Grain yield and physiological traits of rice lines with the drought yield QTL qDTY12.1 showed different responses to drought and soil characteristics in upland environments

To improve yield in upland conditions, near-isogenic lines (NILs) of the major-effect drought yield quantitative trait locus qDTY(12.1) in rice (Oryza sativa L.) were developed in the background of the upland variety Vandana. These NILs have shown greater water uptake a larger proportion of lateral roots, and higher transpiration efficiency under drought than Vandana, and one NIL (481-B) was selected as having the highest yield. In this study, the NILs were assessed in two greenhouse and 18 upland field trials for their response to drought and different soil textures. Performance of qDTY(12.1) NILs was not affected by soil texture but showed a notable response to drought stress severity. The yield advantage of 481-B over Vandana was highest in field trials with intermittent drought stress, in which the mean trial yield was greater than 0.5 t ha(-1), and in the least favourable well watered trial. The effects of qDTY(12.1) on water uptake were most apparent under mild to moderate stress but not in very severe drought or well watered treatments, whereas the lateral root and transpiration efficiency responses were observed under a range of conditions. These results highlight the varying response of qDTY(12.1) across upland environments and the complexity of multiple mechanisms acting together to confer an effect on rice yield under drought.