Phenomics-assisted genetic dissection and molecular design of drought resistance in rice

Dissecting the mechanism of drought resistance (DR) and designing drought-resistant rice varieties are promising strategies to address the challenge of climate change. Here, we selected a typical drought-avoidant (DA) variety, IRAT109, and a drought-tolerant (DT) variety, Hanhui15, as parents to develop a stable recombinant inbred line (RIL) population (F₈, 1262 lines). The de novo assembled genomes of both parents were released. By resequencing of the RIL population, a set of 1 189 216 reliable SNPs were obtained and used to construct a dense genetic map. Using above- and belowground phenomic platforms and multimodal cameras, we captured 139 040 image-based traits (i-traits) of whole-plant phenotypes in response to drought stress throughout the entire rice growth period and identified 32 586 drought-responsive quantitative trait loci (QTLs), including 2097 unique QTLs. QTLs associated with panicle i-traits occurred more than 600 times on the middle of chromosome 8, and QTLs associated with leaf i-traits occurred more than 800 times on the 5' end of chromosome 3, indicating the potential effects of these QTLs on plant phenotypes. We selected three candidate genes (OsMADS50, OsGhd8, OsSAUR11) related to leaf, panicle, and root traits, respectively, and verified their functions in DR. OsMADS50 was found to negatively regulate DR by modulating leaf dehydration, grain size, and downward root growth. A total of 18 and 21 composite QTLs significantly related to grain weight and plant biomass were also screened from 597 lines in the RIL population under drought conditions in field experiments, and the composite QTL regions showed substantial overlap (76.9%) with known DR gene regions. Based on three candidate DR genes, we proposed a haplotype design suitable for different environments and breeding objectives. This study provides a valuable reference for multimodal and time-series phenomic analyses, deciphers the genetic mechanisms of DA and DT rice varieties, and offers a molecular navigation map for breeding of DR varieties.