Drought Stress Affects Agronomic Performance of Tall Fescue Genotypes.

Drought stress is one of the most important constraints on agricultural profitability and sustainability worldwide. Demand for new and suitable plant materials is a long-term issue and is increasing continuously. The objective of this study is to measure the production potential of tall fescue genotypes and identify agronomic traits relating to growth and quality under marginal environments. A total of 252 genotypes of tall fescue were planted at the University of Wyoming under irrigated and rain-fed conditions. These genotypes were originated from a cross between a highly sensitive and a drought tolerant tall fescue. Each genotype was planted 1 m apart and replicated three times in August 2008. Total number of genotypes in each condition was 756. Data collection included biomass production, visual vigor score (0-10 scales, where 0=dead and 10=highest vigor), other agronomic parameters, relative water content, and forage quality. Starting in 2009, 2-3 harvests were made each year depending on weather conditions. Data indicates that there is large variation between treatments (irrigated vs. rain-fed) and among the 252 tall fescue genotypes for several desirable traits. Average visual vigor scores were much higher in irrigated conditions compared to rain-fed conditions. Variations were observed in plant height and tiller number under both conditions however, little variations were noticed in leaf width. Dry weight ranged 1-445 g plant^-1 in irrigated plots while this range was 0-361 g plant^-1 in rain-fed plots. Relative water content of some of the highly productive genotypes in rain-fed conditions was similar to some of the highly productive genotypes under irrigation, hence indicating their high drought tolerance. Forage quality varied among genotypes but not between irrigated and rain-fed plots, e.g., crude protein ranged 140-220 g kg^-1. Many of the tall fescue genotypes show promise in respect to their growth and productivity.