| Breeding triploid varity of mulberry is the trend of development in sericulture at home and abroad . getting tetriploidy mulberry is the groundwork of it . There is rarely tetriploidy mulberry in nature and poor practical character, so it can not be predecessor. These days , tetriploidy mulberry has been obtaining from reduplicating diploid cell chromosome in farmland. It is affected by weather and season and it is localized existing native variety which has little genotype. Techniques of chemical method and hybridization and vitro culture are associated for induction and breeding of mulberry tetriploid in the study. The seedling hybridization hypocotyls of mulberry were used for the study of in vitro culture system.; rapid micropropagation system was established from callus to plantlet regeneration. Polyploid plants of mulberry were obtained by colchicines treating seed end shoot cluster .The results were as following:(1) The seeds were suitably sterilized with H2O2 or NaClO.(2) The better calli with shoot organic potentiality could be obtained on the MS medium supplemented with 6-BA in combination with IAA. 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.(3) The plant regeneration rate of cotyledon and hypocotyle which are near the embryo was the highest It arrived in 70percent and the period of the inducement is the shortest.(4) The optimal medium for multiplication was MS+3.0mg/L 6-BA+O.1IAA+30g/L sucrose +7g/L agar.(5) The optimal rooting medium was 1/2MS+0.5IBA+30g/L sucrose +7g/Lagar, with the mean rooting rate of 100%.(6) Polyploid induction rate was higher with treating shoot cluster than seed;colchincine soaking was better than colchincine dripping; 0.2% colchincine...
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