Genetic analysis of yield and agronomic traits under reproductive-stage drought stress in rice using a high-resolution linkage map.

Drought stress at the reproductive stage of rice crop leads to a huge loss in grain yield. Identification and introgression of large effect drought tolerant QTLs are necessary to develop drought-tolerant rice varieties. Compared to the high-density linkage maps, widely spaced markers lead to the identification of QTLs with large confidence intervals which are difficult to incorporate in a breeding program. A previously generated genotyping-by-sequencing (GBS) based linkage map consisting of 4748 SNP markers was used to map QTLs in Cocodrie × N-22 recombinant inbred line (RIL) population. Twenty-one QTLs were discovered for days to flowering (DTF), plant height (PH), leaf rolling score (LRS), plant dry matter content (DM), spikelet fertility (SF), grain yield (GY), yield index (YI), and harvest index (HI) under drought stress. A major QTL qPH1.38 was identified in a narrow confidence interval on chromosome 1. The QTLs, qDTF3.01 and qPH1.38, overlapped with the previously identified QTL qDTY1.1 and Hd9, respectively. Another large-effect QTL qLRS1.37 was identified close to the sd1 locus on chromosome 1. A grain yield QTL qGY1.42 located on chromosome 1 contained only 4 candidate genes. There was no overlapping of QTLs for the root traits and the yield attributes. The important candidate genes present within the large effect QTL regions are MYB transcription factors, no apical meristem protein (NAC), potassium channel protein, nuclear matrix protein1, and chlorophyll A-B binding protein. The large effect QTLs (qDTF3.01, qPH1.38, and qLRS1.37) and a novel grain yield QTL qGYS1.42 can be used to incorporate in elite breeding lines to develop drought-tolerant rice varieties.