Turnip Mosaic Virus Strains in Cruciferous Hosts in Taiwan

and Leguminosae were inoculated. Green, S. K., and Deng, T. C. 1985. Turnip mosaic virus strains in cruciferous hosts in Taiwan. For strain differentiation, four of nine Plant Disease 69:28-31. Chinese cabbage cultivars, PI 418957, PI An islandwide survey of the major vegetable production areas of Taiwan was conducted to 41905, Tropical Delight, and Crusad determine the presence, distribution, and prevalence of strains of turnip mosaic virus (TuMV) used by Provvidenti (20) for TuMV str affecting Chinese cabbage (Brassica campestris subsp. pekinensis), radish (Raphanus sativus), and classification were chosen for their ability smooth-leaf mustard (B.juncea). In addition to the four strains of the virus described in the United to differentiate the four strains. Ten States, a fifth strain (TuMV-C5) was found that is capable of systemically infecting the plants of each cultivar were inoculated multiresistant Chinese cabbage PI 418957. The physical and serological properties of strain C5 with each TuMV isolate. After inoculation, were indistinguishable from the other strains except for its low absorbance values in enzyme-linked all plants were maintained in an immunosorbent assay. TuMV-C4 appeared to be the most widespread strain, followed in artificially lighted, controlled-environment decreasing prevalence by C2, C3, C5, and C1. Resistance to TuMV-C5, as well as to the other four growth room (12-hr photoperiod, day strains, was found in plants of the Chinese cabbage line AVRDC Acc. 730. temperature 26 C, night temperature 20 C). Back-inoculations to C. amarantieolor were made 4 wk after inoculation to Turnip mosaic virus (TuMV) is resistant to TuMV-Cl, but Chinese confirm presence of the virus. Particle geographically widespread and has been cultivars were more often resistant to C2. morphology was determined from leaf reported in North America (2,19-21,26), Resistance to C3 and C4 was found preparations of systemically infected B. Europe (3,24,25), Africa (14), Asia only in Chinese cultivars. This clearly juncea tissues, diced in 2% uranylacetate, (1,5-9,13,17,18,23,27,28), and Australia demonstrates the importance of using all and examined in an electron microscope. and New Zealand (4,12). In contrast to available strains of TuMV in any The dilution end point (DEP) was cauliflower mosaic virus, which is program aimed at developing cultivars determined by serial dilutions of crude confined to cruciferous crops, TuMV has with durable TuMV resistance. With this sap of infected B. juncea in 0.01 M a wide natural host range, which includes in mind, a survey was initiated in 1982 phosphate buffer, pH 7.0. The thermal not only many members of the genus (15) to determine the presence and inactivation point (TIP) was tested by Brassica but also legumes (9,14,19) and prevalence of TuMV strains infecting immersing l-ml samples of crude sap in a ornamental plants belonging to different commercially grown cruciferous vege- water bath of a given temperature for 10 families (21,25,26). In Asia, TuMV is tables in Taiwan and to use those strains min, followed by rapid cooling under considered the most important virus of for the development of stable yielding, running tap water. For longevity in vitro cultivated cruciferous cash crops such as disease-resistant, and heat-tolerant (LIV), crude extracts were incubated at Chinese cabbage, radish, and smooth- Chinese cabbage cultivars in the breeding 25 C. Infected B. juncea leaves served as leaf mustard and has caused significant program of the Asian Vegetable Research the virus source and C. amaranticolor yield losses (23). Resistance is considered and Development Center (AVRDC). was used as the local lesion assay host. the only effective means of control, and TuMV-C5 was purified from systemiprograms aimed at finding TuMVresistant cultivars and breeding stock MATERIALS AND METHODS cally infected leaves of B.juncea Acc. B96 have been initiated in severalcountries of Leaves of field-grown Chinese cabbage following the method of Choi et al (10). Asia (6,16,18,23). (Brassica campestris subsp. pekinensis For antiserum production, rabbits were Provvidenti (21) recently suggested L.), radish (Raphanus sativus L.), and given at weekly intervals four intrathat resistance to TuMV in Chinese smooth-leaf mustard (B. juncea (L.) muscular injections of a purified virus cabbage is strain-specific and that several Cosson) were collected during 1982-1983 preparation emulsified in Freund's independently inherited genes for from the major vegetable-growing areas incomplete adjuvant. The resulting resistance are involved. He isolated four of Taiwan, including AVRDC. TuMV antiserum had a titer of 1:64 in sodium strains of the virus in cabbage, Chinese was isolated by sap inoculation to dodecyl sulfate (SDS) agar gel doublecabbage, and turnip in New York State. Nicotiana tabacum L. 'White Burley,' a diffusion test (22). Serological tests, using After screening 46 Chinese cabbage nonhost for cauliflower mosaic virus, partially purified antigens from systemcultivars of Japanese and Chinese origin radish enation mosaic virus, turnip ically infected mustard leaves, were done for resistance to TuM V-Cl, C2, and C3, crinkle virus, and turnip yellow mosaic by double-antibody sandwich enzymehe observed that TuMV resistance in virus. Before they were used for linked immunosorbent assay (ELISA) as Chinese cabbage varied with its origin, determination of morphology, host described by Clark and Adams (11). Most Japanese cultivars were immune or range, physical properties, and serology, Gamma globulins and enzymeeach isolate of TuMV was passed through conjugated gamma globulins prepared three successive single local lesion from antiserum to a German isolate of AVRDC journal paper 84. transfers on Chenopodium amaranticolor TuMV (cabbage blackring strain) were Coste & Reyn. All isolates were obtained from H. J. Vetten (BBA