Dwarf Rice Research Articles

Phylogenetic and recombination analysis of rice black-streaked dwarf virus segment 9 in China.

Rice black-streaked dwarf virus (RBSDV) is an economically important virus that causes maize rough dwarf disease and rice black-streaked dwarf disease in East Asia. To study RBSDV variation and recombination, we examined the segment 9 (S9) sequences of 49 RBSDV isolates from maize and rice in China. Three S9 recombinants were detected in Baoding, Jinan, and Jining, China. Phylogenetic analysis showed that Chinese RBSDV isolates could be classified into two groups based on their S9 sequences, regardless of host or geographical origin. Further analysis suggested that S9 has undergone negative and purifying selection.

Impact of on farm trials(OFT)on agro-technology for sustainable productivity of rice-utera cropping system in Chhattisgarh plains

The research work was conducted in ten rainfed villages of Mahasamund and Rajnandgaon district of Chhattisgarh state, where the project work (NATP-RRPS-34) was carried out. A total of 12 farmers practicing rice-utera cropping system from each selected village were selected randomly. In this way, a total of 120 farmers were taken as respondents. The data were collected through personal interview method. The findings of the study revealed that, the On farm trials in rice-utera cropping system were helpful in increasing the yield. The other important perceptions about OFTs were dissemination of technology and variety replacement. The trends of cultivation of rice varieties before and after OFTs showed that Mahamaya, HMT, MTU-1010 were gaining more area. The high yielding dwarf rice varieties were gaining popularity over traditional varieties. The impact of OFTs on productivity showed that the rice yield was increased followed by Lathyrus. It indicates that due to implementation of OFTs the average yield of rice as well as utera crops was increased significantly. The impact of OFTs on productivity showed that rice yield was increased by more than 58 per cent and maximum 140.9 per cent increase was recorded in grasspea followed by 108.33 per cent in lentil. It indicates that the high yielding dwarf rice varieties were gaining popularity over traditional varieties and the average yield of rice as well as utera crops was increased significantly. Therefore, it is recommended for profitable rice-utera system, proper crop management practices should be initiated from rice to utera crops.

DWARF3 Participates in an SCF Complex and Associates with DWARF14 to Suppress Rice Shoot Branching

Strigolactones (SLs) are a novel class of plant hormones that inhibit shoot branching. Currently, two proteins in rice are thought to play crucial roles in SL signal transduction. DWARF14 (D14), an α/β hydrolase, is responsible for SL perception, while DWARF3 (D3), an F-box protein with leucine-rich repeats, is essential for SL signal transduction. However, how these two proteins transmit SL signals to downstream factors remains unclear. Here, we characterized a high-tillering dwarf rice mutant, gsor300097, which is insensitive to GR24, a synthetic analog of SL. Mapping and sequencing analysis showed that gsor300097 is a novel allelic mutant of D3, in which a nonsense mutation truncates the protein from 720 to 527 amino acids. The D3 gene was strongly expressed in root, leaf, shoot base and panicle. Nuclear-localized F-box protein D3 played a role in the SCF complex by interacting with OSK1, OSK5 or OSK20 and OsCullin1. In addition, D3 associated with D14 in a GR24-dependent manner in vivo. Taken together, our findings suggested that D3 assembled into an SCF(D3) complex and associated with D14 to suppress rice shoot branching.

Isolation and characterisation of a dwarf rice mutant exhibiting defective gibberellins biosynthesis

We have isolated a severe dwarf mutant derived from a Ds (Dissociation) insertion mutant rice (Oryza sativa var. japonica c.v. Dongjin). This severe dwarf phenotype, has short and dark green leaves, reduced shoot growth early in the seedling stage, and later severe dwarfism with failure to initiate flowering. When treated with bioactive GA3 , mutants are restored to the normal wild-type phenotype. Reverse transcription PCR analyses of 22 candidate genes related to the gibberellin (GA) biosynthesis pathway revealed that among 22 candidate genes tested, a dwarf mutant transcript was not expressed only in one OsKS2 gene. Genetic analysis revealed that the severe dwarf phenotype was controlled by recessive mutation of a single nuclear gene. The putative OsKS2 gene was a chromosome 4-located ent-kaurene synthase (KS), encoding the enzyme that catalyses an early step of the GA biosynthesis pathway. Sequence analysis revealed that osks2 carried a 1-bp deletion in the ORF region of OsKS2, which led to a loss-of-function mutation. The expression pattern of OsKS2 in wild-type cv Dongjin, showed that it is expressed in all organs, most prominently in the stem and floral organs. Morphological characteristics of the dwarf mutant showed dramatic modifications in internal structure and external morphology. We propose that dwarfism in this mutant is caused by a point mutation in OsKS2, which plays a significant role in growth and development of higher plants. Further investigation on OsKS2 and other OsKS-like proteins is underway and may yield better understanding of the putative role of OsKS in severe dwarf mutants.

Genetic, Physiological, and Gene Expression Analyses Reveal That Multiple QTL Enhance Yield of Rice Mega-Variety IR64 under Drought

BackgroundRice (Oryza sativa L.) is a highly drought sensitive crop, and most semi dwarf rice varieties suffer severe yield losses from reproductive stage drought stress. The genetic complexity of drought tolerance has deterred the identification of agronomically relevant quantitative trait loci (QTL) that can be deployed to improve rice yield under drought in rice. Convergent evidence from physiological characterization, genetic mapping, and multi-location field evaluation was used to address this challenge.Methodology/Principal FindingsTwo pairs of backcross inbred lines (BILs) from a cross between drought-tolerant donor Aday Sel and high-yielding but drought-susceptible rice variety IR64 were produced. From six BC4F3 mapping populations produced by crossing the +QTL BILs with the −QTL BILs and IR64, four major-effect QTL - one each on chromosomes 2, 4, 9, and 10 - were identified. Meta-analysis of transcriptome data from the +QTL/−QTL BILs identified differentially expressed genes (DEGs) significantly associated with QTL on chromosomes 2, 4, 9, and 10. Physiological characterization of BILs showed increased water uptake ability under drought. The enrichment of DEGs associated with root traits points to differential regulation of root development and function as contributing to drought tolerance in these BILs. BC4F3-derived lines with the QTL conferred yield advantages of 528 to 1875 kg ha−1 over IR64 under reproductive-stage drought stress in the targeted ecosystems of South Asia.Conclusions/SignificanceGiven the importance of rice in daily food consumption and the popularity of IR64, the BC4F3 lines with multiple QTL could provide higher livelihood security to farmers in drought-prone environments. Candidate genes were shortlisted for further characterization to confirm their role in drought tolerance. Differential yield advantages of different combinations of the four QTL reported here indicate that future research should include optimizing QTL combinations in different genetic backgrounds to maximize yield advantage under drought.

Life cycle of phytoreoviruses visualized by electron microscopy and tomography

Rice dwarf virus and Rice gall dwarf virus, members of the genus Phytoreovirus in the family Reoviridae,are known as agents of rice disease, because their spread results in substantial economic damage in many Asian countries. These viruses are transmitted via insect vectors, and they multiply both in the plants and in the insect vectors. Structural information about the viruses and their interactions with cellular components in the life cycle are essential for understanding viral infection and replication mechanisms. The life cycle of the viruses involves various cellular events such as cell entry, synthesis of viral genome and proteins, assembly of viral components, viral egress from infected cells, and intra- and intercellular transports. This review focuses on the major events underlying the life cycle of phytoreoviruses, which has been visualized by various electron microscopy (EM) imaging techniques, including cryo-electron microscopy and tomography, and demonstrates the advantage of the advanced EM imaging techniques to investigate the viral infection and replication mechanisms.

16. Mutation analysis in dwarf rice induced by LETmax irradiation

16. Mutation analysis in dwarf rice induced by LETmax irradiation

Pre-breeding and Population Improvement

Pre-breeding refers to all activities designed to identify desirable characteristics and/or genes from unadapted (exotic or semi-exotic) materials, including those that, although adapted, have been subjected to any kind of selection for improvement. It is an essential part of germplasm diversification strategies. Pre-breeding is the most promising alternative to link genetic resources and breeding programmes. As pre-breeding is being carried out, the resulting materials are expected to have merit to be included in ordinary breeding programmes. There are at least three distinct uses of genetic enhancement. The first is to prevent genetic uniformity and consequent genetic vulnerability. Only recently has pre-breeding-genetic enhancement-become a necessary, frequent and planned part of all plant breeding activities, an essential part of germplasm diversification strategies. Genetic enhancement has a second important purpose that of raising yield levels to new heights. This goal is more often hoped for than achieved, but it is true that most breakthrough cultivars have highly diverse parentage. The semi-dwarf wheat, the high yield dwarf rice, the first US hybrid sorghums and even the first US Corn Belt dent maize cultivars are examples. In each case, extensive pre-breeding preceded development of the breakthrough, high-yield cultivars. The pre-breeding was used to adapt diverse kinds of germplasm to new genetic backgrounds and new geographic locales. Genetic enhancement is used to bring in new quality traits not found in local cultivars. New levels of protein percentage in wheat or unusual starch properties in maize are examples.

Downregulation of OsPK1 Contributes to Oxidative Stress and the Variations in ABA/GA Balance in Rice

Abscisic acid (ABA) is a phytohormone that aids plants in coping with stress conditions. ABA and gibberellin (GA) are hormone partners that function via a complicated and antagonistic network. In ospk1, a dwarf rice mutant, the contents of ABA in the youngest leaf sheaths of 6-week-old seedlings and the uppermost internodes of heading stage plants were both increased, and the synthesis of bioactive GAs was suppressed, which may disharmonize ABA/GA balance. In ospk1, expression of three putative enzyme genes related to stress response was upregulated. A strong browning symptom was observed in the second internode (Int2, counted from the top) and part of panicles of ospk1 at the late productive phase. Furthermore, higher levels of H2O2 in flag leaf and Int2 were observed in ospk1 than those in wild type. These data suggest that ospk1 may undergo certain stress, especially oxidative stress. Here, we provide evidences that the downregulation of OsPK1 (a cytosolic pyruvate kinase) in ospk1 mutant results in variations in ABA/GA balance in rice and contributes to oxidative stress, which provide a new clue for understanding the connection of pyruvate kinase, ABA/GA balance, and oxidative stress in rice.

Endophytic Cephalotheca sulfurea AGH07 reprograms soybean to higher growth

Gibberellins (GAs) are well known for plant growth promotion. GAs production by fungi has received little attention, although substantial work has been carried out on other aspects of plant growth-promoting fungi (PGPF). We investigated GAs production and plant growth-promoting capacity of an endophytic fungus isolated from the roots of soil grown soybean plants. The endophytic fungus is reported as GAs producer and as PGPF for the first time in this study. Nine endophytic isolates were collected from the roots of soybean, and culture filtrates (CFs) obtained from their pure cultures were screened on Waito-C, a dwarf rice cultivar, for the presence of GAs. Of these, seven fungal isolates promoted shoot length as compared to control (distilled water), while one inhibited it. Three fungal isolates were selected on the basis of higher shoot elongation as compared to wild type Gibberella fujikuroi, which was used as positive control. The growth-prompting capacity of selected fungal isolates SB5-1, SB3-2, and SB3-3 was bio-assayed on soybean cv. Hwangkeumkong. Fungal isolate SB5-1 provided maximum plant height (31.6 cm), shoot length (21.1 cm), whole plant fresh biomass (2.41 g), shoot fresh biomass (1.99 g), and leaf area (24.37 cm2). The CF of isolate SB5-1 was analyzed for the presence of GAs, and it was found that all physiologically active GAs were present (GA1, 0.15 ng/ml, GA3, 1.2 ng/ml, GA4, 7.37 ng/ml, and GA7, 3.18 ng/ml) in conjunction with physiologically inactive GA5, GA9, GA15, GA19, GA20, and GA24. The fungal isolate SB5-1 was identified as a new strain of Cephalotheca sulfurea through molecular and phylogenetic approaches.

OsDOG, a gibberellin-induced A20/AN1 zinc-finger protein, negatively regulates gibberellin-mediated cell elongation in rice

The A20/AN1 zinc-finger proteins (ZFPs) play pivotal roles in animal immune responses and plant stress responses. From previous gibberellin (GA) microarray data and A20/AN1 ZFP family member association, we chose Oryza sativa dwarf rice with overexpression of gibberellin-induced gene ( OsDOG) to examine its function in the GA pathway. OsDOG was induced by gibberellic acid (GA 3) and repressed by the GA-synthesis inhibitor paclobutrazol. Different transgenic lines with constitutive expression of OsDOG showed dwarf phenotypes due to deficiency of cell elongation. Additional GA 1 and real-time PCR quantitative assay analyses confirmed that the decrease of GA 1 in the overexpression lines resulted from reduced expression of GA3ox2 and enhanced expression of GA2ox1 and GA2ox3. Adding exogenous GA rescued the constitutive expression phenotypes of the transgenic lines. OsDOG has a novel function in regulating GA homeostasis and in negative maintenance of plant cell elongation in rice.

ChemInform Abstract: Synthesis and Biological Activity of 2,3-Diol Stereoisomers of 28-Homobrassinolide and Brassinolide.

As possible candidates for natural products and metabolites, three 2,3-diol stereoiosomers of 28-homobrassinolide (28-HBL) and those of brassinolide (BL) were synthesized and their biological activities evaluated by a modified dwarf rice lamina inclination assay, indicating that the biological activity decreased in the order 2α,3α-, 2α,3β-, 2β,3α- and 2β,3β-diol isomers of both the 28-HBL and BL series, suggesting that epimerization of configuration at the 2,3-diol position is an inactivation step in metabolism.

Physiological and morphological responses of rice (Oryza sativa L.) to varying water stress management strategies.

Sustainability of rice production under limited water conditions is threatened by increasing irrigation water scarcity. Therefore, physiological and morphological responses of rice to varying water stress management strategies should be determined. The physiological and morphological responses of a semi dwarf rice (Hashemi cultivar) to water stress intensities (mild and severe, i.e., short-duration of stress with early recovery and long-duration stress with late recovery, respectively) and timing (mid-tillering, booting and 50% of flowering) were studied in a pot experiment. The severe water stress at mid-tillering significantly (P<0.05) decreased plant height and the number of panicle per hill and delayed flowering. The severe water stress at different growth stages caused substantial yield losses by large percentage of unfilled grains. Root weight was highest under mild water stress at 50% of flowering followed by severe water stress at mid-tillering. Relative transpiration (RT) was not lowered until the thresholds of the fraction of transpirable soil water (FTSW), plant available water (PAW) and soil water tension (h) reached to 0.46 (-), 0.9 (-) and 78.0 kPa, respectively. These values were approximately close to those obtained for the relative leaf development rate (RL), as 0.44 (-), 0.91 (-) and 74.6 kPa, respectively. These results indicated that transpiration and leaf development rates have the same sensitivity to water deficits. However, in the mid-tillering, RL was more sensitive to water deficit than RT. The results of thresholds for RT indicated that booting stage is more sensitive than other stages. It is concluded that water tension of 1500 kPa as considered for permanent wilting point is not suitable for rice. Therefore, PAW can not be a suitable soil-water criteria for rice plants that are sensitive to water deficit. Furthermore, It is concluded that Hashemi cultivar is very sensitive to mild and severe drought stress during reproductive stage.

Farmers' Perceptions on Rice Varieties in Sikasso Region of Mali and their Implications for Rice Breeding

AbstractRice is an important staple food and cash crop. Although many varieties of rice have been developed to date, few are adopted possibly because researchers did not take into account farmers’ preferences and perceptions on varieties during the development process. Because farmers increasingly rely on low‐yielding landraces, production fails to meet demand. To provide an understanding of farmers’ preferences for rice cultivars and perceptions on drought stress and management practices as inputs to rice breeding research, this study was conducted in the Sikasso region of Mali in September 2005 using participatory rural appraisal approach. A total number of 125 farmers were randomly selected from 10 villages in three ecologies and interviewed individually and in groups. Results showed that farmers’ preferences, crop management practices and ranking of production constraints differed significantly across ecologies. Whereas farmers in the irrigated ecologies preferred high‐yielding, long duration rice varieties, those in the upland and lowland ecologies preferred tall plants of short duration. While upland and lowland farmers preferred red and white long grains, respectively, irrigated ecologies were indifferent about grain colour. Farmers appeared willing to trade‐off yield for grain quality and plant height, inconsistent with traditional breeders’ selection criteria. The high preference for tall varieties among farmers in the upland and lowland ecologies also contrasted sharply with the model of dwarf rice varieties responsible for the green revolution in Asia. The implication of these findings for rice breeders is that different plant idiotypes complemented by effective drought management practices should target different ecologies to increase impact.

Production of biologically active human interferon-.ALPHA. in transgenic rice

Interferon-a (IFN-a) is a principle cytokine that plays a key regulatory role in mammalian immune systems. The recombinant DNA of IFN-a is composed of the signal sequence region for rice 10 kDa prolamin cDNA, the amino- terminal region of b-glucuronidase DNA, and the mature polypeptide region of human IFN-aDNA, and is expected to produce a biologically active form of IFN-a. This chimerical DNA for coding IFN-a under the control of a cauliflower mosaic virus 35S promoter and a 5� -intron of rice cytosolic superoxide dismutase gene (sodcC1), was transformed into dwarf rice by an Agrobacterium-mediated system. Three lines of transgenic rice plant expressing various levels of IFN-a polypeptide were finally generated. The expression level of the recombinant polypeptide in each line was analyzed by an IFN-a antiviral activity assay and enzyme immunoassay. Higher expression of IFN-a was achieved in developing seed endosperm in two of transgenic rice lines. The replacement of the native signal peptide of IFN-a with the prolamin signal peptide was effective for transporting the IFN-a polypeptide into the ER-derived protein body of developing seed endosperm. These results suggest that rice can be used to produce many biologically active mammalian proteins that accumulate in target organelles such as protein bodies.

Agricultural innovation and biotechnology development towards sustainable goals: can we make it more pro-poor?

Agriculture continues to change – driven by innovation and new technology. Genetics and breeding have revolutionised agricultural systems, and the 'Green Revolution', based on higher yielding varieties of dwarf wheat and rice, is arguably the greatest achievement in food crop development. Gene technologies now offer additional opportunities, where new traits improving crop protection characteristics, post-harvest properties, abiotic stress tolerances and nutritional qualities in genetically improved crops, hold particular prospect. About 8.25 million farmers in 17 countries grew genetically modified crops on 81 million hectares in 2004. Approximately 90% of these farmers were resource-poor. For low-income countries agriculture remains the lead sector for catalysing economic development and poverty alleviation.

Effects of Grape Berry Developmental Stages on Ammonium Nitrate-enhanced Penetration of Gibberellin A3

The effects of ammonium nitrate (AMN) on the penetration of Gibberellin A3 (GA3) into berries of `Kyoho' (Vitis labruscana Bailey) grape during berry development were studied. Treatment solutions of GA3 (100 ng·μL-1) and GA3 + AMN (20 millimolar concentration) were applied to the surface of grape berries under field conditions. The amount of GA3 penetrated was assayed using dwarf rice (Oryza sativa L., cv. Tan-ginbozu). At full bloom, the addition of AMN significantly enhanced GA3 penetration 24, 48 ad 72 hours after application by 13%, 16% and 21% of the applied GA3, respectively, representing a 1.7- to 2.4-fold increase over GA3 alone. At 4 weeks after full bloom (WAFB) at 24 hours after application, 20% of the applied GA3 penetrated in the presence of AMN compared to 15% in the absence of AMN. From varaison (7 WAFB) to maturity (10 WAFB), GA3 penetration decreased, from 6% to 2%, respectively, in the presence of AMN, and from 3% to 1% in the absence of AMN. The addition of AMN to the GA3 solution increased GA3 penetration relative to GA3 alone at all berry developmental stages. On the other hand, Cuticular wax density on the berry surface at 4 WAFB was 1.10 μg·mm-2, 5.8-fold greater than at full bloom (0.19 μg·mm-2). The thickness of the epidermal tissue doubled during the first 2 WAFB, but was maintained almost constant over the next 6 weeks. GA3 penetration was more closely related to the cuticular wax levels than the epidermal tissue thickness.

Preparation of an Endosperm Protoplasts from a Dwarf Rice Variety and Transient Expression of Green-Fluorescent Protein

Vital protoplasts were isolated from developing dwarf rice endosperms about 10 days post anthesis. A yield of 0.98x105±0.12 protoplasts was obtained from 10 developing grains. These protoplasts were viable for at least three days in the culture medium. Transient expression of the green-fluorescent protein (GFP) was detected after four hours of introduction of the GFP gene by the polyethylene glycol (PEG)-mediated DNA transfer. As expected, the fluorescence of GFP without the targeting sequence was observed diffusely in the cytoplasm. On the other hand, the fluorescence of the fusion protein for rice prolamin followed by the GFP was observed in the small particles and the ER-network. These endosperm protoplasts had no autofluorescence upon excitation with 490 nm (blue) light. The vital protoplasts obtained from this dwarf rice variety are very useful for the physiological, biochemical and molecular biology studies of rice endosperm.

Gibberellins do not act against abscisic acid in the regulation of bulb dormancy of Allium wakegi Araki

Abscisic acid (ABA) is involved in bulb dormancy of Alliumwakegi Araki. We examined the antagonistic role of gibberellins(GAs)against ABA in the regulation of this dormancy. The concentrations of ABA andGAs in the basal leaf sheaths or bulbs of A. wakegi cv.Kiharawase were investigated during growth in the field and postharveststorage.The concentration of ABA in the basal leaf sheaths began to increase about onemonth before they began to swell, reached a maximum shortly after bulbharvesting, and decreased during postharvest storage. The plants showed bulbdormancy accompanied with the change in ABA concentration. GA1,GA3, GA4, GA12, GA15, GA19, and GA20 were identified in the basal leaf sheaths of A. wakegi from Kovats retention indices (KRI) andfull-scan mass spectra by gas chromatography - mass spectrometry (GC-MS)analysis. The concentrations of all classes of GAs in the basal leaf sheathsestimated by the dwarf rice micro-drop assay increased transitorily shortlybefore they began to swell, and decreased rapidly during bulb development. Bulbdormancy had already been induced when the concentration of the GAs becamemaximum. All the GAs in the bulbs remained at a low level during postharveststorage, when bulbs were gradually released from dormancy. The concentrationsof GA1+3, GA4, GA15, and GA20 inthe bulbs increased after sprouting of the bulbs planted in moist vermiculite.Hence, the state of bulb dormancy is considered to be independent of the GAconcentrations of in the basal leaf sheaths or bulbs of A.wakegi.

Hosetsu-dwarf; Useful Rice for Molecular Biological Research on Plant Seed Development.

Rice is one of the most important crops in the world, and thus as a model plant it has been the subject of much research. But many kinds of rice species are not easy to handle in a laboratory space. To investigate the dwarf rice’s suitability for experimental work, we analyzed the characteristics of Hosetsu-dwarf. Hosetsu-dwarf has small body size, a short life cycle, and normal seed formation. We established a standard method for its hydroponic cultivation. We found as well that its endosperm polypeptide compositions and the morphological observation were not unusual. Thus we propose that Hosetsu-dwarf is an excellent tool for basic studies of seed development.