OTHER VIRUS DISEASES the Occurrence of Satsuma Dwarf Virus

OTHER VIRUS DISEASES

The Occurrence of Satsuma Dwarf Virus in China

Zhou Changyong, Zhao Xueyuan, Jiang Yuanhui and He Xinhua

ABSTRACT. From 1985 to 1991,84 samples from satsuma mandarins, mandarin hybrids and navel oranges, imported from Japan in recent years, were collected from eight provinces, and indexed for satsuma dwarf virus (SDV) by using the indicator plants, White sesame, Blackeye cowpea and Satisfac- tion kidney bean, and by ELISA. Miyamoto satsuma samples collected trom Huangyan, Zhejiang Province and from Fengjie, Sichuan Province were infected with SDV, while all the others were SDV-free. Nine cultivars of extreme early satsuma, especially those collected from Huangyan and Huaning, Yunnan Province, were infected with citrus tatter leaf virus (CTLV). Other than satsuma, 25 important citrus cultivars collected from the National Citrus Genetic Resources Collection at Chong- qing were found to be SDV-free by ELISA. The results suggest that the occurrence of SDV in China is limited to a few cultivars in a few locations.

Satsuma dwarf is an economically Hashimoto, Ichifumi, Imada, Inaba, important virus disease in Japan. The Ishitsuka, Kitaguchi, Mitake, typical symptom, the so-called "boat- Miyamoto, Oomura, Ooura, Tanimoto, shaped leaf," appears on the spring Takabayashi, Toku mori, Ueno, flush. Since the first record in 1950 (5), Wakiyama and Yamakawa No. 3), it has become widespread in almost all early satsuma (Kamei, Matsuyama, the citrus areas of Japan (3). SDV has Miyagawa, Okitsu and Tachima), mid- also been reported from Turkey (1)and dle satsuma (Aoe, Dobashibeni, Korea (4). Satsuma mandarin was im- Hayashi, Kunou, Morita, Mukaiyama, ported into China from Japan, and in Nankan No. 4, Nankan No. 20, Owari, recent years, some cultivars of ex- Seto, Suruga, Tomono and Yonezawa), treme early satsuma have also been in- late satsuma (Aoshima, Ikeda and troduced. In many satsuma plantings Ishikama), navel orange (Shirayanagi in China, boat-shaped leaves have been and Suzuki) and mandarin hybrid found. In order to determine whether (Amanatsu, Hassaku and Miyauchi SDV is present in China or not, samples iyokan). were collected from eight provinces In the autumn of 1991, an additional and indexed by using herbaceous indi- 25 important citrus cultivars were cator plants, and ELISA from 1985 to collected from the National Citrus 1991. Additional indexing was done to Genetic Resources Collection at Chong- determine if citrus tatterleaf (CTLV) qing for ELISA indexing for SDV, in- was present in these samples. cluding sweet orange (Anliucheng, Xinhuicheng, Jingcheng, Edangan No. MATERIALS AND METHODS 8, Taoyecheng, Bintangcheng, Xuegan, Robertson navel, Washington navel, From 1985to 1991,84samples were Valencia, Hamlin, Tarocco blood, Ruby collected from eight provinces, namely blood and Washington Sanguine),man- Sichuan, Zhejiang, Hunan, Hubei, darins (Dahongpao, Ponkan, Jiaogan, Guangxi, Jiangxi, Yunnan Provinces Nanfengrniju, Shiju, Manju, Zaoju, and Shanghai Municipality. Forty-four Fuju, Bendizao and Nianju) and cultivars originally introduced from Eureka lemon. Japan were involved, including ex- Ordinary sap-inoculation tech- treme early satsuma (Guchi No. 4, niques (1 g young leaf tissue in 5 ml Twelfth ZOCV Conference

0.05M K2HP0, solution) was used for leaves. Symptoms on Blackeye cowpea indexing SDV on the herbaceous indi- and Satisfaction kidney bean were local cators, White sesame, Blackeye lesions on the inoculated leaves, and cowpea and Satisfaction kidney bean. mottling, vein-clearing and local le- Five to 20 seedlings of each indicator sions on the upper leaves, and necrotic were used for indexing each sample, streaks on the petioles and stems. Con- and observed for symptoms, and every trol seedlings produced negative re- sample has been identified at least sults in each test. The indexing results twice. The positive control seedlings of the different samples were as fol- were sap-inoculated with SDV from an lows: SDV-infected plant, and negative con- (a) Miyamoto satsuma collected trol seedlings were rubbed with the sap from Huangyan, Zhejiang Pro- of the young shoots of a healthy sat- vince and from Fengjie, Sic- suma seedling. Test plants were held huan Province, which were im- in the laboratory at 20-24 C for about ported from Japan in early 20 days. 1980s,reacted positively on the The double-antibody sandwich three indicators. ELISA technique (2) was used for SDV (b) Nine cultivars of extreme early indexing, and the absorbance values satsuma, including Wakiyama, were measured at 410nm in a DG-3022 Ichifumi, Hashimoto, Ishit- ELISA Reader. The SDV-antiserum suka, Takabayashi, Toku mori, and alkaline phosphatase-linked anti- Oomura, Kitaguchi, and Inaba body used were made in October 1990 collected from Huangyan, by Plant Protection Assoc. Res. Inst. Zhejiang, Wakiyama and of Japan and kindly supplied by Dr. A. Ichifumi from Huaning, Yun- Sasaki from Hirosima Fruit Tree Exp. nan and Wakiyama and Toku Sta., Japan. Each sample was tested mori collected from Chongq- by ELISA at least twice. Positive and ing, produced positive reac- negative control extracts were pre- tions on Satisfaction kidney pared by grinding young shoots of bean and Blackeye cowpea, but SDV-infected satsuma and of healthy no reaction on White sesame. satsuma, respectively. These results indicate that During the indexing, some samples these extreme early satsumas were found to react positively on Satis- are infected by other viruses, faction kidney bean and Blackeye but not by SDV. cowpea, but did not react on White Detection of SDV by ELISA. In sesame or in ELISA tests. In order to 1990-1991, 109 samples collected from determine the cause, indexing for eight provinces were indexed for SDV CTLV was done on Rusk citrange, in by ELISA. Both Miyamoto satsumas the spring and autumn of 1991. Each collected from Huangyan and Fengjie sample mentioned above was grafted were infected with SDV, but all the onto four Rusk citrange plants. others were free of the virus. Indicator indexing of CTLV. Typ- RESULTS ical symptoms of CTLV on Rusk citrange were observed in the autumn of Indexing for SDV by herbaceous 1991 and the spring of 1992. All of the indicators. In general, symptoms ap- extreme early satsuma samples, which peared 1-2 weeks after inoculation. caused positive reactions on cowpea Positive control seedlings of the three and kidney bean but negative reactions indicators produced positive results in on sesame, wereinfectedwith CTLV. all tests. Symptoms on White sesame were local lesions on inoculated leaves DISCUSSION followed by systemic infection; the sys- temically infected leaves showed vein In this study, two samples of necrosis and mottled, malformed Miyamoto satsuma imported from Other Vims Diseases 351

Japan in the early 1980s were found to Typical symptoms of satsuma be infected with SDV, while 76 other dwarf, such as the boat-shaped leaf, satsuma samples collected in eight pro- have been found in many satsuma provinces were SDV-free. Mandarin hyb- ducing areas. Most samples tested rids (Hassaku, Miyauchi iyokan and were collected from the trees which Amanatsu), and navel oranges showed the boat-shaped leaf (Shirayanagi and Suzuki) imported symptoms. However, the ELISA and from Japan were also found to be SDV- indicator tests indicate that SDV is not free. Other than satsuma, mandarin present. The boat-shaped leaf is there- hybrids and navel oranges introduced fore caused by factors other than SDV from Japan, 25 important citrus cul- infection. Zhou et al. (6) have shown tivars collected in Chongqing, were previously that this boat-shaped leaf also found to be SDV-free. The results symptom is graft-transmissible. The suggest that the history of SDV occur- diagnosis of satsuma dwarf in the field rence in China is recent, and its distri- should therefore be confirmed using bution is limited in a few cultivars and the sesame test andlor by ELISA. in a few locations. LITERATURE CITED

1. Azeri, T. 1973. First report of satsuma dwarf virus disease on satsuma mandarins in Turkey. Plant Dis. Rep. 57: 149-153. 2. Clark, M. F., and A. M. Adams 1977. Characteristics of the microplate method of enzyme-linked immunosorbent assay for the detection of ~lantviruses. J. Gen. Virol. 34: 475-483. 3. Imada, J. 1981. Satsuma dwarf, p. 38-40. In: Citrus Diseases in Japan. T. Miyakawa and A. Yamaguchi (ed.). Japan Plant Protection Assoc. Press, Tokyo. 4. Moon, D. Y.- 1986. Viral diseases of horticultural subtrodcal and troaical cram in Korea. a. 12-18. In: Food and Fertilizer Technology Center for the ~sianand pacific ~e*on(~ai~ei,-~aiwan). 5. Yamada, S., and K. Sawamura 1950. Satsuma dwarf. Proc. Congr. Hort. Soc. Japan, p. 36-37. (Abstr.) 6. Zhou, C. Y., X. Y. Zhao, Y. H. Jiang and X. H. He 1990. The preliminary studies on the cause of boat- or spoon-shaped leaf of satsuma mandarin. Chinese Citrus No. 4: 12-14.