Abstract:

In this study， we evaluated the salt tolerance of 15 germplasm lines of buffalo grass （Buchloe dactyloides） using a soil culture method. These materials were obtained from places such as Texas and Nebraska in the USA. The germplasm lines were cultivated under saline stress， which was imposed by irrigation with 600 mmol·L^-1 NaCl solution. A total of 13 traits were measured and the data submitted to principal component and membership function analyses. The 13 traits were： phenotypic characteristics （plant height and stem diameter） and physiological and biochemical indexes ［relative water content of leaves， peroxidase （POD） activity， superoxide dismutase activity， contents of malondialdehyde （MDA）， proline， and osmotic adjustment substances， i.e.， glucose， sucrose， and starch， and activities of enzymes related to carbohydrate metabolism， i.e.， α-amylase， β-amylase， and total amylase］. On univariate analysis of the traits separately， we detected significant differences in salt tolerance among the germplasm lines （P<0.05）. Principal component analysis found four principal components （PCs） with eigenvalues greater than 1. PC1 （eigenvalue 3.835） was interpreted as reflecting growth and tolerance under salt stress； PC2 （eigenvalue 2.623） reflected starch metabolism under salt stress； PC3 （eigenvalue 1.814） reflected osmotic regulation capacity under salt stress； PC4 （eigenvalue 1.452） reflected carbohydrate metabolism and energy supply under salt stress. Using a combination of principal component analysis and the membership function method， we constructed a multivariate evaluation system for the assessment of the salt tolerance of B. dactyloides. Among the tested materials， Bd324 and Bd769 showed higher multivariate scores， and their average membership function （D） values were 0.85 and 0.75， respectively. Using stepwise regression to predict the D value from the original 13 variables， we obtained the following regression equation for evaluating the salt tolerance of B. dactyloides： D=0.351+0.266X₁-0.211X₂-0.191X₃+0.121X₄+0.144X₅+0.093X₆，_{where X1 to X6 correspond to MDA， starch content， POD， total amylase activity， stem thickness， and relative water content of leaves， respectively. The germplasm identified in this study as having superior salt tolerance traits will be useful for breeding new salt-tolerant varieties of B. dactyloides. Our findings and collected germplasm also provide a theoretical basis and useful materials for the ecological restoration of saline-alkali land.}

Key words: Buchloe dactyloides, salt tolerance, physiological indexes, principal component analysis, regression equation