Evaluation Of Meristem-tip Of Sweet Potato Longyan7-3 Culturing Virus Elimination Effect

Liancheng County is famous for the "the country of Chinese dried red sweet potato ." In recent years, the sweet potato virus disease occurred generally and cause serious harm,which became an important restriction factor in development of the dried red sweet potato processing industry.In order to solve the serious problems of sweet potato virus disease in Liancheng County acute hazard and provide a scientific theory basis for promoting application of the virus-free in Liancheng County,we use Longyan7-3 sweet potato as a example ,have a study on meristem-tip culture virus-free and rapid multiplication, the hazards of virus disease,meristem-tip culture of sweet potato,virus detection of sweet potato and application of the virus-free seedlings of the main cultivation The main results showed: 1.By investigations of virus disease,the detection of virus infection rate using led I.setosa as identification hosts,the identification of virus types with serological methods,the results showed:the rate of virus infection in Longyan7-3 varieties was as high as 95.3 %,the main symptoms of virus infection seedlings was mesh of vein mosaic,followed by the grouper of faded green and yellow.The main type of virus infection was sweet potato feathery mottle virus (SPFMV),followed by the sweet potato latent virus (SPLV),and the two type viruses infected frequently sweet potato together.2.The orthogonal design experiment of Meristem-tip of Longyan7-3 sweet potato were cultured on MS medium supplemented with 6-BA, NAA and GA3 of various concentrations demonstrated that,the best culturing programmes for Longyan 7-3 meristem-tip tissue culturing was MS + 1.0mg/LBA +0.01mg/LNAA +0.2mg/LGA3 +30g/LSugar +7g/L agar,the time of meristem shifting was the 18th days,.and the plantlet ratio reached 72.4% from meristem-tip.By screening tests,we found that the most appropriate culturing programmes for large quantities rapid propagation of Longyan 7-3 was MS +0.1 NAA +30g/L consumption of sugar,culturing in the shallow liquid medium(12.5ml culturing medium in each bottle).By this programmes, the training cycle was 25 days, the seedling reached as high as 6.27cm, the seedling was more healthy and more strong,the coefficient of reproduction was about 6, and the cost of ingredient in this medium could be greatly reduced than that of regular propagation medium MS +30 g / L Sugar +7 g / L agar.3.The virus detection including the survival rate of the scion grafting in I.setosa ,the incidence and the morbidity degree and the morbidity latent period of I.setosa with indicator plant on the seedling from meristem-tip culturing was researched which were detected in different periods and making scions from different parts of sweet potato seedling.The results showed that the most appropriate time of virus detection by using I.setosa as indentification hosts was in May -June,followed by September-October, not in the July-August because this time had the high temperature.The scion for grafting detection should be make from the lower part of the stem,but not be make scion from the top of the stem .The appropriate time of detection used indicator plant and the scion made from appropriate location of seedling could improve the accuracy of the virus detection.The rate of virus elimination from meristem-tip culture in Longyan 7-3 sweet patato was 41.2% by virus detection using indicator plant in this research.4.The application effects of virus-free seedling was studied by comparative trial of yield in field plot ,the results showed that yield–increasing of the virus-free seedlings of Longyan7-3 sweet potato was extremely significant,the yield of virus-free seedlings increased 18.4 % compared with the normal seedlings.The reason for yield increasing of virus-free seedlins was mainly due to the increase of the number and the weight of the large roots, but the roots number of single seedling has no obvious difference.The dynamic of growth charater of virus-free seedling and its normal seedling was studied by investigation of root in different growth stage. The virus-free seedlings performed stronger growth than the normal seedlings in early growth stages,which including the vines grow fast, the root expansion of early and rapid.Meanwhile ,the vines growth and the index of leaf area of virus-free seedling were better than its normal seedling.The T/R valus showed that the virus-free seedlings growth more fit together between the department of ground and underground than that of the normal seedlings.