Non-enzymatic conjugation of fenoxaprop-ethyl with glutathione and cysteine in several grass species

Laboratory studies have shown that the amounts of glutathione (GSH) and cysteine are higher in grass species that are moderately tolerant, such as wheat (Triticum aestivum L., cv. Fredrick), and moderately susceptible, such as barley (Hor deum vitlgare L., cv. Legér) and triticale (cv. OAC Trillium), to fenoxaprop-ethyl (FE) than in species that are very susceptible to the her bicide, such as oat (Avena saliva L., cv. OAC Woodstock), wild oat (Avena fatua L.), yellow foxtail (Setaria glanca (L.) Bcauv.), large crab grass (Digitaria sanguinalis (L.) Scop.) and bar nyard grass (Echinochloa crus-galli (L.) P.B.). The safener, fenchlorazole-ethyl (FCE) was found to increase and decrease, respectively, the amounts of GSH and cysteine in the moderately tolerant and moderately susceptible species but had no effect on the susceptible species. It is sug gested that in the moderately tolerant and moderately susceptible species, especially following FCE treatment, more GSH is available to detoxify the herbicide. Glutathione-S-tranferase activity (GST) for FE was found to be very low in all of the species tested. In vitro experiments at physio-logical pH. demonstrated that FE may conjugate with GSH nonenzymatically. Therefore, it is suggested that nonenzymatic conjugation of fenoxaprop-ethyl with glutathione may be an important mechanism for tolerance of some grasses to this herbicide.     

Volatile organic compounds (VOCs) from cereal plants infested with crown rot: their identity and their capacity for inducing production of VOCs in uninfested plants

When infested with Fusarium sp., the cereals Triticum aestivum L. emend. Fiori et Paol. cv. ‘Bombona’, Avena sativa L. cv. ‘Deresz’, and Hordeum vulgare L. cv. ‘Rastik’ can emit volatile organic compounds (VOCs). The VOCs differ both qualitatively and quantitatively from those emitted by non-infested wheat, oat, and barley plants. We detected increased amounts of VOCs released by green leaves (green leaf volatiles – GLVs): (Z)-3-hexenal, (E)-2-hexenal, (Z)-3-hexen-1-ol, (E)-2-hexen-1-ol, (Z)-3-hexen-1-yl acetate, 1-hexyl acetate as well as the other VOCs like (Z)-ocimen, linalol, linaloloxide, benzyl acetate, indole, and β-caryophyllene. The lipoxygenase pathway resulted in the highest release of GLVs in comparison to the other biochemical pathways of volatile production. As a result of Fusarium infestation, the amounts of VOCs varied between tested cereals. We also subjected uninfested wheat, barley, and oat plants to infested wheat plants, and found that these cereals released larger amounts of VOCs compared to control plants. Emitted amounts of VOCs were significantly higher the shorter the distance between uninfested and infested plants.     

Physiological effects of methyl 2-[4(2,4-dichlorophenoxy)phenoxy] propanoate on oat,wild oat,and wheat

Methyl 2-[4-(2,4-dichlorophenoxy)phenoxy]propanoate (dichlofop-methyl) is a selective herbicide for wild oat (Avena fatua L.) control in wheat (Triticum aestivum L.). Dichlofop-methyl inhibited IAA-stimulated elongation of oat and wheat coleoptile segments by 51 and 13%, respectively, at 10 μM concentrations. Dichlofop-methyl alone had no auxin activity at concentrations of 0.1, 1.0, and 10 μM. The inhibitory effect of dichlofop-methyl was overcome partially by increasing the IAA concentration or by application of 3,6-dichloro-o-anisic acid (dicamba), a herbicide with weak auxin activity. The de-esterified free acid metabolite, 2-[4-(2,4-dichlorophenoxy)phenoxy]-propionic acid (dichlofop), at 10 μM inhibited auxin-stimulated oat coleoptile elongation by 23%, but it did not affect wheat coleoptile elongation at the same concentration. Both dichlofop-methyl and dichlofop inhibited root growth in excised shoots and seedlings of wild oat but had no effect on wheat. Dichlofop was a more effective inhibitor of root growth than dichlofop-methyl. The results suggest that dichlofop-methyl functions as a strong auxin antagonist, while the metabolite, dichlofop, inhibits root growth and development by another mechanism. The herbicidal effect of dichlofop-methyl may be the net effect of two biologically active forms of the compound each with a different mode of action acting at different sites within a susceptible plant.     

Abscisic acid as a protectant of Avena fatua L. against diclofop-methyl activity

The imposition of water stress before or al the time of spraying diclofop-methyl reduced efficacy against wild oat (Avena fatua L.). Similar reductions in herbicide performance were obtained by application of 20 μg of the methyl ester of abscisic acid (ABA) to plants with three to four leaves before spraying with I kg ha^?1 diclofop-methyl. Application of 40–100 μg ABA per plant effectively protected plants against damage from diclofop-methyl applied at 1 5–2 0 kg ha ^?1. The application of 20 μg ABA induced rapid stomatal closure and a reduction in leaf extension rate, which were sustained for 7–8 days after treatment. These changes were associated with an overall reduction in shoot growth. ABA-treated plants that were additionally sprayed with diclofop-methyl sustained ABA symptoms, but no additional weight loss or leaf chlorosis. The mechanism of the protective action of ABA on diclofop-methyl has not been determined.     

A comparative assessment of potential components of partial disease resistance to <Emphasis Type="Italic">Fusarium</Emphasis> head blight using a detached leaf assay of wheat,barley and oats

The relative resistance of 15 winter barley, three winter wheat and three winter oat cultivars on the UK recommended list 2003 and two spring wheat cultivars on the Irish 2003 recommended list were evaluated using Microdochium nivale in detached leaf assays to further understand components of partial disease resistance (PDR) and Fusarium head blight (FHB) resistance across cereal species. Barley cultivars showed incubation periods comparable to, and latent periods longer than the most FHB resistant Irish and UK wheat cultivars evaluated. In addition, lesions on barley differed from those on wheat as they were not visibly chlorotic when placed over a light box until sporulation occurred, in contrast to wheat cultivars where chlorosis of the infected area occurred when lesions first developed. The pattern of delayed chlorosis of the infected leaf tissue and longer latent periods indicate that resistances are expressed in barley after the incubation period is observed, and that these temporarily arrest the development of mycelium and sporulation. Incubation periods were longer for oats compared to barley or wheat cultivars. However, oat cultivars differed from both wheat and barley in that mycelial growth was observed before obvious tissue damage was detected under macroscopic examination, indicating tolerance of infection rather than inhibition of pathogen development, and morphology of sporodochia differed, appearing less well developed and being much less abundant. Longer latent periods have previously been related to greater FHB resistance in wheat. The present results suggest the longer latent periods of barley and oat cultivars, than wheat, are likely to play a role in overall FHB resistance if under the same genetic control as PDR components expressed in the head. However the limited range of incubation and latent periods observed within barley and oat cultivars evaluated was in contrast with wheat where incubation and latent periods were shorter and more variable among genotypes. The significance of the various combinations of PDR components detected in the detached leaf assay as components of FHB resistance in each crop requires further investigation, particularly with regard to the apparent tolerance of infection in oats and necrosis in barley, after the incubation period is observed, associated with retardation of mycelial growth and sporulation.     

Competition between Avena sterilis ssp. macrocarpa Mo. and cultivars of wheat

A pot experiment was done in the glasshouse to study the competition between Avena sterilis ssp. macrocarpa Mo. and six wheat cultivars of different lengths of growth cycle. The competitiveness of wild oat was similar for all six wheat cultivars with respect to grain weight, straw weight, number of ears and total accumulation of nitrogen. The cultivar with the longest cycle was the most affected by wild oat competition as regards height, because a large part of its stem extension and some of the heading took place after the panicles of wild oat had expanded. Wild oat competition with wheat plants was greater than the competition among wheat plants themselves. The wild oat had a similar tolerance to all the wheat cultivars.     

Effect of chlorfenprop-methyl, flamprop-isopropyl and benzoylprop-ethyl on 14C2 fixation in Avena fatua L., Triticum aestivum L. and Hordeum vulgare L.

The effect of chlorfenprop-methyl, flampropisopropyl and benzoylprop-ethyl on ¹⁴CO₂ fixation was followed in wild oat (Avena fatua L.), barley (Hordeum vulgare L., cv. Ametyst), and wheat (Triticum aestivum L., cv. Mironovská). Experimental plants were exposed to a ¹⁴CO₂-enriched atmosphere in a special apparatus 2 h, 1, 3, and 9 days after the herbicide treatment. Chlorfenprop-methyl already inhibited ¹⁴CO₂ fixation in wild oat plants 2 h after the treatment. ¹⁴C-metabolite transport to the roots was strongly decreased. Both ¹⁴CO₂ fixation and ¹⁴C-metabolite level in the roots were significantly depressed in A. fatua when compared with untreated plants at the last sampling time. ¹⁴C incorporation into starch was inhibited from the first day after treatment, and on day 9 was lowered more than ten fold in treated plants. Flamprop-isopropyl inhibited ¹⁴CO₂ fixation in wild oat plants from day 3 after treatment, but benzoylprop-ethyl not until day 9. Both herbicides also decreased ¹⁴C incorporation into starch in A. fatua. Chlorfenprop-methyl also slightly decreased ¹⁴CO₂ fixation in barley on day 9. However, assimilate transport into the roots and ¹⁴C incorporation into starch were not affected. Flamprop-isopropyl inhibited ¹⁴CO₂ fixation in barley plants only on the first day after treatment, and assimilate transport was also reduced. By contrast, no differences from untreated plants were found at the end of the experiment. Benzoylprop-ethyl did not decrease either ¹⁴CO2 fixation or assimilate transport to the roots in wheat, but it inhibited starch synthesis. Atrazine depressed ¹⁴CO₂ fixation in wild oat plants by 91%, in wheat plants by 99% compared with untreated plants. Assimilate transport into the roots was also strongly inhibited. In contrast to atrazine, the effect of chlorfenprop-methyl, flamprop-isopropyl, and benzoylprop-ethyl on CO₂ fixation seems to be secondary.     

Differential inhibition of potassium ion absorption by difenzoquat in wild oat and cereals

Over a concentration range of 5.0 × 10^?6?7.5 × 10^?4M, the selective herbicide difenzoquat (1,2-dimethyl-3,5-diphenyl-1H-pyrazolium) caused more pronounced inhibition of potassium ion (K⁺) absorption by excised seedling roots of susceptible wild oat (Avena fatua L.) compared to those of tolerant barley (Hordeum vulgare L. cv. Bonanza) or wheat (Triticum aestivum L. cv. Neepawa). At 2.5 × 10^?5M difenzoquat, the relative inhibition of K⁺ (⁸⁶Rb) absorption by wild oat root segments inceased from 30% with a 10-min uptake period to 75% with an uptake period of 90 min, whereas no inhibition at all was evident for wheat root segments even after a 90-min exposure to the herbicide. An ion efflux compartmental analysis procedure demonstrated that difenzoquat did not affect the passive permeability properties of the plasma membrane of wild oat root cells. The experimental findings indicated that difenzoquat interfered directly with the process of active ion transport across the plasma membrane of root cells.     

Detection of triazine and urea herbicide residues by various characteristics of oat seedlings in bioassays

Atrazine, simazine, diuron, and linuron applied to soil increased the percentage moisture of oat (Avena sativa L.) shoots in bioassays at the lowest dose tested of 0·25 ppm. Further increases occurred up to 2 ppm but at higher concentrations the percentage moisture decreased. At all doses of each herbicide, shoot dry weight was decreased. In oats grown on soil collected from a peach orchard which had received repeated annual applications of these herbicides, the percentage moisture of the oat shoots was higher than the control value whenever the oat dry weight was decreased and provided a method of residue detection as sensitive as dry weight measurements. Treatment of oats by soil application of the above herbicides in bioassays also caused increases in the electrical conductivity of an aqueous extract of the oat shoots per mg of dry weight and this characteristic was slightly more sensitive than dry weight in detecting herbicides in orchard soil. The conductivity of the extract per mg of water in the shoots, however, only increased as percentage moisture decreased. The weight of neutral water-soluble material in oat shoots decreased much more rapidly than dry weight in bioassays with standard herbicide concentrations. Determination of the weight of neutral water-soluble material in oat plants grown on orchard soil samples indicated the presence of herbicide residues in 50% of the cases in which residues were not detectable by dry weight. The weight of neutral material as a percentage of dry weight was almost as sensitive. Chemical analysis of soil in which oat plants had a decreased level of neutral water-soluble compounds indicated that this characteristic had a lower limit of detection for herbicide residues of approximately 0.10 ppm.     

Competition between vegetative plants of wild oat (Avena fatua L.) and wheat (Triticum aestivum L.)

Competition between wild oat (Avena fatua L.) and wheat (Triticum aestivum L.) was studied in two experiments; a replacement series model and a technique for separation of root and shoot systems. Wild oat and wheat in association resulted in a relative yield total very close to unity showing that the two species were‘crowding for the same space’(or competing for the same resources) and were‘mutually exclusive'. Wild oat was more competitive than wheat, as shown by its aggressivity relative to wheat, relative yields, shoot dry weights and other plant attributes. The greater competitive ability of wild oat was predominantly due to its greater root competitive ability, while the two species had similar shoot competitive ability. Root competition had a much greater effect on the relative performance of the two species than did shoot competition. The effects of root and shoot competition were additive.     

Herbicide-resistant crops: yield penalties and weed thresholds for oilseed rape (Brassica napus L.)

An expérimental procedure was designed to provide a simple model for types of analyses necessary to determine weed density thresholds for advantageous use of crop plants engineered for herbicide resistance. Oilseed rape (Brassica napus L., cv. Tower) biotypes resistant (RES) and susceptible (SUS) to atrazine were used as model crop plants, and wild oat (Avena fatua L.) was used as the model weed. Along a wild oat density gradient equivalent to 0–128 plants m^?2, RES plants consistently experienced biomass and yield reductions of approximately 10–20% compared to SUS plants. When atrazine was applied at 1.5 kg ha^?1 to control wild oats competing with RES plants, RES biomasses and yields were stabilized at the same level as that where 25–30 wild oats m^?2 reduce yields of SUS plants. This implies that with wild oat densities of 25–30 plants m^?2, it becomes agronomically advantageous to crop with RES plants plus atrazine rather than to crop with higher-yielding SUS plants.     

Influence of time of emergence of wild oat on competition with wheat

The influence of time of emergence of wild oat (Avena fatua L.) on its competition with wheat (Triticum aestivum L.) was studied, using boxes that allowed separation of root and shoot competition. The relative yield total for mixtures of wild oat and wheat, grown under different forms of competition and with different wild oat sowing times, was very close to unity, indicating that the two species competed fully for limiting resources. Wild oat was more competitive than wheat when the two species were sown simultaneously, due largely to its greater root competitive ability; the two species had similar shoot competitive abilities. When wild oat was sown 3 or 6 weeks later than wheat, wheat was more competitive than wild oat and the production of wild oat panicles was prevented. This was mainly the result of greater root competitive ability of the wheat, although shoot competitive ability was also greater. The effects of root and shoot competition were additive. It is concluded that in order to prevent the return of wild oat seeds to the soil, and hence obtain long-term benefit, it is necessary to control the wild oat seedlings emerging within the first 3 weeks after drilling a wheat crop.     

Influence of 1-aminobenzotriazole (ABT) derivatives on the toxicity of EPTC to monocotyledonous plants

The effect of l-aminobenzotriazole (ABT) and EPTC mixtures on plant growth was investigated in greenhouse experiments by presowing application in sand. The concentration of ABT for 50% shoot growth inhibition (I₅₀) was about 1 mM in the monoctyledons investigated. Both subtoxic and toxic doses of ABT were antagonists of EPTC in maize (Zea mays L.) However, subtoxic doses of ABT were syner-gists of EPTC in wheat (Triticum aestivum L.), barley (Hordeum vulgare L.) and oat (Avena sativa L.). No correlation between ABT and EPTC sensitivity of monocotyledonous plants was found. Some of the C- and N-substituted ABT derivatives (e.g. N-methyl or N-benzyl-ABT) completely reversed the effect of toxic dose of EPTC in maize. These results are considered as indirect evidence for the hypothesis that oxidation by cytochrome P-450 enzymes is the biochemical target of EPTC and is involved in the mode of action of EPTC safeners.     

The effect of chlorffenprop-methyl on 32P uptake, transport and metabolism in Avena fatua L. and Hordeum vulgare L.

The eflect of chlorfenprop-methyl on plant weight, root uptake, transport and metabolism of ³²P in wild oat and barley plants was examined 4 h. 1, 3 and 9 days after treatment. The fresh weight of treated wild oat plants became significantly less than that of the controls by day 9. There was no significant effect on the weight of barley plants during this period. Uptake of ³²P by treated wild oat planus progressively decreased during the experiment and by day 9 was significantly 70% less yhan that in the control: uptake by barley plants showed a significant 30% increase by day 9. Transport of ³²P to the shoots followed a similar pattern. In wild oat plants, transport was significantly inhibited at all sampling dales by 44–91%. In barley plants. ³²P transport to the shoots tended to be enhanced by day 9 after herbicide treatment. Metabolism of ³²P in wild oat plants was affected 4 h after treatment. The content of ³²-P in individual fractions (inorganic, organic, lipidic, and nucleic acid P) was lower in treated plants, especially in the shools. In barley plants. ³²P incorporation into the individual fractions was initially inhibited 4 h after treatment, but later corresponded to that found in the control.     

Effect of benzoylprop-ethyl on uptake, transport and metabolism of 32P in Avena fatua L. and Triticum aestivum L.

The effect of benzoylprop-ethyl on plant weight, root uptake, transport and metabolism of ³²P in wild oat and wheat plants was examined 4 h, 1,3 and 9 days after treatment. The fresh weight of wild oat plants was significantly reduced, due to herbicide action only, by day 9 after treatment. By day 3, shoot weight was decreased while root weight was significantly increased by 47%. No significant changes in plant weight were caused by benzoylprop-ethyl in wheat plants. Uptake of ³²P by treated wild oat plants decreased by 39% compared with the control, by day 9, after an initial increase; uptake of ³²P was not significantly influenced in wheat plants. By day 1 transport of ³²P to the shoots was significantly reduced in wild oat plants by 34%, whereas in wheat plants it was significantly increased by 35%. Metabolism of ³²P was already hampered in wild oat plants 4 h after treatment. The content of ³²P was reduced on the first two sampling dates in both the roots and shoots of treated plants in all fractions except in DNA in the shoots. On day 3, this decrease was apparent especially in organic, lipidic and nucleic acid fractions in the shoots; incorporation of ³²P into lipidic and RNA fractions was significantly inhibited on day 9 in both the roots and shoots of treated wild oat plants. Wheat plants responded most strongly to benzyoylprop-ethyl on day 1 after treatment, when ³²P incorporation into all fractions except DNA was hampered. Differences between treated and control wheat plants gradually levelled off on days 3 and 9 after treatment.     

Chlorophyll production and chloroplast development in norflurazon-treated plants

The chlorophyll production of wheat (Triticum vulgare L. cv. Mericopa), corn (Zea mays L. cv. Everta), and alfalfa (Medicago sativa L. cv. Saranac), treated with the herbicide 4-chloro-5-methylamino-2-(3-trifluoro-methylphenyl)pyridazin- 3-one (norflurazon) and grown under high light intensity (10 760 lux) was markedly reduced. Corn and wheat seedlings germinated and grown for 7 days in an agar medium containing 1 mg/1 norflurazon were almost completely bleached. Alfalfa was even more sensitive to norflurazon, 0.1 mg/1 causing almost complete chlorosis. Under low light intensity (10.76 lux) the influence of norflurazon on chlorophyll production was greatly reduced. It is thought that norflurazon inhibits carotenoid synthesis leaving the chlorophyll of the plant subject to photooxidation. Electron micrographs of chloroplasts from green, partially bleached, and bleached areas of corn leaves treated with norflurazon indicate that the herbicide causes progressive deterioration of the lamellar system.     

Studies on the selectivity of alloxydim-sodium in plants

Alloxydim-sodium, methyl 3-[1-(allyloxyimino)butyl]-4-hydroxy-6,6-dimethyl-2-oxocyclohex-3-enecarboxylate sodium salt, is a selective herbicide which controls grass weeds in a wide range of broad-leaf crops. Spray retention, tested at two growth stages, was generally greater for the broad-leaf crops (cotton, sugarbeet, flax, beans and peas) than for wild oat (Avena fatua L.), blackgrass (Alopecurus myosuroides Huds), barley and couch grass [Agropyron repens (L.) Beauv.], and did not contribute to selectivity between susceptible and tolerant species. Broad-leaf crops tolerated 2820 g alloxydim-sodium ha^?1, three times the recommended rate used to control annual grasses. Differential uptake and translocation were not factors contributing to selectivity. In wild oat, blackgrass and sugarbeet, uptake and translocation of ¹⁴C continued during a period of 14 days after treatment with [¹⁴C]alloxydim-sodium. Translocation in susceptible and tolerant species was predominately symplastic. Over 40% of the applied ¹⁴C was eliminated from treated wild oat, blackgrass and sugarbeet plants within 7 days, due to degradation and volatilisation. A greater proportion of the methanol-soluble radioactivity extracted from leaves and roots was present as water-soluble polar metabolites in sugarbeet, than in wild oats, 7 days after treatment. The proportion of unaltered alloxydim in the organo-soluble fraction of a methanol extract was greater in wild oat than in sugarbeet. Differential metabolism appears to be one of the factors contributing to alloxydim-sodium selectivity between sugarbeet and wild oat.     

A comparison of the dynamics of root growth and biomass partitioning in wild oat (Avena fatua L.) and spring wheat

The dynamics of early root growth and dry matter partitioning were compared in spring wheat (Triticum aestivum L.) and wild oat (Avena fatua L.) grown in solution culture. Total root length was greater in wheat than wild oat throughout the experiment; a result of a greater number of seminal axes and greater production of lateral root length per axis. The final number of adventitious roots was greater in wheat than in wild oat, but their length was similar. Relative growth rates were also similar as was shoot:root dry weight ratio and rate of root respiration. However, wheat used the dry matter partitioned to its roots more efficiently, producing a greater specific root length (SRL, length per unit weight). Caution must be exercised when relating these results to plants growing and compet-ing in the field, but three general points are raised. First, the initial number of seminal axes can have a profound effect on the rate of early root development; second, the adventitious root system of wild oat is not inherently more vigorous than that of wheat; and third, future studies should compare SRL of wheat and wild oat in the field. If differences similar to those in the present study are found they may contribute to the greater competitive ability of wheat.     

UNTERSUCHUNGEN ZUR KONKURRENZWIRKUNG VON KULTURPFLANZEN UND UNKRÄUTERN AUFEINANDER

Summary. A 2-year comparison of the development of Avena fatua L. and Sinapis arvensis L., with spring barley and of Alopecurus myosuroides Huds, with winter wheat gave the following results:

• 1 Avena fatua emerged shortly before barley in both years. Development until tillering was somewhat slower than that of barley, but after tillering the growth of both species was about the same. The first seeds of A. fatua matured shortly before harvest.
• 2 Growth of Sinapis arvensis was slower than that of barley during the- early stages, but after tillering was more rapid. Growth ceased more than 10 days before harvest.
• 3 In 1962–63 Alopecurus myosuroides germinated mainly in spring, but in 1963–64 most germination occurred in autumn, so that early development was different in the two years. After tillering the development WAS much faster than that of wheat and at the flowering stage of A. myosuroides, the shoots were taller than those of wheat. Seed was ripened some time before harvest.
• 4 A comparison of the development of A. myosuroides and Avena fatua alone and in competition with cereals revealed no marked influence of competition on the pattern of development, but competition did cause some reduction in shoot length and a marked reduction in weight of the two weed species.

Compétition entre plantes cultivées et mauvaises herbes. I. Développement absolu el développement retalif des céréales et de quelques espèces de mauvaises herbes     

Studies on the host range of the barley strain of Wheat dwarf virus using an agroinfectious viral clone

Comparative analysis of the host ranges of the barley and wheat strains of Wheat dwarf virus (WDV; family Geminiviridae ; genus Mastrevirus ) in Europe has been severely hampered by the lack of an infectious clone of the barley strain. To remedy this situation an agroinfectious clone of a Hungarian isolate of the barley strain (WDV-Bar[HU]) was constructed and its virulence tested in barley ( Hordeum vulgare ), wheat ( Triticum aestivum ), rye ( Secale cereale ) and oat ( Avena sativa ) by agroinoculation. Although all four species could be systemically infected by the isolate, infections were asymptomatic in the rye and oat cultivars tested. WDV-Bar[HU] induced chlorosis and stunting symptoms typical of WDV in barley, while in wheat low infection rates but high mortality of infected seedlings were observed. In contrast, a much higher percentage of wheat plants agroinoculated with a wheat-strain isolate (WDV-[Enk1]) became systemically infected. WDV-[Enk1] in wheat caused symptoms similar to those caused by WDV-Bar[HU] in barley. WDV-Bar[HU] was leafhopper-transmissible to barley seedlings, in which it caused typical WDV symptoms; geminate virus particles were isolated from the infected leaves. Comparison of the genomic sequences of 11 barley strain isolates from Europe and Turkey revealed that whereas WDV-Bar[HU] represents a typical barley-strain isolate that is not detectably recombinant, the Turkish barley isolate (WDV-Bar[TR]) is probably a recombinant between a barley-strain isolate and an as-yet-undescribed WDV-like mastrevirus species.