Growth and Transpiration Efficiency of Near‐Isogenic Lines for Height in a Spring Wheat

Abstract

The two most commonly used dwarfing genes of bread wheat (Triticure aestivum L.) are Rhtl and Rht2. The Rht3 gene is also a potent dwarfing gene. Information in the literature is limited as to the comparative effects of these genes on transpiration efficiency (TE) and wateruse efficiency (WUE). Carbon isotope discrimination (Δ) has proposed as a criterion to select for improved TE. Four near‐isogenic lines, rhtrht, RhtlRhtl, Rht2Rht2, and Rht3Rht3, in ‘Maringa’ bread wheat background and four of their near‐isogenic F1 hybrids derived from crossing the original lines were used to determine the effects of dwarfing genes on plant height, root dry matter, shoot dry matter including grains, grain yield, total dry matter (TDM), TE (TDM/water transpired), WUE (grain yield/water used), and Δ in well‐watered droughted pot experiments in the glasshouse. The near‐isogenlc lines and their six F1 hybrids were also grown in well‐watered and droughted field conditions. Plant height ranged from 60 to 124 cm and from 53 to 121 em in well‐watered and droughted pot experiments, and it varied from 50 to 94 cm and from 49 to 90 cm in well‐watered and droughted field experiments, respectively. Total dry matter, grain yield, TE, and WUE declined with plant height in well‐watered glasshouse conditions. No significant relationships were found between plant height and these traits in droughted glasshouse conditions. Carbon isotope discrimination was negatively correlated with TE, but significantly so only in the well‐watered pot experiment. Plant height was negatively associated with Δ in both well‐watered and droughted pot and field experiments. Grain yield and shoot dry matter also declined with plant height in field conditions. Negative correlations were observed between Δ and grain yield and Δ and shoot dry matter in well‐watered field conditions. In most cases, the dwarfing genes reduced shoot dry matter more than grain yield and, therefore, harvest index of the semidwarf and dwarf lines was higher than that of the tall standard fine. The dwarfism caused by RhH, Rht2, and Rht3 genes had, in general, depressing effects on TE, WUE, TDM, and grain yield.