Six nonflowering exotic strains were selected from a field study conducted in 1981 for indepth evaluation in 1982. Two strains (T91 and T194) possessed high shoot dry matter production and water use efficiency (WUE) and two strains (184 and T185) exhibited low shoot dry matter production and WUE in 1981. The remaining two strains (T25 and T169) were included as reference material since related data have been collected from these in similar test conditions over the past few years. The objective in the 1982 study was to further evaluate the 6 strains for shoot dry matter production, water use and selected physiological parameters in 2 extreme moisture levels. The evaluation was designed to determine repeatability of strain productivity and WUE, and determine any differential responses of the strains to the optimum and limiting water conditions.

The study was conducted in a rainout shelter which had been pre-plant irrigated to "field capacity'. Thereafter, two moisture regimes were used to provide a dryland treatment and an optimum water treatment. The dryland plots received no other water during the season. The optimum watered plots received weekly irrigations beginning 19 July and ending 10 September. Plant growth was recorded 40, 60, 73, and 90 days after planting. Soil water content to 8 feet was monitored by the neutron probe method. On the day prior to each plant growth measurement leaf water potential, stomatal conductance and gross photosynthesis rates were recorded throughout the day.