Drought response and minimal water requirements of diploid and interploid St. Augustinegrass under progressive drought stress

Abstract

Abstract St. Augustinegrass [ Stenotaphrum secundatum (Walt.) Kuntze] is a popular shade‐tolerant turfgrass but has a higher water use rate compared with other warm‐season turfgrasses. In an effort to improve drought resistance in St. Augustinegrass, the Texas A&M turfgrass breeding program has used embryo rescue technology and developed interploid (polyploid × diploid) hybrids to facilitate the combination of desirable traits from across ploidy levels. In this study, we determined the drought response and minimal water requirements of eight diploid and 18 interploid hybrids compared with ‘Floratam’, ‘Palmetto’, ‘Raleigh’, and ‘TamStar’ during ∼90 d of dry‐down under a rainout shelter in 2015 and 2016. Digital images of percentage green cover were taken weekly and entries with green cover ≤50 ± 1% were supplied with 2.54 cm of water. Genotypic differences were observed, but overall, interploids demonstrated better drought response than diploids, as indicated by longer days to reach 50% green cover and a turfgrass quality of 5.0. Nine interploid hybrids, including TamStar, did not require any water to maintain above 50% green cover in both years as compared with Floratam, Raleigh, and Palmetto. Our results also show that minimum turfgrass quality of 5.0 was not maintained at the 50% green cover threshold and that 75–80% green cover more accurately represents the minimum quality for future drought evaluations in our geographic conditions.