Drought stress responses and recovery of Texas x Kentucky hybrids and Kentucky bluegrass genotypes in temperate climate conditions
Turf quality (TQ) decline due to drought is a major concern in cool-season turfgrass management. The study was conducted to examine whether selected Texas (TBG) x Kentucky bluegrass (KBG) hybrids (HBGs) (Poa arachnifera Torr. x P. pratensis L.) exhibit improved drought stress tolerance and recuperative ability in comparison to commonly-used KBG (P. pratensis) genotypes. Plant material included two HBG selections (HBG568 and HBG668), two commercially-available HBGs (‘Thermal Blue’ and ‘Bandera’), and two KBG genotypes (‘Midnight’ and ‘Baron’). The experiment was conducted in field plots covered with a rainout shelter in 2006 and 2007 in North Brunswick, NJ. Treatments consisted of (i) well-watered controls; (ii) drought stress (withholding irrigation) from June to August; and (iii) recovery (rewatering after a period of drought stress) in September and October. The HBGs Thermal Blue and Bandera generally did not show significant difference in turf growth from the two KBG genotypes in both years. HBG568 maintained significantly higher TQ, relative water content (RWC), cell membrane stability, and canopy density estimated as the reflectance ratio of infrared to red (IR/R, leaf area index) and normalized difference vegetation index (NDVI), compared with the two KBG genotypes and other HBGs following a prolonged period of drought stress (after 20 d of treatment) on most sampling dates in both years. HBG568 exhibited more rapid recovery of TQ, IR/R (IR935/R661), NDVI, and sod tensile strength than the other genotypes in both years, while HBG668 also had better recovery in 2007. The results demonstrate genetic variation in drought stress tolerance and recovery among HBGs and KBGs and the potential for the development of HBGs with improved tolerance to drought stress and performance during recovery.