Environmental and genetic variation in epicuticular wax production in several range plant species

Narrow-sense heritability of epicuticular wax production in alfalfa (Medicago sativa L.) was determined from a 14 parent diallel cross that included selfed progenies and reciprocal crosses. General combining ability was significant (P {dollar}leq{dollar} 0.05) and heritability was estimated to be 35% from 1 harvest in 1985. A subset of 6 parents and their progenies were sampled for 2 more harvests in 1986. The general combining ability by harvest interaction was significant for epicuticular wax production indicating that the true narrow-sense heritability may be lower than 35%.; A line-source sprinkler system under an automated rainout shelter imposed a continuously variable water application on 30 genotypes of alfalfa and 30 genotypes of crested wheatgrass (Agropyron desertorum (Fisch. ex Link) Schultes). Leaf epicuticular wax was determined at 3 contrasting water levels. Epicuticular wax production increased for all genotypes as water declined for all 3 alfalfa harvests and for the first harvest of crested wheatgrass. At the low water level, creeping-rooted alfalfa genotypes produced more epicuticular wax per unit leaf area than noncreeping-rooted alfalfa genotypes. Within the 3 water levels, no correlation was found between epicuticular wax production and yield in alfalfa for any harvest. Yield and epicuticular wax were negatively correlated at the medium and low water levels for crested wheatgrass at Harvest 1 and positively correlated at the high water level for Harvest 2. No consistent relationship was found between epicuticular wax production and water loss rate of excised leaves.; Glaucous plants of a Thinopyrum interspecific hybrid had higher epicuticular wax production, increased leaf reflection of radiation, lower midday canopy temperatures, and higher midday leaf water potentials than nonglaucous plants in the field. A glaucous synthetic of Altai wildrye (Leymus angustus (Trin.) Pilger Dewey) had higher leaf reflection, lower midday leaf temperatures, and lower cuticular transpiration at high soil water content than its nonglaucous isosynthetic in the greenhouse. Shoot yield, total biomass yield, and water use efficiency on both a shoot and a total yield basis were not significantly different between the glaucous and nonglaucous synthetics of Altai wildrye.