The resistant starch content (RSC) of a starch-rich food product is an important indicator of its glycemic index (GI). Foods with high RSC have low GI and are beneficial to human health. In recent years, some studies revealed that the loss function of single or multiple key enzymes in the primary pathway of starch synthesis substantially increases RSC in rice, a staple food for about half of the world population. However, a noteworthy negative characteristic of these high RSC mutants is the substantially increased apparent amylose content (AAC). AAC as a major determinator of rice eating quality, must not be higher than an acceptable limit for most consumers. To date, the research on optimizing AAC or taste quality of high RSC rice was scarcely reported. To address this issue, two promoter editing (PE) strategies were adopted in this study to develop rice germplasms with a better balance between RSC and AAC: one is to edit the promoter of BEIIb in a low AAC rice variety, another is to edit the promoter of Waxy (Wx) gene in a BEIIb function-defective mutant. Using AAC ≤ 20
Global climate change has driven a persistent rise in surface temperatures, posing an existential threat to agricultural productivity and food security. Rice (Oryza sativa L.), the primary staple crop for more than half the global population, is acutely vulnerable to heat stress during reproductive development, particularly at flowering. Brief exposure to temperatures exceeding 35 °C during anthesis severely impairs spikelet fertility, and projected increases of 2–4 °C by mid-century make understanding the mechanistic basis of rice thermo-tolerance a matter of urgency. This review provides a comprehensive, critically integrated synthesis of rice flowering responses to high-temperature stress, covering the sequential processes of floret opening, anther dehiscence, pollen viability, pollen germination, and pollen tube growth at physiological, biochemical, and molecular levels. We systematically evaluate key regulatory networks-including reactive oxygen species (ROS) signaling, calcium (Ca²⁺) second-messenger cascades, phytohormone homeostasis, heat shock protein (HSP) chaperone networks, and the endoplasmic reticulum (ER) unfolded protein response (UPR) and critically synthesize how thermo-tolerance QTLs TT1, TT2, and TT3 interconnect these pathways. We further examine emerging roles for epigenetic regulation and non-coding RNAs in thermo-memory and heat acclimation. Finally, we integrate molecular insights with genetic improvement strategies-ranging from conventional breeding and marker-assisted selection to CRISPR/Cas9 genome editing-alongside evidence-based agronomic practices targeting the anthesis window. By bridging mechanistic understanding with translational applications, this review identifies key unresolved questions and outlines priority research directions for developing thermally resilient rice varieties capable of sustaining productivity under ongoing climate warming.
Bacterial blight of rice causes substantial crop losses in Asia and Africa. The recent introduction of Asian strains into African countries has led to two independent outbreaks detected in 2019, causing severe damage in Madagascar and Tanzania. The strains are highly virulent on local rice varieties and rapidly spread from Tanzania to neighboring countries. Multiplex genome editing of effector-binding elements in the promoter of rice SWEET has successfully generated elite rice lines with broad-spectrum resistance against bacterial blight. While genome-edited crops can be released in countries with genome editing regulations, their use in countries that have yet to establish regulations, e.g., Tanzania and Madagascar, is hindered. To circumvent this, marker-assisted breeding (MAB) of the African elite varieties KombokaP, FARO-44, and NERICA-4 was adopted to introgress resistance genes to confer resistance to Xoo strains identified in Tanzania (iTz) and Madagascar (iMg). We hypothesized that xa13 and Xa21 can confer resistance to the introduced strains, and that a combination of R genes would enhance durability. Resistance gene pyramiding, namely the endogenous Xa1, Xa4 with xa13, and Xa21 genes in the elite rice varieties KombokaP, FARO-44 and NERICA-4 conferred resistance to the introduced iTz and iMg strains as well as select Asian and West African Xoo strains. Our study presents one potential solution by providing rice breeders in East Africa with robust bacterial blight resistance in three local rice varieties for field trials, line registration, and deployment.
Rice blast, caused by Magnaporthe oryzae, is a destructive disease worldwide. Deployment of broad-spectrum resistance (R) genes is an effective strategy for sustainable disease control, but the actual resistance effects of individual genes and their combinations in commercial rice cultivars remain largely unknown. In this study, we evaluated 120 main cultivated rice varieties grown over the past five decades in Chadi, a national rice blast resistance identification nursery, Fujian Province, Southeast China. Fifteen well-known R genes (Pi5/i, Pib, Pid3/25, Bsr-d1, Pi9, Pi2, Piz‑t, Pigm, Pi1, Pik‑p, Pik‑m, Pik, Pid2, Pit, and Pi‑ta) were screened using molecular markers. Seedling, leaf, and panicle blast resistance were evaluated under natural field conditions. The average number of detected R genes per variety was 1.00 in period A (≤ 1980, n = 24), 1.57 in period B (1981–1999, n = 42), and 1.48 in period C (≥ 2000, n = 54), with the highest value observed in period B. Genes including Pigm, Pi1, Pid2, Pid3/25, and Bsr-d1 exhibited significant negative correlations with seedling blast, tillering blast, mature-stage blast, and the comprehensive resistance index (P < 0.01), indicating that their presence is associated with enhanced resistance. These findings demonstrate that pyramiding effective broad-spectrum R genes has significantly enhanced blast resistance in modern rice cultivars and provide practical guidance for gene deployment and breeding programs targeting durable and broad-spectrum resistance.
Cold stress (CS) is a major abiotic factor limiting rice (Oryza sativa L.) productivity and threatening global food security. Nanotechnology has recently emerged as a promising strategy to enhance crop resilience to low temperatures. This review synthesizes recent advances in nanoparticle (NP)-based approaches for improving CS tolerance in rice, highlighting their roles in modulating antioxidant defenses, phytohormone balance, photosynthesis, and cold-responsive gene expression. We integrate insights from rice CS signaling and NP uptake, translocation, and accumulation, providing a mechanistic perspective on how NPs mitigate cold-induced injuries. We also address potential NP toxicity and its implications for plant fitness. Compared to previous reviews, this work uniquely emphasizes the interplay between NP-mediated interventions and cold stress biology, identifies critical gaps such as long-term NP fate and cultivar-specific responses, and outlines future directions for sustainable application of nanotechnology in rice CS management.
