Studies On Strains Identification And Virus Elimination Of Meristem Tip Culture Of Purple Sweet Potato Introduced From Japan

Ipomoea batatas L. (Lam.) is an important crop which can be used as foods, industrial raw materials, feedstuff and health goods, however, it was found out that virus diseases were the key factor to its genetic characterization degeneration, output reduction and quality decline. At present, obtaining virus-free plants by means of meristem tip culture was the available solution to deal with the problem.Purple sweet potato is an excellent type of sweet potato cultivar with distinctive colour properties and economic value which developed recently, and purple sweet potato colorant, derived from purple sweet potato storage roots, is a natural anthocyanin pigment which shows functions of antioxidation and concerned by home and abroad.In this paper, the contents of pigment derived from 14 strains or cultivars of purple sweet potato were compared. In addition, 26 morphological markers and six isozymes (amylase, peroxidase, cytochrome oxidase, superoxide dismutase, malate dehydrogenase and esterase) markers of 14 strains or cultivars of purple sweet potato introduced from Japan were studied, and UPGMA dendrograms of 14 strains or cultivars of purple sweet potato based on morphological and isozyme markers analysis were available. Moreover, the virus infection in 14 strains or cultivars of purple sweet potato introduced from Japan was surveyed. Meanwhile, the meristem tip of purple sweet potato was used as explant to find out effective way of in vitro culture, with orthogonal design, we tried to find out the best medium composition and to establish a technique system of tip culture of virus-free purple sweet potato, and some factors affected on virus elimination of purple sweet potato by stem tip culture and several diagnostic methods for detecting virus diseases were studied. The research work and results were reported as following:1 Comparison of the contents of pigment derived from 14 strains or cultivars of purple sweet potatoThe pigment were extracted from purple sweet potato storage roots by acid solution, and the contents of pigment derived from 14 strains or cultivars of purple sweet potato introduced from Japan were compared. The results show that the contents of pigment were different among the different genotype of purple sweet potato, among them: the contents of pigment derived from A1, A2, A5 ,A7 (OD>0.35) and B1, B2, B3, B7, B8 (0.35 >OD>0.25) were higher, so, the above-mentioned purple sweet potato were worth to select and breed.2 Strains identification of purple sweet potato introduced from Japan26 morphological markers were used to study cluster analysis in 14 strains or cultivars of purple sweet potato introduced from Japan by unweighted pair group method arithmetic averages (UPGMA). The results indicated that 14 strains or cultivars of purple sweet potato were divided into 6 large groups: group I include A1, A2, A7; group II include B1~B3, B7 and B8; group â…¢ only include A5; group â…£ include A3, A4, A6; group â…¤ only include B9; group â…¥ only include "ShanChuanZi".Comparison and analysis of isozyme patterns of the six enzyme (amylase, peroxidase, cytochrome oxidase, superoxide dismutase, malate dehydrogenase and esterase) in stem, leaf , petiole and storage root of purple sweet potato, the results showed that the isozyme bands from leaves were clear and stable, and analysis of isozyme can be used to analyze the affinity among different strains or cultivars of purple sweet potato.The results of isozyme analysis in leaves of strains or cultivars of purple sweet potato show that the number of isozyme bands of peroxidase, cytochrome oxidase and superoxide dismutase were 13, 11 and 10 , respectively. But that of amylase, esterase and malate dehydrogenase were only 4,7 and 7, respectively.The results of cluster in leaves of strains or cultivars of purple sweet potato based on isozyme analysis indicated that 14 strains or cultivars of purple sweet potato were divided into 7 large groups: group â…  include A1, A2, A7; group â…¡ include B1~B3; group â…¢ include B7 and B8; group â…£ only include B9; group V include A3 , A4, A6; group â…£ only include A5; group â…¦ only include "ShanChuanZi".The results of cluster analysis based on morphological markers and isozyme markers were similar, which also show A5, B9 and "ShanChuanZi" were different strains or cultivars of purple sweet potato. Meanwhile, the relationship among A1, A2 and A7, A3, A4 and A6 was much close, respectively. The relationship among B1~B3, between B7 and B8, was much near, respectively.