日 植 病 報 57: 65-69 (1991) 短 報 Ann. Phytopath. Soc. 57: 65-69 (1991) Phytopathological Note

Yellow Streak of Rakkyo ( chinense G. Don), a Newly Recognized Disease Caused by Latent and Yellow Dwarf Virus

IsamuSAKO*, Wataru NAKASONE**, Kiyotugu OKADA**, SatoshiT. OHKI***,Takeshi OSAKI*** and TadaoINOUYE***

Keywords: , yellow streak, onion yellow dwarf virus, garlic latent virus.

In recentyears, meristem tip culturehas been tried to producevirus-free in Allium plantsas well. However,little information is available for identifyingthe viruseswhich infect Alliumplants. we alreadyreported a wideoccurrence of latentinfection with garlic latent virus(GLV, a carlavirus)in rakkyo (A. chinense G. Don)12).In this report,we describe GLV andonion yellow dwarf virus (OYDV, a ) which cause yellow streak of rakkyo. Occurrenceof yellowstreak of rakkyo. Typicalyellow streak symptoms were observedin rakkyo plants in fieldsin Tottoriduring October-November and April-May (Plate I-1-3). Thesymptoms were especially distinct in the basalpart of thenewly developed leaves whichwere thinned and curled.Leaf tips of the severelyinfected plants, which often die, turnedinto white. Mostof the infectedplants were stunted. Distinct symptoms were observed fromspring to autumn, but these were masked usually from December to March. Theoccurrence of yellow streak in rakkyoplants in threeareas of Hojo,Daiei and Fukube in Tottoriwas investigated. The averaged incidence in December,1987 and in May,1988 were 1.4%and 1.0%,respectively. The rates from Hojo, where A. fistulosum and A. wakegiwere cultivatednearby the rakkyo fields, were relatively high (2.7-3.5%). Virus isolates. Isolateswere obtainedfrom rakkyo plants cv. Rakuda,showing yellowstreak symptoms, collected in Hojo.GLV was isolated through single lesion transfers on Viciafaba and maintained in the plants. A rakkyoisolate of OYDV(OYDV-R) was ob- tainedby inoculatingthe sapincubated with antiserum to a rakkyoisolate of GLV(GLV-S)12). OYDV-Rwas maintained in A.fistulosum. Another OYDV isolate (OYDV-O) was obtained fromA. fistulosum collected in Yonago,Tottori. Host reaction. Table1 showsthe result of thehost range study by sapinoculation withGLV, OYDV-R or GLV+OYDV-R.Distinct yellow streak symptoms were observed in the virus-freedrakkyo plants inoculated with GLV+OYDV-R. Host range of OYDV-R wassimilar to thatof OYDVpreviously reported3). The rakkyo plants inoculated with GLV+ OYDV-Rappeared only severe mosaic on theinoculated leaves, however, they showed yellow streaksymptoms on the newlydeveloped leaves after a period. Therakkyo plants cv. rakuda whichhad been inoculated with GLV and inoculated with OYDV-R 60 days after GLV inocula- tionalso appeared distinct yellow streak symptoms. Purificationof OYDV-Oand the antiserumproduction. OYDV-Owas prop- agatedin seedlingsof A. fistulosumcv. Kairyo-Hakushu2. The infection only with OYDV

* Tottori Fruit , Vegetable and Ornamental Crop Experimemt Station, Tottori Prefecture, Daiei, Tottori 689-22, Japan 鳥 取 県 果 樹 野 菜 試 験 場 ** Osaka Agricultural Research Center , Osaka Prefecture, Habikino, Osaka 583, Japan 大 阪 府

農 林 技 術 セ ン タ ー *** College of Agriculture , University of Osaka Prefecture, Sakai, Osaka 591,Japan 大 阪 府 立 大

学 農 学 部 66 日本 植物 病 理 学 会 報 第57巻 第1号 平 成3年1月

Table 1. Host range and symptoms of garlic latent virus and rakkyo-isolate of onion yellow dwarf virus

a) S: systemic infection;L: localinfection; Mo: mosaic symptoms; YS: yellow streak;lat: latentinfec- tion; NS: necroticspot; CS: chloroticspot; -: not infected. was confirmed by immunosorbent electron microscopy (ISEM)8), dot immunobinding assay (DIBA)5,14), and bioassay to several plants. OYDV-O was purified by the procedures previously reported for GLV12). For antiserum production, a rabbit was injected into the muscles with emulsions of equal volumes of the purified virus and Freund's complete adjuvant five times at 8-17-day intervals. Titer of the antiserum obtained was 1/256 by microprecipitin test and 1/1,024 by ISEM with crude sap from the diseased A. fistulosum. The antiserum was further absorbed with sap from healthy A. fistulosum as previously described5). Serology. The rakkyo samples of eight from Tottori and four from Kagoshima which showed typical yellow streak were investigated by ISEM with the antisera to GLV-S12), OYDV- O, OYDV supplied by M. Fukami (OYDV-OF)4) and yellow ,stripe virus (LYSV, a poty- virus)2,9). The decorated filamentous particles were observed when the specimens were treated with antiserum to GLV-S, OYDV-O, or OYDV-OF (Plate I-4-5). All the particles were dec- orated when the specimens were treated with the mixture of antisera to GLV and OYDV. However, no filamentous particles were decorated with the antiserum to LYSV. No spherical were detected in those specimens. Immunodiffusion test using Gelrite10), performed with the antiserum to OYDV-O against crude sap from OYDV-R-infected rakkyo, partially purified viruses from OYDV-R-infected rakkyo and OYDV-O-infected A. fistulosum, showed that the precipitin lines to OYDV-R and OYDV-O were completely fused. OYDV-R in rakkyo plants was clearly reacted by ELISA7) with the antiserum to OYDV-O (data not shown). From these results, we conclude that the yellow streak of rakkyo was caused by the mixed infection with GLV and OYDV. Detection of OYDV by DIBA. Since the detection of GLV in sap by DIBA was already established11,12),detection of OYDV by the method was also examined. OYDV appeared to be effectively detected by the method using the antiserum to OYDV-O diluted to 1/4,000-1/6,000 when the samples were extracted in TTBS buffer (0.02M Tris-HCl, 0.5M NaCl, 0.05% Tween 20, pH 7.5). OYDV in rakkyo plants could be detected in the leaf extract diluted to 1/10-1/1,000. Table 2 indicates the results of DIBA for GLV and OYDV with the rakkyo sample showing yellow streak and no apparent symptoms. GLV was detected from all the samples and OYDV was found only in the plants mixedly infected with GLV, showing yellow streak symptoms. No plants were found infected only with OYDV so far examined. Several viruses including GLV11,12),leek yellows virus1), and tobacco mosaic virus13) have Ann. Phytopath. Soc. Japan 57 (1). January, 1991 67

Table 2. Detection of GLV and OYDV by DIBA in leaf extracts of naturally infected rakkyo plants collected in different districts of Tottori Prefecturea)

a) Rakkyo plants cv. “Rakuda” were collected in December, 1987 and May, 1988.

so far been reported for rakkyo in Japan. Although Yoshino and Yasu15) transmitted a virus similar to OYDV, this may be the first report that OYDV3) occurs in rakkyo. We propose the name •gyellow streak•h of rakkyo which is caused by the mixed infection with GLV and OY-

DV. This disease is considered to be the severest type of •gishuku-byo•h6). The rate of occur- rence of this disease seems to be low (data not shown), however, further studies are needed for controlling both GLV and OYDV to establish stable production of rakkyo.

We thank Mr. M. Izumi, Kagoshima Agri. Exp. Sta., for sending diseased rakkyo samples, Mr. A. Fukumoto, Tottori Fru., Vegi. and Orna. Exp. Sta., for providing virus-free rakkyo plants; and Dr. N.

Inouye, Res. Inst. Biores., Okayama Univ. and Mr. M. Fukami, Chiba Agri. Exp. Sta., for sending anti- sera.

Literature cited

1. Araki, M., Yamashita, S., Doi, Y. and Yora, K. (1981). Luteovirus, potyvirus and carlavirus detected

in Allium species. Ann. Phytopath. Soc. Japan 47: 138 (Abstr. in Japanese). 2. Bos, L., Huijberts, N., Huttinga, H. and Maat, D.Z. (1978). Leek yellow stripe virus and its rela-

tionships to onion yellow dwarf virus; characterization, ecology and possible control. Neth. J. Pl. Path. 84: 185-204.

3. Bos, L. (1976). Onion yellow dwarf virus. CMI/AAB Descriptions of Plant Viruses No.158.

4. Fukami, M., Natsuaki, K.T. and Tomaru, K. (1989). Detection of onion yellow dwarf virus in by gelatin particle agglutination test. Ann. Phytopath. Soc. Japan 55: 542 (Abstr.

in Japanese). 5. Hibi, T. and Saito, Y. (1985). A dot immunobinding assay for the detection of tobacco mosaic

virus in infected tissues. J. gen. Virol. 66: 1191-1194.

6. Kawai, I. (1954). Disease of Horticultural Plants in Japan. Yokendo, Tokyo. pp. 209-210 (in Japa-

nese). 7. Koenig, R. (1981). Indirect ELISA methods for the broad specificity detection of plant viruses.

J. gen. Virol. 55: 53-62. 8. Milne, R.G. and Luisoni, E. (1977). Rapid immune electron microscopy of virus preparations.

In Methods in Virology, Vol.VI (Maramorosch, K. and Koprowski, H. eds.). Academic Press, New York. pp. 265-281.

9. Noda, C. and Inouye, N. (1989). Leek yellow stripe virus isolated from an ornamental Allium plant in Japan. Ann. Phytopath. Soc. Japan 55: 208-215.

10. Ohki, S.T. and Inouye, T. (1987). Use of gelrite as a gelling agent in immunodiffusion tests for identification of plant virus antigens. Ann. Phytopath. Soc. Japan 53: 557-561.

11. Sako, I. (1989). Infection of garlic latent virus in rakkyo (Allium chinense G. Don) and detection of the virus by serological techniques. Bull. Tottori Pref. Hortic. Exp. Sta. 6: 1-16. 12. Sako, I., Nakasone, W., Okada, K., Osaki, T. and Inouye, T. (1989). Occurrence and incidence

of garlic latent virus in rakkyo (Allium chinense G. Don). Proc. Kansai Pl. Prot. 31: 23-29. 13. Sako, N. and Ando, C. (1985). Some virus detected in rakkyo (Allium chinense G. Don). Ann. 68 日本 植物 病 理学 会 報 第57巻 第1号 平 成3年1月

Plate I Ann. Phytopath. Soc. Japan 57 (1). January, 1991 69

Phytopath. Soc. Japan 51: 353 (Abstr. in Japanese). 14. Yoshikawa, N., Poolpol, P. and Inouye, T. (1986). Use of a dot immunobinding assay for rapid detection of strawberry pseudo mild yellow edge virus. Ann. Phytopath. Soc. Japan 52: 728-731. 15. Yoshino, M. and Yasu, M. (1965). Studies on the ecology of yellow dwarf of stone leek (Allium fistulosum L.). Bull. Saitama Pref. Agri. Fxp. Sta. 26: 1-67.

和 文 摘 要

佐 古 勇 ・中 曽 根 渡 ・岡 田 清 嗣 ・大 木 理 ・尾 崎 武 司 ・井上 忠 男:ニ ンニ ク潜 在 ウイ ル ス とネ ギ萎 縮 ウ イ ル ス に よ る ラ ッ キ ョウの 黄 色 条斑 症 状 に つ い て

萎 縮 を伴 う黄 色 条 斑 症 状 を 示 した ラ ッキ ョウか ら2種 の ひ も状 ウ イル ス が分 離 され,そ れ らは宿 主 反 応, 免 疫 電顕 法,二 重 拡 散 法,ELISA法 に よ りニ ン ニ ク潜 在 ウ イ ル ス(GLV)と ネ ギ 萎 縮 ウ イル ス(OYDV)と 同定 され た。 これ らを ラ ッ キ ョウに 汁 液接 種 す る と,GLVの み で は潜 在 感 染 で あ った が,OYDVの 感 染 が加 わ る と明 瞭 な 黄 色 条 斑 症 状 が 再 現 され た 。GLVとOYDVに よ る本 病 の病 名 と して 「ラ ッキ ョウ黄 色 条 斑 病 」 を提 案 した い 。 また,ラ ッ キ ョウにつ い てDIBA法 に よ るOYDVの 圃 場 診 断 の有 効性 が 示 され た 。 (Received July 23, 1990)

Explanation of plate

Plate I 1. A severely stunted rakkyo plant (arrow) naturally infected with garlic latent virus (GLV) and onion yellow dwarf virus (OYDV). The other plants are symptomless and infected only with GLV. 2. Rakkyo plants naturally infected with GLV and OYDV showing yellow streaks especially at the basal part of the leaves, and curling and distortion of the leaves, in autumn. 3. Yellow streaks of the infected rakkyo plants turned into white and dying back from the leaf tips. 4. An electron micrograph of the infected leaf sap treated with the antiserum to GLV-S. Two types of filamentous particles are observed and one of which are decorated with the anti- bodies to GLV. Bar represents 500nm. 5. An OYDV particles detected in the infected leaf sap, decorated with tie antibodies to OY- DV-O. Bar represents 500nm. 6. One of the DIBA sheets detecting OYDV in rakkyo plants.