嫁接黄瓜果面蜡粉形成的环境依赖及砧木互作机制

Grafting is an important agricultural technique to improve the resistance to environmental stress and diseases and to increase yield of protected cucumber, however, the bloom formation on fruit surface of grafted cucumber depends on the rootstock cultivars, even the same rootstock and scion cultivars, there are great differences in bloom quantity in different cultivation seasons. Previous studies have showed that bloom formation on surface of grafted cucumber is closely related to the absorption and distribution of silicon in plant. To investigate the relationship between environmetal factors and bloom formation, non-grafted and grafted cucumbers on rootstocks with different de-blooming ability will be choosed and grown in the plant factory, by simulating the greenhouse environment in summer and in winter seasons.The ultrastructure and formation process of bloom will be observed with TEM, SEM and light microscope, and the expression of silicon transporter protein will also be detected by using qRT-PCR under different environmental conditions. The effects of environmental conditions on active and passive process of silicon absorption and acumulation in grafted cucumber will be proven. The gene expression profile controlling bloom formation in cucumber fruit will be constructed by using high-throughput gene expression profile technology, and followed by identification of candidate genes and detection of their expression characteristics. The purpose of the project is to reveal the mechanism of environmental dependence and interaction with rootstocks of bloom formation on fruit surface of grafted cucumber, and the research results will provide a theoretical guidance to high quality cucumber production.

嫁接是提高设施栽培黄瓜抗病性和抗逆性，增加产量的重要农艺技术，但不同砧木嫁接黄瓜果面蜡粉的发生程度不同，即使相同砧木和接穗，不同栽培季节和环境条件下果面蜡粉量也存在明显差异。前期研究表明，嫁接黄瓜果面蜡粉形成与植株的硅吸收分配特性密切相关。为了探讨环境条件与果面蜡粉形成的关系，本项目选用去蜡粉和不去蜡粉砧木嫁接黄瓜，以自根黄瓜为对照，在人工气候室内模拟冬、夏设施生产条件，借助TEM、SEM电镜和光镜技术观察不同环境条件下黄瓜果面蜡粉形成过程及其发育特征；利用qRT-PCR技术检测不同环境条件下嫁接黄瓜体内硅运转蛋白相关基因的表达特性；探明环境条件对不同砧木嫁接黄瓜硅吸收运转主动和被动过程的影响；通过高通量基因表达谱分析技术，构建黄瓜果实中蜡粉形成相关基因表达谱，筛选与蜡粉形成密切相关候选基因，并研究不同环境条件下的表达特性，以期从分子水平上揭示嫁接黄瓜果面蜡粉形成的环境依赖及砧木互作机制。

果实表面蜡粉是黄瓜重要的商品品质指标。嫁接是促进黄瓜生育，提高抗性和产量的重要农艺技术，但不同砧木嫁接黄瓜果面蜡粉数量不同，且受环境条件影响。为探明环境条件和砧木影响黄瓜果面蜡粉形成的机制，本项目采用去蜡粉能力不同的砧木南瓜嫁接，温室和人工气候室、土培与水培试验相结合，从生理、细胞和分子水平上开展深入系统研究。结果表明：环境条件显著影响黄瓜果面蜡粉的形成，冬春茬黄瓜果面蜡粉量显著高于秋冬茬；高温、强光显著促进黄瓜果面蜡粉形成，且温度的影响大于光照；砧木通过改变黄瓜对硅的吸收分配进而影响果面蜡粉形成。硅浓度和环境条件影响黄瓜对硅元素的主、被动吸收过程，强光、高温下被动吸收占比较大，且温度对被动吸收占比的影响大于光强；增加外源硅浓度，被动吸收的占比增加；相同外源硅浓度下，被动吸收占比以‘黄诚根2号’嫁接黄瓜最大，‘云南黑籽南瓜’嫁接黄瓜次之，自根黄瓜最小。CSiT-1和CSiT-2基因在黄瓜根系和叶片中均有表达，CmLsi1、CmLsi2-1、CmLsi2-2和CmLsi3基因在‘云南黑籽南瓜’嫁接黄瓜和‘黄诚根2号’嫁接黄瓜根系中均有表达，并且均表现为低硅促进和高硅抑制；相同硅浓度下，自根、嫁接黄瓜叶片和根系硅转运蛋白基因表达量均以高温、强光下最高，低温、弱光下最低。转录组分析表明，温光诱导的开花前子房蜡粉差异基因主要参与了次生代谢、植物激素信号转导和糖代谢3类代谢途径，商品成熟期果实蜡粉差异基因主要富集在糖代谢、脂肪酸代谢、氨基酸代谢等途径；蛋白组学分析表明，温光诱导的开花前子房差异表达蛋白主要富集在次生物质代谢和植物激素信号转导等途径；开花前子房转录组和蛋白组关联分析表明，相同光照、不同温度比对组合的差异表达基因（蛋白）较多，共同上调的差异表达基因（蛋白）多富集在次生代谢和植物激素信号转导等途径。本研究结果对通过砧木选择和栽培环境调控来改善嫁接黄瓜果实品质和商品性具有重要意义。