Drought is the major abiotic factors that limit crop productivity worldwide. To withstand stress conditions, plants alter numerous mechanisms for adaption and tolerance. Therefore, in the present study, 106 rice varieties were screened for drought tolerance phenotype via exposing different concentrations of polyethylene glycol 6000 (PEG) in the hydroponic nutrient medium at the time interval of 1, 3, and 7 days to evaluate the changes in their root system architecture. Further, based on root phenotype obtained after PEG-induced drought, two contrasting varieties drought-tolerant Heena and -sensitive Kiran were selected to study transcriptional and physiological alterations at the same stress durations. Physiological parameters (photosynthesis rate, stomatal conductance, transpiration), and non-enzymatic antioxidants (carotenoids, anthocyanins, total phenol content) production indicated better performance of Heena than Kiran. Comparatively higher accumulation of carotenoid and anthocyanin content and the increased photosynthetic rate was also observed in Heena. Root morphology (length, numbers of root hairs, seminal roots and adventitious roots) and anatomical data (lignin deposition, xylem area) enable tolerant variety Heena to better maintain membrane integrity and relative water content, which also contribute to comparatively higher biomass accumulation in Heena under drought. In transcriptome profiling, significant drought stress-associated differentially expressed genes (DEGs) were identified in both the varieties. A total of 1033 and 936 uniquely upregulated DEGs were found in Heena and Kiran respectively. The significant modulation of DEGs that were mainly associated with phytohormone signaling, stress-responsive genes (LEA, DREB), transcription factors (TFs) (AP2/ERF, MYB, WRKY, bHLH), and genes involved in photosynthesis and antioxidative mechanisms indicate better adaptive nature of Heena in stress tolerance. Additionally, the QTL-mapping analysis showed a very high number of DEGs associated with drought stress at AQHP069 QTL in Heena in comparison to Kiran which further distinguishes the drought-responsive traits at the chromosomal level in both the contrasting varieties. Overall, results support the higher capability of Heena over Kiran variety to induce numerous genes along with the development of better root architecture to endure drought stress.

干旱是限制全球农作物生产力的主要非生物因素。为了承受压力条件，植物会改变多种适应和耐受机制。因此，在本研究中，通过在1、3和7天的时间间隔内在水培营养培养基中暴露不同浓度的聚乙二醇6000（PEG），筛选了106个水稻品种的耐旱表型。根系统架构。此外，基于PEG诱导的干旱后获得的根表型，两个相反的品种耐旱的Heena和敏感的Kiran选择相同的应激时间研究转录和生理变化。生理参数（光合作用速率，气孔导度，蒸腾作用）和非酶抗氧化剂（类胡萝卜素，花色苷，总酚含量）的产生表明，Heena的性能优于Kiran。在Heena中还观察到较高的类胡萝卜素和花青素含量积累和光合速率的增加。根系形态（长度，根毛数，精根和不定根）和解剖学数据（木质素沉积，木质部面积）使耐性变种海娜更好地保持膜的完整性和相对含水量，这也有助于干旱条件下海埃纳的生物量积累相对较高。在转录组分析中，在两个品种中均鉴定出了明显的干旱胁迫相关差异表达基因（DEG）。Heena和Kiran分别发现了1033和936个独特上调的DEG 。DEGs的显着调节主要与植物激素信号传导，应激反应基因（LEA，DREB），转录因子（TFs）（AP2 / ERF，MYB，WRKY，bHLH），并且参与光合作用和抗氧化机制的基因表明Heena在抗逆性方面具有更好的适应性。此外，QTL映射分析显示，与基兰相比，Heena的AQHP069 QTL有大量与干旱胁迫相关的DEG，这进一步区分了两个对比品种在染色体水平上的干旱响应性状。总体而言，研究结果支持了海埃那（Heena）在基兰（Kiran）品种上具有更高的诱导多种基因的能力，以及更好的根系结构发展以抵抗干旱的能力。