Goutam Kumar Dash

Grain size is the key determinant of yield potential and consumer preference in rice, making it a primary target for genetic improvement. However, the allelic architecture underlying the traits needs to be resolved for precision breeding. Here, we conducted a haplotype-based dissection of four major grain size regulating candidate genes (OsGS3.1, OsGW2, OsGW7 and OsGW8) using high-quality single nucleotide polymorphism (SNP) data from 197 indica accessions of the 3K rice genome panel. Neutrality and diversity analyses revealed heterogeneous evolutionary histories. OsGS3.1 exhibited reduced haplotype diversity consistent with directional selection, whereas OsGW7 and OsGW8 showed strong negative Tajimas’ D (< -1.2) and Fus’ Fs (< -2.5), indicating an excess of rare alleles under purifying or expansion-driven selection. The LD block structure varied markedly across loci, suggesting selective retention of favourable alleles in OsGW2. Marker-trait associations identified exonic SNPs within OsGW2 (chr02_8115620) and OsGW7 (chr07_24666398), explaining up to 5.3 % of the phenotypic variance. Significant haplotype effects were observed in OsGS3.1, OsGW2, OsGW7 and OsGW8, with specific allelic combinations jointly modulating grain length (GL) and grain breadth (GB). These results establish a validated haplotype map and causal SNPs suitable for haplotype-based breeding, marker-assisted selection and genomic prediction models targeting grain size ideotype development in rice.

Despite the recognised role of potassium (K) in crop productivity, limited research exists on how different K fertilisation schedules influence both grain yield and antioxidant quality in black rice. Therefore, a field study was conducted during kharif 2024 to assess the influence of K fertilisation schedules for improved grain yield and antioxidant status in black rice. The experiment was conducted in a split-plot design, with variety assigned to the main plots and K application schedules to the subplots and was replicated 3 times. Three rice varieties were: BPT 2841 (V1), Kala Bhat (V2) and RNR 15048 (V3). Four K application schedules were: K100-0-0 (100 % recommended dose of K (RDK) as basal), K50-50-0 (50 % RDK at basal + 50 % at active tillering), K50-0-50 (50 % RDK at basal + 50 % at panicle initiation) and K50-25-25 (50 % RDK at basal + 25 % at tillering + 25 % at panicle initiation). The data generated from the study concluded that, V2 recorded the highest available soil K (156.3 kg ha-1), total K content (0.48 %) and antioxidant properties (anthocyanin (57.72 mg 100 g-1), flavonoid (43.28 mg 100 g-1) and phenolic (614.53 mg 100 g-1)), while V3 produced the highest grain yield (4.84 Mg ha-1). Among application timings, the K50-25-25 split was most effective, enhancing soil K, total K in grain, yield and antioxidant levels. Three splits of K found were most effective to enhanced both quantity and quality of black rice grain

Rice (Oryza sativa L.) is a staple food crop of global importance, with grain quality traits playing a crucial role in consumer preference. Distinctness, Uniformity and Stability (DUS) testing, alongside the evaluation of cooking quality parameters to assess the extent of genetic variability and to determine character association study among cooking attributing traits. So, a study was conducted during the Kharif season (2024-25) at the Post Graduate Research Farm of Centurion University of Technology and Management, Odisha, to evaluate 45 rice genotypes for DUS and cooking quality traits using Randomised Complete Block Design with three replications. Analysis of variances revealed significant variance for kernel length, kernel length after cooking, seed protein content and amylose content. High heritability and high genetic advance as a percentage of the mean (GAM) were noted for all the characters, indicating the presence of additive gene action. Path coefficient analysis revealed that kernel length had the highest positive direct effect on kernel linear elongation ratio, while kernel length after cooking showed a very high negative effect. Positive correlations between kernel linear elongation ratio and seed protein content, amylose content and kernel length affirm their influence. Ketki Joha and Shilkote recorded with maximum kernel breadth and kernel breadth after cooking, respectively. Highest protein content exhibited by Bygon manjira, amylose content raised high for PB1886, kernel linear elongation ratio shown by Nefbi julsi. Kernel length and amylose content emerged as the pivotal, highly heritable traits defining rice cooking quality, offering clear prospects for breeding premium grain quality.

The wild relatives of cultivated rice offer crucial resistance genes for combating stresses like drought. Developing rice varieties with drought tolerance is possible through chromosome segment substitution lines (CSSLs), which blend the genetic background of a high-yielding parent with specific chromosome segments from a donor parent. This study aimed to study the effect of drought stress on various root traits of chromosome segment substitution lines (CSSLs) and their relationship with specific molecular markers. Ninety-six genotypes, including 80 chromosome segment substitution lines (Curinga x O. rufipogon and Curinga x O. meridionalis), 9 New Rice for Africa (NERICAs) and 7 controls were grown in Basket and PVC pipe methods for phenotyping different root traits. Under drought stress (DS), MER16, MER20, RUF10, RUF16, RUF44, NERICA1, and NERICA3 showed superior performance for most of the root traits. These evaluations were supplemented with association analysis of 17 root trait-linked simple sequence repeat (SSR) markers with root phenotypic traits. The marker RM201 is strongly associated with multiple root traits, found to be independent of three growth conditions (well-watered “WW” under Basket, WW condition and DS conditions under PVC pipe). The marker RM316 is associated with root volume, and the marker RM7424 and RM1054 show maximum root length. In conclusion, these markers can be used in marker-assisted breeding programs, and the lines carrying them can be used as parental lines in variety-development programs for drought tolerance.

Rice is an ideal crop for improvement of nitrogen use efficiency (NUE), especially with urea, its predominant fertilizer. There is a paucity of studies on rice genotypes contrasting for NUE. We compared low urea-responsive transcriptomes of contrasting rice genotypes, namely Nidhi (low NUE) and Panvel1 (high NUE). Transcriptomes of whole plants grown with media containing normal (15 mM) and low urea (1.5 mM) revealed 1497 and 2819 differentially expressed genes (DEGs) in Nidhi and Panvel1, respectively, of which 271 were common. Though 1226 DEGs were genotype-specific in Nidhi and 2548 in Panvel1, there was far higher commonality in underlying processes. High NUE is associated with the urea-responsive regulation of other nutrient transporters, miRNAs, transcription factors (TFs) and better photosynthesis, water use efficiency and post-translational modifications. Many of their genes co-localized to NUE-QTLs on chromosomes 1, 3 and 9. A field evaluation under different doses of urea revealed better agronomic performance including grain yield, transport/uptake efficiencies and NUE of Panvel1. Comparison of our urea-based transcriptomes with our previous nitrate-based transcriptomes revealed many common processes despite large differences in their expression profiles. Our model proposes that differential involvement of transporters and TFs, among others, contributes to better urea uptake, translocation, utilization, flower development and yield for high NUE.

Drought stress severely affects plant growth and development, causing significant yield loss in rice. This study demonstrates the relevance of water use efficiency with deeper rooting along with other root traits and gas exchange parameters. Forty-nine rice genotypes were evaluated in the basket method to examine leaf-level water use efficiency (WUEi) variation and its relation to root traits. Significant variation in WUEi was observed (from 2.29 to 7.39 µmol CO₂ mmol⁻¹ H₂O) under drought stress. Regression analysis revealed that high WUEi was associated with higher biomass accumulation, low transpiration rate, and deep rooting ratio. The ratio of deep rooting was also associated with low internal CO₂ concentration. The association of deep rooting with lower root number and root dry weight suggests that an ideal drought-tolerant genotype with higher water use efficiency should have deeper rooting (>30% RDR) with moderate root number and root dry weight to be sustained under drought for a longer period. The study also revealed that, under drought stress conditions, landraces are more water-use efficient with superior root traits than improved genotypes.