Grain yield and water use efficiency of diploid,tetraploid and hexaploid wheats

Three diploid (T. boeoticum, AA; Ae. speltoides, BB and Ae. squarrosa, DD), two tetraploid (T. dicoccoides, AABB and T. dicoccum, AABB) and one hexaploid (T. aestivum, AABBDD) wheats were evaluated for their root biomass, above-ground biomass, grain yield, water consumption for transpiration and water use efficiency under different water and nutrient regimes in order to (i) understand the differences in grain yield and water use efficiency among species across the ploidy level in the wheat (ii) assess the effects of water and nutrient regimes on these traits. Our results showed significant differences on biomass, grain yield and water-use between the ploidy levels in the wheat. In the evolution of wheat from diploid to tetraploid and hexaploid, root and aboveground biomass all increased firstly and then decreased, but grain yield increased significantly which is related to the remarkable increase of harvest index. The grain yield decreased in this order: T. aestivum T. dicoccum T. dicoccoides Ae. squarrosa Ae. speltoides T. boeoticum. Water stress significantly decreased all of the measured growth indices. Under given water level, increase on nutrient supply increased aboveground biomass, grain yield and harvest index. However, at higher nutrient treatment root biomass decreased as compared to the lower nutrient treatment. With the sequence of wheat evolution, water consumption for transpiration decreased significantly which correlated with the decreasing crop maturity period. However, both water use efficiency for biomass and grain yield increased significantly in the evolution of wheat. For six wheat materials, water use efficiency for grain yield decreased in the same order with grain yield. Water stress significantly decreased water consumption for transpiration of six wheat genotypes by 47%-52%, but increased water use efficiency for biomass by 3%-40%. However, the increasing effect of water stress on water use efficiency for grain yield decreased with increase of wheat ploidies, and even decreased the water use efficiency for grain yield of T. aestivum by about 19%. Water consumption for transpiration, water use efficiency for biomass and grain increased under higher nutrient levels compared to those of low nutrient level across the different water levels.