Variation in Transpiration Efficiency in Sorghum.

Declining freshwater resources, increasing population, and growing demand for biofuels pose new challenges for agriculture research.  To meet these challenges, the concept of a “Blue Revolution” (more crop per drop) was proposed to improve water productivity in agriculture.  We have identified several sorghum lines with substantial increases in transpiration efficiency (TE), applying a high throughput lysimetric screening procedure.  Four hundred and six lines were initially screened, from which twenty-five lines were selected to conduct re-confirmation studies at two locations having different environmental conditions and water regimes.  Significant variation in TE was identified at both locations.  The high TE in the superior lines is associated with increased biomass accumulation rather than reduced transpiration.  Gas-exchange analysis of eight selected lines indicated that decreased internal CO2 concentration can result from enhanced PEP carboxylase activity, which may contribute to the increased TE observed in some lines.  The results indicate that considerable genetic variation in TE exists in sorghum germplasm collections, which may be exploited to improve water use efficiency in sorghum.