51(7)'69 183～187

論 文 A Needle Blight of Taxodium distichum RICH. caused by Cercospora sequoiae ELLIS et EVERHART*

Yoshiyuki ZINNO**

Cercospora sequoiaeに よ る ラ ク ウ シ ョ ウ の 赤 枯 病*

陳 野 好 之**

要 旨: 1967年 の 秋 に,高 知 県 下 で 発 見 さ れ た ラ ク ウ シ ョウ(Taxodium distichum RICH.)の 葉 枯 性 病 害 に つ い て,そ の 病 徴,病 原 菌 の 形 態 お よ び 病 原 性 な ど を 調 査 し た 。 被害葉に形成された菌の子実体および数種の培地上における培養上の性質はスギの赤枯 病 菌, Cercospora sequoiae ELLIS et EVERHARTの そ れ に 一 致 し た 。 本 菌 お よ び ス ギ 赤 枯 病 の 被 害 葉 か ら分 離 さ れ たC. segaiaiaeの 菌 株 を 用 い て,ス ギ お よ び ラ ク ウ シ ョウ に 交 互 接 種 を 行 な っ た 結 果,両 菌 株 と も ス ギ,ラ ク ウ シ ョ ウ に 対 し て 明 ら か な 病 原 性 を 示 し た 。 し か し,い ず れ も ス ギ に 対 し て は 強 い 病 原 性 を 示 し た が,ラ ク ウ シ ョ ウ に 対 し て は 比 較 的 微 弱 で あ っ た 。 ま た,ス ギ 上 で の 病 徴 は ス ギ 赤 枯 病 菌 に よ る病 徴 と 全 く 一 致 し た 。 これ らの 結 果 か ら,筆 者 が 観 察 した ラ ク ウ シ ョ ウ の 葉 枯 性 病 害 はCercospora sequaiae ELLIs et EVERAARTに よ っ て 起 こ さ れ た こ と が 明 ら か で あ る 。 ー 方,本 菌 が ラ ク ウ シ ョ ウ に 寄 生 す る と の 報 告 は み あ た ら な い の で,本 病 を ラ ク ウ シ ョウ の 新 病 害 赤 枯 病 と し て 記 載 し た 。

Summary: A needle blight disease of Bald cypress, Taxodium distichum RICH., caused by a Cercospora was observed in the fall of 1967 in Kochi Prefecture, Shikoku District of Japan. No record has been found on the needle disease of Taxodium, so the symptoms of the disease, morphology and pathogenicity of the causal pathogen were examined. Morphologic characters of the fruiting bodies and appearances of mycelial colony of the fungus on several kinds of media were very similar to Cercospora sequoiae ELLIS et EVERHART which has been known as the causal pathogen of the needle blight and canker of Japanese cedar, Cryptomeria japonica D. DON, in Japan. Cross inoculations with the isolates from the blighted needle of Taxodium distichum and Cryptomeria japonica were performed to Taxodium and Cryptomeria-seedlings, respec tively. Infections with two isolates to the seedlings of both tree species were successful, and typical conidia of the fungus were produced on lesions of all affected seedlings. Intensity of the disease was heavier on Cryptomeria japonica than on Taxodium distichum. Symptoms on the needles of Cryptomeria japonica and of Taxodium distichum attacked by the isolate from Taxodium distichum were very similar to those attacked by Cercospora sequoiae from Cryptomeria japonica. From the results of the observations and experiments, the author came to the conclu sion that the needle blight disease of Taxodium distichum is caused by Cercospora sequoiae ELL. et Ev., and that Taxodium distichum is a new host of the fungus.

Experiment Station, Kochi, Japan. The fungus Introduction produced on the lesions of the affected needles was In mid-October 1967, the author observed that very similar to Cercospora sequoiae ELL. et Ev. about 6-year-old Bald cypress, Taxodium distichum (syn. C. cryptomeriae SHIRAI) described by KITA RICH., was affected distinctly by a needle blight JIMA2), SAWADA2), ITO et al.3-5) as a pathogen fungus in the arboretum of Kochi Prefecture Forest causing blight and canker of Japanese cedar, Cryp * A part of this paper was submitted at the 80th annual meeting of the Japanese Forestry Society held on April 4, 1969. ** Shikoku Branch, Gov. For. Exp. Sta., Kochi農 林 省 林 業 試 験 場 四 国 支 場 184 日林誌

tomeria japonica D. DON, in Japan. The needle blight disease of Taxodium distichum caused by Cercospora has not been reported. This paper presents morphology and pathogenicity of the Cercospora on Taxodium through the compa rative study with Cercospora sequoiae ELL. et Ev. on Cryptomeria. The author wishes to express his special appre ciation to Dr. Osamu CHIBA, Head of Forest Disease Section, and to Dr. Takao KOBAYASHI, Chief of Laboratory of Forest Pathology, of the Government Forest Experiment Station, for their helpful sugges tions given during the study. He is also indebted to Mr. Hideaki NISHIMURA,Kochi Prefecture Forest Experiment Station, for his kind assistance in the field work.

Symptoms of the disease Symptoms of the disease began to appear on the needles in late July and a typical symptom was observed in mid-September. The disease was ob served more severely on the needles of the lower Photo 2. Blighted needles of T. distichum severely attacked by C. sequoiae ELLIS et EV. part than the upper part of the branches. Symp toms on naturally affected needles are summarized as follows:

Photo 1. Taxodium distichum attacked by Cercospora sequoiae ELLIS et EV.

Lesions appear at first as small, irregular, yellowish to pale-brown spots on the needles, and then the spots become larger and brownish, usually extending nearly the entire length of the needles. In the case of severe infection, the affected needles are curled Fig. 1. Conidia and conidiophores of Cercospora and frequently defoliated, and the disease occurs sequoiae ELLIS et EV. on the needle of Taxo not only on the needles but also on the green cur dium distichum 51(7)'69 185

rent year's shoots, resulting in the death of many end, often slightly constricted at the septum, 39 •` 88ƒÊ•~5-7.5ƒÊ (Fig. 1, Photo 3 and 4). young twigs. On the lesions formed on both sur faces of the needle, a number of small dark, greenish Host: Taxodium distichum RICH. (Numasugi), Kochi fruit-bodies of the fungus are produced. Prefecture, October 17, 1967, by Y. ZINNO. The morphologic characteristics of the fungus, in Morphology of the fungus respect to the size, as well as shape and color, of

Stroma amphigenous, densely scattered, dark conidia and conidiophores, are quite identical with brown to black; conidiophores light yellowish brown Cercospora sequoiae ELL. et EV. causing needle blight to brown, straight or slightly curved, pale and nar of Cryptomeria japonica in Japan described by rower toward the apex, 1•`2-septate, not branched, KITAJIMA1), SAWADA2), ITO et al.3•`5), as shown in 31•`88ƒÊ•~4-5ƒÊ; conidia light yellowish brown to Table 1. olivaceous, clavate or cylindric, straight or slightly curved, echinulate, 3•`10-septate, rounded at the Mycelial growth of the fungus

Macroscopic appearance of the fungous colony: Mono-conidial isolates from Taxodium distichum and

Cryptomeria japonica were cultured on potato-sucrose -agar at 25•Ž. Colonies grew slowly and were pale

yellowish green, then they turned to dark green and elevated from the surface of agar with white aerial mycelia in central part.

Photo 3. Conidiophores of C. sequoiae ELLIS et EV. on blighted needle of T. distichum Photo 5. Mycelial colonies of Cercospora sequoiae ELLIS et EV. on potato-sucrose-agar

(after 25 days) left: Isolate from T. distichum right: Isolate from C. japonica

Mycelial growth of the fungus: Two isolates mentioned above were cultured on the four kinds

of the solution media, namely potato-sucrose solu tion, SAITO's soy solution, CZAPEK's solution and Cryptomeria-needle decoction. Mycelia cultured at

25•Ž for 14 days with shaker were washed and dried. Dry weight of the mycelia was measured. Results

of the experiment are presented in Table 2. As shown in Table 2, there is no remarkable diffe rence between the mycelial growth of the Cercospora Pnoto 4. Conidia of C. sequoiae ELLIS et EV. from Taxodium and that of Cercospora sequoiae from on blighted needle of T. distichum Cryptomeria.

Table 1. Comparison in the morphology between Cercosporae on Taxodium and on Cryptomeria 186 日林誌

Table 2. Mycelial growth of Cercosporae isolated from Taxodium and from Cryptomeria ( g)

Table 3. Cross inoculations with Cercosporae to Taxodium distichum and to Cryptomeria japonica seedlings

*: Cuttings a): Inoculation was made in May , 1968. b): Inoculation was made in October, 1968. Degree of damage: +, very slight ++, moderate +++, heavy

one month after inoculation, and at the end of the Inoculation experiment experiment, about 50 days after inoculation, the In order to make clear the pathogenicity of the typical conidia of Cercospora sequoiae were produced Cercospora to Taxodium distichum and to Cryptomeria on the lesion of infected needles of both tree species. japonica in comparison with Cercospiora sequoiae, some Experiment 2 inoculation experiments were undertaken. Material and method: The experiment was set Experiment 1 up to see the difference in the susceptibility of both Material and method: Mono-conidial isolates from tree species under field conditions at the arboretum Taxodium distichum and from Cryptomeria japonica of Kochi Prefecture Forest Experiment Station. On were cultured on potato-sucrose-agar at 25•Ž for August 20, 1968, several pots with healthy 2-year about 10 days. The cultured mycelia were crushed old seedlings of Taxodium distichum and Cryptomeria in sterile water, and filtered through a sheet of japonica were placed under the affected T. distichum cotton cloth. Mycelial suspensions were sprayed on trees. About 50 days after exposure, degree of in 2-year-old seedlings of Taxodium and Cryptomeria, fection was observed. and on cuttings of Taxodium. The inoculated plants Result: As shown in Table 4, all tested seedlings were kept in a humid chamber covered with poly were severely affected. The degree of infection was ethylen bag at 25-27•Ž for 4 days. The check plants were sprayed with sterile water instead of the fun Table 4. Result of natural infection of Taxodium gous suspensions. and Cryptomeria-seedlings placed underneath Result: As shown in Table 3, it is clear that the the diseased trees of T. distichum isolate from Taxodium as well as the isolate from Cryptomeria is able to cause the needle blight of Taxodium distichum and Cryptomeria japonica.

However, the intensity of the disease was heavier on Cryptomeria japonica than on Taxodium distichum.

The first appearance of the symptom occurred about *+, slight ++, moderate +++, heavy 51(7)'69 187

more distinctive on Cryptomeria japonica than on Cercospora sequoiae was pathogenic to Cryptomeria

Taxodium distichum. This result accords with that japonica, Chamaecyparis pisifera and C. oblusa. As obtained in the experiment 1. Symptoms on the no other record has been found on the host range needles of Cryptomeria japonica are very similar to of Cercospora sequoiae, Taxodium distichum RICH, is those of the blight caused by Cercospora sequoiae. considered to .be a new host of C. sequoiae.

Conclusion Literature cited From the results mentioned above, the author 1) KITAJIMA, K.: On the red-plague of "Sugi" came to the conclusion that the needle blight fungus seedlings (in Japanese). Bot. Mag. Tokyo 30: of Taxodium distichum is identified as Cercospora 411•`414, 1916 sequoiae ELL. et EV. (syn. C. cryptomeriae SHIRAI) 2) SAWADA, K.: Fungi inhabiting on conifers in which has been known as the most virulent pathogen the Tohoku District I. Fungi on "Sugi" (Crypto of the needle blight and canker of Cryptomeria japo meria japonica D. DON). Bull. Gov. For. Exp. nica in Japan. Sta. 45: 27•`53, 1950 In Japan, the fungus was first described by KITA 3) ITO, K., SHIBUKAWA, K. & KOBAYASHI, T.: JIMA1) under the name of Cercospora cryptomeriae Etiological and pathological studies on the needle SHIRAI as a pathogen of the needle blight of Cryp blight of Cryptomeria japonica I. Morphology tomeria japonica seedlings. ITO et al.3,4) confirmed and pathogenicity of the fungi inhabiting the through inoculation experiments that it was a most blighted needles. Bull. Gov. For. Exp. Sta. 52: important pathogen causing needle blight and canker 79•`152, 1952 of Cryptomeria japonica, and that the severe blight 4) •\,•\,•\: Blight of Sequoia disease of Sequoiadendron giganteum BUCHH. observed gigantea seedlings caused by Cercospora crypto in many forest nurseries in Japan was also attributed meriae SHIRAI (in Japanese). J. Jap. For. Soc. to Cercospora cryptomeriae SHIRAI. 40: 407•`410, 1958 Recently, from the results of a comparative study 5) •\, KOBAYASHI, T. & SHIBUKAWA, K.:•@ between Cercospora cryptomeriae SHIRAI and C. Etiological and pathological studies on the needle•@ sequoiae ELL. et EV. which was described by ELLIS blight of Cryptomeria japonica III. A comparison•@ and EVERHART6)as a pathogen inhabiting Sequoia between Cercospora cryptomeriae SHIRAI and•@ dendron giganteum in North America, ITO et al.5) Cercospora sequoiae ELLIS et EVERHART. Bull.•@ demonstrated that Cercospora cryptomeriae SHIRAI Gov. For. Exp. Sta. 204: 73•`90, 1967 was synonymous with C. sequoiae ELL. et EV. 6) ELLIS, J. B. & EVERHART, B. M.: Additions to On the other hand, HODGES7)noted the following Cercospora, Gloeosporium and Cylindrosporium. tree species as the hosts of Cercospora sequoiae: J. Mycol. 3: 13•`22, 1887 Sequoiadendron giganteum, Thuja orientalis, Cupressus 7) HODGES, C. S.: Comparison of four similar fungi arizonica, C. lusitanica, C. macrocarpa, C. semper from Juniperus and related conifers. Mycol. 54: virens, Juniperus verginiana, and Chamaeeyparis 62•`69, 1962 pisifera. In 1967, ITO et a1.5) reported through (Received April 8, 1969) their inoculation experiments on some conifers that