Changes in Transpiration Efficiency of Wheat Varieties Released Over Recent Decades - Any Potential for the Future?

Abstract

Wheat productivity is commonly limited by a lack of water in rain-fed farming systems. Given this limitation and the variability in rainfall across the season, an increase in crop transpiration efficiency (TE), i.e. more crop per drop, could assist in improving crop productivity. But have breeders already selected indirectly for traits related to TE over the last decades?Fifteen Australian elite wheat varieties released between 1973 and 2012 were grown in a recently-developed greenhouse platform for TE phenotyping. Genotypes were chosen for their wide adoption and narrow phenological range.When grown in irrigated pots at normal field density, no significant change in total plant biomass was observed in respect to the year of release. However, the biomass partitioning among organs changed in recent cultivars, with more biomass allocated to the stems and heads, less to the leaves, and with no substantial change for the roots. Cumulated transpiration up to flowering was also reduced with the year of variety release, and overall, a slight increase in TE was observed in modern cultivars. Given the range of genetic variability observed in TE across a wider range of lines and the relatively high heritability of this trait reported in the literature, we believe that additional progress can be made to improve TE.Combining this rapid phenotyping method with speed breeding technologies could assist breeders to prepare for the future with the development of lines that produce more crop per drop.