| Almost all Tillered-onion ( A/hum. cepa L. var. mu/tip/cans Bailey syn. Var. Agrogatum Don)being cultured in Heilongjiang province are infected by viruses. Hundred percent of Tillered-onion plants in Acheng, Binxian and Wuchang county of 1-leilongjiang were infected by viruses, the index is 62.13%, 71.07% and 49.87% respectively. The infection induces typical mosaic symptoms of yellow streak as well as curling on leaves, withering of leaf-tips, dwarfism on the plants, and resulting in the degeneration and reduction of size of bulbs. Virus infection produces important reductions of quality and yield in Tillered-onion.This disease was demonstrated to be caused by several viruses which could be transmitted by the sap of the diseased plants. A.cepa L , A Ilium sativum, Ahhiumfistulosum L. and vicia faba were infected systemically by sap inoculation, Local lesions were produced on the inoculated leaves of Che. A,naranticola and Gomphrena globosa. Electron microscopic observations of the natually infected Tillered-onion revealea that there are fiexuous filamentous particles 300?450nm long, with 500?00nm as the norm. 32.67% are 550~?50nm, 9%are 650?00nm and 3扵.6~T%are 700~800nm in particles, About 80% of the particles in the range of 550?00nrn. Typical pinwheel type, bundle, scrool and circular cytoplasmic inclusions are found in the cytoplasm of the mesophyll cell could be observed by ultrathin section of leaves, the chlorophylls are destroied. In sap ,it properties were thermal inactivation point (TIP) between55~?5~C,dilution end point (DEP) was l0-~, long in vitro (LIV) of extract at room temperature was 3d. Indirect-ELISE of leaf extracts of Tillered-onion plants showed positive reaction with the antisera against onion yellow dwarf virus, complex garlic viruses. Evidence from study, Heilongjiang Tillered-onion is jointly infected by several kinds of viruses, but need to be identified continuelly.Virus-free plants of tillered-onion were obtained from in vitro meristem tip apex tissue culture with the basical medium of MS. Each of medium was added 3.0%sucrose and 0.8% agar and the medium pH value is 5.7~5.8. Aseries of optimization experiment for cultural medium composition, concentration of phytohormones were investgated with a view to acclerate the propagation of virus0free plants. The result of virus elimination by meristem tip culture of purpie-skined Tillered-onion commonly grown in Acheng showed that the best medium shooting wasMS+NAAO.lmg/l+BAO.4mg/l, On average, 3.lshoots formed from one meristem tip without callus formation. and that for rooting was 1/2 MS+NAAO.Olmg/I+IBAI.5mg/l+PP3330.l mg/I. Effects of virus-free culture with different meristem tips in size and heated-treated are discussed. The result showed thatpretreatment of cloces with 80~Cthermotheray for 10mm, the obtained virus-free plants by using 0.3~?.5mm meristem tip.This paper deals with studies on in vitro culture of meristem tip of Tillered-onion, including callus induction and differentiation, plantlet root, development and transplantation. Results showed: (1) callus were obtained on media containing different kinds of phytohormone.lt was advantageous to callus induction on MS basal medium supplemented with 2,4-D2.Omg/l and KTO.Smg/l. the frequency of callus induction was 100%; (2) The combination of NAAO.lmg/l and BAO.4mg/l was best medium for callus differentiation of which ratio was 88.33%, Most of callus was aggrandized again and induced green bud spots then formed multiplying clumpy buds, the mean number of plantlets per callus was 10.2, These results could meet the technology requirements of rapid propagation in large scale production; (3) 100% of the regenerated plantlets treated with NAAO.Olmg/l and IBA1.Smg/l and PP3330.1 mg/I could develop their roots, grew robustly and robust green leaves, after the regenerated plantlets were transplanted to soil, they could adapt to environment. The survival ratio of transplanting reached 100%.Incubation temperture and photoperiod were essential re...
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