Physiological and morphological characterization of a high-yielding rice introgression line, YTH183, with genetic background of Indica Group cultivar, IR 64

Increasing rice production to feed the world's growing population will be a significant challenge, particularly in the developing countries where Indica Group cultivars are predominantly grown. Rice genotypes suitable for water-saving conditions are also necessary to cope with current and predicted water scarcities. Here, we report a high-yielding introgression line, YTH183, derived from new-plant-type rice with an Indica Group cultivar ('IR64') genetic background. 14 trials in three countries (Philippines, Indonesia, and Lao PDR) and comparison of grain yield with IR 64 and Philippine's high-yielding cultivars showed the superior performance of YTH183 under flooded and water-saving conditions. YTH183 significantly increased harvest index without increasing total shoot biomass in the most of the trials. Among the yield components, 1000-grain weight significantly and stably contributed to increased grain yield in YTH183. Genetic analysis revealed greater 1000-grain weight is controlled by the putative quantitative trait loci (QTL), qGW5-YP5. Morphologically, YTH183 had steep root phenotype, a thicker culm, and a greater number of vascular bundles at the panicle neck than IR 64. Physiologically, we found greater flow of non-structural carbohydrates from sources to sinks during the grain filling stage, an altered grain-filling pattern, and greater single grain weight in any of positions in the panicle of YTH183. Overall results suggested that these changes in morphological and physiological traits contributed to the genetic improvement of yield potential in YTH183. YTH183 would also provide insights into the complex genetic control of morphological and physiological characteristics linked with high yield.