Research On Rooting Inhibitor And Asexual Propagation Of Eucalyptus Dunnii

Eucalyptus dunnii Maiden was introduced into China in the early 1980's for itscold-tolerance property. Through more than 20 year's introducing trail and research, it showsgood potential for developing in colder area in the south of China. But there is a great problemin E.dunnii, that is the propagating method. Since the earliest introduction from Australia, ithavn't flowering and fruiting at all in China, and even in Austrialia it is a low seed productioneucalypt. Meantime, E.dunnii have a great difficulty in rooting by asexual propagationincluding cuttings and tissue culture as well. For this problem, this paper carried out researchon the rooting inhibitor of E.dunnii's aqueous extraction and seeking to the medium of tissueculture. The main results were as following.(1) As the addition of concentration of aqueous extraction from E.dunnii cuttings, thegrowing indexes of tested material generally decrease as well. When the aqueous extractionconcentration reaches to some extent, it shows obvious inhibiting effect. For example, bytreated by aqueous extraction of 2g/ml concentration, the seed germination rate, total length ofall roots, average length of root of cabbage separately are 74.18%, 22.27%, 35.73% of CK, andthe seed germination rate, total length of all roots, average length of root of E.dunnii separatelyare 69.42%, 27.49%, 66.62% of CK, and the total root number, average root number, totallength of all roots, average length of root of mung bean stem separately are 25.37%,75.37%,55.45%,76.39% of CK. The aqueous extraction concentration that the growing indexes ofE.dunnii seeds are inhibited needs is lower than these of the other tested materials.(2) Aqueous extractions from different materials have different effect on tested materials.Totally, all growing indexes of tested materials treated by four aqueous extractions fromE.dunnii are inhibited. The inhibiting extent of two aqueous extractions from 3-year-oldE.dunnii tree, including stalks and leaf, is the similar and which is strongest, and the inhibitingextent of aqueous extractions from cutting stalk and seedling stem is also the similar and whichis stronger. The concrete effect on all growing indexes of tested mateials trested by extractionfrom DH32-29 cutting stalk is different, but the growing indexes affected by DH32-29extractions are almost higher than E.dunnii's. (3) The result of chemical test shows that there is phenol existing in the extraction fromE.dunnii cuttings, and the concentration and materials effect of chemical test has a similar trendwith the effect of biological test basically. These shows that phenol have a inhibiting effect onrooting in the E.dunnii extractions. By analyzing of GC-MS, it reveals that the compents ofextraction which are alcohol and its deriving substance primarily and of which the 1,8-cineol isthe most is similar to the compents of oil distilled from leaf of many eucalypts.(4) Sterilizing explants of E.dunnii with 0.1%MC for 3min is effective. The time is tooshort and the contamination rate is too high, while the time is too long and the death rate has agreat increase, so both have a worse sterilizing effect totally and the survival rate is too low.Meantime, there is a great difference in sterilizing effect between different individuals, thecontamination rate of the bad individual is quite high and reach to 86.7%, while the goodindividual is not almost contaminated and the survival rate, reaching to 74.2%, is quite high.(5) Taking MS+0.4mg/L6-BA+0.2mg/LNAA as inducing medium of E.dunnii explant isgood and the sprouting rate arrives more than 2 times, of which the length of 41.7% sprouts ismore than 0.7cm, 31.3% is between 0.7cm and 0.3cm and 27.1% is less than 0.3cm. The wholeinducing effect of this medium is relatively good, but in the following subculture andpropagating culture the cytokinin concentration need to reduce. When 6-BA/NAA is0.08/0.12～0.14mg/L, it can attain a good effect and the propagating seedlings can be used forrooting, while the cytokinin concentration and the vessel size have an important effect on thenormal growing of propagating seedlings.(6) Taking 1/4MS as the basic rooting medium of E.dunnii is relative good, but the rootingrate is still too low. Through carring out a series of experiments including the selection to auxintypes and auxin concentrations, the optimizing and comparison of medium composition,adding AC and adding other nutritive substances and so on, the rooting rate did not increaseand even it has no root-genesis as well. Meantime, root inducing with only auxin often makethe callus of the base of seedlings get too large, which is not good at the connect between rootand stem and can affect root-genesis to some extent. Adding low concentration cytokinin canmake the callus get transparently smaller.