Screening of tall fescue genotypes for relative water content and osmotic potential under drought stress

Background

Tall fescue (Festuca arundinacea Schreb.) is an important cool-season perennial grass. Its persistence and forage yield can be severely affected by drought stresses during the hot, dry summers of the southern USA.

Methods

One thousand tall fescue genotypes were evaluated in the greenhouse for high relative water content (RWC) and low cell sap osmotic potential (OP). Fifty contrasting genotypes for the two traits were identified and used in further greenhouse and field studies. These genotypes were also screened with 30% PEG8000. Root and shoot characteristics were studied in 10 genotypes.

Results

The genotypes differed for RWC (33.7%–97.3%, mean: 79.7%) and had an almost fivefold difference in OP (−0.5 to −2.4 MPa, mean: −1.2 MPa). Significant variation (p < 0.001) for the main effects of environment and genotypes was found for RWC and OP. Apart from the greenhouse trial, no correlation was found between RWC and OP, indicating that differences in RWC might have been due to factors other than osmotic adjustment. Genotypes with either long roots or high root weights, and high root/shoot ratios demonstrated high RWC and low OP.

Conclusions

Genotypes with consistently high RWC and low OP were identified and used for the development of mapping populations and transcriptome studies.