Studies On Technique Of Sweet Potato Meristem Tip Culture, Rapid Propagation For Virus-free And The Mechanism Of Increase In Production

Sweet potato(Ipomoea batatas (L.)Lam)is an important crop. It can be used as foods,industrial raw materials,feedstuff and health goods. It was found out that virus diseases were the most important factor that lead to quality devolution and output falling of sweet potato at present. Obtaining virus-free plants by means of meristem tip culture was the available measure to deal with the problem.The meristem tip of sweet potato was used as explant to find out effective way of in vitro culture and rapid propagation．With random combine and orthogonal design, we tried to find out the best medium composition and establish a technique system of tip culture and rapid propagation of virus-free sweet potato, and studies the mechanism of increase in production about virus-free sweet potato．The results were as follows:1,After the meristem tip of sweet potato were sterilized by 0.1% mercuric chloride solution for 8 minutes, then washed 4-5 times with the sterile water, it can reach the ideal result of disinfecting , and survival rate can be up to 86.8%.2,With orthogonal design the optimum media of tip culture suitable for different genetypes was obtained: MS+1.0 mg/L BA+0.05 mg/L NAA+0.5 mg/L GA3.The survival rate of seeding could reach 79.5%. Organic supplements as coconut milk, banana juice, et al. can improve the survival ratio of seeding. Culturing in hormone media can make meristem tip survive once time, and the result is better than two-time-cultivation.3,The meristem tip with two phyllomes(0.3-0.4mm in size)were found to suitable for virus-free seeding culture that were cut from aseptic seeding, which led to higher survival and virus-free ratio, up to 72.1%and 54.2%. 20-day heat treatment (37±1℃) to sweet potato seeding before the meristem tip being cut down could improve the virus-free ratio, up to 62.2%.4 MSJ is a simplified media which regard MS as the basic media,replace socrose with edible sugar,disuse the organic composition and agaragar,regard filter paper as carrier. It can save 87.63% of cost if being used for rapid propagation of virus-free sweet potato. We also proved that MS media supplemented low density of NAA (0.1 mg/L , 0.2 mg/L ) can be help rapid propagation of virus-free sweet potato at the same time.5,Up to 95% of virus-free seeding could survive after one week-day's treatment and being transplanted in loam. Covering membrane and spraying Urea(25g/m2 )after three week can accelerate growth of virus-free sweet potato. 6,Yield advantages and physiological characteristics of different gene types of virus-free sweet potato were studied. The results showed that the nutrition growth of virus-free seeding become more vigorously; the LAI and the contents of chlorophyll were higher than CK, and efficiency of photosynthesis improved; at the same times virus elimination promoted the metobolism of nitrogen, the nitrate reductase activity increased and the root tuber expands early and fast. So the yields of virus-free seeding of three cultivars were significant higher than that of controls obviously and increase production range up to 15.2-27.1%.7,The analysis of POD,SOD isoenzyme patterns indicated that the isoenzyme patterns of virus-free seeding were different with the control. The activations of SOD, POD of virus-free seeding increased obviously and resistibility of adverse environment was strengthened when it was infected by the virus.