基于代谢组学技术研究嫁接影响红茶品质形成的物质基础

The compositions of secondary metabolites of scion are affected through the change of root in grafting system, which may influence the tea quality. However, the study on the effect of grafting on tea quality is still very weak, and the change of substance basis related to the tea quality after grafting has not yet been elucidated. In our study, two kinds of materials, which obtained by grafting between “yinghongjiuhao” as scion and two types of stocks, are used as the research objects. And own root seedlings and self-grafting seedlings of scion are used as control. Differences of characteristic quality components in fresh tea leaves between grafting and control materials can be analyzed through UHPLC-QTOF/MS combined with chemometrics analysis, and the qualitative analysis and pathway analysis of differential compounds will be performed, which can explore the effects of grafting on the metabolic product in fresh tea leaves. As well as the effect of grafting on chemical composition for aroma and flavor of broken black tea will be revealed by metabolic profiling based on GC-MS and UHPLC-QTOF/MS combined with chemometrics analysis, respectively. To parse the relationship among grafting, the quality of fresh tea leaves and the quality of broken black tea, comprehensive association analysis of results including metabolic profiling analysis, botany properties and organoleptic evaluation of broken black tea will be performed. The study is expected to reveal the substance bases of black tea quality affected grafting and illuminate the effect of grafting on the formation and transformation of quality components, providing a theoretical foundation for the further research of the characteristic quality components of tea.

嫁接技术通过改换根系影响接穗部分次生代谢产物的含量和组成，从而影响茶叶品质。目前针对嫁接影响茶叶品质的研究还很薄弱，尚未阐明嫁接影响茶叶品质形成的物质基础。本项目利用英红九号为接穗获得的两类嫁接材料为研究对象，以自根苗和自嫁苗的英红九号为对照，拟利用UHPLC-QTOF/MS结合化学计量学技术，分析嫁接材料与对照材料茶鲜叶的特征性差异化合物并进行通路分析，探究嫁接对茶树鲜叶代谢产物的影响；采用基于GC-MS、UHPLC-QTOF/MS结合化学计量学技术的代谢组学分析手段，分别分析嫁接对红碎茶香气和茶汤化学成分的影响；综合代谢组轮廓分析结果、植物学性状调查结果及红碎茶感官审评结果进行关联分析，解析嫁接-茶树鲜叶品质-红碎茶品质之间的相关性，揭示嫁接影响红茶品质的物质基础。研究结果有望揭示嫁接对品质成分的形成、转化等规律的影响，为茶叶品质构成成分的研究奠定基础。

本项目针对嫁接是否可以改变茶树植物学性状并稳定维持，是否影响茶鲜叶代谢物及成茶香气品质开展了研究。以不同砧木嫁接后的英红九号接穗为研究对象，调查了接穗的叶片表型、茶鲜叶代谢组分和成茶香气物质。主要结果如下：(1) 不同砧木嫁接能够不同程度的影响茶树叶长、叶宽、叶色等表型，通过对嫁接后接穗的3年表型调查发现，仅有白毛2号砧木引起的叶长显著增加能够稳定维持。（2）建立了完善的茶叶代谢物分析方法，以及扩充了茶树代谢物谱库。（3）基于UHPLC-QTOF/MS结合化学计量学的代谢组学技术，分析了4类砧木对接穗鲜叶代谢物的影响，与对照英红九号相比较，共定性得到31种化合物；不同砧木对代谢物的影响不同，其中五岭红和白叶单丛作为砧木嫁接对英红九号的鲜叶代谢物影响较大，而以白毛2号和黑叶水仙砧木对英红九号鲜叶代谢产物影响较小，且五岭红砧木会显著提高接穗鲜叶中的大部分代谢物含量；差异代谢物富集到3个代谢通路：苯丙素生物合成，类黄酮生物合成，黄酮和黄酮醇生物合成。（4）通过GC-MS结合化学计量学技术，分析了6类砧木对接穗英红九号红碎茶香气品质的影响。不同砧木嫁接会对英红九号红茶香气感官品质有不同程度的影响，仅有黄枝香单丛砧木能够使接穗红碎茶带有明显的花香；与对照相比较，共定性到41种挥发性化合物，包括10个醇类物质、13个醛类物质、8个酮类物质、5个酯类物质、3个烯烃类物质和2个烷类物质；6类砧木对接穗红碎茶香气物质呈现不同程度的改变，其中白叶单丛砧木的影响最小；黄枝香单丛嫁接的接穗红碎茶中表现花香的物质得到显著上调，从而使得其呈现花香感官品质。研究结果拓宽和加深了嫁接对茶树品质影响研究的广度和深度，为嫁接技术的应用提供理论基础。