Rice Science最新文献

This investigation aimed to establish the geographical traceability of Malaysian rice by assessing the elemental composition in paddy soil. Multi-element determination in combination with a chemometric approach was applied to evaluate the elemental concentrations of paddy soil from granaries cultivated with the same rice variety and to assess the relationship between elements in the soil and rice (SAR) system. A total of 29 elements (aluminum, arsenic, barium, bromine, calcium, chlorine, cobalt, chromium, cesium, europium, iron, gallium, hafnium, potassium, lanthanum, lutetium, magnesium, manganese, sodium, rubidium, antimony, scandium, samarium, thorium, titanium, uranium, vanadium, ytterbium and zinc) were successfully determined in paddy soil from Kedah, Selangor and Langkawi by neutron activation analysis. A significant difference (P < 0.05) between 18 elements in the soil samples was obtained. The chemometric approaches of principal component and linear discriminant analyses demonstrated clear discrimination and highly corrected classification (100%) of the soil samples. A high classification (98.1%) was also achieved by assessing 10 elements (aluminum, arsenic, bromine, chlorine, potassium, magnesium, manganese, sodium, rubidium and zinc), which similarly applied to rice geographical origin determination. Similar elements in SAR were also observed for differences in the pattern of correlation and bioaccumulation factor between the granaries. Furthermore, the generalized Procrustes analysis showed a 98% consensus between SAR and clear differences between the studied regions. The canonical correlation analysis demonstrated a significant correlation between the chemical profile of SAR (r² = 0.88, P < 0.001). Therefore, the current work model provides a reliable assessment to establish rice provenance.

Rice is often grown as multiple seasons in one year, alternating between flooded and upland systems. A major constraint, introduced from the flooded system, is a plough pan that may decrease rooting depth and productivity of follow-on upland rice. Roots penetrating the plough pan under flooded rice system can leave a legacy of weaker root growth pathways. Deeper rooting rice cultivars could have a bigger impact, but no direct evidence is available. To explore whether a deep rather than a shallow rooting rice cultivar grown in a flooded cropping cycle benefited deeper root growth of follow-on rice in an upland, reduced tillage cropping cycle, a simulated flooded paddy in greenhouse was planted with deep (Black Gora) and shallow (IR64) rooting cultivars and a plant-free control. Artificial plough pans were made in between the topsoil and subsoil to form different treatments with no plough pan (0.35 MPa), soft plough pan (1.03 MPa) and hard plough pan (1.70 MPa). After harvest of this ‘first season’ rice, the soil was drained and undisturbed to simulate zero-tillage upland and planted rice cultivar BRRI Dhan 28. The overall root length density (RLD), root surface area, the numbers of root tips and branching of BRRI Dhan 28 did not vary between plough pan and no plough pan treatments. Compared with the shallow rooting rice genotype, the deep rooting rice genotype as ‘first season’ crop produced 19% greater RLD, 34% greater surface area and 29% more branching of BRRI Dhan 28 in the subsoil. In the topsoil, however, BRRI Dhan 28 had 28% greater RLD, 35% greater surface area and 43% more branching for the shallow rather than deep rooting genotype planted in the ‘first season’. The results suggested that rice cultivar selection for a paddy cycle affects root growth of a follow-on rice crop grown under no-till, with benefits to subsoil access from deep rooting cultivars and topsoil proliferation for shallow rooting cultivars.

Identification of immunity-associated leucine-rich repeat receptor-like protein kinases (LRR-RLK) is critical to elucidate the LRR-RLK mediated mechanism of plant immunity. Here, we reported the map-based cloning of a novel rice SPOTTED-LEAF 41 (OsSPL41) encoding a putative LRR-RLK protein (OsLRR-RLK41/OsSPL41) that regulated disease responses to the bacterial blight pathogen Xanthomonas oryzae pv. oryzae (Xoo). An 8-bp insertion at position 865 bp in a mutant spotted-leaf 41 (spl41) allele led to the formation of purple-brown lesions on leaves. Functional complementation by the wild type allele (OsSPL41) can rescue the mutant phenotype, and the complementary lines showed similar performance to wild type in a number of agronomic, physiological and molecular indices. OsSPL41 was constitutively expressed in all tissues tested, and OsSPL41 contains a typical transmembrane domain critical for its localization to the cell membrane. The mutant exhibited an enhanced level of resistance to Xoo in companion of markedly up-regulated expression of pathogenesis-related genes such as OsPR10a, OsPAL1 and OsNPR1, while the level of salicylic acid was significantly increased in spl41. In contrast, the over-expression lines exhibited a reduced level of H₂O₂ and were much susceptible to Xoo with down-regulated expression of pathogenesis-related genes. These results suggested that OsSPL41 might negatively regulate plant immunity through the salicylic acid signaling pathway in rice.

The main goals of rice breeding nowadays include increasing yield, improving grain quality, and promoting complete mechanized production to save labor costs. Rice grain shape, specified by three dimensions, including grain length, width and thickness, has a more precise meaning than grain size, contributing to grain appearance quality as well as grain weight and thus yield. Furthermore, the divergence of grain shape characters could be utilized in mechanical seed sorting in hybrid rice breeding systems, which has been succeeded in utilizing heterosis to achieve substantial increase in rice yield in the past decades. Several signaling pathways that regulate rice grain shape have been elucidated, including G protein signaling, ubiquitination-related pathway, mitogen-activated protein kinase signaling, phytohormone biosynthesis and signaling, microRNA process, and some other transcriptional regulatory pathways and regulators. This review summarized the recent progress on molecular mechanisms underlying rice grain shape determination and the potential of major genes in future breeding applications.

Heading date is one of the most important agronomic traits of rice, which critically affects rice ecogeographical adaptation, yield and quality. In this study, a late heading date 3 (lhd3) mutant was screened from the ⁶⁰Co-γ irradiation mutant library. The lhd3 delayed heading date in rice under both short day and long day conditions. Map-based cloning combined with Mutmap strategy was adopted to isolate the causal LHD3 gene. The LHD3 gene encodes a DNA_J domain protein, which was ubiquitously expressed in various plant organs, and dominant expressed in stems and leaves. Subcellular localization analysis showed that LHD3 was localized to nucleus, indicating that LHD3 may interact with other elements to regulate the expression of flowering genes. The transcriptions of the heading activators Ehd1, Hd3a and RFT1 significantly decreased in the lhd3 mutant, suggesting that LHD3 may control the heading date through the Ehd1-Hd3a/RFT1 photoperiodic flowering pathway. The variation and haplotype analyses of the genomic region of LHD3 showed that there were 7 haplotypes in the LHD3 region from 4 702 accessions. The haplotypes of LHD3 can be divided into two classes: class a and class b, and the heading dates of these two classes were significantly different. Further study showed that two single nucleotide polymorphisms (SNPs), SNP10 (G2100C) in Hap II and SNP3 (C861T) in Hap VII, may be the functional sites causing early and late heading in accessions. Nucleotide diversity analysis showed LHD3 had been selected in the indica population, rather than in the japonica population. Therefore, the present study sheds light on the regulation of LHD3 on heading date in rice and suggests that LHD3 is a novel promising new target for rice molecular design and breeding improvement.

Soil salinization and/or alkalization is a major constraint to crop production worldwide. Approximately 60% of the cultivated land is affected by salt, over half of which is alkalized. Alkaline soils are characterized by high alkalinity and typically high salinity, which creates a complex saline-alkaline (SA) stress that affects plant growth. Rice cultivation has been accepted as an important strategy for effective utilization of SA land if water is available for irrigation. Nevertheless, as a salt-sensitive plant, rice plants suffer severe SA-induced damage, which results in poor plant growth and grain yield. Various approaches have been employed to improve rice productivity in SA land. Among them, the priming technique has emerged as a powerful method for enhancing SA tolerance in rice plants. In this review, we summarized how SA stress damages rice plants, and then presented how priming treatment can mitigate such damage.

Leaf rolling (LR) is one of the defensive mechanisms that plants have developed against adverse environmental conditions. LR is a typical drought response, promoting drought resistance in various gramineae species, including wheat, maize, and rice. Rice cultivation faces the formidable challenge of water deprivation because of its high water requirements, which leads to drought-related symptoms in rice. LR is an important morphological characteristic that plays a key role in controlling water loss during water insufficiency, thereby regulating leaf area and stature, which are crucial agronomic traits determining yield criteria. Bulliform, sclerenchyma, mesophyll, and vascular bundles are the cells that engage in LR and commonly exhibit adaxial or abaxial types of rolling in rice. The specific genes linked to rolling, either adaxially or abaxially, are discussed here. In addition to the factors influencing LR, here is a short review of the morphological, physiological and molecular responses of this adaptation under drought stress. Moreover, this review highlights how LR combats the consequences of drought stress. The eco-physiological and molecular mechanisms underlying this morphological adaptation in rice should be further explored, as they might be useful in dealing with various degrees of drought tolerance.

As an abiotic stress, adverse germination temperatures cause serious disruptions in physiological and biochemical processes involved in seed germination. Using a factorial experiment, we examined the effects of different seed priming treatments on enzymatic and biochemical performances of rice seed germination under different temperatures. Each of the rice genotypes (Hashemi, Sadry-domsefid, IRON-70-7053-7 and NORIN-22) was primed with hydro-hardening, KCl, CaCl₂ and ascorbic acid (AsA) and without a priming agent as a control at low (15 ºC), optimum (25 ºC) and high (35 ºC) germination temperatures. The results showed that the enzymatic and biochemical performances of all the rice genotypes were affected by the seed priming agents, especially under the low germination temperature. At 15 ºC, seed priming with AsA was found to be the best agent for the activities of amylase, α-amylase, catalase (CAT), peroxidase (POX), ascorbate peroxidase (APOX) and superoxide dismutase (SOD) as well as the content of soluble sugars in the NORIN-22 genotype, and for protease activity and soluble protein content in the IRON-70-7053-7 genotype. SOD at the low germination temperature and CAT, POX and protease at the optimum and high germination temperatures were the most important enzymes in occurrence of germination potential in terms of seedling length, vigor index, normal seedling rate and germination rate. Under the priming agents, the highest changes in normal seedling rate were observed at the low and optimum germination temperatures by AsA priming in the Hashemi and NORIN-22 genotypes, and at the high germination temperature under KCl priming in the Hashemi genotype.