Study On The Propagation And Production Of Sweet Potato Virus-free Seedling 'Longshu No.9'

In this study,the sweet potato variety'Longshu 9'was used as the experimental material to study the tissue culture,hydroponic propagation system,tube miniature potato induction and field test.In the tissue culture,the best formula of shoot tip meristem culture and bud induction were explored.The hydroponic experiment explored the formula of proprietary nutrient solution for virus-free seedling propagation which was compared with the conventional formula.The effects of temperature difference between day and night and PP₃₃₃ and NAA on tube miniature potatoes were studied by using MS solid medium and perlite as the matrix.The effect of different potassium application levels on the yield of'Longshu 9'was studied in the field experiment.In the end,we tried to establish a production system of virus-free seedlings and virus-free potatoes of'Longshu9'to provide technical reference for high quality and high yield of sweet potato.The results are as follows:?1?In the tissue culture study,the average budding rate,average rooting rate and seedling rate of shoot tip meristems obtained on 1/2 MS+NAA 0.1 mg/L+6-BA 1mg/L+GA₃ 0.2 mg/L were the highest.The optimal medium of shoot induction was 1/2MS+6-BA 2 mg/L+NAA 0.2 mg/L.The second shoot induction test was based on the first best formulation and different concentrations of AgNO₃ were added.AgNO₃ had an effect of promoting differentiation on callus and improved the quality of virus-free seedlings,but the induction effect on cluster buds was not obvious.?2?In the hydroponic experiment the macroelement and trace elements of MS liquid medium were used as the solutions of virus-free sweet potato soilless cultivation.The element content in the solution was periodically sampled and the morphological change of the aboveground part was recorded.According to the correlation between the two,a hydroponic formulation of virus-free seedlings was developed and compared with MS and other general hydroponic formula for validation.The results showed that the double new formula was most favorable for a hydroponic propagation.?3?Studies on sweet potato production from virus-free seedlings include two parts:induced tube miniature potato production and field potato production.In the early stage of induced tube miniature potato formation,MS solid culture medium was used as the substrate to study the effects of PP₃₃₃ and temperature difference between day and night on induced tube miniature potato formation.It was found that at a temperature difference between day and night at 15/25°C,MS+6-BA 1 mg/L+NAA 0.2 mg/L+PP₃₃₃ 200 mg/L+agar 5.8 g/L+sucrose 30 g/L?pH 5.8?had the most significant effect.In the later stage of the experiment,perlite was used as the substrate,and 1/2 Hoagland and Arnon general formula culture were used to study the effect of NAA on the induction of tube miniature potatoes.It was found that NAA can effectively promote the expansion of plantlet roots,of which 6-BA 1 mg/L+PP₃₃₃ 200 mg/L+NAA 3 mg/L?pH 5.8?was the best.In the field test,four application levels of K,215,322,and 429 kg/hm² were set on the same basis of N and P application rates.The results showed that potassium application could increase the stem length,stem node length and total number of branches of sweet potato,the weight of individual potato block and the yield.Finally,the optimal fertilization amount was 215kg/hm².