Physiological responses of different perennial ryegrass genotypes to ice encasement

Abstract Perennial ryegrass ( Lolium perenne L.) is an important cool-season turfgrass species; however, its poorly understood susceptibility to ice encasement stress limits its widespread use, particularly in northern regions. Therefore, this study aimed to better understand whether common traits related to stress tolerance are impacted by ice encasement and if there is variation in genotypes of PRG for ice encasement tolerance. Carbohydrate dynamics, proline accumulation, and lipid peroxidation were measured. Two relatively tolerant (P2G38 and P2) and two susceptible (P2G9 and P1) genotypes were found after exposure to three durations of ice encasement stress (0, 15, and 20 days) under ice and non-ice conditions in two experimental runs (2023–2024 and 2024–2025) in a controlled environment study in East Lansing, MI, USA, with 4 replicates each. P2G38 and P2 exhibited lower malondialdehyde (MDA) accumulation, retained greater carbohydrate reserves, and had higher proline levels after 15 or 20 days of ice encasement stress. These traits were positively associated with recovery rate following stress. Crown showed a greater reduction in proline content and total non-structural carbohydrate (TNC) compared to roots. Moreover, plant recovery was higher in plants with higher TNC, water-soluble carbohydrates, storage carbohydrates, proline, and lower MDA levels. Furthermore, variation in carbohydrate reserves, proline, and MDA levels among the tolerant and susceptible genotypes was lower under no-ice conditions than under ice encasement. Therefore, retaining higher levels of carbohydrates and proline, along with lower MDA, is crucial for ice encasement tolerance in PRG. The variation displayed among the genotypes could indicate potential for breeding winterkill-resistant PRG.