In Vitro Culture And Polyploid Induction Of Eucalyptus 12ABL

The seedling hypocotyls of Eucalyptus 12ABL (E.camaldulensis E.tereticornis) were used for the study of in vitro culture system. A rapid micropropagation system was established from callus to plantlet regeneration. Polyploid plants of Eucalyptus 12ABL were obtained by colchicines treating calli and cespitose buds . The results were as following:(1) The seeds were suitably sterilized with H2O2 or NaClO .(2) The tight red calli with shoot organic potentiality could be obtained on the modified medium H supplemented with 6-BA in combination with NAA. Only loose white calli without shoot organic potentiality were obtained on any medium containing 2,4-D. The former could form adventitious buds but the latter couldn't. Coconut milk or high sucrose concentration had no any effect for inducing callus. The optimal medium for inducing calli was modified H+0.5mg/L 6-BA + 0.1 mg/L NAA + 40g/L sucrose +7 g/L agar.(3) The calli began to form adventitious buds after 15 days. The optimal medium for inducing adventitious buds was modified H+1mg/L 6-BA + 0.1 mg/L NAA + 40 g/L sucrose +7g/L agar. The callus would become big in the process of propagation, and thick clustered buds were formed on the callus surface after three propagations;(4) The optimal medium for multiplication was MS+1mg/L 6-BA + 0.1 mg/L NAA + 30g/L sucrose +7g/L agar ,with a propagation coefficient of 3.4.(5) The optimal rooting medium was 1/2MS+0.5mg/L IBA + 30g/L sucrose+7g/L agar, with the mean rooting rate of 100% and root number of 3.6;(6) There were three methods of colchicines treatment, including colchicines soaking, colchicines dripping and adding colchicines into the medium. With the first method the best result was by immersing calli with 0.75% colchicines for 10 h and 0.25% for 22 h, the polyploid induction rates were all up to 40%. With the second method the best result was by dripping calli and clustered buds with 0.25% colchicines , the polyploid induction rate reach42.9% and 26.7% respectively. And with the last method the best result was by adding colchicines 40mg/L into themedium treated clustered buds for 10 days, the polyploid induction rate reached 22.5%. Colchicines soaking was the best method, which had higher induction rate and wasted less colchicines. Polyploid induction rate was higher with treating calli than treating clustered buds.(7) By comparing the polyploid plants with normal diploid ones in morphology, leaves of polyploid plants were thicker, larger, more deep green in color, and with larger Stomata and less in number, and stems were more vigorous.(8) The chromosome number of polyploid plants that had been identified in morphology was 2n=4x=44,while that of dipoid was 2n=2x=22. The preparation of chromosome specimen was also discussed.