Abstract:

【Objective】To shorten the regeneration cycle of Cucurbita pepo L. and obtain tissue culture seedlings with strong disease resistance.【Methods】Several Cucurbita pepo L. varieties were used as experimental materials and germinated on MS medium（30.0 g/L sucrose and 6.5 g/L agar）for 3 d. The germination rates，contamination rates and bud lengths of different Cucurbita pepo L. varieties were analyzed. Using Hongchang 211 as the research object，in vitro rapid propagation was used to examine the effects of various cotyledon explant types and sizes，hormone ratios，and seedling cultivation techniques on in vitro regeneration of Cucurbita pepo L..【Results】In the seed germination test of different Cucurbita pepo L. varieties，Hongchang 211 had higher germination rate，more seeds with bud length exceeding 3 cm and lowest contamination rate. Using Hongchang 211 as the tissue culture material，taken 1/2 cotyledons close to the hypocotyl as explants had the best induction results. The primary culture hormone ratio of 2.0 mg/L 6-BA+0.5 mg/L TDZ（thidiazuron）resulted in the highest plant height（3.423 cm）and largest plant width（4.565 cm）. When the ratio of rooting hormone was 2.0 mg/L 6-BA+0.5 mg/L NAA，the root length was the longest（5.72 cm），the root weight was the heaviest（0.602 g），the average number of roots was the largest（5.62），and the rooting rate was the highest（100%）. When the plant had 5 true leaves，the artificial climate chamber was partially opened for 1 d then fully opened for 1 d，the survival rate of transplanting reached 97.75%. After 60 d of transplanting，the disease indexes of powdery mildew and virus disease between tissue cultured seedlings and conventional seedlings were significantly different（P<0.05）. The regeneration cycle for tissue culture seedlings were roughly 45 d.【Conclusion】The tissue culture seedlings of Cucurbita pepo L. variety Hongchang 211 had short regeneration cycle and high disease resistance. The optimal ratio of primary culture hormone was 2.0 mg/L 6-BA+0.5 mg/L TDZ and the optimal ratio of rooting hormone was 2.0 mg/L 6-BA+0.5 mg/L NAA. The plants had best transplanting result when they had 5 true leaves，the artificial climate chamber had been partially opened for 1 d then fully opened for 1 d.

Key words: Cucurbita pepo L., In vitro rapid propagation, Explants, Disease resistance, Regeneration cycle