Deepak Sharma

Main conclusion This study deciphers the genetic architecture of rice bran nutraceuticals, providing elite germplasm, molecular markers, and candidate genes for breeding biofortified, heart-healthy rice varieties. Abstract Rice bran oil is uniquely rich in nutraceuticals, such as γ-oryzanol and tocols, which confer anti-inflammatory, antidiabetic, and cardioprotective properties. Despite their nutritional and economic value, the genetic basis of variation in these traits in rice remains poorly understood. We investigated 192 diverse rice genotypes from the globally significant Chhattisgarh germplasm collection. Using multi-year biochemical profiling, we quantified the natural variation in bran oil content, γ-oryzanol, and total tocols. Genome-Wide Association Studies used both the GLM and BLINK models for statistical robustness with 1K-Rice Custom Amplicon (1K-RiCA) SNP genotyping data. We observed wide genetic variation, with oil content reaching 21.8%, γ-oryzanol exceeding 14,000 ppm, and tocols reaching up to 170 ppm. Genome-wide association studies identified three consistent SNP-trait associations: two (chr01_28142020 and chr10_19217152) with oil content across all seasons and one (chr12_8070782) with γ-oryzanol in two seasons. Candidate gene mining within ± 1 Mb revealed lipid metabolism and transport genes, including OsLACS4, multiple OsLTP2 family members, and a CXE carboxylesterase that is putatively involved in γ-oryzanol turnover. These genes showed seed-, panicle-, and embryo-specific expression, supporting their roles in oil biosynthesis and storage. This study uncovers the genomic regions and candidate genes underlying nutritionally important compounds in rice bran oil and highlights the underutilized value of Chhattisgarh rice germplasm. By linking specific SNPs to metabolic functions, we provide molecular targets for marker-assisted selection and biofortification strategies aimed at developing rice varieties enriched with health-promoting oil components. These findings establish a foundation for breeding “heart-healthy rice” and contribute to edible oil self-sufficiency.

Characterization of grain nutritional and quality traits was done in a total of 192 exotic and indigenous rice genotypes were genetically characterized for 16 grain nutritional and quality traits. Substantial genetic variability was observed for all the traits. The coefficient of variation was maximum for flavonoid content (87.10%) and minimum for kernel breadth (11.90%). The estimated coefficient of skewness and kurtosis indicated the presence of genetic interaction among the traits. Based on grain shape 4, 37, 31, 65 and 55 rice genotypes were classified as short slender, short bold, medium slender, long slender and long bold respectively. Further, kernel length was negatively associated with zinc, iron, phenolics and flavonoid contents. Amylose content was positively associated with protein, phenolics and flavonoid contents suggesting that such relationship could serve as grain indices for indirect selection of genotypes. Four genotypes- Oryza officinalis, Oryza latifolia, IC435559 and IC135877 were identified as donors for zinc and iron contents. The genotypes- IC74637, IC301547, IC301589 and IC301625 were identified as potential donors for both phenolics and flavonoid. Five genotypes viz., IC379109, IC331668, Mancha (M:1028), Dubraj (D:1251) and Laxmibhog (L:708) were identified for grain yield, quality and nutritional traits. The identified donors will be useful to develop nutrient dense biofortified varieties.

Arsenic (As) is a toxic environmental pollutant and a group-1 carcinogen, posing serious concern for human health. Rice and rice-based food products are considered as one of the major sources for As contamination into the human food-chain. Hence, world-wide concerted research efforts are going on, either to identify and/or develop low-As accumulating rice genotypes. The present study evaluated the natural accessions of rice, comprising of landraces and farmer’s varieties, under the naturally As-contaminated sites of Chhattisgarh, India, which is well-known for its richness in terms of rice production as well as varietal diversity. The wide-range spectrum of grain-As was obtained in 120 selected genotypes, with 90 and 81 accessions having As-accumulation above the WHO permissible limit for white (0.2 mg kg ⁻¹ ) and brown (0.3 mg kg ⁻¹ ) rice, respectively. The lowest grain-As accumulation among the varieties was seen in cultivated varieties (Badsabhog Sel 1 and Bahadur Sel 1) and landraces (Bastul and Kanaklata), which can be either cultivated or used as suitable donor in breeding programs. Among different agronomic traits, the plant height was identified as most-responsive parameter for assessing As-toxicity. The comparative assessment of agro-morphological traits although showed variations under naturally As-contaminated site; however, no significant correlation was seen in terms of grain-As accumulation, indicating the complexity for on-site field screening of low As-accumulating genotypes. Taken together, the results identified the potential low-As accumulating genotypes and highlighted the grain-As accumulation, as a complex multi-genic trait.

In the present study, 58 rice genotypes were evaluated for three consecutive seasons to enucleate the elite lines with high Fe and Zn contents. ANOVA revealed significant differences among the genotypes for Fe and Zn contents during all three seasons. Furthermore, PCV and GCV were moderate to high for Fe and Zn content during all three seasons. Similarly, high level of heritability and genetic advance were also recorded for both the traits. Iron content of Safri mutant 17-2-48 was consistently high for all the seasons whereas zinc content of Loktimachi was high for two seasons. Interestingly, rice genotypes Chhindmauri, Badsahbhog, Rudra, Danighoda and Suapankhi have been identified to have moderate to high Fe and Zn contents which could be used as donors for developing bio-fortified rice varieties. Stability analysis revealed that the genotypes Jhimiprass, Loktimachi, and CG Zinc Rice 2 for iron content and Rela Dhan, Chhindmauri, and CG Zinc Rice-1 for zinc content have had an average response to environment, making them appropriate for all seasons.

Mutation breeding offers a simple, fast and efficient way to rectify major defects without altering their original identity. The present study deployed radiation (gamma rays @ 300Gy)-induced mutation breeding for the improvement and revival of three traditional rice landraces, viz., Samundchini, Vishnubhog and Jhilli. Among the various putative mutants identified in the M2 generation, only three, ten and five rice mutants of Samundchini, Vishnubhog and Jhilli, respectively, were advanced to the M4, M5 and M6 generations, along with their parents and three checks for evaluations based on 13 agro-morphological and 16 grain quality traits. Interestingly, all the mutants of the three landraces showed a reduction in days to 50% flowering and plant height as compared to their parents in all the three generations. The reduction in days to 50% flowering ranges from 4.94% (Vishnubhog Mutant V-67) to 21.40% (Jhilli Mutant J-2-13), whereas the reduction in plant height varies from 11.28% (Vishnubhog Mutant V-45-2, Vishnubhog Mutant V-67) to 37.65% (Jhilli Mutant J-15-1). Furthermore, two, six and three mutants of Samundchini, Vishnubhog and Jhilli have increased their yield potential over their corresponding parents, respectively. Interestingly, Samundchini Mutant S-18-1 (22.45%), Vishnubhog Mutant V-74-6 (36.87%) and Jhilli Mutant J-13-5 (25.96%) showed the highest yield advantages over their parents. Further, a pooled analysis of variance based on a randomized complete block design revealed ample variations among the genotypes for the studied traits. In addition, all the traits consistently showed high to moderate PCV and GCV and a slight difference between them in all three generations indicated the negligible effect of the environment. Moreover, in the association analysis, the traits, viz., fertile spikelets/panicle, panicle length, total tillers/plant, spikelet fertility percent and 100-seed weight showed the usual grain yield/plant, whereas the traits hulling (%) and milling (%) with HRR (%) consistently showed high direct effects and significant positive correlations. The SSR marker-based genome similarity in rice mutants and corresponding parents ranged from 95.60% to 71.70% (Vishnubhog); 95.62% to 89.10% (Samundchini) and 95.62% to 80.40% (Jhilli), indicating the trueness of the mutants. Moreover, the UPGMA algorithm and Gower distance-based dendrogram, neighbour joining tree and PCA scatter diagram assured that mutants were grouped with their respective parents and fell into separate clusters showing high similarity between mutants and parents and dissimilarity among the 24 genotypes. Overall, the information and materials generated from the current study will be very useful and informative for students, researchers and plant breeders. Additionally, our results also showed that irradiation could generate a considerable amount of genetic variability and provide new avenues for crop improvement and diversification.

Rice production needs to be sustained in the coming decades, as the changeable climatic conditions are becoming more conducive to disease outbreaks. The majority of rice diseases cause enormous economic damage and yield instability. Among them, rice blast caused by Magnaportheoryzae is a serious fungal disease and is considered one of the major threats to world rice production. This pathogen can infect the above-ground tissues of rice plants at any growth stage and causes complete crop failure under favorable conditions. Therefore, management of blast disease is essentially required to sustain global food production. When looking at the drawback of chemical management strategy, the development of durable, resistant varieties is one of the most sustainable, economic, and environment-friendly approaches to counter the outbreaks of rice blasts. Interestingly, several blast-resistant rice cultivars have been developed with the help of breeding and biotechnological methods. In addition, 146 R genes have been identified, and 37 among them have been molecularly characterized to date. Further, more than 500 loci have been identified for blast resistance which enhances the resources for developing blast resistance through marker-assisted selection (MAS), marker-assisted backcross breeding (MABB), and genome editing tools. Apart from these, a better understanding of rice blast pathogens, the infection process of the pathogen, and the genetics of the immune response of the host plant are very important for the effective management of the blast disease. Further, high throughput phenotyping and disease screening protocols have played significant roles in easy comprehension of the mechanism of disease spread. The present review critically emphasizes the pathogenesis, pathogenomics, screening techniques, traditional and molecular breeding approaches, and transgenic and genome editing tools to develop a broad spectrum and durable resistance against blast disease in rice. The updated and comprehensive information presented in this review would be definitely helpful for the researchers, breeders, and students in the planning and execution of a resistance breeding program in rice against this pathogen.