Evaluating Variability In Water Use Efficiency of Some Selected Sorghum Genotypes.

Sorghum [Sorghum bicolor (L.) Moench] is a C4 crop that is well adapted to semi-arid environments and grown primarily in regions in the world with limited moisture.  Transpiration efficiency (TE), the biomass produced per unit water transpired, could be a potential trait to further improve sorghum yield in areas where irrigation is limited. A high TE trait could either enable plants to produce more biomass from the same amount of available soil water, delay the onset of detrimental water deficit stress by conserving soil water, or a combination of both. The objectives of this study were to (i) quantify variability in transpiration efficiency among 8 sorghum genotypes exhibiting different leaf temperatures and grain yields, (ii) quantify and compare water use efficiency (WUE) of the above genotypes. This experiment was conducted under controlled experiments. Parameters measured include above ground and root biomass and leaf area at early vegetative, flowering and maturity stages, water use, transpiration rate, photosynthetic rate, plant height and grain yield. Results showed significant differences in photosynthetic rate, transpiration rate and stomatal conductance. There was also variability in biomass produced, total root length, root length for different root classes (based on root diameter) as well as water use among the genotypes used. On average fine roots (≤ 1mm diameter) accounted for 89% of the total root length. Total root length and root length for fine roots (diameter <0.25 mm) was passively correlated to cumulative water use.