Classification of Genetic Variation for Drought Tolerance in Tall Fescue using Physiological Traits and Molecular Markers

Drought stress is a major factor limiting turfgrass growth. The objectives of the study were to determine genetic variation in major physiological traits associated with drought tolerance in a collection of tall fescue (Festuca arundinacea Schreb.) germplasm and to examine genetic diversity and relationships among germplasm varying in drought tolerance via molecular marker classification. Plants of 44 accessions from Africa, Europe, America, and Australia were exposed to well-watered conditions or drought stress by withholding irrigation for 11 d in a trial conducted in June 2009 and for 13 d during a repeated trial conducted in September 2009 in a greenhouse. Visual evaluation of turf quality, leaf relative water content, electrolyte leakage, chlorophyll content, and evapotranspiration rate demonstrated wide phenotypic variation contributing to drought tolerance in this collection of tall fescue germplasm. A hierarchical cluster analysis was conducted based on physiological traits and among 44 tall fescue accessions, 12 accessions were classified as most tolerant, 17 as moderately tolerant, and 15 as susceptible. The genetic similarity matrix from molecular marker analysis demonstrated similarity indexes ranging from 0.51 to 0.83. Among the 44 accessions, SH-3-AM-US from America and PI598949-EU-IT from Europe were genetically distinct, but both were classified as drought-tolerant germplasm based on physiological data. Screening genetically diverse germplasm to identify superior drought tolerance through the combined approach of physiological and molecular marker analysis could prove useful in breeding programs for further improvement of drought tolerance in tall fescue turfgrass.