Abstract

Future food security will be affected by human and environmental requirements, pushing higher production and yield. Wheat is one of the most important crops for history, knowledge and distribution. The main increase in performance was by the number of grains, but the increase in weight was less. Therefore, it is necessary to understand grain structures and physiological components that determine the potential grain weight. Moreover, the features associated pericarp and grain weight, both can generate a new determinant of yield. Two spring wheat cultivars contrasting in kernel weight potential (Bacanora and Kambara) were sown at field conditions in Estación Experimental Agropecuaria Austral (Universidad Austral de Chile), 2012-13 and 2013-14.Exp1, sown two seeding density: control (370 pl/m2) and low density (44 pl/m2). Exp2, similar 2012-13 more plot increasing night temperature (>6°C) with greenhouse. From flowering were dissected the pericarp of 8 kernel (G1 and G2) harvested from 4 spikes, each 4 day. At harvest, kernels of all grain position were sized and weighed. The pericarp fresh weight (12.2 -16.4 mg), dry weight (4.3 to 5.7 mg) and water (10.8 to 8.1 mg) increased to 150-200 °C day, later decreased exponentially. The pericarp achieves the maximum weights at 12 AAD. Kambara have pericarp and grain heavier than Bacanora (p > 0,05). At harvest, G2 is heavier than G1, G3 and G4. The pericarp relation with grain weight were y = 5,75x - 17,68 (r2 = 0,72), y = 14,18x - 5,17 (r2 = 0,62) and y = 7,83x - 11,61 (r2 = 0,55). The pericarp dynamic is different to length, high, volume or weight dynamic, register in previous studies. The dynamic component can be affected for genotype, grain position or AAD, also could determine the weight of grains.