Quantifying Potential Genetic Gains in Wheat Yield Using a Conceptual Model of Drought Adaptation

Abstract

Many candidate physiological traits have been suggested for wheat improvement under moisture stress and genetic diversity is present in the wheat gene pool for most of them. The objective of this study was to quantify the probable yield effect associated with variation in the expression of such traits within two sets of germplasm;Sisters(from an elite x elite cross) showing a range of drought adaptation, andDiverselines (representing synthetic-derived wheat as well as selected landraces) assembled for favourable expression of one or more of the following traits under moisture stress: final biomass, ability to extract water at depth from the soil, remobilization of stem soluble carbohydrates, and transpiration & water-use efficiency (WUE). Agronomic and physiological traits were measured in NW Mexico in 2005 under post-anthesis moisture stress that resulted in yield reductions of up to 65% compared with irrigated plots, depending on the genotype. There was a significant range of expression for all traits measured and calculations were performed to gain an idea of the relative potential contribution to crop performance if trait expression were maximized in the highest-yielding backgrounds. Theoretically, remobilization of stem carbohydrates would be associated with 7% yield gains forSisterand 20% forDiverse Lines. Maximizing WUE could achieve 16% and 4% gains in yield inSisterandDiverse Linesrespectively, despite the already strong association of the trait with yield, and similar results were found for transpiration efficiency. In both sets of germplasm, putting the best expression for water extraction (to 120cm) in the highest yielding background was associated with yield gains of 13%. Taken together these results suggest substantial yield gains under moisture stress are achievable if the genes representing these traits were to be combined using a complementary-trait based approach to breeding