| Steviol glycoside is a new natural sweetener extracted from the leaves of stevia rebaudiana which belongs to Composite plants. It has unique properties of high sweetness and low calorie. The sweetness of it is300times than cane sugar, but only1/300calorie. It is known as "the third source of sugar in the world". However, due to the following aspects of stevia, its production has been limited. Therefore, in view of the main production problems, the experiment used plant tissue culture technology, ion beam mutation breeding and polyploidy breeding methods to breed good characters, large leaves and high stevioside content new varieties. The major results were as follows:1. The study used the orthogonal design experiments to filter out the most suitable medium for rapid propagation of stevia rebaudiana and the most suitable medium for rooting of stevia rebaudiana. The results suggested that:the most suitable medium for rapid propagation of stevia rebaudiana is MS+0.1mg/L6-BA+0.05mg/L NAA+30g/L sucrose; the most suitable medium for rooting of stevia rebaudiana is1/2MS+1.0mg/L6-BA+0.5mg/L NAA+30g/L sucrose.2. Different doses of N ion beam irradiation processed stevia seeds, the results showed that:First, N+ion beam in a certain dose range could promote germination. Does of400×2.5×103N+/cm2N+ion beam had significant impact on germination energy and germination rate. Second, after N+ion beam irradiation irradiated, nine high-glucosidase mutants were selected in the M1generation plants.3. The result of colchicine treating stevia tissue culture seedlings was:First, the highest inducing rate that0.1%colchicines inducting for24h is26.7%.Second, in the130survival polyploid,six stevia had very significantly impact on total glycosides and RA glucosinloate. In the highest glucoside polyploid,3.1times the total glycoside content of the control,6.7times RA glucosinolate content of the control group. Third, after colchicine treated,the biological traits of stevia such as chloroplast content, chromosome number and porosity both had changes. The chromosome numbers of stevia diploid and polyploid were22and44.4. The results of colchicine on root tip cells of stevia tissue culture seedlings:when the concentration of colchicine in0.01%processing12h to0.1%processing24h, it had stimulative effect on the cell division of root tip cell.When the concentration of colchicine in0.1%processing24h, the mitotic index reached the highest was30.99%. When the dosage continued increasing, the mitotic index declined, high dose of colchicine inhibited the cell division of root tip cell. Colchicine mutagenic treatment also caused nuclear aberration as the type of micronuclei, nuclear budding etc and chromosome aberration as the type of chromosome bridges, lagging chromosomes etc on root tip cells of stevia. |
