The area to be sampled was divided into five plots (Fig.1). The soil which is of tertiary sedimentary origin, isshallow and of low fertility. The surface is impervious witha whitish-grey layer 15 to 45 cm deep, overlying a heavyclay. All plots except No 5, had previously been loggedand before the first soil-sampling, the vegetation was slowgrowing and in poor condition. The dominant specieswere E. g/oboidea Blakely, E. consideniana Maiden,Angophora tloribunda (Sm) Sweet, with a shrub un­derstorey which included Banksia serrata L.t. andXanthorrhoea hastilis R.Br. The plots were sampled fourtimes between November 1972 and October 1973 (Table1), to determine the presence of P. cinnamomi. Thenumber of sampling points along predetermined surveylines varied with plot size, but the distance between them,was either 40 or 60 m. At each point, the top 16 cm of soilwas removed with a mattock and the next 10 cm (I.e. from16-26 cm) was collected. The mattock was sterilized withalcohol prior to collecting each sample.

Within 3-4 days of collecting the soil samples, they weretaken to the laboratory and baited for P. cinnamomi usingthe blue lupin (1,10) and E. sieberi cotyledons (6) techni­ques, The lupins and cotyledons were plated on 3P agar(2) and the presence of the fungus determined.

Table 1 - Frequency of detection of P. cinnamomi in soil samplescollected at different times, from Naghi State Forest, N.S.W.

Samples % of samples positivePlot No. collected Nov/Dec April August October

(Total) 1972 1973 1973 1973

1 28 40 32 36 68

2 19 63 47 53 68

3 18 88 52 83 94

4 16 87 75 81 75

5 15 80 40 53 66

The results (Table 1) show that there was a high fre­quency of detection of P. cinnamomi throughout the areasurveyed. The lowest levels of detection in all plots oc­curred in April and August, but there was a highly signifi­cant difference (P=0.01) in the level of detection betweenplots, and between times of sampling. The frequentlyrecorded high levels of isolation of the fungus couldreflect the high population or activity of P. cinnamomiunder these conditions. Alternatively, the environment insuch an ecosystem may restrict the population or activityof organisms antagonistic to P. cinnamomi or its isolation.Results of an investigation in soils similar to these (4) sup­port the latter hypothesis. Areas like the one we havestudied are neither extensive nor significant in the woodproduction of the region. They do, however, justify sur­veillance, as environmental changes might lead to an in­crease in the inoculum level of the fungus and itspathogenicity. Furthermore, the pathogen could spread tomore productive areas.

ACKNOWLEDGEMENT

We acknowledge the assistance of Mrs. Sybil Town­send during this investigation.

REFERENCES(1) Chee, K. H. and Newhook, F. J. (1965) - Improved

methods for use in studies on Phytophthora cinnamomiRands and other Phytophthora species. New ZealandJournal of Agricultural Research 8: 88-95.

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(2) Eckert, J. W. and Tsao, P. H. (1962) - A selective antibioticmedium for isolation of Phytophthora and Pythiumspecies from plant roots. Phytopathology 52: 771-777.

(3) Felton, K. C. (1972) - Eucalypt die-backs in Tasmania. Ap­pita 26: 207-208.

(4) Gerrettson-Cornell, L. (1975) - A study of the mycoflora ofa forest soil inhabited by P. cinnamomi and of their an­tagonistic relationships with this fungus in vitro. Inter­national Journal of Experimental Botany (Argentina) 33:15-21.

(5) Marks, G. C., Kassaby, F. Y. and Reynolds, S. T. (1972) ­Die-back in the mixed hardwood forests of eastern Vic­toria: a preliminary report. Australian Journal of Botany20: 141-154.

(6) Marks, G. C. and Kassaby, F. Y. (1974) - Detection of P.cinnamomi in soils. Australian Forestry 36: 198-203.

(7) Oxenham. L. and Winks, B. L. (1963) - Phytophthora rootrot of Pinus in Queensland. Queensland Journal ofAgricultural Science 20: 355-366.

(8) Pegg, K. G. and Alcorn, J. L. (1972) - Phytophthora cin­namomi in indigenous flora in southern Queensland.Search 3: 257.

(9) Podger, F. D., Doepel, R. F. and Zentmyer, G. A. (1965)­Association of P. cinnamomi with a disease of E.marginata forest in Western Australia. Plant DiseaseReporter 49: 943-947.

(10) Pratt, B. H. and Heather, W. A. (1972) - Method for rapiddifferentiation of P. cinnamomi from Phytophthoraspecies isolated from soil by lupin baiting. Transactionsof the British Mycological Society 59: 87-96.

(11) Pratt, B. H. and Heather, W. A. (1973) - The origin and dis­tribution of P. cinnamomi Rands in Australian native com­munities and the significance of its association with par­ticular plant species. Australian Journal of BiologicalSciences 26: 559-572.

(12) Weste. G. M. and Taylor, P. (1971) - The invasion of nativeforest by P. cinnamomi. 1. Brisbane Ranges, Victoria.Australian Journal of Botany 19: 281-294.

Viruses Infecting Commercial GladiolusCultivars in Queensland

Beverley Reynolds and D. S. Teakle

Department of MicrobiologyUniversity of Queensland, St. Lucia, Qld. 4067

During June and July, 1975 a survey was made of theviruses infecting commercial gladiolus cultivars on fiveproperties in the Redlands Bay district of South EastQueensland. On each property 20 plants of each of fivecultivars (if present) were selected at random and sampl­ed at or near the heading stage. Indexing for viruses wasdone by inoculating sap from each leaf sample into plantsof French bean (Phaseo/us vutqeris cv. Bountiful) andcowpea ( Vigna sinensis cv. Blackeye), using 1% K2HPO.and carborundum to aid infection.

Symptoms which developed in the test plants indicatedthe presence of three viruses; bean yellow mosaic virus(BYMV), cucumber mosaic virus (CMV), and tobaccoringspot virus (TRSV). BYMV was indicated by yellowmosaic in French bean, CMV by pin point necrotic locallesions in cowpea, and TRSV by tip blight and chloroticand necrotic ringspots in French bean and cowpea, andby hypocotyl necrosis in cowpea.

Table 1. Percentage of field infection in gladiolus, as determined by infectivity tests using Phaseolus vulgarisand Vigna sinensis

No. of plants Percentage of plants infected withCultivar sampled BYMV CMV TRSV BYMV and CMV Arty virus

Hunter's Moon 80 21 14 0 4 31

White Lass 100 14 17 0 3 28

Spic and Span 100 22 17 4 2 41

Lohengrin 100 45' 26 0 14 57*

Oscar 80 24 20 0 4 40

All five cultivars 460 25.4 18.9 0.9 5.4 39.8

, Significantly greater infection than other cultivars at (P = 0.01).

The identity of these viruses was confirmed by subse­quent studies on their host ranges, symptoms in hostplants and particle morphologies in crude and partiallypurified preparations, which agreed with those previouslydescribed for these viruses (3,4,9). The identity of TRSVwas further confirmed in tests which showed that theQueensland virus was serologically related to, but notidentical with, an isolate of TRSV obtained from gladioluscv. Spic and Span in South Australia (6). This is the firstreport of TRSV in Queensland, but BYMV and CMV havepreviously been recorded from gladiolus and other hostsin this State (7).

The results of the survey (Table 1) show that one ormore viruses were recovered from approximately 40% ofall gladiolus plants indexed, and from 57% of plants of thecultivar Lohengrin. These figures are probably lowbecause the gladiolus crops were rogued by growersbefore sampling, and because the recovery of BYMV andCMV from infected gladiolus plants was sometimeserratic. Symptoms and virus content as shown by index­ing were found to be poorly correlated.

Virus infections of gladiolus are important becauseyield is decreased, flowers showing colour break may beunsaleable and plants are predisposed to fungal attack(2,5). Furthermore, gladiolus can act as a reservoir ofviruses damaging to other crops (8). For example, TRSVcauses relatively mild symptoms in gladiolus, butproduces severe bud blight diseases of legumes such assoybeans (1) and French beans. TRSV must therefore beregarded as a potential threat in Queensland and Spicand Span gladiolus as a TRSV carrier. The affected Spicand Span gladiolus was originally brought to Queenslandin 1968 from the Mt. Gambier area of South Australia andVictoria, and further importations should be avoided.

We wish to thank Margaret McKay, Horticulture Branch,Queensland Department of Primary Industries, forassistance with the field survey.

REFERENCES(1) Allington, W. B. (1946) - Bud blight of soybean caused by

the tobacco ringspot virus. Phytopathology 36: 319-322.

(2) Beute, M. K. (1970) - Effect of virus infection on suscep­tibility to certain fungus diseases and yield of Gladiolus.Phytopathology 60: 1809-1813.

23

(3) Bos, L. (1970) - Bean yellow mosaic virus, C.M././AAB.Descriptions of Plant Viruses No. 40.

(4) Gibbs. A. J. (1970) - Cucumber mosaic virus. C.M././AA.B.Descriptions of Plant Viruses No.1.

(5) Jenkins, J. M., Milholland, R. D., Lilly, J. P. and Beute, M. K.(1970) - Commercial production of Gladiolus in NorthCarolina. Extension Circular of the North CarolinaArgricultural Experiment Station 448 (Revised).

(6) Randles, J. W. and Francki, R. I. B. (1965) - Some proper­ties of a tobacco ringspot virus isolate from SouthAustralia. Australian Journal of Biological Sciences 18:979-986.

(7) Simmonds, J. H. (1966) - Host index of plant diseases inQueensland. Department of Primary Industries,Queensland.

(8) Smith, F. F. and Brierley, P. (1961) - Ornamental plants asvirus reservoirs. Journal of Economic Entomology 54:506-508.

(9) Stace-Smith R. (1970) - Tobacco ringspot virus.C.M././AAB. Descriptions of Plant Viruses No. 17.

Control of Germination of Clavicepspha/aridis Walker, with Urea.

C. E. Nuzum

Biological and Chemical Research Institute,Department of Agriculture, Rydalmere, N.S.W. 2116.

Since 1940, small but significant quantities of asclerotial fungus have been found in samples of Pha/aristuberosa L. seed produced in Victoria and southernN.S.W. Generally the sclerotia in seed lots are present inonly small amounts, mostly less than the 1.5% allowablefor inert matter in a seed sample, but sometimes largerquantities (up to 6%) are found. They are easily detectedby visual examination, but often it is very difficult toseparate sclerotia from seed commercially as both aresimilar in size and density.

This fungus, known only from south eastern Australia,was described by Walker (1) as C. pha/aridis, but subse­quent studies (on its systemic infection) suggest it is not atrue species of C/aviceps. Investigations on the biology ofC. ,ohalaridis have shown that sclerotia are transportedwith seed and germinate to produce stalked perithecial