New mite-borne virus isolates from rakkyo,shallot and wild leek species

Flexuous viruses were transmitted from rakkyo (Allium chinense) and wild leek species (especiallyA. commutatum) to plants of crow garlic (A. vineale), by transfer of dry bulb mites. By electron microscope decoration tests using three antisera and by inoculations onto test plants, it was concluded that from each of the two natural host species at least two viruses were isolated. The viruses from wild leeks are both pathogenic onAllium spp. and may be of economic importance. Decoration tests on a virus mixture from shallot obtained earlier, revealed another new mite-borne virus in this species. The mite-borne viruses ofAllium spp. appear to be very common; they are largely diverse and their identification remains difficult.     

Efficiency of eradication of four viruses from garlic (Allium sativum) by meristem-tip culture

Mechanical inoculation tests and ELISA with sap from garlic plants used for sanitation by meristem-tip culture revealed four viruses, viz. garlic common latent virus (GCLV) (carlavirus), the garlic strains of leek yellow stripe virus (LYSV-G), onion yellow dwarf virus (OYDV-G) (aphid-borne potyviruses), and onion mite-borne latent virus (OMbLV-G) (taxonomically unassigned virus). The same tests performed on explants grownin vitro showed elimination efficiencies of 100% for LYSV-G, 92% for OYDV-G, 62% for GCLV, and less then 54% for OMbLV-G.Meristem tips excised from garlic cloves and bulbils, 0.15–1.0 mm in size, were tested for regeneration and efficiency of virus elimination after transfer to Murashige and Skoog medium. Successful regeneration into plantlets was obtained with 71% of the meristems from cloves and 72% of those from bulbils, but virus elimination was easiest from cloves: 38% of all explants from cloves and 25% of those from bulbils were virus-free. The efficiency of elimination increased with increasing weight of the cloves, irrespective of the virus. Small tip size seemed to favour virus elimination, but sizes smaller than 0.4 mm led to increasing failure of regeneration.Micropropagation was most successful when cytokinins were omitted from the medium and the garlic shoot was split. Multiplication factors of 3–6 were obtained.     

Carlavirus isolates from cultivated Allium species represent three viruses

From 12 cultivated and mostly vegetatively propagatedAllium species and varieties tested for carlavirus infections, 94 virus isolates were obtained which varied greatly on indicator hosts.Chenopodium amaranticolor, C. quinoa, Celosia argentea var.plumosa Geisha,Nicotiana hesperis accession 67A andN. occidentalis accession P1 proved valuable for detection, isolation and propagation of part of the isolates. The latter three species are new experimental hosts for carlaviruses ofAllium species. Other isolates could only be transmitted toAllium species such as crow garlic (A. vineale) leek (A. ampeloprasum var.porrum) and onion (A. cepa var.cepa). The isolates were grouped into three viruses by differential hosts and host reactions and their reaction with four antisera.Shallot latent virus (SLV) was found in ever-ready onion (A. cepa var.perutile), grey shallot (unidentifiedAllium species), multiplier onion (A. cepa var.aggregatum), pearl onion (A. ampeloprasum var.sectivum), rakkyo (A. chinense), shallot (A. cepa var.ascalonicum), and Welsh onion (A. fistulosum). Virus isolates from garlic and Asian shallot, fully reacting with antiserum to SLV but differing in host reactions from the SLV type-isolate, are now described as garlic strain (SLV-G) and Asian shallot strain of the virus, respectively. The garlic latent virus from garlic described in Japan is now considered identical with SLV-G.A carlavirus almost universal in garlic, and also found in great-headed garlic (A. ampeloprasum var.holmense), in an unidentifiedAllium species, and occasionally in leek, did not react with the antisera to SLV and the Japanese garlic latent virus, and is now described as the new garlic common latent virus (GCLV). It appeared identical to a virus erroneously identified in Germany as garlic latent virus.The new Sint-Jan's-onion latent virus (SjoLV) from Utrechtse Sint-Jan's onion (unidentifiedAllium species) from the Netherlands and similar crops originating from other countries, did not induce reactions in test plants and could only be detected by electron microscope decoration tests. It reacted equally wellwith the antisera to SLV and GCLV. It was also present together with SLV in ever-ready onion, pearl onion, rakkyo, shallot, and Welsh onion. Garlic latent virus reported in Japan from hosts other than garlic should be regarded as SLV, SjoLV, or a mixture of these viruses.The carlaviruses were not detected in wild plants of ramsons (A. ursinum), and of the predominantly vegetatively propagated crow garlic (A. vineale), field garlic (A. oleraceum), and sand leek (A. scorodoprasum), collected in the Netherlands.Severe reactions in the indicator hosts incidentally revealed soil-borne viruses in shallot (the nepovirusesArabis mosaic virus (ArMV) and tomato black ring virus) and crow garlic (ArMV and the tobravirus tobacco rattle virus). Tobacco necrosis virus (necrovirus) was detected in roots of shallot.     

Incidence of Viruses Infecting Allium Spp. in Greece

A survey identified viruses infecting garlic, leek and onion crops and wild Allium species in Greece. Virus identification was based on ELISA, immunoelectron microscopy, and occasionally on RT-PCR. Samples of cultivated Allium species were collected from five districts, whereas samples of twenty-seven wild Allium species were also collected from all over Greece. Onion yellow dwarf virus (OYDV) and Leek yellow stripe virus (LYSV) were identified in 98.5% and 83.7% of all samples, respectively, and were found in all regions. Allexiviruses were also detected in all regions and their incidence ranged from 62.5% to 70.5% (depending on region and type of allexivirus). Garlic common latent virus (GCLV) was detected in samples from Arcadia (97.6%) and Evia (18.0%) and in one field in Larissa (23.0%). Shallot latent virus (SLV) was found only in two areas (Evros and Theva) and in fields planted with imported propagative material, from Iran and China. The incidence of virus-like symptoms in leek crops ranged from 10.0% to 90.0% in different regions and fields and all symptomatic plants were found to be infected by LYSV. Onion yellow dwarf virus was only found in seven symptomatic onion samples from southern Greece. Allium ampeloprasum spp. ampeloprasum and Allium flavum, were the only wild Allium species found to be infected with LYSV. Finally Turnip mosaic virus (TuMV) was found in A. sphaerocephalon, A. guttatum, A. subhirsutum, and A. neapolitanum.     

Survey and characterization of potyviruses and their strains of Allium species

Nearly 5700 plants of 14 cultivated and 8 wildAllium species and varieties from the Netherlands and other parts of the world, were tested for infection with aphid-borne potyviruses by ELISA, electron microscope decoration tests and/or inoculation onto test plants. This resulted in the detection of two known viruses, viz. leek yellow stripe virus (LYSV) and onion yellow dwarf virus (OYDV), and the discovery and characterization of two new viruses, viz. shallot yellow stripe virus (SYSV) and Welsh onion yellow stripe virus (WoYSV), and of six strains of these viruses. ‘Garlic mosaic’, ‘barlic yellow streak’, ‘onion mosaic’, ‘shallot mosaic’, ‘shallot X’, and ‘shallot yellows’ viruses, incompletely described in the literature, are now reidentified as well-known viruses or as strains or mixtures of such viruses. ‘Garlic yellow stripe virus’ is also a complex containing a potyvirus possibly differing from the viruses found in this survey. The symptoms of the potyviruses studied varied widely and ranged from mild to severe chlorotic to yellow striping of leaves, and they are of little diagnostic importance.LYSV was found in vegetatively propagated pearl onion (A. ampeloprasum var.sectivum) from Europe and Asia. It has decreased in leek crops (A. ampeloprasum var.porrum) in the Netherlands since the 1970, apparently due to resistance in new cultivars. OYDV was common in onion (A. cepa var.cepa) from the former USSR and North Africa, and in European cultivars of shallot (A. cepa var.ascalonicum), with the exception of the highly resistant ‘Santé’, but was not detected during this survey in Asian shallot. European samples of ever-ready onion (A. cepa var.perutile), multiplier onion (A. cepa var.aggregatum) and tree onion (A. cepa var.viviparum) contained OYDV. It was also found in sand leek (A. scorodoprasum) from european gene collections. A strain of OYDV from onion and shallot in Morocco and Spain was virulent on onion and shallot cultivars resistant to common OYDV, as reported early for a similar isolate in the USA.Asian shallot appeared generally infected with the new SYSV, similar to OYDV in host range and symptoms but serologically distinct. It was not detected in onion and shallot from Europe or North Africa. A virulent strain of this virus caused striping in sap-inoculated garlic (A. sativum) and Formosan lily (Lilium formosanum). The new WoYSV, infecting Welsh onion in Indonesia and Japan, was earlier described in Japan as OYDV from rakkyo and Welsh onion. It appeared serologically closely related to SYSV and distantly to OYDV, but differed in its host range.Host-specific strains of LYSV and OYDV were detected in garlic, wild garlic (A. longicuspis), an unidentifiedAllium species (suffix-G), and great-headed garlic (A. ampeloprasum var.holmense) (suffix-GhG)., LYSV-G and OYDV-G infected on average 45% and 73%, respectively, of the garlic samples of worldwide origin. Symptoms of isolates of both strains varied in severity, implying the necessity of serological tests for disease diagnosis and health certification. LYSV-GhG was the cause of yellow striping in 93% of the great-headed garlic plants tested, mainly from the Mediterranean area. One sample was also infected with OYDV-GhG.Many samples from vegetatively propagated crops grown from non-certified planting stock contained a few plants free of potyviruses, implying the possibility to obtain healthy (and possibly resistant) selections of such cultivars avoiding meristem-tip culture. Cross-protection of garlic sets by a mild potyvirus isolate seems to be an alternative to the use of vulnerable virus-free sets.Generally, viruses and virus strains could not be transmitted to anyAllium species other than their natural host, except to the highly susceptible crow garlic (A. vineale). This species, and other predominantly vegetatively propagating wildAllium spp. (field garlic,A. oleraceum; ramsons,A. ursinum; sand leek), were found not to be reservoirs of viruses that might infectAllium crops in the netherlands. Streaking in vegetatively propagated wild leeks (A. ampeloprasum and closely related species) originating from the Mediterranean area and Asia was due to an undescribed miteborne virus. The survey confirmed that spread of potyviruses inAllium crops in the Netherlands is from planting sets, and from a neighbouring crop only if of the same species.     

Double-edged effects of the cryogenic technique for virus eradication and preservation in shallot shoot tips

Plant virus eradication is a prerequisite for the use of virus-free propagules for sustainable crop production. In contrast, virus preservation is required for all types of applied and basic research of viruses. Shoot tip cryopreservation can act as a double-edged strategy, facilitating either virus eradication or virus preservation in cryoderived plants. Here, we tested the efficacies of shoot tip cryopreservation for virus eradication and preservation in shallot (Allium cepa var. aggregatum). In vitro stock shallot shoots infected with onion yellow dwarf virus (OYDV) and shallot latent virus were thermotreated for 0, 2, and 4 weeks at a constant temperature of 36℃ before shoot tip cryopreservation. Results showed that viruses were preserved in recovered shoots when thermotherapy was not applied. Although thermotherapy lowered the regrowth levels of cryotreated shoot tips, the efficiency of virus eradication increased from 5% to 54%. Immunolocalization of OYDV and histological observation of cryotreated shoot tips showed the high frequency of virus preservation was due to the viral invasion of cells close to the apical meristem and the high proportion of cells surviving. Four weeks of thermotherapy drastically decreased the distribution of OYDV, as well as the percentage of surviving cells within the shoot tips, thereby promoting virus eradication. Virus-free plants obtained from combining thermotherapy with cryotherapy showed significantly improved vegetative growth and bulb production. The present study reports how thermotherapy can act as a trigger to facilitate either the safe preservation of Allium viruses or the production of virus-free shallot plants.     

Further Evidence that Shallot Yellow Stripe Virus (SYSV) Is a Distinct Potyvirus and Reidentification of Welsh Onion Yellow Stripe Virus as a SYSV Strain

ABSTRACT An antiserum to shallot yellow stripe virus (SYSV) was raised and used in combination with a range of other antisera to potyviruses of Allium spp. in electron microscopic decoration experiments. The serological results corroborated an earlier finding that the type isolates of SYSV and Welsh onion yellow stripe virus (WoYSV) are closely related to each other and only distantly related to onion yellow dwarf (OYDV) and leek yellow stripe (LYSV) viruses, the two other major potyviruses infecting Allium spp. Moreover, the decoration results indicated that Japanese potyviruses named OYDV and Wakegi yellow dwarf virus are isolates of SYSV. Sequence analysis of the 3'-terminal regions of the SYSV and WoYSV ge-nomes revealed coat protein (CP) amino acid and 3'-nontranslated region (3'-NTR) nucleotide sequence identities of 95 and 89%, respectively. The CP amino acid and 3'-NTR nucleotide sequences of these viruses differed from those of OYDV and LYSV by >25 and >67%, respectively. The serological and molecular studies showed that SYSV and WoYSV are different strains of a potyvirus distinct from OYDV and LYSV. For priority reasons, we propose that these strains together with the Wakegi-type isolates of OYDV described in Japan be referred to as SYSV and that SYSV isolates from Allium spp. other than shallot be designated as the Welsh onion strain of SYSV (SYSV-Wo).     

Lonicera latent virus,a new carlavirus serologically related to poplar mosaic virus: some properties and inactivation in vivo by heat treatment

A virus with elongate particles (656 nm) was isolated from severalLonicera species. This virus, apparently belonging to the carlavirus group, is serologically distantly related to shallot latent virus and closely related to poplar mosaic virus. The inability to infect poplar and two other hosts of poplar mosaic virus characterizes the virus fromLonicera as a new virus which was namedLonicera latent virus.The virus was easily sap-transmissible but was not transmitted byMyzus persicae.Dilution end-point was about 10^–3, thermal inactivation between 65°C and 80°C and ageing in vitro 1–6 days.Heat treatment, combined with tip-rooting appeared to be a good method to eliminate the virus from severalLonicera species and cultivars.Samenvatting In verschillende soorten en cultivars van het geslachtLonicera (kamperfoelie) blijkt een virus voor te komen dat gemakkelijk door sapinoculatie kan worden overgebracht op kruidachtige planten.Een tegen gezuiverd virus bereid antiserum had een titer van ca. 4096. Er kon mee worden aangetoond dat het virus van kamperfoelie serologisch nauw verwant is met populieremozaïekvirus (Tabel 1). Het virus van kamperfoelie is echter niet in staat om populier,Phaseolus vulgaris Bataaf enVigna sinensis te infecteren en wordt mede daarom als een afzonderlijk virus beschouwd. Het wordt aangeduid als latent kamperfoelievirus (Lonicera latent virus) en behoort evenals populieremozaïekvirus tot de carlavirusgroep (aardappelvirus-S-groep).Het virus blijkt vrij gemakkelijk te kunnen worden geëlimineerd door besmette kamperfoelieplanten gedurende ongeveer zes weken een warmtebehandeling (37°C) te geven en daarna de uiterste toppen (1 cm) te stekken. Van verschillende cultivars werd op deze wijze virusvrij uitgangsmateriaal verkregen.     

Characterization of two races of the stem and bulb nematode (Ditylenchus dipsaci) in Israel

Two distinct races ofDitylenchus dipsaci in Israel were identified: one, which infects and damages onion and garlic, reproduces on pea, but does not infect phalaris grass; and a second, which infects and damages phalaris—and, probably, also ‘Saia’ oats—but fails to infect onion and garlic. A new ‘garlic’ race of the nematode does not appear to have been introduced into Israel together with the ‘Lavinia’ garlic cultivar, as previously speculated, but rather the introduced Lavinia clone is highly susceptible to the existing ‘onion and garlic’ race ofD. dipsaci.     

Evaluation of morphology of infection structures in distinguishing between different Allium rust fungi

Fifteen isolates of rust fungi were collected in the United Kingdom and in the Netherlands from severalAllium species. The samples represented three putative rust species. The morphology of the telia, teliospores and urediniospores was investigated. From urediniospores infection structures were induced on leek, and their morphology was described. Telia and teliospores were not available on every sample. Morphology of the infection structures clearly differentiated between ‘leek’ type and ‘chive’ type isolates. The morphology of infection structures ofPuccinia mixta is very similar to that ofUromyces ambiguus, but clearly distinct fromPuccinia allii sensu Jennings from leek. Quantitative differences in urediniospore characters differentiated between the putative species, but there was overlap between the taxa. We conclude that morphology of infection structures of urediniosporelings is a useful trait for identification of rust isolates fromAllium. This is especially true where more than one rust species may occur on the same host species, as withAllium fistulosum.     

Survey for viruses infecting onion, garlic and leek crops in Iran

Surveys to identify virus diseases affecting garlic ( Allium sativum ), onion ( Allium cepa ) and Persian leek ( Allium ampeloprasum var. persicum ) were conducted from 1999 to 2002. Surveys covered different regions of Iran (Tehran [different vegetable markets, farmer fields and cultivation areas], Noushahr, Chalous, Roudbar, Sari, Hamadan, Touyserkan, Ghazvin and Jiroft). A total of 2045 (1285 garlic, 525 onion and 230 leek) samples showing symptoms of virus infection were collected and tested by ELISA; and in some cases tests were also confirmed by immunoelectron microscopy (IEM) for the presence of Allium viruses. ELISA results showed that the following viruses were detected: Onion yellow dwarf virus (OYDV), Leek yellow stripe virus (LYSV) (genus Potyvirus , family Potyviridae ), Garlic common latent virus (GarCLV), Shallot latent virus (SLV) (genus Carlavirus ), Garlic virus D (GarV-D), Garlic virus B (GarV-B) and Garlic virus C type (GarV-C) (genus Allexivirus ). None of the samples reacted with antibodies to Shallot yellow stripe virus (SYSV) genus Potyvirus , family Potyviridae ), Shallot virus X (ShVX) and Garlic virus A (GarV-A, genus Allexivirus ). GarCLV, SLV, GarV-D, GarV-B and GarV-C are reported for the first time from Allium crops in Iran.     

Pathogenicity and mycotoxin production by <Emphasis Type="Italic">Fusarium proliferatum</Emphasis> isolated from onion and garlic in Serbia

Fusarium proliferatum can occur on a wide range of economically important vegetable plants but its role in disease is not always well established. In 2000 and 2001, from forty-one field samples of wilting onion and garlic plants in Serbia, F. proliferatum as the predominant fungal species was isolated from root and bulbs. Seventy isolates were firstly characterized for their sexual fertility and were shown to be mostly members of Gibberella intermedia (sixty-seven of seventy isolates, the remaining three isolates were unfertile), the sexual stage of F. proliferatum (syn. mating population D of G. fujikuroi complex). A selected set of eleven F. proliferatum isolates from both hosts were also tested for their pathogenicity and toxigenicity. Although onion and garlic plants were susceptible to all isolates, onion plants showed a significantly higher disease severity index. Six of the eleven isolates of F. proliferatum produced fumonisin B₁ from 25 to 3000 μg g⁻¹, and beauvericin from 400 to 550 μg g⁻¹; ten isolates produced fusaric acid from 80 to 950 μg g⁻¹ and moniliformin from 50 to 520 μg g⁻¹. Finally, all isolates produced fusaproliferin up to 400 μg g⁻¹. These results confirm F. proliferatum as an important pathogen of garlic and onion in Europe and that there is a potential mycotoxin accumulation risk in contaminated plants of both garlic and onion.     

Investigation of the host ranges of the leaf blotch pathogens of onion (Cladosporium allii-cepae) and leek (C. allii)

Inoculation of a range of Allium species and two non-alliaceous species with isolates of Cladosporiumallii-cepae and C. allii , obtained from onion and leek, respectively, demonstrated that the two pathogens had distinct host ranges. Conidia of C. allii-cepae, applied either dry or in aqueous suspension, infected A. altaicum, A. fistulosum (Japanese bunching onion), A. cepa (bulb onion), A. cepa var. ascalonicum (shallot), A. galanthum, A. pskemense and A. vavilovii . Dry conidia of C. allii applied at a high concentration caused atypical necrosis on A. altaicum, A. fistulosum, A. cepa var. ascalonicum, A. galanthum, A. pskemense, A. vavilovii, A. sativum (garlic), A. ampeloprasum and A. porrum (leek). Only A. ampeloprasum and A. porrum became typically infected following inoculation with conidia applied dry at low concentration or in aqueous suspension. Isolates of C. allii from leek failed to infect A. vineale, the type host. The length of conidia of a single isolate of C. allii-cepae varied significantly on different Allium spp.     

Improved PCR detection of potyviruses in <Emphasis Type="Italic">Allium</Emphasis> species

Protocols for producing virus-free Allium plants require an indexing system that is more sensitive than DAS-ELISA and can detect low virus concentrations in infected plants. In the present work, degenerate primers were designed and a one-step IC-RT-PCR protocol was developed to differentiate between Leek yellow stripe virus (LYSV) and Onion yellow dwarf virus (OYDV) in single and mixed infections in several Allium spp. A 566-bp band was observed for LYSV, a 489-bp band for OYDV in single infections, and two bands of the same sizes in mixed infections in different species of Alliaceae. A 508-bp band of Shallot yellow stripe virus and a 594-bp band of Turnip mosaic virus were also amplified with the same primers. RT-nested-PCR was also conducted directly in microtitre plate wells after negative or questionable reactions were produced in an ELISA experiment. The detection limit of the DAS-ELISA for LYSV was 16.5–27.3 ng ml⁻¹. The RT-nested-PCR done after DAS-ELISA was 10² times more sensitive than the DAS-ELISA alone. In parallel, an IC-RT-nested-PCR in microcentrifuge tubes was 10⁴ times more sensitive than the DAS-ELISA. The DAS-ELISA-RT-nested-PCR enables the initial screening of samples by DAS-ELISA to eliminate a high percentage of virus-positive plants, considerably reducing the number of plants to analyze further by RT-PCR.     

Incidence of viruses in <Emphasis Type="Italic">Alstroemeria</Emphasis> plants cultivated in Japan and characterization of <Emphasis Type="Italic">Broad bean wilt virus-2, Cucumber mosaic virus</Emphasis> and <Emphasis Type="Italic">Youcai mosaic virus</Emphasis>

Alstroemeria plants were surveyed for viruses in Japan from 2002 to 2004. Seventy-two Alstroemeria plants were collected from Aichi, Nagano, and Hokkaido prefectures and 54.2% were infected with some species of virus. The predominant virus was Alstroemeria mosaic virus, followed by Tomato spotted wilt virus, Youcai mosaic virus (YoMV), Cucumber mosaic virus (CMV), Alstroemeria virus X and Broad bean wilt virus-2 (BBWV-2). On the basis of nucleotide sequence of the coat protein genes, all four CMV isolates belong to subgroup IA. CMV isolates induced mosaic and/or necrosis on Alstroemeria. YoMV and BBWV-2 were newly identified by traits such as host range, particle morphology, and nucleotide sequence as viruses infecting Alstroemeria. A BBWV-2 isolate also induced mosaic symptoms on Alstroemeria seedlings.     

A novel approach to spider mite control based on expression of sarcotoxin IA peptidevia a virus-vector system in plants

Control of the spider miteTetranychus cinnabarinus Boisduval is problematic, and there is a pressing need for efficient, non-hazardous and inexpensive strategies for limiting the damage it causes. The gene for the anti-bacterial peptide sarcotoxin IA of the flesh flySarcophaga peregrina was cloned into the nonpathogenic potyvirus-based vector system ZYMV-AGII (Zucchini yellow mosaic virus-AGII). Expression of this peptidevia the AGII vector was detected in infected squash leaves and was not deleterious to the host plant. Leaf discs of squash infected with the recombinant virus AGII-sarcotoxin IA were tested for spider mite control under laboratory conditions. Spider mite egg production on plants expressing the sarcotoxin IA gene was decreased by a factor of two or three compared with that on AGII-infected plants or healthy leaf discs, respectively. In contrast to its effect on oviposition, sarcotoxin IA expressing squash did not significantly affect the mortality and the ability to repel spider mites. Crude extract from squash leaves infected with AGII-sarcotoxin IA was also found to cause a significant decrease of mite fecundity compared with extracts from AGII-treated or healthy plants and also caused a rise in mite mortality. Our results demonstrate that sarcotoxin IA affects mite fecundity and, to a lesser degree, mortality, and shows potential for controlling spider mites in the field.     

Genetic variation among <Emphasis Type="Italic">Fusarium</Emphasis> isolates from onion,and resistance to <Emphasis Type="Italic">Fusarium</Emphasis> basal rot in related <Emphasis Type="Italic">Allium</Emphasis> species

The aim of this research was to study levels of resistance to Fusarium basal rot in onion cultivars and related Allium species, by using genetically different Fusarium isolates. In order to select genetically different isolates for disease testing, a collection of 61 Fusarium isolates, 43 of them from onion (Allium cepa), was analysed using amplified fragment length polymorphism (AFLP) markers. Onion isolates were collected in The Netherlands (15 isolates) and Uruguay (9 isolates), and received from other countries and fungal collections (19 isolates). From these isolates, 29 were identified as F. oxysporum, 10 as F. proliferatum, whereas the remaining four isolates belonged to F. avenaceum and F. culmorum. The taxonomic status of the species was confirmed by morphological examination, by DNA sequencing of the elongation factor 1-α gene, and by the use of species-specific primers for Fusarium oxysporum, F. proliferatum, and F. culmorum. Within F. oxysporum, isolates clustered in two clades suggesting different origins of F. oxysporum forms pathogenic to onion. These clades were present in each sampled region. Onion and six related Allium species were screened for resistance to Fusarium basal rot using one F. oxysporum isolate from each clade, and one F. proliferatum isolate. High levels of resistance to each isolate were found in Allium fistulosum and A. schoenoprasum accessions, whereas A. pskemense, A. roylei and A. galanthum showed intermediate levels of resistance. Among five A. cepa cultivars, ‘Rossa Savonese’ was also intermediately resistant. Regarding the current feasibility for introgression, A. fistulosum, A. roylei and A. galanthum were identified as potential sources for the transfer of resistance to Fusarium into onion.     

Differentiation between two potyviruses inAlstroemeria

Alstroemeria mosaic virus (AlMV) is one of the viruses known to occur inAlstroemeria spp. Its detection in DAS-ELISA needed improvement. The often simultaneous presence of a second potyvirus has been mentioned by various authors. The recently detected virus inAlstroemeria, tentatively namedAlstroemeria streak virus [AlSV; Wong, 1992] was multiplied in indicator plants and had a host range similar to that of AlMV, although the symptoms in these hosts were less severe. Both viruses reacted with antisera prepared in the Netherlands and in Great Britain to AlMV-isolates purified from infectedAlstroemeria plants, and fromNicotiana clevelandii, respectively. Where AlSV occurs separately, distinction from AlMV is possible by its negative reaction with potyvirus group-specific monoclonal antibodies.     

Identification of blackeye cowpea mosaic virus from germplasm of yard-long bean and from soybean,and the relationships between blackeye cowpea mosaic virus and cowpea aphid-borne mosaic virus

Two potyvirus isolates, one from germplasm of yard-long bean (Vigna unguiculata ssp.sesquipedalis) introduced into the Netherlands, and another one from soybean plants (Glycine max) in Indonesia, were compared with two virus isolates of blackeye cowpea mosaic virus (BICMV) from the USA and a Moroccan isolate of cowpea aphid-borne mosaic virus (CAMV). It is proposed that all five isolates be now considered BICMV on the basis of host ranges, symptoms and serology. From our results, and a reassessment of the literature it is suggested to drop the name CAMV in favour of BICMV.Samenvatting Twee potyvirussen, de een in Nederland ingevoerd met genenmateriaal vanVigna unguiculata ssp.sesquipedalis en de ander uit planten van sojaboon (Glycine max) in Indonesië, werden vergeleken met twee isolaten van blackeye cowpea mosiac virus (BICMV) en een Marokkaans isolaat van cowpea aphid-borne mosaic virus (CAMV). Op grond van waardplantenreeksen, symptomen en serologie stellen de auteurs voor om alle vijf isolaten te beschouwen als BICMV. Gebaseerd op de verkregen resultaten en een kritische beschouwing van de literatuur wordt de aanbeveling gedaan om de naam CAMV te laten vallen ten gunste van BICMV.