Roles of abscisic acid‐dependent/independent pathways in low‐temperature tolerance of eight bermudagrass genotypes under field conditions

Abstract

Bermudagrass ( Cynodon spp.) is a widely used warm‐season turfgrass species, but low winter temperatures shorten its green period and restrict its application in transitional climatic zones. This 2‐year field study evaluated the winter cold tolerance of eight bermudagrass genotypes and investigated physiological and molecular mechanisms underlying genotypic differences. Based on subordinate function analysis of green duration, turfgrass quality, chlorophyll content, photochemical efficiency, electrolyte leakage, and malondialdehyde content, sau00106 and sau02067 were identified as the most cold‐tolerant and the most sensitive genotype, respectively. Cold stress significantly altered endogenous hormone levels; cold‐tolerant genotypes, particularly sau00106, accumulated greater levels of abscisic acid (ABA) and gibberellic acid than cold‐sensitive ones, with both hormones showing significant positive correlations with cold tolerance. In addition, cold stress markedly increased contents of sucrose, fructose, and glucose across all genotypes, with sau00106 exhibiting the greatest levels of both soluble sugars and expression level of CdSPS1 for sucrose synthesis. Cold stress also significantly regulated ABA‐dependent pathway components as well as ABA‐independent pathway components. Cold‐tolerant genotypes showed significantly greater expression of ABA‐dependent ( CdABF1 , CdLEA3 , and CdDHN1 ) and ABA‐independent ( CdCBF1 , CdCOR440 , and CdSPS1 ) genes. Correlation analysis further confirmed positive relationships between these parameters and cold tolerance. These findings suggest that the superior cold tolerance of sau00106 is associated with enhanced soluble sugar accumulation, maintenance of hormone homeostasis, and coordinated activation of both ABA‐dependent and ABA‐independent transcriptional pathways. Sau00106 represents a promising genetic resource for promotion and application in transitional and temperate zones.