Carbon Isotope Discrimination as a Tool to Improve Water‐Use Efficiency in Tomato

Abstract

ABSTRACTCarbon isotope discrimination (Δ) is a property that may be used to improve water‐use efficiency (WUE). This study tested the association between Δ and WUE with plant materials and growth conditions likely to disrupt the link between Δ and WUE. The cultivated tomato, Lycopersicon esculentum Mill. cv. UC82B, a drought‐resistant related species, L. pennellii (Cor.) D'Arcy accession LA716, and the F1 and F2 generations of the L. esculentum × L. pennellii cross were grown in containers in wet and dry field environments. The wet environment was repeated in a second year and plants were split into groups terminated early and late in the season. The F1 generation had greater mean WUE and dry weight (DW) than L. esculentum, but the DW advantage was not maintained in the F2 generation. Low Δ of L. pennellii suggested that leaf WUE was high, but its whole plant WUE varied relative to the other plant materials in the different environments. There was a negative correlation between Δ and WUE in the F2 generation, and WUE was generally positively correlated with DW. However, low Δ was associated with large DW in only one environment and with small DW in three environments. Averaged across environments, the top 10% of the plants ranked by WUE had 47% greater WUE than the bottom 10%. In comparison, the bottom 10% ranked by Δ had an average of 16% greater WUE than the top Δ group, but in three of the four environments the bottom group accumulated 33 to 47% less DW than the top Δ group. This study on tomato suggests that WUE can be increased by selecting low Δ, but selecting low Δ alone may identify a subpopulation of small plants. Dry weight could probably be increased by traditional breeding techniques.