, cloning and sequencing of all begomovirus components from two plants from different fields showed the plants to be infected by Tomato yellow leaf curl virus (TYLCV) and Ageratum yellow vein virus (AYVV). Both viruses have previously been shown to be present in Japan, although this is the first identification of AYVV on mainland Japan; the virus previously having been shown to be present on the Okinawa Islands. The plant harboring AYVV was also shown to contain the betasatellite Tomato leaf curl Java betasatellite (ToLCJaB), a satellite not previously shown to be present in Japan. No betasatellite was associated with the TYLCV infected tomato plants analyzed here, consistent with earlier findings for this virus in Japan. Surprisingly both plants were also found to harbor an alphasatellite; no alphasatellites having previously been reported from Japan. The alphasatellite associated with both viruses was shown to be Sida yellow vein China alphasatellite which has previously only been identified in the Yunnan Province of China and Nepal. The results suggest that further begomoviruses, and their associated satellites, are being introduced to Japan. The significance of these findings is discussed.

Pea (Pisum sativum) plants exhibiting leaf distortion, yellowing, stunted growth and reduction in leaf size from Rampur, Nepal were shown to be infected by a begomovirus in association with betasatellites and alphasatellites. The begomovirus associated with the disease showed only low levels of nucleotide sequence identity (91%) to previously characterized begomoviruses. This finding indicates that the pea samples were infected with an as yet undescribed begomovirus for which the name Pea leaf distortion virus (PLDV) is proposed. Two species of betasatellite were identified in association with PLDV. One group of sequences had high (78%) nucleotide sequence identity to isolates of Ludwigia leaf distortion betasatellite (LuLDB), and the second group had less than 78% to all other betasatellite sequences. This showed PLDV to be associated with either LuLDB or a previously undescribed betasatellite for which the name Pea leaf distortion betasatellite is proposed. Two types of alphasatellites were identified in the PLDV-infected pea plants. The first type showed high levels of sequence identity to Ageratum yellow vein alphasatellite, and the second type showed high levels of identity to isolates of Sida yellow vein China alphasatellite. These are the first begomovirus, betasatellites and alphasatellites isolated from pea.

Tobacco leaf curl Japan virus, Honeysuckle yellow vein mosaic virus and Tomato yellow leaf curl virus are three begomoviruses that infect tomato crops in Japan. Tomato infection by begomoviruses has increased in Japan after the development of a high level of resistance to certain insecticides in some populations of the vector B. tabaci biotypes ‘B and Q’. Ty-1 and Ty-2 homozygous tomato hybrids were evaluated for reaction to monopartite begomovirus species in Japan by Agrobacterium-mediated inoculation. Test plants were evaluated by a disease assessment scale (DAS), varying from 1 = no symptoms to 4 = severe symptoms, and systemic infection was evaluated by polymerase chain reaction (PCR), using specific begomovirus primers for each virus. Ty-1 hybrids showed tolerance to HYVMV and with a large number of plants being neither virus-free nor symptom-free. The response of Ty-1 hybrids was also resistant to moderately resistant against TbLCJV. The response of Ty-2 hybrids was resistant to highly resistant against the three monopartite begomoviruses, when compared with susceptible plants.

A begomovirus associated with yellow mosaic disease in lima bean (Phaseolus lunatus) was cloned, sequenced. The virus has a bipartite genome of which DNA-A is 2745 nucleotides length and DNA-B 2669 nucleotides, and has a typical bipartite begomovirus genomic organization from the Old World. The sequences showed the highest levels of nucleotide identity (99.2 % for DNA-A and 98.9 % for the DNA-B) to the ‘Indian’ strain of Mungbean yellow mosaic India virus (MYMIV).

A putative Potexvirus was detected from bottle gourd (Lagenaria siceraria) showing mosaic and mottle symptoms in Myanmar in 2007. The virus was designated Lagenaria mild mosaic virus (LaMMoV) and was further characterized. In artificial inoculation tests, infectivity of LaMMoV was limited to two families: Chenopodiaceae and Cucurbitaceae. The host range of LaMMoV differs from those of the two cucurbit-infecting potexviruses, Alternanthera mosaic virus (AltMV) and Papaya mosaic virus (PapMV). Sequence analyses of LaMMoV showed that the C-terminal 3,859 nucleotides, excluding the poly-A tail, includes the C-terminal region of an RNA-dependent RNA polymerase (RdRp), a triple gene block (TGB), a coat protein (CP), and a 3′ untranslated region (UTR), all of which are typical of potexviruses. Although LaMMoV is related closely to AltMV and PapMV, its nucleotide sequences differ from those of other previously reported potexviruses. Therefore, we report LaMMoV as a new species of the genus Potexvirus that occurs in the cucurbit bottle gourd.

New recombinant strain and genotype of PVY, designated as PVY(NTN-NW) and SYR-III, respectively, shared properties with PVY(NTN) and PVY(N)W has been reported recently. PVY(NTN-NW) predominated in potato fields in Syria and was able to induce potato tuber necrotic ringspot disease (PTNRD). Due to the rapid spread of the recombinant strains of PVY which might be the case of PVY(NTN-NW), a specific and reliable detection method is an essential step to control this strain and minimize its spread. The shared properties of PVY(NTN-NW) and SYR-III with PVY(NTN) and PVY(N)W, however, complicate their identification involving multiple detection methods. Therefore, a multiplex polymerase chain reaction (PCR), that relies on a combination of previously published and newly designed primers was developed for the detection and identification of PVY(NTN-NW) and SYR-III in single or mixed infections with the main PVY strains, PVY(O), PVY(N), PVY(NTN) and PVY(N)W. In addition, the present PCR assay was able to detect the recombination points in the P1 region enabling the differentiation of the variable genotypes of the recombinant strains PVY(NTN-NW), PVY(NTN) and PVY(N)W. The reliability of this PCR assay was confirmed using a significant number of well characterized PVY isolates collected from Syria and Japan including those of PVY(NTN-NW), SYR-III, PVY(O), NA-PVY(N), PVY(N)W and PVY(NTN).

Detailed characterization of a number of isolates of PVYSYR, a novel recombinant strain of Potato virus Y (PVY) from Syria, was conducted to elucidate their origin, assess their significance and achieve a final classification of PVYSYR. Recombination analysis grouped isolates of PVYSYR into three recombination patterns, SYR-I, SYR-II and SYR-III, which varied in the first 700 nucleotides of their genomes, with the second recombination pattern, SYR-II, the most frequent. PVYSYR isolates shared highest genomic identity and close phylogenetic relationships with PVYNTN and PVYNW isolates from Syria, suggesting a common origin and local emergence of these isolates in Syria. All PVYSYR isolates (total of 20) induced tobacco veinal necrosis, but reacted to a PVYO monoclonal antibody, typical characteristics of the previously reported PVYNW (or PVYN:O). In potato, however, four isolates tested (one of SYR-I and three of SYR-II) induced potato tuber necrotic ringspot disease (PTNRD), which is the characteristic phenotype of PVYNTN. Given the shared properties of SYR-I and SYR-II isolates with PVYNTN and PVYNW, it was decided that they represent a new recombinant strain of the PVYN strain group, with the proposed name PVYNTN-NW. The classification of SYR-III will be possible only after testing the phenotype in potato. The high prevalence of PVYNTN-NW in potatoes and weeds, as well as its ability to induce PTNRD, demonstrates its importance and the necessity for its control.

Bottle gourd [Lagenaria siceraria (Mol.) Standl.] plants showing leaf mosaic and mottle were observed in Myanmar in 2007 and shown by RT-PCR and ELISA to be infected with Cucumber green mottle mosaic virus (CGMMV). This is the first report of the virus occurring in Myanmar. Despite considerable differences in geographical origins, natural host species and year of sampling of 22 CGMMV isolates, we found low genetic variation of the CP gene except for isolates GR3 and GR5, which showed similarity higher than 97%; based on the MP gene, and 16 CGMMV isolates showed similarity higher than 94% in nucleotide identities by pairwise comparison. Using MluI restriction endonuclease for CP genes, the CGMMV isolates fell into three types: Type I and Type II were included in the SH group and Type III in the W group. The two CGMMV isolates from Myanmar were found to belong to Type I and Type III, respectively.

Le Zucchini yellow mosaic virus (ZYMV) est le virus le plus prevalent sur cucurbitacees en Syrie. Deux isolats syriens du ZYMV, SYZY-1 et SYZY-3, collectes dans un champ de courgette en 2006 ont ete caracterises pour la premiere fois en utilisant des moyens moleculaires et biologiques. Ces isolats presentaient une diversite biologique en ce qui concerne leur pouvoir pathogene et les symptomes. SYZY-1 est plus agressif sur cucurbitacees et Chenopodium amaranticolor, mais ne peut pas induire d'infection sur Fabaceae. En revanche, SYZY-3 ne peut pas infecter les concombres et les melons, induit des symptomes legers sur courgette et pasteque mais induit des infections systemiques locales et occasionnelles sur les Fabaceae testees. Neanmoins, selon leurs caracteristiques moleculaires, SYZY-1 et SYZY-3 sont tres proches. Les sequences des nucleotides et des acides amines de la capsule proteique de SYZY-1 avaient 99.5% et 100% de similarite avec celles de SYZY-3, respectivement. La forte similarite des sequences des nucleotides de la capsule proteique de SYZY-1 et SYZY-3 avec celles d'un isolat allemand du ZYMV suggere une origine commune. L'adaptation des differents hotes pourrait avoir cause les variations de proprietes biologiques de ces isolats syriens du ZYMV.

Two bacteria, isolated from the surface of banana fruits, one forming a creamy white colony and the other, dry yeast like colony were screened for in vitro antagonism toward Lasiodiplodia theobromae . Both isolates, identified as Bacillus amyloliquefaciens , were further tested for antibiosis against other crown rot-causing pathogens ( Thielaviopsis paradoxa , Colletotrichum musae , and Fusarium verticillioides ). The creamy white colony strain, coded as B. amyloliquefaciens DGA14, was subjected to laboratory and field studies. B. amyloliquefaciens DGA14 produced a diffusible metabolite that inhibited all test pathogens in culture. In addition, bacteria moved and attached to pathogens significantly affecting mycelial growth and conidial germination in liquid medium. Following inoculation, B. amyloliquefaciens DGA14 survived and colonized banana fruits after 2 d. Interparasitic relationships were observed between the antagonist and pathogens on artificial media and the natural substrate. Postharvest application of B. amyloliquefaciens DGA14 in the packing house reduced the incidence of crown rot to a level significantly lower than in fungicide treated or control fruits.

Based on inoculation experiments and morphological and molecular phylogenetic studies, Cylindrocladium damping-off of strawberry and Cylindrocladium blight of coral bells in Japan were demonstrated to be caused by Cylindrocladium canadense. This is the first report of a disease on strawberry and coral bells caused by this fungus.

In a previous study on a Syrian isolate of Potato virus Y (PVY), namely PVY-12, a point mutation in the coat protein (CP) was detected. This mutation caused the double reactivity of this isolate to monoclonal antibodies specific to O and N serotypes. We report here the biological and molecular characteristics of PVY-12. In potato, PVY-12 behaved like a PVY NTN isolate inducing potato tuber necrotic ringspot disease although it induced mosaic in tobacco like PVY°. The genomic analysis grouped PVY-12 with the recombinant PVY NTN isolates, which is consistent with the phenotype in potato. PVY-12 HC-Pro had the two amino acids K400 and E419 that were previously reported as determinant keys of the tobacco necrotic response. This indicates the involvement of other determinants in this phenotype yet to be determined. This is the first report on a PVY NTN isolate that induces mosaic in tobacco, implying that the induction of potato tuber necrosis does not require the ability to induce the tobacco necrosis. PVY-12 genome had four recombinant points in the PI, HC-Pro/P3, 6K2/NIa and C terminal region of the CP gene identical to those of PVY NTN isolates 12-94 and 34/01. The PVY-12 central genomic part flanked by nucleotide positions 2414 and 8604 had highest similarity with that of the Syrian isolate SYR-NB-16 suggesting a common origin of these isolates. This common origin was supported using the phylogenetic analysis of this region. In addition, the phylogenetic analysis of the whole genome of the reported North American PVY N:O and the European PVY N W along with other PVY isolates suggests that PVY N:O might have descended from PVY N W with the isolate SASA-207 as a nearest-known relative.

A survey of Potato virus Y (PVY) was carried out on weeds growing in and around potato fields in Syria during the autumn growing seasons of 2002,2004 and 2006. A total of 59 samples of eight weed species and three tobacco (Nicotiana tabacum) samples were tested by ELISA using PVY antisera. Among them 15 samples belonged to Solanum nigrum (7 samples), Physalis sp. (6 samples) and tobacco (2 samples) were PVY infected. This suggests that weed hosts and neighbouring tobacco fields are natural reservoirs of PVY in Syria. According to their biological, serological and molecular characteristics, the majority of weed PVY isolates belonged to the PVY SYR variant indicating a possible correlation between the high incidence of PVY SYR in potato and weed hosts. This is the first report on the occurrence and characterization of weed PVY isolates from Syria.

Fungi isolated from the surface of banana fruits were evaluated for in vitro antagonism towards Lasiodiplodia theobromae. Thirteen fungi exhibiting pronounced growth inhibition of test pathogens were further tested for antibiosis against Thielaviopsis paradoxa, Colletotrichum musae, and Fusarium verticillioides. Clonostachys byssicola, Curvularia pallescens, Penicillium oxalicum, and Trichoderma harzianum were antagonistic to all test pathogens. Inhibition by C. pallescens and P. oxalicum to pathogens was at a distance, while C. byssicola and T. harzianum directly parasitized and killed the pathogens. The metabolites of C. byssicola, C. pallescens, and T. harzianum significantly affected the mycelial growth and conidial germination of the pathogens. In the artificial inoculation study, the antagonists survived and colonized banana fruits after 3 d. Interfungal parasitic relationship was observed between the antagonist and pathogen on artificial media and natural substrate. Postharvest application in the packing house showed that the incidence of crown rot in antagonist-treated banana was significantly lower when compared to fungicide and untreated control fruits.

Potato virus Y (PVY) is the main potato virus in Syria but no information is available on the prevalence of other potato viruses. A survey was conducted by ELISA using specific antibodies to nine potato viruses. PVY, Potato virus S (PVS), Cucumber mosaic virus and Potato leafroll virus were detected with infection rates of 54.2, 8.4, 3.7 and 0.9%, respectively. The overall virus infection rate was as high as 72.9% in ware potato fields. A preliminary characterization was carried out on PVS isolates. Syrian PVS isolates infected Chenopodium amaranticolor only locally and therefore were classified as PVSO. Phylogenetic analysis of the coat protein gene showed that PVS comprised two main clusters, cluster-O and cluster-A, which contained the ordinary and Andean strains respectively. Cluster-O was separated into two subclusters, O1 and O2. Two Syrian PVS isolates, PVS3-5 and PVS6-2, fell into the O1 subcluster. PVS3-5 coat protein, however, shared the highest nucleotide identity with European isolates of the O1 subcluster, whereas PVS6-2 was closely related to Asian isolates of the same subcluster. Owing to the high incidence of PVY and PVS in Syria, a duplex reverse-transcription PCR was developed to detect these two viruses in a single PCR.

In the plant virus world, there are six genera of plant viruses with dsDNA genomes and six genera with ssDNA (Fauquet et al., 2005). The dsDNA viruses are comprised of 4 genera in the Caulimoviridae, the genus Badnavirus and the genus Tungrovirus. The ssDNA viruses are comprised of four genera in Geminiviridae, and the two genera Nanovirus and Babuvirus in the Nanoviridae. The genera Babuvirus and Badnavirus are not well studied in Asia. However, we recognized the significance of two species, Banana bunchy top virus (BBTV) in the genus Babuvirus and Banana streak virus (BSV) in the genus Badnavirus, during the survey of banana viruses in Asia. Their main characters will be introduced in this mini-review.

Brown leaf spot disease caused by Cylindrocladium was found on Howea belmoreana on Hachijojima Island, Tokyo, Japan, in December 2001. Typical symptoms were incited after artificial inoculation. A culture of white mycelia, isolated from leaf spot symptoms, produced reddish perithecia of a nectriaceous fungus. Based on morphological and molecular analyses, this fungus was identified as Calonectria ilicicola (anamorph: Cylindrocladium parasiticum). Pathogenicity of this fungus on five plants cultivated on Hachijojima Island was confirmed by artificial inoculation. This report is the first on Cylindrocladium brown leaf spot of H. belmoreana caused by C. ilicicola (anamorph: Cy. parasiticum).

Crown rot, a disease complex caused by various fungi, is an economically significant postharvest disease in bananas. Control of banana crown rot-causing fungal pathogens, such as Lasiodiplodia theobromae, Colletotrichum musae, Thielaviopsis paradoxa, and Fusarium verticillioides by inorganic salts, as well as a surfactant, was evaluated. The conidial germination of pathogens was totally inhibited for 2 d at 4 g l−1 of Na2CO3, 5 g l−1 of NaClO, NaHCO3, CaCl2, and 6 g l−1 of NaCl. The same concentrations of salts completely controlled the conidial germination of all pathogens for 7 d with the amelioration of surfactant. This study elucidated how the surfactant enhanced the protective value of the salt to suppress the conidial germination of the pathogens. However, control of the mycelial growth of the pathogens required a higher dosage of salt. Some inorganic salts were not effective in controlling the mycelial growth of the pathogens, although they were ameliorated by the surfactant. The effective treatments to control crown rot of bananas were 5 g l−1 of NaClO, NaHCO3, and 5 g l−1 CaCl2+surfactant. Some salts, when ameliorated with surfactant, had a phytotoxic effect on banana fruits.

A Syrian isolate of Potato virus Y (PVY), named PVY-12, reacted to two monoclonal antibodies that are specific to PVY(O,C) and PVY(N) strains, although its coat protein (CP) belongs to the PVY(N) strain. Analysis of the CP of PVY-12 revealed that a point mutation in its N terminus switched it from PVY(N)-like to PVY(O)-like at this position. This mutation changed the second nucleotide of the codon that encodes the 29th amino acid of the CP of PVY-12 from A to G, which resulted in one amino acid substitution from Glu(29 )to Gly(29). The role of Gly(29) in the binding of PVY-12 to PVY(O,C)-specific monoclonal antibody was confirmed by gene expression in Escherichia coli. The N terminus of the CP gene of PVY-12 and another PVY isolate of the N serotype with identical CP to PVY-12 except for one amino acid substitution from Gly(29 )to Glu(29) was cloned and expressed in E. coli using a pUC18 vector. Resulting antigens showed similar reactivity to the relevant antibodies as same as the native CPs of these two isolates. Further analysis of the CP of PVY isolates showed that Gly(29) was conserved in the CP of PVY(O), PVY(C), PVY(N)W, and non-potato isolates of PVY while Gln(17) and Glu(31 )were conserved in the CP of PVY(N/NTN). Therefore, these amino acids are characteristic of the CP for these strain groups and subgroups in agreement with the serotype and phylogenetic relationships previously determined.