Research Projects

Rice, a staple food for over half of the global population, particularly in Asia and Africa, is predominantly cultivated under puddled transplanted (PTR) conditions. The PTR system is highly water-intensive and contributes significantly to GHG emissions. The increasing adoption of the direct-seeded rice (DSR) system offers a more sustainable alternative, reducing water shortage and GHG emissions. However, despite several advantages, the DSR system could be highly vulnerable to the occurrence of concurrent drought (mild to moderate) and heat stress, particularly at key developmental stages. Limited soil moisture can increase heat stress severity because stomatal opening is necessary for transpirational cooling under heat, but limited soil moisture could induce stomatal closure to ensure water conservation. Hence, the co-occurrence of drought and heat under DSR warrants systematic investigation on key parameters that regulate plant water relations. While root system architecture (RSA) facilitates water uptake from deeper soil layers under limited soil moisture, stomatal traits dynamics could regulate water flow and carbon assimilation under varying moisture and temperature regimes. Rice responses to drought and heat stress are studied extensively. However, the combination of heat and drought stress presents unique physiological challenges that require unique adaptations at the root and stomatal levels. This project addresses this critical gap in our understanding of how rice plants respond to the combined impact of drought and heat stress, specifically within the DSR context. It focuses on two core physiological traits: root system architecture (RSA) and stomatal traits that collectively govern the plant water uptake, transpiration and stress avoidance. Despite the well-documented roles of roots and stomata under heat and drought individually, their dynamic interaction and bidirectional regulation (effect of root traits on regulation of stomatal characteristics and vice versa) under the co-occurrence of heat and drought remain unexplored. It is imperative to focus on the avoidance mechanism in DSR because stress resilience needs to be achieved without compromising the yield potential of a genotype. This study aims, for the first time, to comprehensively phenotype root and stomatal traits for their plasticity under heat stress with varying soil moisture regimes, using a diverse panel of approximately 200 rice genotypes at the active root growth stage. Subsequently, we will perform genome-wide association studies (GWAS) using high-quality SNPs to identify putative QTLs and candidate genes associated with root and stomatal plasticity under combined heat and drought stress. To validate the functional relevance of the identified gene(s) and elucidate the underlying mechanisms of combined stress tolerance, we will employ a multi-omics approach involving transcriptomics, including quantitative PCR (qPCR), targeted proteomics and global metabolome. Finally, the potential gene will be functionally validated through CRISPR/Cas9-mediated gene editing. Eventually, the validated edited lines will serve as potential donors for dissecting heat and drought stress responses and for targeted improvement of heat and drought combination stress tolerance in elite cultivars such as Samba Mahsuri. The integrative use of high-throughput phenotyping, association genetics, multi-omics, and gene editing offers a robust framework to dissect the genetic regulation of complex traits such as RSA and stomatal dynamics, along with their interaction. A well-established gravimetric pot system in our lab will simulate realistic, field-relevant stress conditions for controlled phenotyping, while parallel field phenotyping under DSR conditions will be conducted at CAU, Imphal. Advanced gene editing and speed breeding facilities at NABI, Mohali, will support the development of gene-edited lines for future deployment in elite, climate-resilient varieties.