**6. Conclusions**

The selection of stress-tolerant genotypes might be a promising approach to alleviate the detrimental effects of abiotic stress and cultivate natural fiber crop productivity in the cooler regions. In the present study, the results show that the cold-induced inhibition of growth was significantly ameliorated in Y49 and M33 varieties, as manifested by physiological indices, such as much better adaptation with much higher chlorophyll, proline, and soluble sugar contents; lower levels of ROS, and lipid peroxidation; higher enzymatic antioxidant activities, especially SOD, POD, CAT, APx; and higher levels of non-enzymatic activities like TFC, TPC, and GSH. On the contrary, Y38, T8, and Y1 varieties exhibited more sensitivity by low temperature by increasing cell membrane damage through a high level of MDA and H2O2. Furthermore, for PCA or cluster heat map, seven varieties created three different groups effectively, where Cluster I (Y49 and M33) indicated the low-temperature tolerant varieties. To summarize, our data demonstrate the role of several antioxidants and non-enzymatic activities in modifying physiological and biochemical responses associated with cold tolerance. Thus, the results would provide the theoretical guidance to the evaluation of jute varieties under cold stress, cold tolerance response mechanisms, and cropping adjustment on cooler regions.

**Author Contributions:** Conceptualization, S.D., D.L. and A.B.; Methodology, S.D., D.L. and A.B.; Supervision, D.L., S.H., Y.D. and A.B.; Data curation, S.D. and A.B.; Formal analysis, A.B., S.D. and Z.M.B.; Validation S.H., J.Z., Y.G. and L.L.; Investigation Y.D., A.X., J.L., Original draft writing, S.D. and A.B.; Review and editing, A.B. and D.L., Funding acquisition, D.L. All authors have read and agreed to the published version of the manuscript.

**Funding:** This research was supported by the Chinese Agriculture Technology Research System (CARS -16-E04) and Agricultural Science and Technology Innovation Program (ASTIP-IBFC03).

**Institutional Review Board Statement:** Not applicable.

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** On request, the corresponding author will provide the data used to support the findings of this study.

**Acknowledgments:** The authors would like to express their gratitude to the Chemistry Department of the Institute of Bast Fiber Crops for allowing them to utilize their facilities for this work.

**Conflicts of Interest:** The authors disclose that they have no conflict interests.
