Historical improvement in drought adaptation of Australian wheat varieties has coencided with changes in biomass partitioning, transpiration efficiency and root architecture

K Chenu, A Fletcher, V Vazquez-Carrasquer and JT Christopher

The University of Queensland, Queensland Alliance for Agriculture and Food Innovation (QAAFI)

Wheat productivity is commonly limited by a lack of water in rain-fed farming systems worldwide, particularly in Australia. Although wheat breeders have historically bred for increased yield, grain quality and disease resistance, indirect selection for other traits would also be anticipated. A set of elite wheat varieties with wide adoption and a relatively narrow phenological range was chosen to study breeding progress achieved in Australia between 1958 and 2012. Experiments in irrigated pots revealed changes in seedling root angle, whole-plant transpiration efficiency, biomass partitioning and leaf senescence rate in varieties released over recent decades. While plant biomass did not change significantly over time, differences in partitioning were observed. Modern cultivars tended to have a greater proportion of biomass allocated to the heads and stems, but reduced allocation to the leaves. Interestingly, modern cultivars also tended to have narrower seedling root angle. a proxy trait for deep mature roots, which are believed to allow increased late water extraction from drying deep soils. In addition, a significant increase over the years was observed for whole-plant transpiration efficiency. While changes in biomass partitioning are approaching biological limits, the results of this study highlight potentials for possible improvement in root architecture and transpiration efficiency. Combining rapid phenotyping methods with speed breeding technologies could assist breeders to prepare for the future with the development of lines that produce more 'crop per drop' through better transpiration efficiency and/or root architecture.