【目的】棉花（Gossypium hirsutum）虽是较耐盐碱的作物，但不同品种间耐盐性差异较大。本研究旨在探讨新疆各年代不同基因型棉花苗期耐盐特性，挖掘棉花本身耐盐遗传资源，筛选耐盐性快速鉴定指标并建立可靠的棉花耐盐性数学评价模型，为棉花耐盐新品种选育及大规模品种耐盐性评价奠定基础。【方法】以17个棉花品种为试验材料，按NaCl盐与草炭、蛭石复合基质重量比设置0（CK）、0.6%两个处理水平，棉种经消毒、催芽后播于复合基质，通过苗期盐土栽培持续胁迫的方式，可反映棉株在大田条件中的实际胁迫环境及真实抗逆机制。对各处理下各品种出苗率（ER）、幼苗鲜重（FW）、干重（DW）、植株含水量（PWC）、第一片真叶面积（LA）、叶片净光合速率（Pn）、叶绿素含量（Chl）和相对电导率（REC）等11个生理指标进行测定，以各单项指标的耐盐系数作为衡量耐盐性的依据，运用主成分分析、聚类分析和逐步回归等方法对其耐盐性进行综合评价及分类，并分析各耐盐类型棉花品种生理表现特征。【结果】通过主成分分析，本试验将盐胁迫处理下棉花幼苗叶片的11个单项指标转换成6个彼此独立的综合指标；通过隶属函数分析，得到不同棉花基因型幼苗耐盐性综合评价值（D值），并通过聚类分析，将17个棉花品种划分为4种耐盐类型，其中盐敏感型3个品种，弱耐盐及中度耐盐型各6个，高度耐盐型2个；进一步利用逐步回归方法建立了可靠的棉花幼苗耐盐性评价回归模型D=-1.192+0.402REC+0.119LA+0.274FW+0.086Pn+1.019Chl，方程决定系数R2=0.9921，同时筛选出显著影响棉花幼苗耐盐能力的5个单项指标，即Pn、Chl、LA、FW和REC，对回归方程的估计精度进行评价，各品种估计精度均大于94.44%，表明所筛选鉴定指标对棉花耐盐性影响明显，该方程可用于棉花耐盐性评价。本研究对逐步回归与聚类结果进行相互验证，得到各耐盐类型棉花幼苗的生理表现特征。结果发现，与盐敏感品种相比，强耐盐棉花品种幼苗在盐胁迫下REC较低，Pn、Chl、LA和FW则能保持较高水平，且其幼苗真叶面积可达其它类别品种近2倍。【结论】强耐盐棉花品种幼苗叶片在盐碱环境中受到伤害较轻，能保持较高的真叶面积和光合能力，有利于提高植株耐盐能力和光合产物积累，降低土壤中离子毒害，增强植株耐盐性。在相同逆境中，通过测定REC、Pn、Chl、LA和FW等5个鉴定指标，可进行品种耐盐性强弱的快速鉴定和预测。%Objective]As one of the salt-tolerance crops, there is a great difference among different varieties. So, the objective of this study was to investigate the salt tolerance of cotton seedlings of different genotypes which are grown widely in different eras in Xinjiang, to excavate their own salt tolerance genetic resources, to screen suitable evaluation indicators of salt-tolerance, and to establish a mathematical evaluation model for salt tolerance, which would provide a theoretical basis for discovery and promotion of salt tolerant germplasm, breeding of new salt-tolerant varieties and evaluation on salt tolerance of a large number of cotton varieties.[Method]Seventeen varieties that are widely grown at different decades in Xinjiang of China were selected as test materials in this study. Compared to the control, the mass ratio of NaCl to growing medium was 0.006 in salt stress, and the composition of matrix is 1 part grass charcoal plus 1 part vermiculite. After being disinfected and pregermination, cotton seeds of seventeen different genotypes were to sow in the medium. This is helpful to reflect the actual stress environment in field conditions and explain the mechanisms of the tolerance by means of continuous salt stress at seedling stage. The salt comprehensive evaluation of salt tolerant coefficient (STC) about the emergence rate (ER), fresh weight (FW), dry weight (DW) and plant water content (PWC) of each variety, leaf area of the first true leaf (LA), the net photosynthetic rate (Pn), chlorophyll content (Chl) and relative electric conductivity (REC) in leaves of cotton seedlings of different genotypes under salt stress (0.6%) were evaluated by principal components analysis, hierarchical cluster analysis and regression analysis. Physiological performance characteristics of various salt-tolerant types of cotton varieties were analyzed, too.[Result]The results showed that the 11 single indexes in leaves of cotton seedlings of different genotypes under salt stress could be classified into 6 independent comprehensive components by means of principal components analysis. According to the salt-tolerance comprehensive evaluation value (D value) of different cotton varieties, which was calculated from the subordinate function analysis, the 17 cotton cultivars were divided into four salt-tolerant types by cluster analysis, 3 of the 17 varieties were salt-sensitive type, 6 varieties were weak salt-resistance type, 6 were medium salt-resistance type, and 2 were high salt-resistance type. A mathematical evaluation model for cotton salt tolerance was established by means of regression analysis, and D=-1.192+0.402REC+0.119LA+0.274FW+0.086Pn+1.019Chl (R2=0.9921). Five indexes closely related to the salt tolerance, LA, REC, FW, Pn and Chl, were screened, too. Evaluation accuracy of all varieties were more than 94.44%, this shows that the five indexes in the regression equation obviously affect the salt resistance of cotton seedlings, and this equation can be used in salt tolerance evaluation of cotton cultivars. Furthermore, the regression analysis and clustering results were mutual authentication. The results showed that, compared with salt-sensitive cotton varieties, REC of cotton leaves of high salt-resistance type was lower than that of other cultivars after treated with 0.6%salt stress, Pn, Chl, LA and FW were higher, LA of high salt-resistant cotton seedlings especially was nearly 2 times larger than other categories varieties.[Conclusion]Higher salt tolerant varieties, which had lighter injury, higher leaf area and photosynthetic capacities under salt stress, were able to maintain higher accumulation ability of salinity and photosynthetic products, decreased ion toxicity from soil, and enhanced salt tolerance of plants. Determination of the five indicators under the same condition can be used for rapid identification and prediction of other cotton varieties, which is very useful for the breeding, promotion, identification and screening of salt tolerant germplasm.
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