Selecting Jingxin No.1 watermelon (pumpkin seedlings for grafting) as material,using two factors and four levels random design method,the effects of topdressing different ratios of nitrogen and potassium fertilizer on physicochemical properties and microorganisms of soil,and fruit quality of watermelon were studied during fruit enlargement period with domestic urea (N≥46％) and domestic potassium sulfate (K2O ≥50％) as fertilizer source.The results showed that increasing nitrogen fertilizer,the available nutrients and organic matter content in the soil decreased,the physiochemical properties of soil became worse,the microbial population showed a significant reduction,and the fruit quality significantly declined.The fruit enlargement period of watermelon needs a lot of potassium fertilizer.When applying potassium fertilizer which less than 450 kg/hm2,the available nutrients and organic matter content in the soil increased,the physicochemical properties of soil got better,the quantity and diversity of microorganisms in soil became richer,the proportions of fungi and actinomycetes declined,and the soil transformed into bacterial form.Meanwhile,the fruit quality was improved to a certain extent.

1 我国西瓜嫁接种苗产业现状 我国是西瓜生产和消费大国,西瓜栽培面积和产量位居世界第一.据世界粮农组织(FAO)统计,2009年我国西瓜种植面积221万hm2,总产量6 820万t,分别占世界的58％和68％.我国西瓜主要集中在华东、中南两大地区,西瓜产量占全国75％.其余分布在西北地区,产量占10.2％;华北地区,产量占9.9％;以及东北地区,包括黑龙江、辽宁和吉林省,产量占5.4％.据2010年统计,河南省西瓜产量一直保持占全国总产量的20％,为西瓜生产第一大省;山东省西瓜产量约占全国产量的16％,为西瓜产量第二大省;安徽省西瓜产量约占全国总产量的7％,为西瓜产量第三大省.这三个西瓜主产省西瓜产量占全国43％以上.

A high frequency watermelon regeneration system had been developed by using watermelon cultivar X173 and Xiaoqilin.The results showed that MS+6-BA 1.0 mg·L-1+IBA 0.5 mg·L-1 was the most suitable medium for bud organogenesis from cotyledon explants of X173 and MS+6-BA 2.0 mg·L-1+IAA 0.2 mg·L-1 for Xiaoqilin,with regeneration frequency of 92.6% and 89.7%,respectively.The suitable shoot elongation medium for both cultivars was MS+KT 0.2 mg·L-1.The favorable rooting medium for both cultivars was MS + IBA 0.2 mg·L-1.Warm and humid condition is necessary for plantlets to survive after transplant into soil.Our regeneration system should be helpful watermelon genetic transformation and genetic improvement via in vitro technology.