| Sweet potato [lpomoea batatas (L.) Lam. ] as a kind of crop for energy sources, foodstuff, feedstuff or health food, has been extended quickly with the development of production, adjustment of agricultural structure and change of dietary pattern of people. As a crop of asexual reproduction, viruses easily infect sweet potato and reproduce rapidly which results in lower yield and worse quality. There is no effective germicide or antibiotic to prevent and cure them, and no anti-virus sweet potato cultivars, too. The virus diffusion is very slow in stem-apex meristem of sweet potato, so there is no or little virus in stem-apex meristem of sweet potato. It is reasonable method by culturing stem-apex meristem to obtain virus-free young plant. So far, there were many reports about stem-apex meristem culture, but the conditions of culture were various and different. Two sweet potato varieties were used as experimental material to definitude the culture medium type and the condition, to analyze growth characteristics of virus-free sweet potato and to investigate the effects of N, P, K and density as well as their interaction on the yield of sweet potato.The results showed that when the stem tip apex tissue culture was 0.3～0.5mm, disinfected by 0.05 sodium hypochlorite solution marinate for 10min, with two leaf primordium in medium with 0.5 mg/L BA, 0.1mg/L IAA and 0.1mg/L GA~3, could significantly increase the formation of callus and buds. Variant varieties had difference plantlet regeneration rate, plantlet regeneration rate of Beijing553 was 86.8% .The suitable time of preculture was 18～21d. Addition of 0.1-0.5 mg/L IBA(or NAA)into MS medium was beneficial to plantlet regeneration from subcultured tip meristem in sweet potatoes, and IBA was superior to NAA. Comparison with MS medium without any auxins, the MS medium supplemented with IBA 0.5mg/L could increase tip meristem culture plantlet ratio by 16.5% and reduce mean time of plantlets by 8.6d. When concentration of IBA(or NAA) was excessively high(1.0 mg/L), tip meristem explants of sweet potatoes produced much callus, plantlet ratio from subcultured tip meristem in sweet potato decreased and the average plantlet time was delayed. The suitable temperature was 28~C, and illumination time was 14～16h/d.Growth analysis showed that the dry matter weight of stem, leaf and earthnut, LAI,RGR and NAR of virus-free sweet potato were significantly higher than those of non-virus-free sweet potato. The effect of virus-free on production was difference between cultivars, the production of Yushu7 increased by 48.59%,Yushu8 increased by 43.56%.The effect of N, P, K and density on virus-free sweet potato production was K>N>density>P. The highest production of virus-free Yushu7 could reach 53.0 t/hm~2. The best agricultural management methods of yield of more than 45.0 t/hm~2 were 63.42-74.73 N kg/hm~2, 67.76～82.24 P~2O~5 kg/hm~2, 106.7～127.71 K~2O kg/hm~2 and 46000～53000 plants/hm~2. |
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