Rice Science最新文献

Iron (Fe) toxicity, generated from excess reduced ferrous Fe (Fe²⁺) ion formation within the soil under submerged condition, is a potent environmental stress that limits lowland rice production. Total 11 diverse Thai rice genotypes, including a recognized tolerant genotype Azucena and a susceptible genotype IR64, were evaluated against 5 Fe²⁺ levels [0 (control), 150, 300, 600 and 900 mg/L] to screen the tested genotypes for their Fe-toxicity tolerance and to classify them as a sensitive/tolerant category. The evaluation was conducted by a germination study, followed by a polyhouse study on growth, yield and physiochemical performances. Results showed significant variations in Fe²⁺-tolerance across genotypes. Increasing Fe²⁺ level beyond 300 mg/L was detrimental for germination and growth of all the tested genotypes, although germination responses were negatively affected at Fe²⁺ ≥ 300 mg/L. Physiochemical responses in the form of leaf greenness, net photosynthetic rate, membrane stability index and Fe contents in leaf and root were the most representative of Fe²⁺-toxicity-mediated impairments on overall growth and yield. Difference in physiochemical responses was effectively correlated with the contrasting ability of the genotypes on lowering excess Fe²⁺ in tissues. Analysis of average tolerance and stress tolerance index unveiled that the genotypes RD85 and RD31 were the closest to the tolerant check Azucena and the sensitive check IR64, respectively. The unweighted pair group method with arithmetic means clustering revealed three major clusters, with cluster II (four genotypes) being Fe²⁺ tolerant and cluster I (four genotypes) being Fe²⁺ sensitive. Principal component (PC) analysis and genotype by trait-biplot analysis showed that the first two components explained 90.5% of the total variation, with PC1 accounting for 56.6% and PC2 for 33.9% of the total variation. The identified tolerant rice genotypes show potentials for cultivation in Fe²⁺-toxic lowlands for increased productivity. The findings contribute to the present understanding on Fe²⁺-toxicity response and provide a basis for future genotype selection or rice crop improvement programs against Fe²⁺-toxicity.

Crop yield and quality are often limited by the amount of phosphate fertilizer added to infertile soils, a key limiting factor for sustainable development in modern agriculture. The polyphosphate kinase (ppk) gene -expressing transgenic rice with a single-copy line (ETRS) is constructed to improve phosphate fertilizer utilization efficiency for phosphorus resource conservation. To investigate the potential mechanisms of the increased biomass in ETRS in low phosphate culture, ETRS was cultivated in a low inorganic phosphate (Pi) culture medium (15 μmol/L Pi, LP) and a normal Pi culture medium (300 μmol/L Pi, CP), respectively. After 89 d of cultivation in different concentrations of phosphate culture media, the total phosphorus, polyphosphate (polyP), biomass, photosynthetic rate, nonstructural carbohydrate (NSC) contents, related enzyme activities, and related gene expression levels were analyzed. The results showed that ETRS had a high polyP amount to promote the photosynthetic rate in LP, and its biomass was almost the same as the wild type (WT) in CP. The NSC content of ETRS in LP was higher than that of WT in LP, but slightly lower than that of WT in CP. PolyP notably promoted the sucrose phosphate synthase activities of ETRS and significantly down-regulated the expression levels of sucrose transporter genes (OsSUT3 and OsSUT4), resulting in inhibiting the transport of sucrose from shoot to root in ETRS. It was concluded that polyP can stimulate the synthesis of NSCs in LP, which improved the growth of ETRS and triggered the biological activities of ETRS to save phosphate fertilizer. Our study provides a new way to improve the utilization rate of phosphate fertilizer in rice production.

Nitrate (NO₃^–) and ammonium (NH₄⁺) are two main inorganic nitrogen (N) sources during crop growth. Here, we enhanced the expression of OsAMT1.1, which encodes a NH₄⁺ transporter, using the NO₃^–-inducible promoter of OsNAR2.1 and an ubiquitin promoter in transgenic rice plants. Under field condition of 120 kg /hm² N, agronomic N use efficiency, N recovery efficiency and N transport efficiency, and grain yield of the pOsNAR2.1:OsAMT1.1 transgenic lines were increased compared with those of the wild type (WT) and the pUbi:OsAMT1.1 transgenic plants. Under 2.0 mmol/L NO₃^– + 0.5 mmol/L NH₄⁺ and 0.5 mmol/L NO₃^– + 2.0 mmol/L NH₄⁺ conditions of hydroponic culture, compared with the WT, both biomass and total N content were increased in the pOsNAR2.1:OsAMT1.1 transgenic lines. However, biomass was significantly reduced in pUbi:OsAMT1.1 transgenic plants under 0.5 mmol/L NO₃^– + 2.0 mmol/L NH₄⁺ condition. The lines expressing pOsNAR2.1:OsAMT1.1 exhibited increased OsAMT1.1 expression and ¹⁵NH₄⁺ influx in roots under both 2.0 mmol/L NO₃^– + 0.5 mmol/L NH₄⁺ and 0.5 mmol/L NO₃^– + 2.0 mmol/L NH₄⁺ conditions. Our study showed that expression of OsAMT1.1 can be promoted when driven by the OsNAR2.1 promoter, especially under high-level nitrate condition, leading to enhancement of NH₄⁺ uptake, N use efficiency and grain yield.

Rice storage proteins (RSPs) are plant proteins with high nutritional quality. As the second largest type of storage substance in rice, it is the main source of protein intake for people who consume rice as a staple food. The content and type of RSPs affect the appearance, processing quality and eating quality of rice. These effects involve the distribution of RSPs in rice grains as well as the interactions of RSPs with other components such as starch in rice grains. In the past two decades, some progress has been made in the genetic improvement of RSPs. However, the determination mechanism of protein content and composition in rice is still unclear, and the mechanism of the effect of RSPs on rice quality has not been elucidated. In this review, the composition, biosynthesis and distribution of RSPs, and quantitative trait loci mapping and cloning of RSP genes are summarized, the research progress of the influence of RSPs and their components on rice quality are reviewed, and the research directions in the future are proposed.

Improved rice varieties (IRVs) play a significant role in establishing food security and improving livelihood in the Global South since its introduction in the 1960s. However, the adoption of new IRVs has remained relatively low. This low adoption poses a challenge to rice-producing and consuming countries as they are increasingly threatened by production shortages, malnutrition, and poor rice quality. Many empirical studies have attempted to identify the determinants influencing the adoption of IRVs by distinguishing the characteristics between adopters and non-adopters. This review showed a consensus on the important determinants influencing the adoption of IRVs in the Global South. Findings synthesized from 99 studies suggested that variables (farm size, education, information access and farm location) examined extensively are not necessarily the most important determinants of adoption when undertaking a weighted analysis. Terrain, source of seed and technology-related attributes (perceived yield, maturity, ease of use, marketability and technical efficiency) are more important determinants of adoption, with determinants changing according to adoption type (probability or intensity of adoption), variety type and region. The recommendations for future adoption studies include: incorporating more technology-specific variables, increasing research for overlooked regions and variety types, shifting away from predominant static analysis by capturing the dynamics of the adoption process, and considering the potential biases in analyses. This review will facilitate the development of targeted interventions and policies that promote IRV adoption in the Global South.