Physiological response of Xinjiang wild walnut germplasm to low temperature stress

We examined the physiological response of 1-year-old branches of 37 Xinjiang wild walnut germplasm resources in Gongliu wild walnut forest under cold temperatures (-20 ℃ and 4 ℃) for 12 hours, compared the responses with that of Juglans mandshurica. The relative conductivity (REC), free proline (PRO), soluble sugar (SS), malondialdehyde (MDA) content and peroxidase (POD) activity were measured in an artificial climate chamber by simulating spring low temperature. Subordinate function and principal component analysis were used to evaluate the physiological response of walnut germplasm to low temperature. The results showed that the REC, PRO, SS, MDA content and POD activity of Xinjiang wild walnut were increased. By evaluating the relationship between low temperature resistance and habitat, we found that cold tolerance level was middle valley > east valley > west valley > general valley. Xinjiang wild walnut showed stronger cold tolerance than J. mandshurica. Seven germplasm with cold resistance were selected from the total 37 wild walnut germplasm in Xinjiang, which provided a reference for improving walnut varieties and their responses to sudden weather change in late spring and other growing stages.