An experiment was carried out to evaluate the response of sorghum stay-green quantitative trait locus (QTL) introgression lines under induced post-flowering drought stress. The QTL introgression was done in 2006 to 2008 from known stay-green lines to the locally adapted varieties through marker assisted backcrossing. The field experiment was carried out in 2009/2010 and involved two irrigation levels and 14 genotypes organized in a split plot design with three replications. Analysis of variance showed significant difference among the genotypes for all the measured nine morpho-physiological quantitative characters. Significant differences were also observed in leaf area, head exsertion, grain yield and hundred seed weight for irrigation indicating that the two irrigation levels were able to differentiate the genotypes for these characters. Genotype-by-irrigation interaction was significant only for head weight and 100 seed weight. In general, a yield reduction of up to 49% was observed in an induced post-flowering moisture deficit. Grain yield had strong positive correlation with head weight (r=0.66) and hundred seed weight (r=0.52) under conditions of moisture deficit. Most of the stay-green introgression lines included in this experiment maintained at least 25% of their green leaf area until maturity though some showed early leaf senescence, but there was no associated increase in grain yield. Possible reasons are discussed.
Key words: Drought, introgression, post-anthesis, QTL, stay green, sorghum.