Notes and brief articleslevels in strains of Verticillium using a Coulter counter.Journal of General M icrobiology 101, 177-1180.

WILLETTS, H . J., BYRDE, R. J. W . & FIELDING, A . H.

(1977) . The taxonomy of the brown rot fungi (M oniliniaspp.) related to their extracellu lar cell wall-degradingenzymes. Journal 0/ General Microbiology 103 , 77-83.

FUSARIUM EQUISETI PATHOGENIC TO PINE

BY Z. SOLEL*, G. B. RUNION AND R. I. BRUCK

Department of Plant Pathology, North Carolina State University, Raleigh,North Carolina 27695-7616, U .S.A.

Fusarium equiseti isolated from a dead branch of loblolly pine caused a grey lesion andepinasty of the apex when inoculated on wounded young seedlings. On older seedlings aslight lesion developed on stems, but no wilt occurred.

Shoot dieback is a common symptom of pitchcanker of loblolly pine (Pinus taeda L.) caused byFusarium moniliforme Sheldon var. subglutinansWollenw. & Reink. (syn. F. subglutinans (Woll-enw. & Reinking) Nelson, Toussoun & Marasas)(Dwinell, Barrows-Broaddus & Kuhlman, 1985;Kuhlman et al., 1978). While collecting thispathogen from 4-year-old loblolly pines growing inNorth Carolina, one shoot yielded a different speciesof Fusarium subsequently identified (P . E . Nelson,pers. comm.) as F. equiseti (Corda) Sacco On potatodextrose agar (PD A) the colony first developedwhite dense aerial mycelium, which later becamelight tan ; the underside was pigmented darker tan.Radial growth at 25 °C was rapid, t6 mm days -I,compared with 8'3 mm days:" of F. moniliformevar. subglutinans, In r-week-old cultures, singlephialides produced abundant sickle-shaped macro-conidia with distinctly foot-shaped basal cells. Inz-week-old cultures, globose, thick-walled chlamy-dospores were observed singly and in chains orclumps. F. equiseti is common in soils of temperateregions and is predominantly a root pathogen(Booth, 1971; Joffe & Palti, 1969). It has beenisolated from diseased nursery-grown pine seed-lings (Bloomberg, 1981), and from diseased pinecrowns (D eL ucca et al., 1982; Kuhlman et al.,1978 ), but was not strongly pathogenic (K uhlmanet al., 1978).

The pathogenicity of a single-conidial culture ofthe F. equiseti isolate was studied. After 10 daysgrowth on PDA at 25°, conidia were washed fromculture plates with sterile water, filtered throughcheesecloth, and the concentration of spores wasadjusted to 106 conidia ml - I. The inoculum, a drop-let of approx. lOlli, was injected through a tiny and

* Present address: Department of Plant Pathology,Agricultural Research Organization, The Volcani Center,Bet Dagan, Israel.

shallow wound into the stem of 5-month-old andi -year-old loblolly pine seedlings, half-sib family8-68 unless otherwise stated, using a hypodermicsyringe. The plants were maintained in a green-house at 20-26°. On 5-month-old seedlings, inocu-lated 4-5 cm below the apex, disease symptomswere apparent after 3 days. An 8-10 mm long greylesion was formed at the point of inoculation, andthe upper part of the stem became epinastic. Thesymptoms resemble those of pitch canker, but lackthe purple discoloration of the F. moniliforme var.subglutinans lesion, and develop in half the time.On i -year-old seedlings, inoculated in the mainstem or lateral shoots, a restricted lesion, extendingto 6-12 mm at the point of inoculation, slightlysunken and with light discoloration, became ap par-ent after 3 weeks. Hi stological examination of crosssections revealed mycelium in the cortex, xylemand pith. Some resin accumulated adjacent to thepoint of inoculation on inoculated and water controlseedlings. There was no wilt of shoots, whichfrequently occurs with infection by F . moniliformevar. subglutinans. Placing an inoculum dropletwithout wounding the stem, or inoculating withsterile water, did not cause any disease symptoms.

Pathogenicity of cultures maintained on PDA at4° was reassessed after 6 months. Aggressivenesswas considerably reduced. No infection occurredon i -year-old seedlings, and infection of y-month-old seedlings took longer, 2-3 weeks, to becomeapparent. Isolates from those stems were no moreaggressive. Inoculation of young stems of half-sibfamily 8-61 was frequently negative, thus con-firming the relative resistance of this family to F .moniliforme var. subglutinans (unp ub l.) .

Our study demonstrated that a strain of F.equiseti, when entering through a wound, ispathogenic to loblolly pine. It is, however, unlikelyto be a threat to pine stands, due to it s lowinfectivity to mature stem or branches.

Trans. Br. mycol. Soc. 91 (3), (1988) Pr im ed in Great Britain

Notes and brief articles 537Paper No. 11451 of the Journal Series of the

North Carolina Agricultural Research Service,Raleigh, North Carolina.

REFERENCES

BLOOMBERG, W. J. (1981). Disease caused by Fusarium inforest nurseries. In Fusarium: Disease, Biology, andTaxonomy (ed. P. E. Nelson, T. A. Toussoun & R. J.Cook), pp. 178-187. Pennsylvania, U.S.A.: The Penn-sylvania State Universtity Press.

BOOTH, C. (1971). The Genus Fusarium. Kew: CABInternational Mycological Institute.

DELUCCA, A. J., DUNN, J. J., CIEGLER, A. & KUHLMAN,E. G. (1982). The inability of Fusarium species extractsto induce dieback in pines. Mycopathologia 7fJ, 105-108.

DWINELL, L. D., BARROWs-BROADDUS, J. B. & KUHLMAN,E. G. (1985). Pitch canker: A disease complex. PlantDisease 69, 270-276.

JOFFE, A. Z. & PALTI, J. (1969). Fusarium equiseti (Cda)Sacco in Israel. Israel Journal of Botany 16, 1-16.

KUHLMAN, E. G., DWINELL, L. D., NELSON, P. E. &BOOTH, C. (1978). Characterization of the Fusariumcausing pitch canker of southern pines. Mycologia 70,113 1-1143.

PECTINOLYTIC ACTIVITY IN SOME ERICOID MYCORRHIZAL FUNGI

BY F. CERVONE AND R. CASTORIA

Dipartimento di Biologia Vegetale dell' Uniuersita di Roma 'La Sapienza', 00185 Roma, Italy

P. SPANU AND P. BONFANTE-FASOLO

Centro di Studio sulla Micologia del Terreno del CNR and Dipartimento di Biologia Vegetaledell'Uniuersita di Torino, Italy

Some mycorrhizal fungi isolated from ericoid mycorrhizas and related to the speciesHymenoscyphus ericae produce pectinolytic enzymes identified as polygalacturonases (PG). Acomparative analysis between the in vitro enzyme synthesis by the mycorrhizal fungi andthat shown by some phytopathogenic fungi demonstrates that PG activity of the latter was atleast 30 times higher than that of the symbiont fungi. The results are discussed in relation tothe differences between pathogenic and symbiotic fungi.

Phytopathogenic fungi attack and colonize hostplants by producing cell wall degrading enzymes.Polygalacturonase (PG), the first hydrolyticenzyme produced by many pathogens, not onlydisorganizes the plant cell wall allowing fungalcolonization but also releases from the host cellwall oligosaccharides that elicit plant defencemechanisms such as synthesis of phytoalexinsand hypersensitive necrosis (Lee & West, 1981;Cervone et al., 1987).

Mycorrhizal fungi are also expected to synthesizea certain amount of pectinolytic enzymes. In factthey colonize plant cells by partly dissolving themiddle lamella as many cytological observationssuggest (Bonfante-Fasolo, 1984; Bonfante-Fasolo& Gianinazzi-Pearson, 1982). Moreover someectomycorrhizal and ericoid fungi are capable ofutilizing pectic polymers as a carbon source (Lyr,1963; Ritter, 1964; Lamb, 1974; Pearson & Read,1975; Lindeberg & Lindeberg, 1977) and some ofthem have been shown to produce pectinolyticactivity (Nieuwdorp, 1969).

This brief article supports the hypothesis of cellwall degrading enzyme production by mycorrhizalfungi. We report that some ericoid mycorrhizal

fungi produce pectinolytic activity and comparethe in vitro enzyme synthesis of these strains withthat of some phytopathogenic fungi.

Four different mycorrhizal fungi isolated fromericoid mycorrhizas and related to the species Hy-menoscyphus ericae (Read) Korf & Kernan (syn.Pezizella ericae Read) (Table 1) and three phyto-pathogenic fungi (Fusarium moniliforme Sheld.,Rhizoetonia fragariae Husain & McKeen andRhizoctonia solani Kuhn) were used. All fungi werecultured at 25°C in Czapek-Dox broth mediumcontaining 1 % pectin (Sigma Chern. Co., U.S.A.)as a sole carbon source.

Fungal culture filtrates were dialysed at 4°overnight against distilled water and pectinolyticactivity was determined by measuring the decreasein relative viscosity of a 0'6 % (w Iv) solution ofsodium polypectate (NBC Corp., U.S.A.) in 50mM sodium acetate buffer, pH 5'0, in Cannon-Fenske no. 300 viscometers, at 30°. One relativeviscometric unit (RVU) was defined as the amountof enzyme causing a 50 % reduction in the viscosityof 6 ml of the reaction mixture in 1 min. Theproducts formed by the action of the enzymeon sodium polypectate were examined by the

Trans. Br. mycol. Soc. 91 (3), (1988) Printed in Great Britain