Abstract

Investigating the key traits associated with genetic gains in grain yield (GY) is essential for developing winter wheat (Triticum aestivum L.) breeding strategies. The study objectives were: (a) quantifying the photosynthetic contribution of flag leaf and ear to the grain filling; (b) analyzing if their contributions are associated with the genetic gains in GY; and (c) analyzing their relationship with other agronomical and physiological traits. Thus, six winter wheat genotypes of different release years were grown under optimal conditions in a greenhouse trial during 2019. Grain yield increased by 126 kg h(-1) yr(-1), with the harvest index's change being the key factor affecting these gains. Compared to the control treatment, ear shading decreased ear contribution to grain filling by 16.35%, while both flag leaf and awn removal increased contribution to grain filling by 4.46 and 5.90%, respectively. Ear photosynthetic contribution estimated by source manipulation treatments showed a significant increase with the release year (0.54% yr(-1)). Whole ear gas exchange measures correlated positively with GY, and both dark respiration and gross photosynthesis showed positive correlations with the release year. The main findings of the study were: (a) GY gains in Chile were mainly due to the increased harvest index (HI), while the aerial biomass (AB) did not play a significant role in these gains; (b) the increased ear size besides the terminal heat stress during the study highlighted the ear role as the primary photosynthetic contributor to grain filling; and (c) using source manipulation techniques as an indirect selection trait for high ear photosynthesis appeared to be promising.