Response of wild barley (Hordeum spontaneum) and winter wheat (Triticum aestivum) to sulfosulfuron: The role of degradation

Wild barley (Hordeum spontaneum) is one of the most troublesome weed species in winter wheat (Triticum aestivum) in Iran. Two bioassay experiments were conducted in order to study the response of wild barley and wheat to different herbicides and to study the efficacy of pre‐emergence (PRE), postemergence (POST), and PRE followed by POST applications of sulfosulfuron on wild barely. Moreover, the degradation of sulfosulfuron was studied by liquid chromatography coupled with tandem mass spectrometry (LC‐MS/MS). The results showed that wild barley was highly tolerant to clodinafop‐propargyl and its dry weight was reduced by only 15%, compared to the control, at the recommended dose (64 g ai ha^?1). Sulfosulfuron reduced the wild barley biomass by ≤50% at the highest dose (90 g ai ha^?1) in the first bioassay but by not more than 20% and 12% at the recommended dose (22 g ai ha^?1) in the first and second bioassay, respectively. Significant differences were found among the application methods of sulfosulfuron, with the POST application being the least effective method. In contrast to the POST application, wild barley was severely injured by the PRE application of sulfosulfuron, with an ED₅₀ dose of 7.3 g ai ha^?1. The degradation study showed that wild barley can metabolize sulfosulfuron that is applied POST, but at a lower rate than wheat. By 4 h after application, wild barley had metabolized 26% of the sulfosulfuron, compared to 46% by wheat. In conclusion, wild barley can metabolize the recommended dose of sulfosulfuron that is applied POST; thus, the PRE application of sulfosulfuron or other integrated methods should be considered for the effective control of wild barley in wheat.     

Occurrence and transmission of sowbane mosaic virus in seed from naturally infected plants of spinach (Spinacia oleracea)

Sowbane mosaic virus was isolated as a single infectious component from seedlings and seeds from a seed-lot of spinach (Spinacia oleracea) propagated in Hungary, and was identified by experimental host-range, thermal-inactivation point, dilution end-point, electron microscopy and serology.Chenopodium quinoa was more susceptible and/or sensitive to infection thanC. amaranticolor and was a better indicator host, butC. amaranticolor is of diagnostic value. This is the first report on natural infection of spinach by the virus and on its natural seed-transmission in spinach. Growing-on tests on whole seeds and infectivity tests on separate embryos and seed-coats showed that over 30% of the seeds' embryos were infected and c. 80% of the seed-coats contained the virus. The incidence of infection in the spinach crop from which the seed was obtained must have been high.     

Mechanical transmission of maize rayado fino marafivirus (MRFV) to maize and barley by means of the vascular puncture technique

Maize rayado fino marafivirus (MRFV) was mechanically transmitted to kernels of three Costa Rican maize cultivars by the vascular puncture technique. A transmission rate of up to 43.2% was obtained for cultivar HC-57. The rate of MRFV transmission to maize was possibly affected by the morphology of the kernel, which may influence physical access to the vascular tissue after water imbibition. Transmission to maize was confirmed by western blot and immunosorbent electron microscopy. By slight modifications of the procedure, MRFV was also transmitted to barley. This is the first report of MRFV infecting a species outside the supertribe Andropogonodae. Virus infection and replication in barley were confirmed by RT-PCR detection of MRFV RNA and by detection of the virus by ELISA.     

Broad bean wilt virus: Host range,purification, serology,transmission characteristics,and occurrence in faba bean in West Asia and North Africa

A virus affecting faba bean in West Asia and Norht Africa was identified as broad bean wilt virus (BBWV) by host reactions, particle morphology and size, serology and transmission characteristics. An isolate from Syria (SV3-88) and one from Egypt (EV319-86) were found to be serologically identical and of serotype I. In host-range studies, the Syrian isolate infected systemically 59 out of 87 plant species tested. The virus was transmitted non-persistently by four aphid species naturally prevalent in Syria, but most efficiently byMyzus persicae. Inoculation of faba bean with SV3-88 14 weeks (pre-flowering) and 6 weeks after sowing (flowering) led to 25.8 and 1.8% yield loss and seed-transmission rates of 0.6 and 0.4%, respectively. The isolate SV3-88 was purified from systemically infected faba bean and yield 1.5–2 mg of partially purified virus per 100 g of leaves. When samples, with symptoms suggestive of virus infection, were collected during 1985–1989 from a number of countries in West Asia and North Africa and tested by ELISA, the virus was detected in 8 out of 127 samples tested (8/127) from Egypt, 0/44 from Lebanon, 1/23 from Morocco, 38/485 from the Sudan, 38/385 from Syria and 23/138 from Tunisia.Samenvatting Een virus uit veldboon of faba boon (Vicia faba) in West Azië en Noord-Afrika werd als tuinboneverwelkingsvirus (Fabavirus-groep) herkend aan zijn waardplantreacties, deeltjesvorm en grootte, serologie en wijze van overdracht. Een isolaat uit Syrië (SV3-88) en één uit Egypte (EV319-86) bleken serologisch identiek te zijn en te behoren tot serotype I van het virus. Met het Syrische isolaat kon in 59 van de 87 getoetste plantesoorten systemische infectie worden verkregen. Met vier veel in Syrië voorkomende bladluissorten kon het virus worden overgebracht, maar metMyzus persicae naar de meeste plantesoorten. Inoculatie van veldboon met SV3-88 vóór de bloei (14 weken na het zaaien) en tijdens de bloei (16 weken na het zaaien) gaf aanleiding tot respectivelijk 25,8 en 1,8% opbrengstreductie en tot 0,6 en 0,4% zaadoverdracht. Bij zuivering van isolaat SV3-88 uit systemisch geïnfecteerde fababoon was de opbrengst tot 1,5 à 2 mg gedeeltelijk gezuiverd virus per 100 g blad. Bij ELISA-toetsing in 1985–1989 van een groot aantal monsters afkomstig uit een aantal landen in West-Azië en Noord-Afrika werd het virus aangetoond in 8 van de 127 (8/127) monsters uit Egypte, 0/44 uit Libanon, 1/23 uit Marokko, 38/485 uit Soedan, 38/385 uit Syrië en 23/138 uit Tunesië.     

Pea seed-borne mosaic virus: occurrence in faba bean (Vicia faba) and lentil (Lens culinaris) in West Asia and North Africa,and further information on host range,transmission characteristics,and purification

In a survey for viruses of cultivated legumes in West Asia and North Africa, pea seed-borne mosaic virus (PSbMV) was found in faba bean, lentil and pea. Using ELISA, it was detected in 107 out of 1554 faba bean samples and 40 out of 496 lentil samples with virus-like symptoms collected in Algeria, Egypt, Ethiopia, Jordan, Lebanon., Libya, Morocco, Sudan, Tunisia and Turkey.A pea isolate (SP9-88) from Syria was further characterized. Out of 57 plant species tested, 35 were found susceptible, 19 of which are newly reported hosts of the virus. The virus was transmitted efficiently in the non-persistent manner by five aphid species, especiallyMyzus persicae. Purification from systemically infected faba bean plants yielded 10–15 mg of purified virus per kg of infected tissue. Sap-inoculation of the food and forage legume species chickpea, faba bean, lentil, pea,Vicia narbonensis, V. sativa, Lathyrus ochrus andL. sativus at flowering stage led to 66.0, 40.5, 44.6, 49.2, 31.7, 7.5, 35.7 and 12.0% yield loss, respectively, and to seed-transmission, rates of 0.7, 6.0, 10.8, 1.1, 0.3, 0.2 and 0.4%, respectively. No transmission was detected in chickpea seed embryo axes. However, the virus was detected in the seed coat of SPbMV-infected chickpea at an estimated rate of 1.81%.     

Potato leafroll virus (PLRV): its transmission and control

This review provides a wide assessment of the present state of knowledge about the potato leafroll luteovirus (PLRV), a pathogen which is seriously devastating potato crops in many parts of the world. The main biological, physical and chemical properties of this virus are described. The transmission of PLRV by aphids, which are the only transmitters of this virus under natural conditions, is characterized. Special attention is given to the control of PLRV through the use of resistant potato cultivars. Recent advances in obtaining resistant transgenic plants are outlined.     

The effects of co‐infection by different Potato virus Y (PVY) isolates on virus concentration in solanaceous hosts and efficiency of transmission

The influence of co‐infection on concentration and accumulation of genetically different isolates of Potato virus Y (PVY) in potato and tobacco plants and the efficiency of transmission by Myzus persicae of PVY isolates from doubly versus singly infected plants were evaluated. The vector ability to simultaneously transmit two virus isolates was examined. Eight PVY isolates represented three strain groups: PVY^O (pathotype and serotype O), PVY^NW (pathotype N and serotype O), and PVY^NTN (pathotype and serotype N). Different diagnostic methods, including DAS‐ELISA, multiplex RT‐PCR, aphid transmission tests and bioassays, were applied to detect the presence of PVY isolates in source and assay plants. Significant reductions in concentrations of certain PVY isolates during co‐infection with other isolates were found both in potato and tobacco plants. The observed effects were both isolate‐ and host‐dependent in form. The highest rates of virus transmission by single aphids were recorded with PVY^NTN isolates, and the lowest ones with PVY^O isolates. Individual aphids of M. persicae were able to simultaneously transmit two PVY isolates. The frequency of transmission was generally low, but it reached as high as 20% for one of the isolate combinations. The findings presented in the work provide proof for antagonistic within‐plant interactions between isolates of PVY, with some implications of these interactions for virus transmission by aphid vectors. Consequently, this research contributes to a better understanding of the epidemiology of the disease caused by PVY.     

Early intracellular punctures by two aphid species on near-isogenic melon lines with and without the virus aphid transmission (Vat) resistance gene

The Vat resistance gene (in Cucumis melo L.) inhibits the transmission of non-persistent viruses by Aphis gossypii Glover, but does not affect transmission by Myzus persicae (Sulz.). To see whether this difference was behaviourally determined, we investigated the stylet penetration behaviour of these two aphid species by recording EPGs (Electrical Penetration Graphs) of 8 and 20 min on two sets of susceptible and resistant isogenic melon lines. During the 20 min EPG study, inoculation with CMV (Cucumber Mosaic Virus) was also investigated. For both sets of isogenic lines, the two aphid species were able to detect the presence of Vat. The mean duration of individual intracellular punctures on the resistant genotypes was significantly reduced for both M. persicae and A. gossypii (-10% and -8% respectively for duration of pattern ‘pd’ in the 20 min experiment); this reaction appeared faster for M. persicae, a species for which melon was not a suitable host-plant. Therefore, in contrast to Vat's anti-transmission effect, this behavioural effect was not aphid species-specific. Also, the frequency of intracellular punctures on the resistant genotypes was significantly reduced in A. gossypii (but not in M. persicae): on average, this frequency dropped from ≈0.65 pd.min^-1 on the susceptible genotypes to ≈0.5 pd.min^-1 on the resistant ones. It was concluded that (intracellular?) chemical cues were detected very early by aphids probing on the resistant genotypes carrying the Vat gene. However, a comprehensive analysis of the behavioural traits of both aphids on the two genotypes could not alone account for the complete inhibition of transmission which was found only to occur for A. gossypii on resistant genotypes. None of the differences detected (between aphid species or between plant genotypes) could account for the Vat phenotype, although they may explain quantitative differences in transmission efficiencies between aphid species. It was thus concluded that Vat effect was primarily chemically mediated. Finally, some intracellular punctures bearing typical subphases have been identified in both aphid species and were designated as ‘long potential drops’ (pd-L). For A. gossypii, these were observed early after plant contact and their mean duration was twice that of standard intracellular punctures (≈8.5 s vs ≈4.2 s). Although not necessary for CMV inoculation, the duration of such phases was positively correlated with a high transmission efficiency by A. gossypii on the susceptible genotype. The nature of this pattern and a putative mechanism of action of the Vat gene are discussed.     

Broad bean mottle virus: Identification,host range,serology, and occurrence on faba bean (Vicia faba) in West Asia and North Africa

One of the faba bean viruses found in West Asia and North Africa was identified as broad bean mottle virus (BBMV) by host reactions, particle morphology and size, serology, and granular, often vesiculated cytoplasmic inclusions. Detailed research on four isolates, one each from Morocco, Tunisia, Sudan and Syria, provided new information on the virus.The isolates, though indistinguishable in ELISA or gel-diffusion tests, differed slightly in host range and symptoms. Twenty-one species (12 legumes and 9 non-legumes) out of 27 tested were systemically infected, and 14 of these by all four isolates. Infection in several species was symptomless, but major legumes such as chickpea, lentil and especially pea, suffered severely from infection. All 23 genotypes of faba bean, 2 of chickpea, 4 of lentil, 11 out of 21 ofPhaseolus bean, and 16 out of 17 of pea were systemically sensitive to the virus. Twelve plant species were found to be new potential hosts and cucumber a new local-lesion test plant of the virus.BBMV particles occurred in faba bean plants in very high concentrations and seed transmission in this species (1.37%) was confirmed.An isolate from Syria was purified and two antisera were produced, one of which was used in ELISA to detect BBMV in faba bean field samples. Two hundred and three out of the 789 samples with symptoms suggestive of virus infection collected in 1985, 1986 and 1987, were found infected with BBMV: 4 out of 70 (4/70) tested samples from Egypt, 0/44 from Lebanon, 1/15 from Morocco, 46/254 from Sudan, 72/269 from Syria and 80/137 from Tunisia. This is the first report on its occurrence in Egypt, Syria and Tunisia. The virus is a potential threat to crop improvement in the region.Samenvatting Eén van de in West-Azië en Noord-Afrika in faba-boon aangetroffen virussen werd geïdentificeerd als het tuinbonevlekkenvirus (broad bean mottle virus) op grond van waardplantreacties, deeltjesvorm en-grootte, serologische eigenschappen en granulaire, vaak gevacuoliseerde celinsluitsels. Verder onderzoek aan vier isolaten uit respectievelijk Marokko, Tunesië, Soedan en Syrië verschafte nieuwe informatie, over het virus.De in ELISA of gel-diffusietoetsen serologisch niet te onderscheiden isolaten verschilden enigszins in waardplantenreeks en symptomen. Van 27 getoetste plantesoorten werden 21 systemisch geïnfecteerd (12 vlinderbloemigen, en 9 niet-vlinderbloemigen) waarvan 14 door alle vier isolaten. In vele ervan was de infectie symptoomloos, maar belangrijke als gewas geteelde vlinderbloemigen, zoals erwt, linzen en kekererwt, leden ernstig onder aantasting. Alle 23 getoetste faba-boongenotypen, beide van kekererwt, alle vier van linzen, 11 van de 21 getoetste vanPhaseolus-boon en 16 van de 17 van erwt bleken systemisch gevoelig voor het virus. Twaalf plantesoorten, bleken nieuwe potentiële waardplanten en komkommer een nieuwe lokale-lesietoetsplant voor het virus te zijn.In faba-boneplanten kwam, het virus in hoge concentratie voor en overdracht met zaad (1.37%) in deze soort kon worden bevestigd.Een Syrisch isolaat werd gezuiverd en twee antisera werden bereid, waarvan één werd gebruikt voor de detectie van het virus in te velde verzamelde monsters. Van 789 in 1985 tot en met 1987 verzamelde bladmonsters, met symptomen die deden denken aan virusinfectie, bleken 203 het virus te bevatten en wel 4 van de 70 (4/70) uit Egypte, 0/44 uit Libanon, 1/15 uit Marokko, 46/254 uit Soedan, 72/269 uit Syrië en 80/137 uit Tunesië. Het virus was nog niet eerder aangetoond in Egypte, Syrië en Tunesië.De grote verbreiding, grote kunstmatige waardplantenreeks, overdracht met zaad, en pathogeniteit voor een aantal belangrijke vlinderbloemige gewassen maken het virus tot een potentiële bedreiging van de programma's tot verbetering van de teelt van de bedoelde gewassen in het betrokken gebied.     

Spread and interaction of Pepino mosaic virus (PepMV) and Pythium aphanidermatum in a closed nutrient solution recirculation system: effects on tomato growth and yield

Pepino mosaic virus (PepMV) was shown to be efficiently transmitted between tomato plants grown in a closed recirculating hydroponic system. PepMV was detected in all plant parts after transmission via contaminated nutrient solution using ELISA, immunocapture RT‐PCR, RT‐PCR, electron microscopy, and by inoculation to indicator plants. Detection of PepMV in nutrient solution was only possible after concentration by ultracentrifugation followed by RT‐PCR. Roots tested positive for PepMV 1–3 weeks after inoculation, and subsequently a rapid spread from the roots into the young leaves and developing fruits was found within 1 week. PepMV was only occasionally detected in the older leaves. None of the infected plants showed any symptoms on fruits, leaves or other organs. Pre‐infection of roots of tomato cv. Hildares with Pythium aphanidermatum significantly delayed PepMV root infections. When mechanically inoculated with PepMV at the 2–4 leaf stage, yield loss was observed in all plants. However, only plants of cv. Castle Rock recorded significant yield losses when infected via contaminated nutrient solution. Yield losses induced by infection with PepMV and/or P. aphanidermatum ranged from 0·4 up to 40% depending on experimental conditions.