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: 1) quantifying the photosynthetic contribution of flag leaf and ear to the grain-filling; 2) analyzing if their contributions are associated with the genetic gains in GY; and 3) 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. GY 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: 1) GY gains in Chile were mainly due to the increased HI, while the aerial biomass (AB) did not play a significant role in these gains; 2) 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 3) using source manipulation techniques as an indirect selection trait for high ear photosynthesis appeared to be promising.