The Hongyang kiwifruit (Actinidia chinensis var. chinensis ‘Hongyang’) has high economic and nutritional values and good prospects for market development. However, in recent years Hongyang kiwifruit production areas such as Yunnan and Sichuan have been subjected to extreme weather such as inversions on several occasions, and its poor cold resistance has limited its scope for development. In this study, ethyl methanesulfonate (EMS) was used to induce mutants of Hongyang kiwifruit in a tissue culture process, which led to the screening of cold-tolerant mutants and the investigation of their stress response mechanisms through transcriptome analysis. In this study, mutants were induced using EMS induction technology using Hongyang kiwifruit leaves as experimental material in tissue culture (4.4 g·L-1 MS + 4.5 g·L-1 agar + 1.5 mg·L-1 6-BA + 0.1 mg·L-1 NAA + 15 g·L-1 sucrose + 0.01-0.10 g·L-1 EMS) and screened for cold-tolerant mutants under low temperature. Selected cold-tolerant mutants and normal Hongyang kiwifruit tissue culture seedlings were subjected to 4℃ 12 h cold stress treatment, while later, transcriptome sequencing analysis was performed. The results were as follows: (1) According to the preliminary phenotypic identification, some of the mutants induced by the 0.06 g·L-1 EMS were phenotypically resistant to cold; (2) In the GO functional enrichment analysis of transcriptome sequencing data, the most enriched entries were in the biological processes; (3) When using KEGG database analysis, a total of 21 differentially expressed genes (DEGs) were annotated in 15 pathways, and which were all up-regulated. The protein processing pathway (ath04141) in the endoplasmic reticulum had the most DEGs, and sHSF, Hsp70, and NEF in this pathway may be related to the regulation of cold-tolerant mechanisms. The above findings provide a material basis and theoretical rationale for the research and utilization of cold-tolerant germplasm resources of Hongyang kiwifruit.
