Miyake, Chuichi

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Gibberella Saubt"netz.i (Mont.) Sacc. as a Causal Fungus 。fthe Wi1t-disease of Horse-bean. with Plate XIV-XV. By Chuichi Miyake. [July 1， 19:.13] 1. Introduc世on.It was in June 1919. that a wilt-disease in the Horse-bean (Vt'cia Faba L. var. equina Pers.)自凶 cameunder the notice of the author， ata time when the crop was just ready for harvest. In the previous year， inKurashiki， this disease haa caused considerable damage to this plant， reducing the produc-tion of bean by a large戸rcentage. 5ince that date the writer has been pay-ing special attention to this matter， inorder to ascertain the exact cause of the disease; and the following kinds of fungus were found to be associated with it. 1) Plwma sp. 2) Mact'ophoma sp. 3) R.必eoctoniasp. 4) Penicillium sp. 5) Bot:ηItis sp. 6) Sclerotinia sp. 7) Sclerotium sp. (2 kinds) 8) Fusari・umsp.・9) Gibberella Saubinfti・'i(Mont.) 5acc. Among these fungi Gibberella Saubinetii (Mont.) 5acc. seems to the writer， to play the most important role in producing the disease. Through the at-tack of this fungus， the Horse-beans， when they are ful grown and reaay to be picked， gradually wilt， or lose their leaves.. The ripenrung of the pods is checked， and it hap戸nsthat the whole plant completely withers away with町 riousresults to the bean crop. 50 far as the writer Is aware， there exists no extended experiment on the Gibberella-disease of the Horse-bean; hence it is thought worth while to put this paper into publication. F. L. 5TEVENS.) reports from America that the conidial stage of G. Sau-binetii causes dise白esin clover and alfalfa， toth hosts belonging to the 436 C. MIYAKE: Leguminosae. The Horse-bean is also a member of the same family. Through the cultural and infection ex戸rimentsmade by him， it was demon-strated that the fungus which attacks clover is identical with that found on wheat， barley， rye， spelt， emmer and oats. O. KIRCHNERS) makes very short mention of G. Saubinetii in his handbook， saying that it attacks Vi'cia Faba 1. It appears to the pre民 ntwriter， that this statement of KIRCHNF.R is the only statement upon the Gibberella diseぉeof the Horse-beaa that h田 sofar been made in other countries.' 2. Symptoms of the disease. This disease occurs， inlate spring， upon Horse-beans which have been planted in fields where rice was planted under irrigation in the previous year. The writer has never observed the host plant， when planted in dry soil， tosuffer from this disease. The symptoms are various， but generally speaking the diseased plants develop slender， the戸dsproduced are always few in number and smaller 出anusual. When the plant is almost at the ripe stage， inthe middle of May， ifthe weather is moist， this disease makes its appearance in such a way as to attract our attention. The fungus appears in the basal part of the stem， from ground surface upward to a limit of 2 or 3 inches; and in the a能ctedpart， the reddish growth of fungus mycelium is always to be noticed. By this time whole plant tends to wilt; the leaves droop and hang down; the majority of the pods wither and somc blackish s戸cksappear upon them; while the beans themselves are covered with brownish spots. The rootlets， being attacked in the early戸riodof the disease， are com-pletely destroyed sooner or later， and it is very easy to pull out the diseas-ed plants as only the main root is left. The lower a能ctedparts of the stem are blackish in color， and the cortex of that portion is entirely destroyed. In this portion minute black peri由民ia，sometimes singly but generally in groups， are easily found with the unaided eye. 3. Predioposition. Surrounding conditions seem to have an important bearing on the oc-curr.ence of the disease. This disease often appears after a long spell of wet W白 ther，.when the water-content of the soil is high， without regard to other soil conditions. In Kurashiki and its neighbourhood the underground water σUJbtrt//a. Saubinttii (M∞t.) Sacc. as a Ca凶 a1Fungus of the Wilt-disease of Horse-bean. 437 is rather high and precipitation is often abundant. The following figures are shown to indicate the precipitation amount during from March ti1 June， since 1918 tm 1923・Freq国 ncy Amount Remarks 町I.m.1918 唱4 496.3 Disease very beavy. 1919 34 400.9 " rare. 19:Z0 44 。68 " comparative1y heavy. 1921 47 642.3 " very heav}'、1922 30 305.5 " rare. 19:Z3 44 688.6 " very heavy. 4. Morphology of the causal fungus. A) Coniほ'ialstage. Fusarium graminearum SCHWARBE is the name given to the conidial stage of this fungus. The ascospores develop very easi1y on many artificial or natural substrata. After they have been cultured for a few days， many tufts of aerial mycelium are produced. Aerial mycelium is septate， branched， and hyaline， but becomes staind afterwards to a pinkish， brownish， or yel10wish tint. Conidia are borne on conidiophores which branch out of mycelium. Conidia are sickle shaped， hyaline in color， curved to one side， and so for-ming a dorsi-ventral distinction， broadesl in the part immediately above the middle， then gradual1y tapering towards both ends. At the ba坦 1end of conidia a rudimentary pedicel is visible. Dimensions of conidia are 26-51 X3・7-5μ，the average being 34・7X4・5μ. The number of septum is 3 -5， in majority of cases being 3， and in rare cases 6. B) Pe:γ~'tlucial s.拘'ge.Many minute blackish perithecia are produced， ra陀Iysingly but com-monly in aggregations， on the basal stem part of the diseased plant. As viewed with the naked eye the surface is seen to be rough and when ob-served under the rnicrosco戸 itap戸arsjagged and irregular. The cel1s com-posing outer part of the perithecium are thick walled and have a beatiful bluish or inky-black color. The shape of perithecia is spherical or egg-form， and provided with an ostiolum on the up戸rpart， and measure 60 -280 X 50-250 p， the average being 198 X 172μ. Those produced in cultures on rice extract agar measured 95 -330 X95 -310 p， the average being 228 X 195・5p. Ascus is hyaline， (but if gathered together is of a pale brownish color，) cluトsha戸d，a litle swol1en at the attaching basal part， perishes easi1y， containing 438 C. MIYAKE: eight ascospores arranged in two oblique rows， 55-1∞?< 10--15μlarge， averaging 79.8 X 12μ. Ascospores are hyaline， curved， fusiform， obtuse at both ends， 3-septate， eonstr允tedat septum， and small~r or larger oi1 globules are found while young; dimensions are 17 -28 X 3.8-5.6μ， the average of 600 spores which were obtained from the natural host v分iaFaoa， being 22・4X4.5μj while those from perithecia， produced on rice extract agar， have somewhat larger dimensions being 21・5-36x4-6.2μjthe average of 1∞ spores being 25.9 X4・9μ.Ascospores germinate easily in disti1led water at the room temperature in middle of June， the germ-tube reached 15-30μwithin 6 hours. ln ge-neral， germination takes place from one of the terminal cells of the spor~， and when a germ-tube is thus elongated and branched， the other cel1 sends out another. ParaphySes of rather peculiar shape and inconspicuous are found standing among the asci. They are very flexible; broken bits are often ob-served， while perfect ones are very rarely found. Paraphyses are composed of several ovoid cel1s， and are very deeply constricred at the舘 ptum. The民cells are various， the larger ones measuring 35 X 24μ， while the smaller measure 10 X 11μ. Both larger and smaller cells， are arranged straight ir-regularly， the basal cell being smaller than the others and club-shaped. The length of paraphyses is difficult to measure as they are easily broken as men-tioned above， however there are many which are a litle longer than the ascus. Under higher magnification of the microscope the paraphyses are difi-cult to see， whereas on the contra庁 under3∞-400 magnification they are easi1y observed. 5. C叫.tur叫 cbarac旬，rs.The materials used for this study were those collected on June 20， 1919 from a Horse-bean field in Otakamura， a vi1lage near Kurashiki. A single ぉcosporewas used in the starting culture. Mycelial growth from this iso-lation culture was taken， and transplanted upon the following substrata， and the results obtained thereby will be briefly given. 1) Rice extract agar. Test-tube cultures in a thermostat of 30oC. (Rice-stem 2∞gr， agar 18 gr， distiled water 10∞c.). Growth was vigorous， provided with long white aerial mycelium. Con・idia were produced after 5 days， and after 2 weeks white knots of mycelium were found in or near the surface of the substratum. These knots become larger and numerous after 3 weeks. They are stroma for the perithecia. The diameter of the colony at the end of 5 days averaged 62 --65 mm， and the Gi66erel/a Sauouutii (Mont・)Sac. as a Caulal Fungu8 of the Wilt.disease of Horse-bean. 439 coloration at the same戸riodof grow出 wasrosy-red. The coloration varied in density and time of appearance. 2) Polato-exlracl agar. Tube-cultures in a thermostat of 30oC. (Raw Jeaves of potato 200 gr， agar 20 gr， water 1000 cc.) A flourishing development of aerial mycelium was observed， the growing tip of mycelium was round and smooth. Conidial production was also nor-mal. The growth after one week measured 51.1 mm， being a litle inferior when ・comparedwith the 64・5mm. of experiment No. I. Many white knots were found， just as in the first experiment. 3訪) Pol，μaμto-s.功，/，~幻.After 2 days dense myc句elia叫1growt出hdeveloped. Rosy coloration ap-peared， and diameter of the growth reached 40 mm. in 3 days， and after 5 days， the central part of the colonies became grayish， the other parts being Cameo Pink， and when observed from outer bottom side of the dish-cultures， these parts appeared Pomegranate purple. No conidial formation was noticed. 4) Steamed potato slem. ln the test-tubes in a thermostat of 25-280C. Growth was vigorous in the second day， and after 3 days diameter of the growth reached 23-30 mm. White aerial mycelium grew conspicuous-ly， but no conidia were found. The whole surface of the substratum was completeJy covered with mycelium after 4 days. The characteristic Crimson color appeared after 8 days， and in 2 weeks white knots were observed. By this teriod of time， conidial production occurred normally， yet there was no trace of the production of perithecia. 5) Horse-bean slem. ln the test-tubes in a thermostat of 25-280C. After 3 days development took place， and grow出 reachedto 90 mm. in diameter in 2 weeks. However， development was found to be not vigorous. White knots were produced after 3 weeks and rosy color began to be denser by this period of time. A number of perithecia was produced. 6) Sleamco n"ce grain. In Petri-dishes at room temperatu問 inthe end of September. Growth diameter was 60 mm. after 3 days， and the central portien of the colony was yellowish， while white aerial mycelium bordering the margin. By the 4th-day the mycelium had completely ct>vered the whoJe surface of the substratum in the dishes， and rosy coloration appeared. On the fifth day few conidia were found and the intensity of the rosy coloration became deeper and deeper. Conidia were produced in small numbers only and no perithecia have developed. 440 C. MIYAKE: 7) Glucose (5%) agaκTest-tube cultures at r∞m temperature in August. Upon this substratum the fungus behaved almost in the same way as in the case of the rice-extract agar， the only difference lying in the greater depth of rosy color il favour of this case. The color， by reflected Iight corresponded to Victoria lake， and Carmine or Ox-blood Red by transmitted light. A large number of perithecia was produced， upon this substratum. 8) Steamed Horse-bean. In the test-tubes at the constant tem戸ratureof 25-280C. Vigorous growth was obtained， the beans being comple旬Iycovered by aerial mycelium which was found fully∞cupying the inner portion of the seed coat i and it was also well developed on the surface of the water which re・mained at the bottom of the tubes. The characteristic deep carmine coloration develo戸din the part of my-celial growth that lay over the water， and conidial production was observed. Stil no perithecia were formed. As has been described above， the formation o( conidia and perithecia was rather rare， or even lacking， inseveral kinds of the cultural substrata used. Even when both conidia and perithecia were formed they were few in number. Perithecial formation was not obtained at a1 on steamed rice grains， potato slices and potato-stems in our experiments. 6. Development in relation to temperature. After few trials having been attempted to ascertain tbis relation， itwas found that the dimensions of the colonies， after 5 days， averaged 44・Smm at 30oC; 27・9mm at 15 oC; and 6.29 mm at 50C. The average maximum air temperature of every March in the 6 years since 1918 til 1923 is 12-160Ci that of April 18ー 190C，that of May 21-2SoC i and that of June 25 -300C. FJom these facts it is thought the optimum temperature for the growth .of this fungus lies between 2S-30oC. And as it makes daily de-velopment of 1.26 mm at SOC， a stil lower temperature seems not to check the growth. The respective minimum temperatures during the four months， from March to June， of these 6 years are 1・34-3.80Cin March; 6.2-7.40C in April; IO.5-I4.loC in May; and I7.6-18.2oC in June. From these data it is obvious that the lower air tem戸raturein the middle or end of March does not hinder the development of this fungus in any way， ifthe other con-ditions are favorable. σ必'kn/laSauTine必・(Mont・)5蹴.回a白山a1FUDguS oC tbe Wilt.di蜘 seoC Horse・bean. 441 7. Summary. 1) The wilt.disease of Horse-bean (Vicia Faba L. var. equina Pers.). in Oka-yama， a district of western Japan， isfound to be caused by a number of fungi such as Phoma， Rhizoctonia， Penicillium， Botrytis， Sclerotinia， Sclero・tium， and Gibberella Saubinetii (Mont.) Sacc. Among these the last named species [Giboerella Saubinetii (Mont.) Sacc.J is t.he most prevalent cause of the disease. 2) The general morphological characters of Gωerella Saゆineti(Mont.) Sacc. as observed upon the host plant， and its cultural results have been des-cribed. 3) The optimum tem戸raturefor the growth of this fungus in cultur白 seemsto lie near 3ooC， but even at 50C a growth of 1.26 mm per day does occur. By compering this optimum with the a釘nospherict~mperature of this district of Japan， the air temperature of J une s町 msto be adeq uatly fitted for the development of this fungus. 4) An unusually heavy precipitation and higher underground water furnish the two important predisposing factors in the appearance of this disease. Acknowledgment. Here 1 wish to express my hearty thanks to Dr. M. KASAI of this In-stitute， who had the kindness to aid me in the preparation of this paper. Sincere thanks are also due to Mr. Y. NISIKADO for his constant guidance. Literature cited. 1) ELUS， J.B. & EVEllHART， B. M.， The Nortb American 町renomycetes.p. 120， 1均2.2) ITo， S.， On tbe Gibberella disease of 0山. (燕多の黒船病lこ航きて}北海道良舎_，第129，第 133-134貌(明治45年 1，2月)3) KlllCHNER， 0.， Krankheiten und Beschadigungen 回目rerLandwi四cbaCtlicbenKu1turpflanzen. p. 63 und p. 128， IS90. 4) STEVENS， F.L. Tbe fungi wbieb cau民 plantdisease. p. 206， 1913・442 C. MIYAXE: E玄plana'世onof the ftgur倒.Plate XIV. Perithecial.t申。fGJ~ルreUasam加 'fji・(M伺1.)Sacc. Fig，・ 1. Looltitudioal sectioo of a戸ritheciumproduced 00 the hOlt plant. (Vitia Fa6暗Lv町 .eguilta. P，剖.)Fig. 2. A group of岨ciand p町宮phy脂 S.Fig. J. Matured and yoUDIt回ci.Fig・-4. A民団porea.Fig.5. Asα国por岨 germinatedin distilled water・Fig.6. Cr叫島町ctioothrough略gregated戸宵iぬeciaupoo the 8troma on the hOlt pla且t.Plate XV. Conidial stage of G副 'I!rdlasa凶;mtii(Mont.) Sacc. Fig・1. Myωlium岨 d∞nidiaobtained in a卯問 cultureon steamed potato Item. Fig. 2. Mycelium with very large conidia found in cultures on steamed stem of the host plant. Fig. J. Myceliuru阻 dconidia developed泊 anOryza dωoct ag町 C叫tu開.

Gibberlla Saubinetii (Mont.) Sacc. as a Causal Fungus of the Wilt-disease of Horse-bean. with Plate XIV-XV.

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