Water Relations, Forage Production, and Photosynthesis in Tall Fescue Divergently Selected for Carbon Isotope Discrimination
- R. C. Johnson *a and
- Li Yangyangb
Carbon isotope discrimination (Δ) has been correlated with the ratio of dry matter production to transpiration (water-use efficiency, WUE) in C3 plants and is potentially useful for breeding crops with improved WUE. Therefore, an assessment of the selection response of Δ and its relationship to plant water status and forage production is needed. Divergent selection for high Δ (low WUE expected) and low Δ (high WUE expected) was completed for two cycles from a ‘Kentucky 31’ tall fescue base (Festuca arundinacea Schreb.) population (Co ). Water relations, forage production, and Δ were evaluated in Co and the selected populations in irrigated and dryland field environments in 1995 and 1996. Average realized heritability for Δ was 0.49, suggesting that Δ could be successfully manipulated in a breeding program. In 1995, leaf pressure potential (turgor) was higher in the populations selected for low Δ, but in 1996, no differences in water relations measurements were observed. High-Δ populations always had lower forage production than observed in Co, but the low-Δ populations never produced more than the Co population. In greenhouse-grown plants, high-Δ populations had higher internal substomatal [CO2] than Co, linking Δ with mechanisms that cause lower WUE. However, the internal [CO2] of the low-Δ populations and Co did not differ, suggesting that selection for low Δ may not have increased WUE as expected. The results show that Δ is a heritable trait in tall fescue, but an absence of increased production in populations selected for low Δ may limit its utility in tall fescue breeding programs.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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