Determination of cold tolerance of native hybrid zoysia grass lines

This study was conducted to determine the cold tolerance of 30 native hybrid Zoysia lines developed through a breeding program at Akdeniz University Faculty of Agriculture, along with six commercial cultivars (a total of 36 genotypes), under low-temperature conditions (0, –3, –6, –9, and –12 °C). The experiment was designed according to a completely randomized block design (with nine replications per genotype), using a total of 324 pots. Before the cold stress application, the plants were subjected to cold acclimation under controlled conditions at temperatures of 8/2 °C (day/night) for four weeks. Subsequently, they were exposed to cold stress at gradually decreasing temperatures down to –12 °C for 24 hours at each temperature level. At each temperature level, measurements were taken for chlorophyll content (SPAD), leaf colour (L, a, b), chlorophyll fluorescence (Fv/Fm, PI/ABS), and cell membrane permeability (NES). Additionally, after the –6 and –12 °C treatments, the regeneration rates and overall turf quality of the plants were evaluated in the greenhouse over a four-week period. The results indicated that the –12 °C treatment caused severe damage and mortality in all genotypes. However, the cold-tolerant lines exposed to –6 °C were able to maintain their chlorophyll content and cell membrane integrity while demonstrating a high regeneration potential. Significant differences were observed among genotypes regarding their ability to maintain cell membrane integrity and sustain photosynthetic activity under low-temperature conditions. In particular, the lines MJe116, MJ31, MJ34, MJ46, MJ73, MJ58, MJ62, MJ17, JM7, and MJ83 exhibited higher cold tolerance, whereas the genotypes OKC, JM35, MZ68, and SURVIVOR were found to be the most sensitive group. Consequently, it was concluded that the native hybrids capable of withstanding cold conditions down to –6 °C have the potential to maintain sustainable turf quality during the winter months.