Phenotypic Plasticity of Root System to Drought Influences Grain Yield In Bread Wheat.

Phenotypic Plasticity of Root System to Drought Influences Grain Yield in Bread Wheat Crop productivity in semiarid regions is mainly limited by water availability. Root characteristics and plasticity to drought may reduce the negative impact of drought on crop yield. A set of near-isogenic wheat-rye translocation lines was used to test the hypothesis that root system plasticity to drought influences grain yield in wheat. Bread wheat Pavon 76 and its 1RS translocation lines, namely Pavon 1RS.1AL, Pavon 1RS.1BL, and Pavon 1RS.1DL were evaluated for root allocation and plasticity in sand-tube experiments under well-watered and droughted conditions across two years. The 1RS translocation lines had greater root biomass per plant ranging from 7.37 to 8.6 compared to 5.81 for Pavon 76. Shallow root weights in 1RS translocation lines were greater then Pavon 76 in both irrigation regimes. Only Pavon 1RS.1AL had greater deep root weight than Pavon 76 under drought, 2.89 and 2.23 g/plant, respectively. Only Pavon 76 showed a positive response to drought by producing more shallow and deep roots in droughted conditions than in well-watered conditions. Thus, at drought intensity of 19%, grain yield in Pavon 76 was reduced only 11% compared to other genotypes with yield reduction ranging from 18 to 24%. However, at drought intensity of 36%, grain yield in Pavon 76 showed maximum reduction indicating that greater root production under drought is advantageous only when plant available water is enough to support grain production. Pavon 1RS.1AL allocated 9.1 and 15.5% dry matter for root production, whereas Pavon 76 allocated 8.5 and 10.9% under well-watered and droughted conditions, respectively. Grain yield was positively correlated with shallow and deep root weight and root biomass under terminal drought. Correlation coefficients between root system components and phenological periods, plant height, and number of tillers and spikes per plant were not significant, indicating that it should be possible to select for root system traits and shoot traits independently.