Orosius Orientalis Research Articles

A New Disease in Limonium latifolium Hybrids. II. Investigating Insect Vectors

Symptoms typical of a phytoplasma infection were observed on a large number of Limonium hybrids in Israel in October 2000. Phytoplasma infection was confirmed by electron microscopy and polymerase chain reaction analysis. To identify the agent of pathogen spread surveys were made of candidate leafhoppers vectors in Limonium hybrid crops: one known phytoplasma vector (Orosius orientalis (Matsumura)) was present in very large numbers, ≈10-fold greater than any other species; three other known vectors were present in low to moderate numbers (Circulifer haematoceps complex (Mulsant et Rey), C. tenellus complex (Baker) and Exitianus capicola Stål); individual specimens of other vectors were occasionally found. Field collected specimens of these four species were shown to vector phytoplasma to healthy Limonium hybrid seedlings; this is the first time E. capicola has been shown to be a phytoplasma vector. A laboratory colony of O. orientalis was additionally shown to be able to acquire the phytoplasma from infected Limonium hybrids and subsequently vector it to healthy seedlings.

First Report of Chickpea Chlorotic Dwarf Virus Infecting Spring Chickpea in Syria.

During May 2003, a high incidence of symptoms suggestive of virus infection in spring chickpea were observed in many fields in Al-Ghab Valley, Syria, the ICARDA farm (near Aleppo, Syria), as well as in other locations in northern Syria, including the Idleb governorate. Symptoms observed were yellowing, stunting, and necrosis. A total of 1,345 chickpea samples with these symptoms (331 from Al-Ghab Valley, 269 from the ICARDA farm, and 745 from the Idleb governorate) were collected and tested for the presence of five viruses with tissue-blot immunoassay (TBIA) (4) at the Virology Laboratory of ICARDA, using the following antisera: monoclonal antibodies for Faba bean necrotic yellows virus (FBNYV, genus Nanovirus) (1); Bean leafroll virus (BLRV, family Luteoviridae) (4B10) (3); Beet western yellows virus (BWYV, genus Polerovirus, family Luteoviridae [ATCC PVAS-647, American Type Culture Collection, Manassas, VA]); and Soybean dwarf virus (SbDV, family Luteoviridae, [ATCC PVAS-650]) and polyclonal antibodies for Chickpea chlorotic dwarf virus (CpCDV, genus Mastrevirus, family Geminiviridae, provided by H. J. Vetten, BBA, Braunschweig, Germany). The most common virus present was BWYV (detected in 54.1% of samples tested), followed by CpCDV (19.2%), BLRV (10.2%), and FBNYV (5.5%). SbDV was not detected in any of the samples tested. Using immunosorbent electron microscopy, infected chickpea samples revealed low numbers of geminivirus-like particles after 15 min of incubation on CpCDV antiserum-coated grids. When CpCDV was purified from infected chickpea plants, the virus coat protein was 32 kDa with sodium dodecyl sulfate-polyacrylamide gel electrophoresis typical of CpCDV coat protein (2) and reacted strongly with CpCDV antiserum in western blots. The CpCDV vector in Syria was found to be Orosius albicinctus Distant, and is thought to be similar to Orosius orientalis (Matsumura), the reported vector of CpCDV (2). FBNYV, BWYV, and BLRV infection of chickpea have been previously reported from Syria, but to our knowledge, this is the first report of CpCDV infecting chickpea in Syria.

Reducing the immigration of suspected leafhopper vectors and severity of Australian lucerne yellows disease

Three newly-sown lucerne stands in the mid Lachlan Valley region of New South Wales, Australia, were sampled, over 50 weeks, for Australian lucerne yellows disease symptom distribution and severity. Leafhopper populations were also monitored. Symptoms developed in all 3 stands within 32 weeks of sowing. There were statistically significant spatial differences in the density of symptomatic plants for 2 dates at this and another site. Two possible insect vectors, Austroagallia torrida and Batracomorphus angustatus were more numerous in some sections of crop margins at 2 sites. These 2 species and a third possible insect vector Orosius argentatus each had a statistically significant spatial and temporal correlation with symptomatic plant numbers for at least 1 site date. Two subsequent border treatment experiments evaluated the effect of crop-margin treatments on leafhopper movement into and from the stand. The second border treatment experiment examined also the treatment effect on Australian lucerne yellows disease symptomatic plant numbers. Treatment with insecticide or herbicide significantly reduced the overall movement of leafhoppers. In addition, the insecticide treatment lowered the incidence of disease expression in adjacent lucerne. Results suggest that there is scope for management of this plant disease by reducing immigration of leafhopper vectors into lucerne from non-crop vegetation.

Spatial dispersion patterns of potential leafhopper and planthopper (Homoptera) vectors of phytoplasma in wine vineyards

SummarySpecies from three subfamilies of Cicadellidae and one species of Cixiidae, all potential vectors of phytoplasmas, were trapped in vineyards over the course of two years. These insects were caught on yellow sticky traps during the spring; virtually none were trapped during the summer months. Molecular analysis (PCR) of selected samples of the leafhoppers and planthoppers for presence of phytoplasma DNA was conducted on most species. Neoaliturus fenestratus was the most abundant known vector species and was positive for stolbur (Stol) and aster yellows (AY) phytoplasma. Circulifer haematoceps complex, which were also positive for Stol and AY, were about 10‐fold fewer than N. fenestratus. Hyalesthes obsoletus, also a known phytoplasma vector, occurred in substantial numbers only late in the season when the vines and leaves were dehiscing and turning brown, but was positive for Stol and AY. A species whose vector status is unknown (Megophthalmus scabripennis) was also caught in large numbers and was shown, by PCR analysis, to be positive for AY. Other known vector species trapped included: Anaceratagallia laevis (positive for AY), Austroagallia sinuata, Dryodurades sp. (dlabolai?) (positive for AY), Macrosteles quadripunctulatus (positive for Stol), and Orosius orientalis. The spatial dispersion pattern of the four most abundant species were investigated by using Moran's spatial statistic; N. fenestratus and M. scabripennis showed significant spatial patterns, whereas C. haematoceps and H. obsoletus did not.

Monitoring phytoplasma‐bearing leafhoppers/planthoppers in vineyards in the Golan Heights, Israel

In the course of identifying the vector(s) of the grapevine yellows (GY) and western‐X (WX) phytoplasmas in the Golan Heights, leafhopper and planthopper species were examined. The planthopper, Hyalesthes obsoletus, was trapped on yellow sticky traps or collected on weeds; there was a relatively small peak during two weeks in June and during four weeks starting mid‐September. The leafhoppers, Neoaliturus spp. and Circulifer sp. (of the haematoceps complex) were both trapped early or very late in summer, but could be collected on weeds throughout the summer. The two remaining leafhopper species, Macrosteles quadripunctulatus and Orosius orientalis (=albicinctus) were only rarely caught on sticky traps, but were found on weeds throughout the summer. Phytoplasmas were found within the body of these five species; all are historically known to be efficient vectors of various phytoplasmas and were therefore chosen for further investigations.

Virus‐vector relationships of chickpea chlorotic dwarf geminivirus and the leafhopper Orosius orientalis (Hemiptera: Cicadellidae)

SummaryChickpea chlorotic dwarf geminivirus (CCDV) is one of the viruses associated with chickpea stunt disease. It is transmitted by the leafhopper Orosius orientalis. The minimum acquisition access period (AAPmin) and inoculation access period (IAPmin) were found to be less than 2 min, while the minimum latency period (LPmin) was less than 2 h. The median AAP, IAP and LP were 8.0 h, 2.3 h and 27.7 h, respectively. No difference in transmission rates (proportion of leafhoppers able to transmit) was observed between male and female leafhop‐pers. In serial transmission experiments, transmission was shown to be persistent, and after a 2‐day AAP about 80% of the leafhoppers transmitted the virus for most of their life. The virus could be detected in individual leafhoppers by DAS‐ELISA. It did not multiply in the leafhopper, but, instead, decreased in concentration during leafhopper feeding on a non‐host of the virus.

Chickpea chlorotic dwarf virus, a new leafhopper‐transmitted geminivirus of chickpea in India1

SummaryA disease of chickpea in India, characterised by chlorosis, severe stunting and phloem browning, was shown to be caused by a geminivirus. This virus was transmitted by the leafhopper Orosius orientalis from chickpea to chickpea and several other plant species. A method for purification of this virus was devised and a polyclonal antiserum produced. The majority of the purified particles were geminate. The size of the coat protein was shown to be 32 kD and the nucleic acid was shown to be circular ssDNA of 2900 nucleotides. By immunosorbent electron microscopy this virus was shown to be unrelated to the leafhopper‐transmitted geminiviruses known to infect dicotyledons such as beet curly top, bean summer death and tobacco yellow dwarf viruses. On the basis of particle morphology, leafhopper transmission, host range and serology this virus was considered to be a new, hitherto undescribed, geminivirus and was named chickpea chlorotic dwarf virus.

LOW LEVEL FLIGHT ACTIVITY OF NESOCLUTHA PALLIDA (EVANS), OROSIUS ARGENTATUS (EVANS) AND ZYGINA ZEALANDICA (MYERS) (HEMIPTERA: CICADELLIDAE) IN SOUTHERN VICTORIA

AbstractLow level flight activity of three cicadellids, Nesoclutha pallida, Orosius argentatus and Zygina zealandica was determined by using suction traps located at La Trobe University (Melbourne) and Toolangi (60 km NE of Melbourne). The lower temperature thresholds for flight were 17.0°C for Z. zealandica, and about 21.5°C for both N. pallida and O. argentatus. Upper temperature thresholds for flight of N. pallida, O. argentatus and Z. zealandica were about 34.2°C, 37.2°C and 31.2°C respectively. Below 4.12 m wind speeds were also found to affect flight activity, wind speeds below 1.0m s−1 being less satisfactory than higher wind speeds, while at wind speeds above 6.1 m s−1 no flights occurred. All species showed a diurnal periodicity, peaks of activity occurring at sunset and sunrise for Z. zealandica and at sunset for N. pallida and O. argentatus. Between 0.38 m and 4.12 m above ground level, density of N. pallida, O. argentatus and Z. zealandica diminished regularly with increasing height; average values for Λ (regression coefficient of log density on log height), based on weekly observations, were ‐0.81 for N. pallida, ‐0.55 for O. argentatus and ‐1.19 for Z. zealandica.

Mycoplasma-like organisms as causal agents of potato purple top wilt in Queensland

The eggplant little-leaf agent was graft transmitted to tomato causing big-bud symptoms. Transmission from the big-bud tomato to potato by grafting or the leafhopper Orosius argentatus resulted in the development of purple top wilt symptoms. Thin-section electron microscopy revealed mycoplasma-like organisms present in the phloem sieve elements of a big-bud tomato plant and purple top wilt potato plants infected by grafting or leafhoppers. When tubers from graft-infected potato plants were planted, 73% produced spindly shoots and 44% of these later developed purple top wilt symptoms. When scions from either field-infected or experimentally infected potato plants showing purple top wilt symptoms were grafted onto tomato plants, 24% and 62% respectively developed big-bud symptoms. The results provide strong evidence for the mycoplasmal aetiology of some, if not all, potato purple top wilt in Queensland.

Some Notes on a Leafhopper of Economic Importance, Orosius orientalis (MATSUMURA, 1914) (Hemiptera : Cicadellidae)

Orosius orientalis (MATSUMURA, 1914) which is distributed in Japan and Formosa is a fairly well-known species as a vector of the legumes witch's broom in the Ryukyu Islands. When the author figured it first, the revision of the type-specimens was requested to ascertain either the specific name is valid or not. As a result of examination of the type-material, some important characters were figured in this paper and the type-species of the genus Orosius DISTANT, 1918, O. albicinctus DISTANT, 1918, which is distributed in India and other lands further to the west, was synonymized with the present species.

Rickettsia-like and mycoplasma-like organisms associated with two yellows-type diseases of strawberries in Queensland

Two yellows-type diseases occur in Queensland strawberries. Affected plants show purple or bronze pigmentation of older leaves, followed by the production of small chlorotic leaves. Flower production is inhibited, and some affected plants die. Thin-section electron microscopy showed that there were two diseases, one associated with rickettsia-like organisms (RLO) and the other with mycoplasma-like organisms (MLO), both of which were found only in sieve tubes. The MLO disease caused flower abortion but not green petals, and was not transmitted by Orosius argentatus (Evans), the tomato big bud vector. The RLO disease produced more bronze pigmentation and the young leaf chlorosis was interveinal rather than marginal. This organism was sensitive to penicillin, and soil drenches of 1 mg/ml every 5 days for 7 weeks caused complete remission of symptoms. No organisms were seen in thin sections of leaves after treatment. Although these RLO morphologically resembled those associated with rugose leaf curl (RLC) disease of legumes, experiments with the RLC vector Austroagallia torrida Evans indicated that they were probably distinct.

Tomato big bud, legume little leaf, and lucerne witches' broom: three diseases associated with different mycoplasma-like organisms in Australia

The pathogens (presumed to be mycoplasma-like organisms) causing tomato big bud, legume little leaf, and a 'mild' form of lucerne witches' broom disease could be distinguished by differential symptomatology and incubation periods in tomato (Lycopersicon esculentum) and Datura stramonium. They were regarded as reference 'type strains' of the Australian yellows disease agents. Incubation periods of the tomato big bud and legume little leaf agents in the leafhopper vector Orosius argentatus were similar, but the pathogen causing mild lucerne witches' broom was not transmissible by this insect. Six species of plants with yellows disease symptoms (shoot proliferation, small leaves, chlorosis, virescence) were collected from northern and southern Queensland. The pathogens were transmitted by O. argentatus to D. stramonium. From symptoms produced in this host, the various isolates were characterized as either the original big bud or little leaf reference strains. An isolate causing 'severe' lucerne witches' broom could not be distinguished from the legume little leaf type strain.

Effects of Tetracycline Antibiotics on Plants Affected by Legume Little Leaf Disease

Nicotiana glutino8a, aster, and tomato plants affected by legume little leaf disease were treated by spraying the foliage with 100 ,..,g/ml aqueous solutions of either Achromycin (tetracycline hydrochloride) or Aureomycin (chlortetracycline hydro-chloride), every 2-3 days for periods of 4-8 weeks. Disease symptoms were sup� pressed in the new growth of all plants during the treatment period, but reappeared 2-4 weeks after the last application of antibiotic. Mycoplasma-like bodies were abundant in the phloem sieve tubes of untreated aster, and in aster which redeveloped symptoms after the antibiotic treatment had been discontinued. In contrast, Mycoplasma�like bodies could not be detected by thin� section electron microscopy in symptomless shoots of Achromycin-treated plants immediately after a period of treatment. In concomitant leafhopper transmission tests with the vector Orosius argentatus, the little leaf agent was not recovered from the symptomless treated shoots, but was readily recovered from diseased shoots which developed after termina-tion of the Achromycin treatment.

Necrotic yellows: A newly recognized virus disease of lettuce

A previously undescribed virus disease of lettuce, for which the name lettuce necrotic yellows is proposed, occurs in epiphytotic proportions in Victoria and, to a similar or lesser extent, in parts of Queensland, New South Wales, and South Australia. Infected plants are extremely chlorotic and have a flattened appearance. They exhibit varying degrees of flaccidity and necrosis, and the mortality rate may be high. Chronically affected survivors have small, slightly distorted, but otherwise normal heart leaves. The tomato spotted wilt virus, which causes an almost identical disease in lettuce, lacks the "recovery" phase. The virus was sap-transmissible from infected lettuce or sowthistle (Sonchus oleraceus L.) to several indicator species, but not to lettuce or sowthistle. Lettuce has been infected on a few occasions with inoculum from Nicotiana glutinosa L. There is no evidence that the virus is transmitted through lettuce or sowthistle seed. The virus was inactivated in N. glutinosa sap between 52 and 54°C, was relatively short-lived in vitro (1–8 hr), and its dilution end-point was close to 10-2. Symptoms are described on known experimental hosts, including N. glutinosa, petunia, and spinach, that are regarded as the best differential indicators. Several lettuce-infesting insects—thrips (Thrips tabaci Lind. and Frankliniella schultzei (Tryb.)), leafhoppers (Orosius argentatus Evans), and aphids (Myzus persicae (Sulz.) and Macrosiphum euphorbiae (Thos.))—failed to transmit the virus from infected lettuce or sowthistle. Transmission was achieved with the aphid Hyperomyzus lactucae (L.) bred on infected sowthistle, the only known source in Victoria of both the vector and the virus. The virus persisted through a moult of the vector, and thus the mode of transmission is of the circulative type. H. lactucae has not previously been recognized as a vector of a "circulative" virus. It is considered unlikely that lettuce necrotic yellows virus is indigenous to Australia, because sowthistle, the only known natural host of both the virus and the vector, is an introduced species.

Legume "Little leaf", a virus disease of subtropical pasture species

A virus of legumes causing a disease described as "little leaf" has infected with differing degrees of severity some 40 per cent. of pasture legumes in experimental plots in subtropical Queensland. The symptoms are similar to those caused by the "big bud-witches' broom" complex of viruses of which it is probably another strain. Transmission studies have shown that the vector is the leafhopper Orosius argentatus (Evans) which also transmits tomato "big bud", lucerne "witches' broom", potato "purple top wilt", and tobacco "yellow dwar"' diseases. The O. argentatus taken direct from the field in Queensland, and its progeny reared in the laboratory, were efficient vectors of "little leaf" whereas the Canberra strain bred in the laboratory would not transmit 'little leaf' and was not an efficient vector of the other "yellows" viruses. The majority of species and strains tested in the genera Crotalaria, Desmodium, Indigofera, and Stylosanthes are susceptible to "little leaf". Within such genera there are a few resistant species or strains with promising agronomic characters. Lucerne and white clover are relatively resistant to "little leaf". The genera Arachis, Centrosema, Doliehos, Glycine, Lespedeza, Leucaena, Pueraria, Phaseolus, Vigna, and Zornia contain species and strains with marked field resistance. Most of the species and strains considered to be promising pasture legumes possess field resistance to "little leaf".

The Transmission of Witches' Broom Virus Disease of Lucerne by the Common Brown Leafhopper, Orosius ARGENTATUS ( EVANS)

The disease was transmitted by Orosius argentatus (Evans) collected in infected lucerne crops, and also by groups of virus-free individuals reared under experimental conditions, after having been fed on plants infected with witches' broom virus.

Yellow dwarf of tobacco in Australia. V. Transmission by Orosius argentatus (Evans) to some alternative host plants.

Tobacco yellow dwarf virus disease was experimentally transmitted to 15 species of plants by the leafhopper, Orosius argentatus (Evans). Eight of these plants are summer annuals and seven are autumn-spring growing plants which provide a continuous succession and wide range of hosts. Their occurrence in the districts where tobacco is grown makes control by the elimination of alternative host plants appear impracticable.