Abstract: In order to determine the salt tolerance of different oat breeding materials at the seedling stage and select elite oat germplasm lines, five screened salt-tolerant oat germplasm lines from a previous experiment (Baiyan No.7, Longyan No.4 and No.5, and Qingyongjiu 30 and 195), were studied in this research. In a sand culture experiment, 3-week old seedlings were treated with 0.9% NaCl solution for 7 days, and the growth characteristics, photosynthetic characteristics, chlorophyll fluorescence parameters, antioxidant enzyme activities, tissue malondialdehyde (MDA) concentration, and osmolyte content were measured. The salt tolerance of the five oat germplasm lines was evaluated by principal component analysis and membership function analysis of the seedling data. It was found that there were significant differences (P<0.05) between the tested germplasm lines for performance under salt stress. Qingyongjiu 195 had a larger root surface area and root volume, a higher K⁺ content, a lower MDA content, and higher net photosynthetic rate, electron transfer rate, photochemical quenching, chlorophyll content and peroxidase activity, than the other 4 tested varieties. Meanwhile, Qingyongjiu 30 had greater superoxide dismutase and catalase activities than other germplasm lines. Through principal component analysis, inorganic osmotic regulation substances, membrane lipid peroxidation and antioxidant enzyme activity were identified as traits which could be used in a multi-trait evaluation index for salt tolerance of oats at the seedling stage. According to the multi-trait index of salt tolerance (D), the salt tolerance of the germplasm lines ranked as follows: Qingyongjiu 195>Baiyan No.7>Qingyongjiu 30>Longyan No.5>Longyan No.4.

Key words: salt stress, oats, principal component analysis, membership function method