Mapping QTLs for Reproductive‐Stage Drought Resistance Traits using an Advanced Backcross Population in Upland Rice

ABSTRACT The reproductive stage of development is the most drought sensitive, and water deficits at that time can lead to a drastic yield reduction in rice (Oryza sativa L.). Understanding the genetic and physiological bases of yield and yield components under reproductive‐stage drought stress will help in the development of resilient cultivars. A population of backcross inbred lines derived from upland cultivars Apo and Moroberekan was used for mapping quantitative trait loci (QTLs) associated with grain yield and other yield‐related traits under reproductive stage drought stress and irrigated (nonstress) conditions in the field. Reproductive traits affect grain yield directly and indirectly in both irrigated and drought conditions. Days to flowering, spikelet fertility, pollen fertility, and panicle exsertion are important traits affecting grain yield under reproductive stage drought. Therefore QTLs associated with grain yield or these reproductive traits that have direct or indirect effect on grain yield are likely to be useful in improving yield under drought. A total of 45 genomic regions were identified for traits observed under reproductive stage drought stress and control conditions. The yield QTL (qYLD4.2) on chromosome 4 colocates with number of spikelets per panicle, number of filled grains per panicle, and number of secondary rachis per panicle. The QTLs qYLD4.1, qYLD6.3, and qYLD12 are other important QTLs identified in this study. Those QTLs with either direct or pleiotropic effects could be used as candidates in marker‐assisted breeding for drought resistance improvement in rice.