**5. Conclusions**

This study was conducted to evaluate the heat tolerance potential of 22 elite GSR lines in comparison with local varieties as controls in Pakistan. We observed a significant variation among the studied germplasm for heat tolerance and identified several heattolerant GSR lines that could be used as a genetic resource for breeding programs. We found that GY, along with other morpho-physiological traits, such as TPP, SY, HI, and CMS, were seriously affected by heat stress in most of the genotypes, while PH, GW, GL, PFP, and NDVI were affected only in a few genotypes. Future studies are required to explore the underlying molecular and physiological mechanisms of heat tolerance in the selected tolerant genotypes.

**Author Contributions:** Conceptualization, S.A.Z., U.R., M.K.N. and M.R.K.; Data curation, S.A.Z., M.H.A., M.K.N., I.U.Z. and B.S.; Formal analysis, M.U., M.K.N., O.U.R., N.R., M.S.F. and N.Z.; Funding acquisition, G.M.A., S.H.Y. and M.R.K.; Investigation, S.A.Z. and N.Z.; Methodology, I.U.Z.; Resources, N.R., J.X., Z.L., J.A., G.M.A. and S.H.Y.; Software, M.H.A. and N.Z.; Supervision, U.R. and M.R.K.; Visualization, M.U. and B.S.; Writing—original draft, M.U. and O.U.R.; Writing—review and editing, S.A.Z., M.U., M.S.F., J.X., Z.L., J.A., S.H.Y. and M.R.K. All authors have read and agreed to the published version of the manuscript.

**Funding:** This study was conducted from the funds of Ministry of National Food Security and Research of Pakistan released for the PSDP-project (743) "Green Super Rice in Pakistan". The publication of the present work is supported by the National Research Foundation of Korea (NRF), grant funded by the Korean government (MSIT) (NRF-2021R1F1A1055482).

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

**Informed Consent Statement:** Not applicable.

**Data Availability Statement:** All the relevant data are within the paper and its supporting information file.

**Acknowledgments:** We appreciate the efforts of PSDP and Ministry of National Food Security and Research (MNFS&R) for providing resources for this study. We are also thankful to Institute of Crop Science, Beijing, China, for providing the GSR lines.

**Conflicts of Interest:** The authors declare no conflict of interest.

**Compliance with Ethical Standards:** This manuscript does not contain any studies with human/animals performed by any of the authors.
