为明确盐胁迫下落羽杉属（Taxodium Rich.）植物Na+和K+流特征及其外排速率QTL定位，以落羽杉〔T. distichum (Linn.) Rich.〕和墨西哥落羽杉（T. mucronatum Ten.）为亲本，以（落羽杉×墨西哥落羽杉）×墨西哥落羽杉回交子代（BC1代）为实验材料，采用非损伤微测技术（NMT）测定盐胁迫（150 mmol·L-1NaCl）下BC1代根尖分生区Na+、K+流速，并采用隶属函数法和Wards聚类分析对BC1代的耐盐性进行综合评价，同时开展Na+和K+外排速率的QTL定位分析。结果显示：盐胁迫下，落羽杉和墨西哥落羽杉的Na+和K+均为外排，且墨西哥落羽杉具有更强的排Na+、保K+潜力；97个BC1代中有89个通过调节Na+和K+外排维持离子稳态，且Na+和K+外排速率变异较大（变异系数分别为68.68%和61.07%）。相关性分析结果显示Na+外排速率与K+外排速率在0.01水平呈显著负相关。基于隶属函数值的Wards聚类分析结果显示：89个BC1代被分为4组，包括高耐盐潜力型（7个BC1代）、较高耐盐潜力型（17个BC1代）、较低耐盐潜力型（40个BC1代）和低耐盐潜力型（25个BC1代）。此外，Na+外排速率定位到3个主效QTL，可解释7.65%～14.35%的表型变异；K+外排速率定位到13个主效QTL，能解释1.20%～3.68%的表型变异；且3个与Na+、K+外排相关的QTL存在重叠。综合分析结果表明：（落羽杉×墨西哥落羽杉）×墨西哥落羽杉BC1代根尖分生区Na+排除能力越强，K+保持能力则越强，筛选出的7个高耐盐潜力BC1代及3个与Na+、K+外排相关的重叠QTL可用于落羽杉属耐盐品种筛选。

To clarify characteristics of Na+ and K+ flows in Taxodium Rich. species under salt stress and QTL mapping for their outflow velocities, T. distichum (Linn.) Rich. and T. mucronatum Ten. were taken as parents and their backcross generations (BC1 generations) of (T. distichum × T. mucronatum) × T. mucronatum were taken as experimental materials, the Na+ and K+ flow velocities in root apical meristem of BC1 generations under salt stress (150 mmol·L-1 NaCl) were measured by using non-invasive micro-test technology (NMT), salt tolerance of BC1 generations was comprehensively evaluated by using membership function method and Wards clustering analysis, and QTL mapping analysis was conducted for Na+ and K+ outflow velocities. The results show that both T. distichum and T. mucronatum exhibit Na+ and K+ outflows under salt stress, while T. mucronatum possesses stronger Na+ outflow and K+ retention capacity; among 97 BC1 generations, 89 BC1 generations maintain ion homeostasis by regulating Na+ and K+ outflows, and the Na+ and K+ outflow velocities have relatively high variations (the coefficients of variation are 68.68% and 61.07%, respectively). The correlation analysis result shows that Na+ outflow velocity has  significant negative correlation with K+ outflow velocity at 0.01 level. The result of clustering analysis based on membership function value shows that the 89 BC1 generations are classified into four groups, including high salt tolerance potential type (7 BC1 generations), relatively high salt tolerance potential type (17 BC1 generations), relatively low salt tolerance potential type (40 BC1 generations), and low salt tolerance potential type (25 BC1 generations). Additionally, Na+ outflow velocity is mapped to three major QTLs, explaining 7.65%-14.35% of phenotypic variation; K+ outflow velocity is mapped to thirteen major QTLs, explaining 1.20%-3.68% of phenotypic variation; and three QTLs associated with Na+ and K+ outflows are overlapped. The comprehensive analysis result reveals that BC1 generations of (T. distichum × T. mucronatum) × T. mucronatum with stronger Na+ outflow capacity in root apical meristem exhibit stronger K+ retention capacity, and the seven BC1 generations with high salt tolerance potential and three overlapping QTLs associated with Na+ and K+ outflows can be utilized for screening salt-tolerant cultivars of Taxodium.