Evaluation Of Genotypic Variation In Heat Tolerance Of Tall Fescue By Functional Traits.

Tall fescue is an important cool season turf grass. Summer high temperature negatively affects the performance of tall fescue in transitional and warm climate zones. To identify heat tolerant materials for tall fescue, 120 tall fescue accessions from the world were collected and subjected to high temperature under the greenhouse and the growth chamber conditions. Average temperature was 43℃ in the greenhouse trail and 38/30℃(day/night) and 25/16℃(control) in the growth chamber experiment. Leaf water content (LWC), leaf dry weigh (DW), leaf fresh weight (FW), turf quality (TQ), survival rate (SR), chlorophyll content (Chl), evapotranspiration rate (ET) and electrolyte leakage (EL) were determined. Significant effects of accessions, duration time and heat treatment on most characteristics were observed. Wide accessions exhibited more variation in most of studied traits than commercial cultivars. Variation coefficients of GR and ET was greater than other traits, suggesting that GR and ET as effective indices would access more differentiate among accessions. Three principal component in controlled chamber experiment and two principal component in greenhouse experiment were extracted. Principal component analysis indicated that common PC1 correlated with TQ, SR and Chl was named as “turf performance component”, which explained 43.17% and 39.34% of genetic variations in the greenhouse and the growth chamber experiment, respectively. PC2 defined as “growth potential component” could explain 23.264% of total variability in the greenhouse experiment and 20.4% in the growth chamber experiment. PC3 was named as “leaf water potential component”. Two regression models (F=0.65×F1+0.35×F2) and (F=0.54×F1+0.28×F2+0.18×F3) were formulated to evaluate heat tolerance of all tall fescue accessions in greenhouse and growth chamber experiments, respectively. Accessions from subtropical monsoon climate zone generally exhibited better heat tolerance. In contrast, accessions from East Asia were heat sensitive. Finally, five accessions including PI 598574, PI608787, PI559374, Pure Gold and PI 527504 were selected as heat tolerant accessions for future tall fescue breeding.