WWRC 97-05yy
Genetic Improvement of Alfalfa to Conserve Water
Abstract
Irrigated alfalfa (Medicago sativa L.) is a high user
of water and has received limited research to
improve its water-use efficiency (WUE). Alfalfa is
grown on approximately one-half of the cultivated
land and has the highest consumptive use of all crops
in Wyoming. Alfalfa lines were developed which
expressed lighter colored and larger leaves. The
water relations and productivity of these lines were
evaluated under a series of soil water levels in a
controlled environment and under field environments
in Wyoming and Montana. In the controlled
environment the WUE of the pale and dark leaf
genetic lines were 1.47 and 1.22 g dry forage kg-1
water, respectively, when averaged across seven soil
moisture levels. Large-leaved alfalfa plants
produced 1.43 and small-leaved 1.29 g dry forage
kg-1 water. Leaf transpiration per unit leaf area of
pale leaves in irrigated field studies ranged from 12
to 17% lower than dark (normal) leaves.
Transpiration of large leaves was 10 to 16% lower
than small (normal) leaves. In field studies, the
forage yield of pale leaves was 25 to 29% higher
than dark leaves. The yield of large-leaved plants
was 17 to 22% higher than small-leaved. These
studies indicate the WUE of alfalfa can be improved
through plant breeding.
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