[Cold-tolerance of walnut cultivars: a comprehensive evaluation].

In order to speed up the cold-tolerance breeding and improve the cultivation efficiency of walnut to further expand its planting area, six walnut cultivars (lines) including Luguo No. 8, N13-1, Luguo No. 12, N17-24, Taile, and Xiangling were taken as test materials and treated at -15 degrees C, -20 degrees C, -25 degrees C, -30 degrees C, and -35 degrees C, with their tissue's water content, membrane permeability, lipid peroxidation, protective enzyme activities, and osmotic adjustment substances determined to detect the cold resistance of the cultivars (lines). There existed greater differences in the ratio of free water to bound water in the branches of the cultivars (lines). Under low temperature treatment, the branches membrane permeability and malondialdehyde content increased, superoxide dismutase activity presented an ascend-descend-ascend-descend trend, catalase activity decreased after an initial increase, and the soluble protein and proline contents increased, but the variation degrees of these parameters differed with cultivars (lines). After the recovery from low temperature, N17-24 and Luguo No. 12 had a significantly higher germination rate than the other cultivars (lines). By using fuzzy mathematics method, the cold-resistance of test walnut cultivars (lines) was evaluated as N17-24 > Luguo No. 12 > N13-1 > Luguo No. 8 > Taile > Xiangling.