Rice is a vital staple food, especially in Asia, but it is highly susceptible to drought, leading to significant yield losses. To ensure food sustainability, drought-tolerant rice varieties are essential. Conventional breeding methods improve drought tolerance by focusing on biometric traits like root depth, avoidance, escape, and tolerance. This involves screening and crossing drought-tolerant varieties with high-yielding ones, followed by selection and evaluation. Techniques such as pedigree selection, recurrent selection, and backcrossing introduce desirable genes to enhance drought tolerance. Induced mutation through radiation exposure is also used. The molecular basis of drought tolerance involves identifying and manipulating genes responsible for rice's response to water stress. Techniques like QTL analysis, transcriptomics, genomics, and proteomics identify genes and QTLs associated with drought tolerance. Important genes involved in drought response include DREB, LEA, and ROS scavenging genes. Identifying QTLs enables the development of molecular markers for efficient screening of drought-tolerant rice genotypes. In conclusion, conventional breeding and molecular approaches are employed to develop drought-tolerant rice varieties. Conventional breeding improves biometric traits, while molecular techniques identify and manipulate specific genes associated with drought tolerance. This combination holds promise for high-yielding and drought-tolerant rice cultivars, contributing to global food security. However, further research is needed to understand the complex genetic mechanisms underlying drought tolerance in rice and enhance breeding precision and efficiency.

The cold-regulated (Cor413) gene family encodes plant-specific, multispanning transmembrane proteins that localize to the plasma and thylakoid membranes; these genes are regulated by environmental stimuli. In this study, the Cor413-1 gene, isolated from the drought and saline-tolerant wild species Saccharum spontaneum, was engineered into the elite sugarcane cultivar Co 86032 to produce a commercially superior cultivar with improved abiotic stress tolerance. Expression analysis of the Cor413-1 gene transgenic lines under drought and salinity stress exhibited distinct gene expression patterns. During stress conditions, transgenic events, such as Cor413-9 and Cor413-3, showed notable resilience to salt stress and had a high relative expression of the Cor413-1 gene and other stress-related genes. The evaluation of physiological parameters showed that under stress conditions, transgenic events experienced milder wilting and less cell membrane injury than the non-transgenic control. Transgenic lines also demonstrated elevated relative water content and better photosynthetic efficiency, with events like Cor413-10 and Cor413-12 showing exceptional performance. Biochemical analyses indicated elevated proline content, higher activity of enzymatic antioxidants such as sodium dismutase (SOD), catalase (CAT), and ascorbate peroxidase (APX), and a low level of malondialdehyde MDA production in the transgenic lines. Thus, demonstrating the potential of the Cor413-1 gene for developing multiple stress-tolerant cultivars.

Non-coding RNA molecules are generally present in a dispersed manner throughout the genome. They may behave as long ncRNAs or convert into small RNAs of around 20–24 nts that are universally categorized using their size, function, or chromosomal position. ncRNAs are thought to play a vital role in regulating and modulating gene expression apart from their prospective role in several epigenetic mechanisms controlling specificity in biochemical pathways and phenotype development in clonal cells. They are also part of the natural defense system against viruses. ncRNA modulates genes by transcriptional and translational control of growth, development, and stress response alongside other RNA molecules. Some modes of action have unraveled in recent years. A lot more needs to be pondered upon for comprehending their involvement in the extremely intricate processes in a more wholesome manner. In this chapter, we will discuss the different ncRNA, their origin, classification, and their role in various physiological processes. Practical examples of the discovery of ncRNA in different crops and their functions have also been elucidated with the required details. The yield and quality enhancement, along with the better stress response being the aim of the crop improvement program, the prospective utilities of ncRNA are also explained in the subsequent part of the chapter.

Phenolic acids are crucial for human health due to their potent antioxidant, anti-inflammatory, and antimicrobial properties, which help protect against chronic diseases and support overall well-being. In this study, 44 rice accessions were evaluated for total phenolic content in three different locations of Tamil Nadu and the marker trait association was done using 208 SSR markers. Among the association panel, Mappillai Samba was identified as having the highest total phenolic content of 1049.936 mg GAE/100 g. The phylogenetic analysis grouped the panel of entries into five genetic structure groups which nearly matched the geographical distance among the entries. Marker-trait association studies using GLM and MLM revealed that SSR markers RM287 and RM19358 were significantly associated with total phenolic content, explaining 23.4% and 19.7% of the observed variability, respectively. These markers were located in genomic regions linked to candidate genes involved in the biosynthesis of trans-cinnamate 4- monooxygenase (C4H) and phenylalanine ammonia-lyase (PAL), key enzymes in the phenolic acid pathway. Identifying these markers provides valuable tools for marker-assisted selection, enabling the development of biofortified rice varieties with enhanced phenolic content. Such advancements promise to improve rice nutritional quality and promoting public health through dietary interventions.

Increasing agricultural productivity and efficient use of limited nutrient resources with significant yield improvement is vital for sustainable agriculture. Phosphorus is the second most important macronutrient for crop growth next to nitrogen and its uptake varies under water-limited and irrigated conditions. However, identifying stable and high-yielding rice genotypes under varied phosphorus levels in combination with differences in water level is vital for current strategies on sustainability. Given this, 145 rice genotypes were raised in four different environments and characterized for phosphorus uptake traits, as well as grain yield and its related traits. Studies on correlation revealed that plant height and number of productive tillers exhibited a positive association with grain yield. Performed stability analysis and calculated stability parameters for dry weight and grain yield. Additive Main effects and Multiplicative Interaction (AMMI) model exposed the best performers as G115 and G47 for dry weight whereas G14 and G1 for grain yield. Based on the Genotype-by-Environment interaction (GGE) biplot, the winning genotypes for dry weight and grain yield were G14 and G1, respectively. Based on the yield stability index parameter, the best performer for dry weight was G27 and grain yield was G14. Ideal ranking of environments revealed that E1 for dry weight and E3 for grain yield can discriminate the genotypes. According to our results, the genotypes identified could be utilized to develop sustainable varieties.