Based on multi-year， multi-site field trials combined with physiological and photosynthetic measurements， in this study we evaluated the cold tolerance and production adaptability of a new Pennisetum purpureum line ‘Yunmu No.1’（YM-1）， in comparison with two local predominant cultivars， P. purpureum ‘Dehong’（DH） and P. purpureum ×P. typhoideum ‘Reyan No.4’（RY-4）. The results indicated that the cold tolerance of the tested materials， in descending order， was YM-1>DH>RY-4. YM-1 had the lowest semi-lethal temperature （LT₅₀） of -5.413℃. Under low-temperature stress， its superoxide dismutase （SOD） activity increased significantly by 237.12%， while malondialdehyde （MDA） content increased only marginally by 1.25%， indicating that it primarily responds to low temperature through an antioxidant mechanism. In contrast， DH mainly responded to low temperature by accumulating osmotic adjustment substances， including soluble sugar （+76.77%） and proline （+60.24%）. RY-4 exhibited weak responses in both antioxidant and osmotic adjustment mechanisms， with an MDA increase of 43.07%. The freezing injury index during the first-frost period was consistent with the above physiological ranking. At an altitude of 2350 m， YM-1 showed the highest sprouting rate （50.4%； i.e.， the proportion of stumps with newly sprouted tillers） and regreening rate （43.0%）. Its three-year average hay yield was 6.1% and 11.3% higher than those of DH and RY-4， respectively. In conclusion， ‘Yunmu No.1’ possesses both strong cold tolerance and high and stable yield potential， making it suitable for cultivation in complex environments below 2000 m elevation on the Yunnan Plateau. A comprehensive evaluation method based on LT₅₀， MDA content， SOD activity， field freezing injury phenotype， and natural overwintering capacity can be used for the systematic identification of cold tolerance in Pennisetum purpureum.

New Pennisetum purpureum line  /  Cold tolerance  /  Production adaptability  /  Freezing injury physiological characteristics  /  Photosynthetic characteristics under low temperature