Colored rice (black, purple, red and brown) has been consumed in China for nearly 4000 years. Recent research has focused on exploring its nutritional and metabolomic profiles and associated health benefits. Due to the improvement in detection and quantification techniques for health-promoting compounds and their activities, the number of studies has increased significantly. In this regard, a timely and updated review of research on nutritional composition, phytochemistry, and metabolite content and composition can significantly enhance consumer awareness. Here, we present a detailed and up-to-date understanding and comparison of the nutritional and phytochemical (metabolite) composition of colored rice. While earlier literature reviews focus on either single type of colored rice or briefly present nutritional comparison or bioactivities, here we present more detailed nutrient profile comparison (carbohydrates, fats, proteins, amino acids, minerals, and vitamins), together with the most recent comparative data on phytochemicals/metabolites (flavonoids, anthocyanins, fatty acids, amino acids and derivatives, phenolic acids, organic acids, alkaloids, and others). We discuss how metabolomics has broadened the scope of research by providing an increasing number of detected compounds. Moreover, directions on the improvement in colored rice nutritional quality through breeding are also presented. Finally, we present the health-beneficial activities (antioxidant, anti-inflammatory, antimicrobial, hypoglycemic, neuroprotective, anti-aging, and antitumor activities) of different colored rice varieties, together with examples of the clinical trials, and discuss which bioactive substances are correlated with such activities.

Interest in glutinous rice consumption has been expanding in East Asia. However, the extent of metabolite variation between common and glutinous rice has not been fully explored to identify metabolic targets for rice quality improvement. Thus, the objective of this study was to provide insights into the variation of metabolites and nutraceuticals between common and glutinous rice. Two black rice (common rice, BL-N, and glutinous rice, BL-G) and two white rice (common rice, WH-N, and glutinous rice, WH-G) types were analysed via LC-MS-based widely targeted metabolic profiling. We identified 441 and 343 types, including 160 key overlapping differentially accumulated metabolites between BL-N_vs_BL-G and WH-N_vs_WH-G, respectively. Glutinous rice showed a higher relative content of most categories of metabolites, except for quinones (in BL-N) and tannins (in WH-N). Seven vitamins, including B6, B3, B5, B13, isonicotinic acid, N-(beta-D-glucosyl)nicotinate, and 4-pyridoxic acid-O-glucoside, were significantly up-regulated in BL-G compared to BL-N. The biosynthesis of cofactors, zeatin biosynthesis, citrate cycle, amino acid metabolism, alpha-linolenic acid metabolism, and glyoxylate and dicarboxylate metabolism was the most differentially regulated pathway. Key differential metabolites in citrate cycle include citrate, isocitrate, fumarate, malate, succinate, and 2-oxoglutarate; in amino acid metabolism (L-serine, L-cysteine, L-lysine, L-glutamine, L-methionine, and L-tryptophan); and in glycolysis (UDP-glucose, D-glucose-1P, D-glucose-6P, and D-fructose-6P). The data resources in this study may contribute to a better understanding of the function and nutritional value of glutinous rice.

Germplasm resources are the foundation for improving crop varieties and a strategic asset for global food security. They also advance plant breeding, agricultural biotechnology and the production of essential agricultural goods. To assess the distribution, diversity and conservation status of food crop germplasm in the Hainan Province, China, we conducted a detailed survey of the Hainan Island. Between 2017 and 2022, we collected 330 food crop germplasm resources, encompassing 16 cereal crops, including rice, maize, sweet potato. The collected germplasm resources exhibited traits of high resistance to both biotic and abiotic stresses, including common diseases and drought stress, as well as superior quality and adaptability to poor soil conditions such as sandy land. However, challenges such as low productivity and hybrid degradation were identified. These resources were primarily found in Haikou City, Baisha County, Danzhou City, Wuzhishan City and Sanya City. Additionally, we collected several ancient local varieties and endangered germplasm resources such as ‘Jiezi rice’ and ‘Wuzhishan maize’. This study serves as a reference for the conservation, development and utilization of local food crop germplasm resources in Hainan Province and lays the foundation for breeding and developing new varieties.

Background: The Calcineurin B-like (CBL) and CBL-interacting protein kinase (CIPK) system constitute critical signaling modules mediating plant responses to abiotic stress. Although these families have been studied across various species, their evolutionary dynamics across grasses and the functional plasticity of specific isoforms remain elusive. Methods: A genome-wide analysis of CBL and CIPK families was conducted across five major Poaceae species (Oryza sativa, Triticum aestivum, Zea mays, Sorghum bicolor, and Saccharum spontaneum). Phylogenetic and synteny analyses were analyzed to family expansion and evolution. Cis-regulatory elements analysis in gene promoter regions were examined to predict potential stress-responsive features. Expression profiles of OsCBL and OsCIPK gene families were examined by qRT-PCR under conditions involving PEG-induced osmotic stress, pathogen strain P6 inoculation, and exogenous application of the phytohormones abscisic acid (ABA) and methyl jasmonate (MeJA). Protein–protein interactions between selected CBL (OsCBL4) and CIPK pairs were assessed via Yeast Two-Hybrid (Y2H) and Luciferase Complementation Imaging assays (LCI). Results: Phylogenetic and synteny analyses indicated that segmental duplications have contributed substantially to the expansion of these gene families. Promoter analysis revealed that the majority of CBL and CIPK family members, exemplified by OsCBL4, traditionally characterized as a salt sensor, possesses a cis-element architecture (rich in ABREs and MBS) heavily biased towards dehydration responsiveness. Expression profiling showed that OsCBL4 is significantly hyper-induced by direct osmotic stress (PEG) but exhibits almost no response to exogenous ABA. A subset of kinases genes (e.g., OsCIPK2, 9, 18) displayed PEG-induced expression patterns resembling those of OsCBL4, whereas OsCIPK30 remained transcriptionally unresponsive under the same conditions. Protein interaction assays demonstrated that OsCBL4 physically interacts exclusively with PEG-responsive transcriptionally activated kinases such as OsCIPK9, but failed to interact with the non-responsive OsCIPK30. Conclusions: Our study provides a genomic characterization of CBL and CIPK families across five major Poaceae species. The combined expression and interaction data reveal that OsCBL4-assembles with specific CIPKs into signaling modules during osmotic stress responses in rice, pointing to roles that go beyond salt stress responses. The findings establish a foundation for further functional dissection of CBL-CIPK pathway diversification in abiotic stress adaptation.

Bacterial blight (BB), caused by Xanthomonas oryzae pv. Oryzae (Xoo), is one of the most devastating diseases in rice worldwide. Common wild rice (Oryza rufipogon Griff.) inhabiting the high-temperature and high-humidity environments of Hainan Island has evolved strong disease resistance through natural selection, representing a valuable genetic reservoir for resistance breeding. However, large-scale characterization of resistance phenotypes, resistance genes, and their combinations remains limited. In this study, we evaluated BB resistance in 1511 Hainan common wild rice accessions against three Xoo strains (HNX004, PXO99^A, and Z173) and analyzed the distribution of ten major known resistance genes (Xa1, Xa3, Xa4, xa5, Xa7, Xa10, xa13, Xa21, Xa23, and Xa27). Phenotypic evaluation revealed distinct strain-specific resistance patterns. Broad-spectrum resistance analysis (defined as moderate resistance or higher) revealed that 35 accessions (2.32%) were resistant to all strains, and 378 accessions (25.02%) showed resistance to two strains. Genotyping of known resistance genes revealed that, except for one accession, which lacked all tested genes but showed resistance to strain PXO99^A, all other accessions carried every tested gene except Xa21 and xa13. Interestingly, different Xoo strains exhibited distinct requirements for resistance genes, revealing a clear strain-specific resistance pattern. Notably, the number of resistance genes did not correlate with resistance level. Instead, specific complementary combinations, particularly Xa1 + Xa10 + Xa23 + Xa4 + Xa7, conferred the strongest broad-spectrum resistance. Our results demonstrate that gene quality and specific complementary combinations are more important than the absolute number of resistance genes. The identified resistant accessions and favorable gene combinations provide valuable resources for rice breeding programs.

To overcome reproductive barriers and utilize beneficial genes from wild rice, total DNA from blast-resistant Oryza officinalis was introduced into elite restorer line R225 via panicle-neck injection (pollen-tube pathway), and after multi-generation selection, the novel restorer ‘Hai Hui 2011′ was developed and crossed with ‘Long Te Fu A’ to produce the hybrid ‘Te You 2011’. Multi-year field trials in Hainan showed that ‘Te You 2011’ yielded 8.48–8.70 t/ha in early seasons, with increases of 2.23–9.70% over the check ‘Te You 009’, and an 8.36% increase in late season, indicating that it has good yield potential. SSR marker RM154 detected a 183bp specific fragment shared with the wild donor in ‘Hai Hui 2011’ and Oryza officinalis but absent in ‘R225’, providing preliminary evidence of genetic relatedness. Marker alleles associated with four known blast resistance loci (Pib, Pik, Pi54, and Pi33) were detected in both ‘Hai Hui 2011’ and ‘Te You 2011’. Under natural field conditions and artificial inoculation with the predominant Hainan YF race group, both lines showed strong resistance. These findings preliminarily suggest that panicle-neck injection of exogenous total DNA may be a potential approach for introducing wild-rice genetic material, and that ‘Te You 2011’ is a promising high-yielding, blast-resistant hybrid for tropical and subtropical rice regions.