Verticillium albo-atrum on Ceanothus in a California Forest

T. C. HARRINGTON, Assistant Professor, Department of Botany and Plant Pathology, University of New Hampshire, Durham 03824, and F. W. COBB, JR., Professor, Department of Plant Pathology, University of California, Berkeley 94720

coastal location, as would be expected for ABSTRACT the dark mycelial form of the pathogen Harrington, T. C., and Cobb, F. W., Jr. 1984. Verticillium albo-atrum on Ceanothusin a California (8). forest. Plant Disease 68:1012. Evidently, wilt caused by V. albo-

Verticillium albo-atrum (dark mycelial type) was found to be the cause of a lethal systemic xylem atrum or V. dahliae has not been repo infection of Ceanothusintegerrimus on a relatively cool coastal forest site in an area with no history previously on Ceanothus spp. (2,6). The of cultivation. This report is apparently the first for Verticillium wilt on Ceanothusspp., the first on host range of the Ceanothus pathogen is natural forest vegetation in western North America, and only the second of V. albo-atrum in not known. In greenhouse inoculations of California. seedlings, the fungus was pathogenic on cotton but not alfalfa, indicating that the strain was distinct from that reported on and Washington (). In August 1981, dead and wilting were inoculated in March 1982. Three alfalfaExamination in Oregon of the literature indicates plants of deer brush (Ceanothus branches (with diameters of <1 cm, that V. tru isextr re in integerrimus Hook. & Arn.), a common about 1 cm, and 1-2 cm) on each plant that V. albo-atrum is extremely rarof shrub of disturbed forest sites in northern were inoculated 1-2 m above the ground. wildland forests (5,7,8). The discover California, were observed on a heavily About 0.2 ml of the conidial suspension Verticillium wilt on a native host in an logged site about 10 km inland from the (8 X 106 conidia per milliliter) was area with no known history of cultivation town of Mendocino on the northern coast introduced into a slit that was cut to a might indicate that V. albo-atrum is of California. No known agriculture has depth of about one-third the diameter of native to the relatively cool coastal forests occurred within 4 km of the site. Prior to the stem. Four control plants were of California. However, we have loo logging 5 yr earlier, the site was occupied treated similarly but injected with beyond the vicinity of the discovery primarily by Douglas-fir, redwood, distilled water. All wounds were covered without detecting the fungus in Ceanotbus tanoak, and alder. Scattered dead and with masking tape. Six-week-old seedlings or other plants. It is posssible that the wilting plants occurred throughout most of alfalfa and cotton were inoculated in pathogen was introduced on plant of the logged area (about 125 ha). Most of the greenhouse as described by Christen material; for instance, Cannabisspp. may the xylem of wilting plants showed and Peaden (1). have been grown illegally in the area. The reddish discoloration from below the susceptibility of Cannabis to the ground into the small, leaf-bearing twigs, RESULTS AND DISCUSSION Ceanothus pathogen is not known, but a suggesting that a systemic infection may The fungus fit the description of V. related crop plant, hop (Humulus lupulus have been responsible for the mortality. albo-atrum Reinke & Berth. (4). It L.), is highly susceptible to V. albo-atrum No such symptoms or disease have been formed dark mycelium but no micro- (4). reported on Ceanothus previously. Thus, sclerotia when cultured on prune-lactose stems of wilting plants were collected for agar (10), and it failed to grow at 30 C. It LITERATURE CITED isolation of the causal agent, and also formed verticillate conidiophores 1. Christen, A. A., and Peaden, R. N. I981. inoculations were made to confirm with pigmented bases on colonized stem Verticillium wilt in alfalfa. Plant Dis. 65:319.-32. 2. Engelhard, A. W. 1957. Host index of pathogenicity, segments incubated on moistened filter Verticillium albo-atrum Reinke and Berth. paper (9). (including Verticillium dahliae Kleb.). Plant Dis. On the basis of xylem discoloration in Rep. (Suppl.) 244:23-49. MATERIALS AND METHODS inoculated stems, 27 of 30 stems were 3. Gubler, W. D., Grogan, R. G., and Greathead, A species of Verticillium was con- A. S. 1978. Wilt of cucumber caused by sistently isolated from discolored xylem infected when examined 5 or 7 m after Verticillium albo-atrum in California. Plant Dis. bsety incu atingsectosofdi s uorfaexinoculation. - Xylem of inoculated stems Rep. 62:786-788. was streaked red for 5-200 cm above and 4. Hawksworth, D. L., and Talboys, P. W. 1970. sterilized stem segments on moistened 00cmblwtepitoinuain. Verticillium albo-atrum. Descriptions of filtr pperandtrasfering0-10 c beow he pintof noclaton, pathogenic fungi bacteria. No. 255. Commonw. pitroduced ond thesetansforriby conidia At the time of examination, only one Mycol. Inst., Kew, Surrey, England. 2 pp. proucdo te sctonsorbyplacing inoculated stem had died and one had 5. Hepting, G. H. 1971. Diseases offorest and shade the stem segments directly on water agar wilted. An incubation period longer than trees of the United States. U.S. Dep. Agric. plates. A conidial suspension of this 5-7 mo or root inoculations may be 6.Agric. Handb. 386. 685 pp. fugswas prepared for inoculation as 6.McCain, A. H., Raabe, R. D., and Wilhelm, S. fungscie bChitnad ean(1. required for substantial stem mortality. 1979. Plants resistant or susceptible to The fungus was readily reisolated from Verticillium wilt. Univ. Calif. Div. Agric. Sci. Ten large Ceanothbusplants growing near discolored xylem of stems. No vascular Leafi. 2703. the site where the disease was discovered dsorainwsedntnthsemof 7. Morehart, A. L., Donohue, F. M., III, and disclortiowa evdentin he tem of Melchior, G. L. 1980. Verticillium wilt of yellow control plants. poplar. Phytopathology 70:756-760. Scientific Contribution 1261 from the New Although V. dahliae Kieb. (micro- 8. Schnathorst, W. C. 1981. Life cycle and Hampshire Agricultural Experiment Station. sclerotial form) is common in California, epidemiology of Verticillium. Pages 81-111 in: partculalyn cutivted rop in arm Fungal Wilt Diseases of Plants. M. E. Mace, A. Accepted for publication 25 July 1984. patclryo utvtdcosi amA. Bell, and C. H. Beckman, eds. Academic regions, our discovery is apparently only Press, New York. Thepulialinoas f iisaricl wrederayd n an the second report of V. albo-atrum sensu 9. Smith, H. C. 1965. The morphology of by page charge payment. This article musi iherefore be stricto in this state. The first report (3) Verticillium albo-atrum, V. dahliae, and V. hereby marked "advertisement" in accordance with 18 was on glasshouse cucumbers at Salinas, tricorpus. N.Z. J. Agric. Res. 8:450-478. U.S.C. § 1734 solely to indicaie ihis fadt. 10. Talboys, P. W. 1960. A culture-medium aiding near the relatively cool Pacific Coast. the identification of Verticillium albo-atrum and @1984 The American Phytopathological Society Likewise, our discovery was in a cool V. dahliae. Plant Pathol. 9:57-58.

1012 Plant Disease/Vol. 68 No. 11