| Ginkgo biloba.L,locally known as Baiguo and Gongsun tree,is special rare planin China. At presellt,only one section, one category,one genus exists,so it is called"living fossil" of gymnospenn and be of vital scientific value in botany.Ginkgo biIoba.L was exploited and uti1ized widely as foodstuff, health careprote ction, medicine, lumber and vire scence since 1980's, so new demand wasput forward on breed of Ginkgo .Bot Ginkgo is a dioecous tree and takes 20-30 yearsthat its seedlings come into bearing. Routine breeding time is very long and itsproductivity also is low so that it restricts seriously early economy benefit anddevelopment of Gingo. In addition, long juvenile period and late fruit are becomeprimary restrictive factors in crossbreed and seed selection.It is very importat in theory and practice to study its molecular principle and todevelop molecular breeding system by establishing Ginkgo tissue cultore and genetictransformation. With the development of modem biological science andtechnology,great progress has been made in tissue culthe as an importam means ofscience study Ginkgo is a gymnosperm, so its tissue culture is especially hard .Atpresent,the research aboot Ginkgo tissue culture and genetic transformation waslimited and it has not been reported abollt its success, so it is very necessary toestablish Ginkgo regeneration system.1 .Browning is serious problem in tissue culture of Gingho biloba L. especially,subculturing of medium. Many researchers have conducted experimellts about it, butnot succeeded. Culture media were compared to find the best medium of gingkgoculture for controlling callus browning by different sugars, antioxidants and sorbents.The result showed that the medium with MS+ZT 1 .0mg/L +NAA 1 .0mg/L+ sucrose50g/L+agar 8g/L+AC 2g/L was the best medium, at l5 days subculturing intervals.2. Different Gingkgo organs and tissues can all induce callus. Cotyledon andhypocotyl's rate and quamity are the most among these explams, and callus canbe obtained in 10 days by cotyledon and hypocotyl. Reversely it is difficult toindue callus with root,and the callus from root is lnde and easy to becomebrowning. The calIus obtained from leaf grows very slow and does not becomebrowning uniill in 2 or 3 months. It takes about 30 days to induce callus withendosperm. So, the rank of inducing callus from easy to hard is cotyledon, hypocotyls, stem, leafstalk, radicel, endosperm,leaf and root.3. Rate of cluster buds induced by different Gingkgo explants is not the same. Among them , cluster buds can be obtained directly from stems and mostly from axillar bud, but the amount is little and differentiation rate is only 20%. There are also different in inducing cluster buds from callus of clone Gingkgo and its other tissues and organs , some callus can induce cluster buds, but others can not . Differentiation rate from the callus of cotyledon can be up to 36% and the number of cluster buds is positive related to the times of subculturing. But cluster buds can not be obtained from the callus of stems and embryo .It has likely relate to the inner structure of callus.lt is very difficult to get embryoid from mature embryo and its inducing rate is very low , and only 11.5% in the media containing N6+BA 1.5mg/L+NAA 0.5mg/L+sucrose 30g/L+agar 8g/L+Ac 2g/L which is the best media for Gingo tissue culture.4. The content of nitrogen has a considerable influence on inducing roots from stems and it is negative effect on inducing roots if the content of nitrogen is too high. IBA +KT is the best of all hormone combinations in inducing roots. The result shows that medium with 1/2 MS +IBA 0.8mg/L+KT 0.50.8mg/L+sucrose 30g/L+agar 8g/L+Ac 2g/L is the most suitable for inducing root.
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