Physiological bases of cultivar differences in average grain weight in wheat: Scaling down from plot to individual grain in elite material

In recent decades, increases in wheat yield have been achieved mainly through grain number per m2 (GNM2) rather than average weight (AGW). Using AGW as a lever to increase would require avoidance of the negative relationship between GNM2 and AGW. It is usually supposed that this trade-off arises from an proportion small grains rises. The proportional being result either (1) secondary tillers spike population or (2) located distal positions within each spike. Either both these two populational effects tend mask any true genotypic differences existence constitutive has already proposed, but without considering full extent confounding effects. Identification component genetic determinism - one truly independent could contribute cultivar developments lead further under future target environments. To address question, we analysed on four, modern, well-adapted bread-wheat cultivars. four chosen cultivars show similar yields contrasting AGWs. analysis was carried out at three hierarchical levels (the plot, single grain) environmental conditions (well-watered vs water-deficit conditions). Regardless environment, no (or only slight) individual size were observed Furthermore weak AGWdemonstrates cannot be attributed spike-level Meanwhile, mass distributions, showed cultivars, originated shifts whole grain-mass distribution, shape changes distribution. This clearly indicates level. are largely constitutive, so may considered independently GNM2: trade-off. Taken together, findings offer new perspective for improvement wheat, should yield.