干旱条件下高水分利用效率（WUE）苹果种质和品种的利用对我国旱区苹果的高效生产有重要意义。项目组前期研究发现‘秦冠’苹果在干旱条件下具有高的WUE，并以其为亲本创制了一批杂交后代。在此基础上，本项目拟结合RNA-seq技术，从光合系统、光电子传递系统、气孔调控特性、叶片结构、碳素代谢等方面系统分析‘秦冠’苹果在干旱条件下高WUE的生物学机制，筛选关键基因，转化烟草进行功能验证，并将关键基因转入主栽品种，获得苹果新种质；采用GBS技术构建‘秦冠’和‘蜜脆’苹果杂交后代的遗传图谱，评价该群体WUE和抗旱性，分析相关性状的遗传特性，并进行精确QTL定位，获得WUE关键QTL。其目的在于探明苹果干旱条件下高WUE的分子机制，挖掘相关基因，摸清苹果WUE遗传特性及其相关的QTL，创建或筛选出干旱下高WUE的苹果新种质资源，为高WUE品种选育及旱区苹果可持续发展提供理论基础与方法。

It is necessary for sustainable apple production in arid regions to understand the mechanism for maintaining high water use efficiency (WUE) in apple plants under drought condition, and to discovery related genes and germplasm to use to improve apple plants. In this project, to understand the biological mechanism that 'Qinguan' apple has higher WUE than other cultivars under drought conditions, we will use RNA-seq technology to systematically investigate and compare the molecular regulation network for the photosynthetic system, photoelectron electronic transmission system, stomatal regulation characteristics, leaf structure, carbon metabolism and other aspects, and then select key genes will be transformed into tobacco to confirm their function in WUE and resisting drought stress. The key genes selected above will be transferred into apple to get new resources. In addition, we will construct the genetic mapping of hybrid offsprings from 'Qin Guan' and 'Honeycrisp' apple using genotyping-by sequencing makers, evaluate WUE and drought resistance in this group, and then analyze genetic characteristic of related traits to get key OTL on controlling WUE in apple. The aim of this study is to verify the molecular mechanism for maintaining higher WUE apple under drought condition and discovery related genes, to know WUE genetic characteristics in apple and its associated QTL, to create and select new apple germplasm resources with high WUE under drought. It will provide the basic theory and method of WUE breeding and improvement of crops in China WUE high and apple sustainable development in dry regions.