Thirty three samples were taken from 29 diseasedbulbs showing the range of symptoms described. P.cepacia was isolated from 9 bulbs and P. gladioli pv.alii/cola was isolated from 5 bulbs, three of which werealso positive for P. cepacla. These pathogens wereisolated only from bulbs having symptoms (b) above.Although in pathogenicity tests, P. cepacla produced acreamy soft rot and P. gladioli pv. alii/cola produced ayellow to mustard coloured soft rot, there were noobvious differences in symptoms between naturallyinfected bulbs positive only for P. cepacla and thosepositive for P. gladioli pv. alii/cola.

P. oepecte is thought to infect inner leaf bases byentry through the neck or leaf blades (9). Whilesymptoms are generally produced in artificiallyinoculated leaves, the bacteria can survive in symptom­less mature leaves (9). No leaf lesions have beenobserved at Narromine prior to maturity. Infections havebeen implicated with contaminated irrigation water (8)and bacteria may gain entry to leaves through breaks inthe epidermis occurring when foliage falls over atmaturity (10). The appearance of symptoms in N.S'w. islimited to bulbs maturing from January onwards and ithas been argued (6) that disruption of host physiologyby high temperatures is involved in the internal break­down syndrome. This disruption may be incidental tothe infection process and may explain the occurrence oflesions (symptoms a and c above) from which nopathogens could be isolated.

Acknowledgement

The assistance of Peter Fahy, B.C.R.I., Rydalmere indetermining the fluorescence spectrum of isolates isgratefully acknowledged.

References

(1) Ballard, R.W., Pal/eroni, N.J., Doudoroft, M.,Stanier, R.Y. and Mandel, M. (1970) ­Taxonomy of the aerobic pseudo monads:Pseudomonas cepec!e, P. marglnata, P.alii/cola and P. caryophylil. Journal of GeneralMicrobiology 60: 199-214.

(2) Bazzi, C. (1979) - Identification of Pseudomonascepacla on onion bulbs In Italy.Phytopatho/ogische Zeltschrift 95: 254-258.

(3) Brown, V.1. and Lowbury, E.J.L. (1965) - Use of animproved cetrimide agar medium and otherculture methods for Pseudomonas aeruglnosa.Journal of Clinical Pathology 18: 752-756.

(4) Burkholder, W.H. (1950) - Sour skin, a bacterialrot of onion bulbs. Phytopathology 40: 115-117.

(5) Cother, E.J., Darbyshire, B., and Brewer, J. (1976)- Pseuodomonas aeruglnosa: Cause ofinternal brown rot of onion. Phytopathology 86:828-834.

(6) Cother, E.J. and Dowling, V. (1985) - Endophyticbacteria associated with internal breakdown ofonion bulbs. (Submitted to Phytopathology).

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(7) Fahy, P.C. and Hayward, A.C. (1983) - Media andmethods for isolation and diagnostic tests. pp337-378 in (Ed) Fahy P.C. and Persley, G.J.Plant Bacterial Diseases: A Diagnostic Guide.Academic Press, Sydney 393 pp.

(8) Irwin A.D. and Vaughan, E.K. (1972) - Bacterialrot of onion and the relation of Irrigation waterto disease incidence. Phytopathology 82: 1103Abstr.

(9) Kawamoto, S.O. and Lorbeer, J,W., (1972) ­Multiplication of Pseudomonas cepacla inonion leaves. Phytopathology 82: 1263-1265.

(10) Kawamoto, S.O., and Lorbeer, J.W., (1972) ­Histology of onion leaves infected withPseudomonas cepacla. Phytopathology. 82:1266-1271.

(11) Palleroni, N.J. and Doudoroff, M., (1972) - Someproperties and taxonomic subdivision of thegenus Pseudomonas. Annual Review ofPhytopathology 10: 73·100.

(12) Pal/eronl, N.J., and Holmes, B. (1981) ­Pseudomonas cepacla sp. nov., nom. rev.International Journal of SystematicBacteriology 31: 479-481.

(13) Rayner, R'w. (1970) - A mycological colourchart. C.M.1. and British Mycological Society,London.

(14) Ridgway, A. (1912) - Colour standards andcolour nomenclature. Ridgway, Washington.

(15) Snel/, J.J.S., Hill, L.R., Lapage, S.P. and CurtisM.A. (1972) - Identification of Pseudomonascepacia Burkholder and its synonomy withPseudomonas kingli Jonsson, InternationalJournal of Systematic Bacgeriology 22: 127­138.

(16) Tesoriero, L.A.. Fahy P.C. and Gunn. L.V. (1982)- First record of bacterial rot of onion inAustralia caused by Pseudomonas gladioli pv.alilicola and association with internal browningcaused by Pseudomonas aeruginosa.Australasian Plant Pathology 11: 56-57.

New Plant Disease Record inTasmania:Poinsettia Mosaic Virus

Paul GuyDepartment of Agriculture

Box 192B G.P.O., Hobart, Tas. 7001

Poinsettia mosaic virus was first described from com­mercially grown poinsettias (Euphorbia pulcherrlmaWild.) in the United States (2), and has since been foundin England (5). Canada (1), and West Germany (3).Infected plants may be symptomless or show varyingdegrees of mottling in their leaves. Infection with the

Australasian Plant Pathology Vol. 14 NO.1 March 1985

Fig. 1. Leaf symptoms of poinsettia mosaicvirus in poinsettia.

virus was common (2.3) and in some instances. nurserystocks were 100% infected (1).

Poinsettias are sold as indoor plants for the Christ­mas market in Tasmania. The poinsettias came fromtwo sources. The majority were imported from inter­state as tubed cuttings while some were struck ascuttings from local nursery stock. Large numbers of the1982/83 and 1983/84 retail consignments. showedvarying degrees of mottling in their leaves (Fig. 1). Thebracteoles were often distorted and failed to developtheir fuil red or cream colouration.

Leaf dip preparations (2% potassium phosphotung­state, pH 7) of affected leaves from both sourcesshowed high concentrations (10 virons/field, 30,OOOX)of tymovirus-Iike virions ca. 25 nm in diameter. Leaf dippreparations from apparently healthy poinsettias oftencontained low numbers of virions' (1 virion/field,30,OOOx). Ultrathin sections of chlorotic leaf tissue fixedin osmium tetroxide revealed cytological abnormalitiestypical of tymovlrus infection. The chloroplasts ofaffected ceils were often rounded and clumped andconspicuously vacuolated. Virions were seen In highconcentration in the cytoplasm of leaf parenchymaceils. Nuclei often contained paracrystals of emptyprotein sheils.

The virions in sap extracted from severely affectedleaves reacted with an antiserum to the type Isolate ofpoinsettia mosaic virus (2) in double diffusion tests inagar gels (1S0mM NaC1; 1SmM Na citrate;pH7) to formsingle preciptin bands. No bands formed under thesame conditions using sap extracted from mildlyaffected or symptomless poinsettias even though tymo-

Australasian Plant Pathology Vol. 14 No. 1 March 1985

virus-like virions were often present in these extracts. Itis possible that poinsettia cryptic virus was also presentin these extracts as Fuilton's antiserum failed to reactwith this virus (3). The poinsettia sap did not react indouble diffusion tests with an antiserum to turnip yeilowmosaic virus.

The virus was difficult to transmit. Fifteen attempts totransmit the virus from leaf and root extracts made inphosphate buffers (30-60 mM, pH 7.0 -8.0), or 30mMHEPES (pH 7.9) or half strength PBS buffer (70mMNaC1, 0.7 mM KH,PO., 4mM Na,HPO., 1.3mM KC1,1.SmM NaN3:pH7.4) only transmitted the virus to 0-10%(0-2/20) of mechanicaily inoculated Euphorbia cyettio­phore plants (2). Repeated attempts to transmit thevirus to Nicotiana benthamiana (5) failed. The virus wasnot transmitted to the following test species which havebeen used as indicators for tyrnovlruses (4): Antir­rhinum meius, Brassica peklnensis, Chenopodiumquince, Cucumis sativa, Hibiscus escutentus, Phaseolusvulgaris, Physalis ttoridene, Pisum setivum, Nicotlanaclevelandii and N. glutinosa.

This is the first report of poinsettia mosaic virusoccurring in Tasmania. The fact that the virus wasdetected in poinsettias imported from interstateindicates that it occurs in other parts of Australia.Poinsettias showing symptoms similar to those used inthe transmission. serology and electron microscopytests have recently been observed by me in Melbourneand Sydney.

The reason that potnsettla mosaic virus has not beendetected previously may be twofold. Firstly. the viruswas difficult to transmit and secondly, the virus isdifficult to detect either serologically in double diffusiontests or by standard electron microscope leaf dippreparations unless there is strong symptom develop­ment in infected plants.

Acknowledgements

I thank Ms. H.M. Blackwell, New Town ResearchLaboratories, Tasmanian Department of Agriculture forpreparing the ultrathin sections; Dr. A.J. Gibbs. VirusEcology Research Group, Research School of Bio­logical Sciences, Australian National University for theuse of antisera and facilities; and Mr. D. Symon, WaiteAgricultural Research Institute Glen Osmond, SouthAustralia for the gift of N. benthamiana seed.

References

(1) Chiko, AW. (1983)- Poinsettia mosaic virus inBritish Columbia. Plant Disease 67: 427-428.

(2) Fulton, RW. and Fulton, J.L. (1980) -- Character­ization of a Tymo-ilke virus common inpoinsettia. Phytopathology 70: 321-324.

(3) Koenig, R. and Lesemann, D.E. (1980) - Twoisometric viruses in Poinsettias. Plant Disease65: 781-784.

(4) Koenig, R. and Lesemann, D.E. (1981) - Tymo­viruses Chapter three of Handbook of plantvirus infections; Comparative Diagnosis. ed. E.Kurstak, Elsevier/North-Holland.

(S) Leseman, D.E., Koenig, R., Huth, W., Brunt, A.A..Phillips, S. and Barton, R.J. (1983) - Poinsettiamosaic virus - a tymovirus? Phytopatho­logische Zaitschrift 107: 250-262.

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