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ARS Home » Plains Area » Mandan, North Dakota » Northern Great Plains Research Laboratory » Research » Publications at this Location » Publication #111505
Title: GAS EXCHANGE AND WATER RELATIONS IN DIPLOID AND TETRAPLOID RUSSIAN WILDRYE.

Author
item Frank, Albert
item Berdahl, John

Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/3/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: Russian wildrye is a productive cool-season bunchgrass that is used for seeding improved pastures in the semiarid Northern Great Plains of the U.S.A. and Canada. It has high drought tolerance and maintains high nutritive value for dormant grazing. Although, poor seedling vigor is a major problem that often leads to stand establishment failures recent cultivar releases have improved seedling vigor, but little is known about the response of the new cultivars to water stress. We conducted field studies to determine gas exchange rates and their relationship to water use-efficiency and carbon isotope discrimination for diploid and tetraploid entries of Russian wildrye grown in a rainout shelter at two water treatments (50 and 150% of mean monthly precipitation for 1 April to 1 November) and two fertilizer rates (10 and 134 kg N/ha). The tetraploid entry exhibited higher carbon exchange rate, stomatal conductance, and transpiration than the diploid entry at the 50% but not at the 150% water treatment. Leaf water potentials were 0.6 and 0.3 MPa greater for the tetraploid entry than the diploid entry at the 50 and 150% water treatment, respectively. The diploid entry had a significantly greater CID than the tetraploid entry, suggesting that water-use efficiency is greater in the tetraploid entry than the diploid. Our results show that the tetraploid entry as compared to the diploid entry exhibited more favorable gas exchange traits under limited water. This along with greater dry matter production and higher WUE suggests that tetraploid Russian wildrye should be emphasized in future breeding and management programs.

Technical Abstract: Russian wildrye is a cool-season forage grass used in seeded pastures in the Northern Great Plains. Seedling vigor is poor and results in poor stand establishment. Tetraploid germplasm has been developed that shows improved seedling vigor compared to standard cultivars. Objectives of this research were to determine gas exchange rates and their relationship to water use-efficiency (WUE) and carbon isotope discrimination (CID) for diploid and tetraploid entries of Russian wildrye. A diploid cultivar (Vinall) and a tetraploid entry were evaluated for 3 yr under two water treatments (50 and 150% of mean monthly precipitation for 1 April to 1 November) and two fertilizer rates (10 and 134 kg N/ha) in a rain shelter. The tetraploid entry exhibited higher carbon exchange rate (CER), stomatal conductance (gs), and transpiration (T) than the diploid entry at the 50% but not the 150% water treatment. Leaf water potentials (LWP) were 0.6 and d0.3 MPa higher for the tetraploid entry than the diploid entry at the 50 and 150% water treatment, respectively. Values of CER averaged across water and N treatments were 12.4 and 14.2 micro mol/m2/s, T averaged 5.2 and 6.0 mol m2/s, and gs averaged 0.21 and 0.28 mol m2/s for the diploid and tetraploid entry, respectively. The diploid entry had a significantly greater CID than the tetraploid entry. CID was significantly less at the 50% water treatment than the 150% water treatment. CID was negatively associated with field-measured WUE. The tetraploid entry exhibited more favorable gas exchange traits under limited water and when with greater dry matter production and higher WUE suggests that tetraploid Russian wildrye should be emphasized in future breeding and management programs.