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Abstract
Turfgrasses suffer damages every year due to abiotic stressors, particularly drought. It is essential to identify underlying traits for stress tolerance and exploit such traits for improving turfgrass resilience. The overall objective of the dissertation projects was to identify physiological, biochemical and molecular traits associated with stress tolerance in seashore paspalum (Paspalum vaginatum). In our first study, membrane stability, early osmotic adjustment and leaf water use efficiency were the major physiological characteristics for variability in drought tolerance of seashore paspalum genotypes when fifteen different genotypes were exposed to drought stress. In the second study, two genotypes (UGP113 and SeaStar) with contrasting drought tolerance were subjected to proteomic analysis. A total of 41 different proteins were differentially expressed and were probably the driving molecular factors for drought tolerance in seashore paspalum. Genotype UGP113 either upregulated or maintained several proteins-involved in plant metabolisms, energy, transcription, signal transduction and defense mechanisms compared to SeaStar. In our third study, UGP113 and SeaStar were re-assessed for their drought tolerance using metabolomic analysis. Results showed a total 196 individual metabolites were differentially regulated in two genotypes under drought stress and were largely enriched in carbohydrate, amino acid, nucleotide and lipid metabolisms. Both UGP113 and SeaStar reduced intermediates of glycolysis and Kreb’s cycle whereas increased accumulation of metabolites involved in the pentose phosphate pathway indicating efficient utilization of limited resources under drought stress. Drought tolerant Genotype UGP113 accumulated greater amount of methionine, γ-aminobutyric acid, cytidine, kaempferol and α-linolenic acid compared to sensitive SeaStar suggesting prominent association of these metabolites with drought tolerance of seashore paspalum. In the subsequent studies, SeaStar and UGP113 seashore paspalum along with TifBlair centipedegrass were exposed to iso-osmotic drought and salinity stresses and biochemical mechanisms of stress tolerance in shoots and roots of turfgrasses were evaluated. Antioxidant metabolisms, homeostatic balance of inorganic and organic compounds and utilization of those compounds for osmotic adjustment were the biochemical strategies utilized by seashore paspalum and centipedegrass in surviving stress conditions. Identified traits from these studies will be useful in enhancing turfgrass stress tolerance by improving selection efficiency or genetically engineering traits to develop resilient transgenic cultivars.