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At least 19 recordsLinked to original sources
PubMed2000

[Application of microsatellite markers for the seed purity examination of a hybrid rice, Gangyou-22].

For seed commercialization of hybrid rice it is necessary to examine the purity of its seeds before field-production, because the seed purity is closely related to their heterosis performance and yield increase. In this research, 160 microsatellite markers were used for PCR amplification of rice seedling DNAs of Gangyou-22, which is a major hybrid rice in China, and its parents, Gang46A(CMS line) and CDR22(restorer line). A microsatellite marker, RM168, was screened out for its ability to produce polymorphic bands specific to each of the two parents but different from other 22 restorer lines and 9 cultivars. This provides an accurate and efficient method to examine the purity of a hybrid rice at an earlier time. Amplification of DNAs extracted from seeds and application of two microsatellite markers in one PCR system can further simplify the procedure and improve the accuracy of the seed purity examination.

Hybridization, Genetic↗
PubMed2005

Photosynthetic light and CO2 utilization and C4 traits of two novel super-rice hybrids.

Characteristics of photosynthetic light and CO2 use efficiency from seedling to heading stage, and C4 pathway enzyme activities in both flag leaves and lemma were compared between two newly developed super-rice hybrids (Oryza sativa L.), Liangyoupeijiu and Hua-an 3, and a traditional rice hybrid, Shanyou 63. At seedling and tillering stages, Liangyoupeijiu and Hua-an 3 had higher net photosynthetic rates (Pn) and light saturated assimilation rates (Asat) than did Shanyou 63, at both normal (360 micromol mol(-1)) and doubled (720 micromol mol(-1)) CO2 concentrations. At the heading stage, the flag leaves of all three rice hybrids had similar Pn and Asat. However, the two super-rice hybrids had higher apparent quantum yield (AQY) and carboxylation efficiency (CE) during all three typical developmental stages, and higher quantum yield of CO2 fixation (PhiCO2) at the tillering and heading stages. In addition, Liangyoupeijiu showed significantly higher activities of the C(4) pathway enzymes in both flag leaves and lemmas than did Shanyou 63. As a result, flag leaves of the two super-rice hybrids had higher Pn at morning, noontime and late afternoon during the daily cycle. Since most of the grain yield of rice comes from the photosynthesis of flag leaves, the similar Asat and much higher AQY, CE and PhiCO2 at heading stage of the two super-rice hybrids indicates that higher photosynthetic efficiency rather than higher photosynthetic capacity may be the primary factor contributing to their higher grain yields.

Carbon Dioxide↗
PubMed2001

[A genetically modified japonica restorer line, C418-Xa21, and its hybrid rice with bacterial blight resistance].

The cloned bacterial blight (BB) resistance gene Xa21 was transferred into C418, a major restorer line of japonica hybrid rice in China, using an Agrobacterium-mediated system. The integrated single copy of transgene displayed a 3:1 segregation ratio in T1 generation in PCR and resistance analyses. The transgenic homozygous C418-Xa21 lines were selected in T2 generation through PCR and resistance analyses. The selected transgenic restorer lines were then crossed with a commonly used sterile line, TijinA, to produce Xa21 transgenic hybrid rice. Molecular analysis revealed that the produced hybrid rice, named as Tiyou418-Xa21, inherited the transgene. Both C418-Xa21 and Tiyou418-Xa21 plants displayed high resistance with a broad spectrum to Xoo races and maintained their normal elite agronomic characters. We also observed that the resistance level of Tiyou418-Xa21 was obviously higher than that of C418-Xa21 which may be attributed to their differences in genetic background. The propagation of this BB resistant hybrid variety with the transgene Xa21 with extend hybrid rice production in north China.

Hybridization, Genetic↗
PubMed2003

[Characteristics of canopy structure of super high yielding japonica hybrid rice community].

In this paper, the characteristics of canopy structure, such as the numbers of seedling, panicle and grain, the distribution of dry matters in different canopy layers and different organs, and the distributions of LAI and of solar radiation in different canopy layers of super high yielding community of japonica hybrid rice were studied, in comparison with normal japonica rice. The results showed that the total the dry matter weight and the dry matter weight of layers below 40 cm, 40-60 cm, 60-80 cm and above 80 cm of japonica hybrid rice canopy were 32.29%, 29.12%, 13.95%, 16.45% and 100.17% higher those that of normal japonica rice, respectively. The ratios of dry leaf (photosynthetic organ) and of dry panicle (sink organ) weight to total dry weight were 24.8% and 12.8%, respectively, which were greater than those of normal japonica rice, while the ratios of dry sheath and stem (storage organs) weight were 33.6% and 28.9%, respectively, which were lower than those of normal japonica rice. The allotment of LAI in different layers of japonica hybrid rice canopy was reasonable, and the LAI of above 40 cm layer at full heading stage reached 5.44. The solar radiation was well-distributed inside japonica hybrid rice canopy, for example, the solar radiation in layers below 60 cm were 13.1%-37.0% higher, but 5.9%-12.2% lower above 60 cm than that of normal japonica rice. The extinction coefficients of solar radiation in layers below 20 cm, 20-40 cm, 40-60 cm and 60-80 cm of japonica hybrid rice canopy were 35.1%, 13.5%, 29.1% and 17.2% lower than that of normal japonica rice, respectively.

Chimera↗
PubMed2002

[Genetic variation of main restorer lines of hybrid rice in China was revealed by microsatellite markers].

A total of thirty-five restorer lines of hybrid rice (Oryza sativa L.) were analyzed by twenty-five SSR (simple sequence repeats) primer pairs, which disperse on 12 chromosomes in rice. Those primers detected 65 alleles among 35 restorer lines of hybrid rice. Per primer pair detected 2.6 alleles on the average. PIC (polymorphism index content) values ranged from 0.206 to 0.682. PIC value is 0.414 on the average. The result from cluster analysis shows that hybrid rice restorer lines have abundant resource in China, but the genetic diversity is small and the genetic background is vulnerable among them. The utilization of rice heterosis was limited seriously.

Genetic Variation↗
PubMed2005

[Cytokinin changes of root exudates, leaves and grains in inter-subspecific hybrid rice].

Using inter-subspecific hybrid rice of IIyou 2070 and IIyou 419 , their restorer lines 2070 and Zhong419, the various forms and levels of root-derived cytokinins(CTKs) in root exudates, and changes of various forms of cytokinins in rice flag leaves and grains were analyzed by HPLC and ELISA after initial heading stage. The results indicated that zeatin had 62.8% to 89.1% of total cytokinins and was the dominant form of cytokinins in root exudates during early grain filling, whereas, the contents of diHZ and diHZR greatly increased during milk ripening. This change was consistent with the dynamic changes of ZRs (Z+ZR)and diHZRs (diHZ+diHZR)in flag leaves of IIyou 2070 and 2070. Different from main cytokinin composition in root exudates, IPAs took high proportion of total CTKs in leaf and grain. We suggested that there were changes of various forms and activities of root-derived cytokinins in root exudates, and this change was related to catabolic enzymes of cytokinins and the different expression of enzyme genes. Meanwhile, the relationship between cytokinin changes of vigorous and weak spikelets and grain filling was disscused.

Chromatography, High Pressure Liquid↗
PubMed2005

[QTL analysis of low-temperature-sensitive pollen sterility in Indica-japonica hybrid rice (Oryza sativa L.)].

There existed a number of biological constraints in exploiting the heterosis of indica-japonica hybrid rice. The low-temperature-sensitive sterility (LTSS) of indica-japonica hybrid has become one of the major problems in indica-japonica hybrid rice breeding after the solution of poor fertility of the hybrids by the finding of wide-compatibility gene. Previous studies revealed that the LTSS might be caused by low-temperature-sensitive pollen sterility (LTSPS). However, the genetic basis of LTSPS remained unclear. To explore the genetic basis of LTSPS in indica-japonica hybrid rice, an F2 genetic population derived from 3037 (indica) and 02428 (japonica) was developed. At the booting stage, pollen fertility of F2 population together with parents were surveyed after the treatment with low temperature daily average of 21-23 degrees C. The linkage map was constructed containing 108 SSR markers distributed throughout the whole 12 chromosomes with average marker interval of 16.26 cM. Using software MapMaker/QTL, two putative QTLs, namely qLTSPS2 and qLTSPS5 on chromosomes 2 and 5 were detected by interval mapping, which could explain the phenotypic variation 15.6% and 11.9% respectively. The additive effects were 0.021 and 0.045, dominant effects were -0.246 and -0.215, and the degrees of dominance were 11.7 and 4.8, respectively for the two QTLs. Therefore, the mode of gene action in response to low-temperature stress was overdominance and LTSPS was mainly the result of interaction between the indica and japonica alleles within each locus. In addition, two-way ANOVA showed that the two QTLs acted essentially independent of each other in conditioning LTSPS.

Alleles↗
PubMed2006

[Canonical correlations of light and temperature with yield and quality characters of F1 ecological populations of hybrid rice].

In this paper, field experiment was conducted to analysis the canonical correlations of light and temperature with the yield and quality characters of F1 ecological populations of 54 hybrid rice breeds. The results showed that the yield and quality characters of the populations were significantly correlated with the accumulated temperature, effective accumulated temperature, extreme temperature difference, and sunshine length through the growth period of hybrid rice. The first canonical correlation coefficient (lambda1) between the light and temperature during vegetative growth stage and the yield characters was 0.9975, with the canonical information accounted for 99.96% of the total canonical information, leading to 99.50% of yield variation. Light and temperature affected the yield of hybrid rice mainly through their effects on the total and effective numbers of grains' spikelet and its fertility. In this aspect, accumulated and effective accumulated temperature played a determinative role during vegetative growth stage, while extreme temperature difference and sunshine length were the key factors during reproductive growth stage. As for the quality characters of hybrid rice, light and temperature mainly affected the percentage of polished to head rice, and in this aspect, accumulated and effective accumulated temperature played a determinative role before filling stage, while extreme temperature difference and sunshine length were the key factors after this

Crosses, Genetic↗
PubMed2004

Development of stem borer resistant transgenic parental lines involved in the production of hybrid rice.

Stem borer resistant transgenic parental lines, involved in hybrid rice, were produced by Agrobacterium-mediated gene transfer method. Two pSB111 super-binary vectors containing modified cry1Ab/cry1Ac genes driven by maize ubiquitin promoter, and herbicide resistance gene bar driven by cauliflower mosaic virus 35S promoter were, used in this study. Embryogenic calli after co-cultivation with Agrobacterium were selected on the medium containing phosphinothricin. Southern blot analyses of primary transformants revealed the stable integration of bar, cry1Ab and cry1Ac coding sequences into the genomes of three parental lines with a predominant single copy integration and without any rearrangement of T-DNA. T1 progeny plants disclosed a monogenic pattern (3:1) of transgene segregation as confirmed by molecular analyses. Furthermore, the co-segregation of bar and cry genes in T1 progenies suggested that the transgenes are integrated at a single site in the rice genome. In different primary transformants with alien inbuilt resistance, the levels of cry proteins varied between 0.03 and 0.13% of total soluble proteins. These transgenic lines expressing insecticidal proteins afforded substantial resistance against stem borers. This is the first report of its kind dealing with the introduction of Bacillus thuringiensis (Bt) cry genes into the elite parental lines involved in the development of hybrid rice.

Animals↗
PubMed2003

[Photooxidation characteristics of super-hybrid rice "Liangyoupeijiu" and its parents].

With comparison of the differences of light absorption and active oxygen metabolism between super-hybrid rice "Liangyoupeijiu" and its parents, this paper provided a physiological foundation of matching and grouping for cultivating anti-photooxidized hybrid rice. TPS-photosynthetic system and FMS2-fluorescence (Hansatech, UK) were used to respectively determine the photosynthetic rate and the chlorophyll fluorescence in the rice leaves that had been processed in artificial photooxidization. Meanwhile, the contents of chlorophyll, protein and malonaldehydic acid (MDA) as well as the activation of superoxide dismutase (SOD) and peroxidase (POD) were determined. The results showed that the photosynthetic rate of "Liangyoupeijiu" was 2.4% lower than that of its female parent, and 23% higher than that of its male parent. After eight days anti-photooxidization process, its chlorophyll content was higher than that of its female parent by 33%, protein by 15%, initial photochemical efficiency by 30%, SOD by 32% and POD by 100%, while its photochemical quince coefficient was lower than that of its female parent by 9% and MDA by 50%. It showed that there was not much difference between the filial generation and its male parent. The super-hybrid rice "Liangyoupeijiu" was very efficient for solar energy utilization under the condition of photooxidization, and had outgrown its parents in the aspect of anti-photooxidization.

Chimera↗
PubMed2005

[Inhibitory effects of exogenous abscisic acid and maleic hydrazide on panicle sprouting in hybrid rice F1].

"On-panicle seed sprouting" is a serious obstacle in hybrid rice seed production. It was reported that exogenous ABA inhibited seed sprouting of hybrid rice F(1) seeds. It was shown that by ABA 1000 mg/L or MH 4000 mg/L application at 21 d after full heading (filling stage)(Fig.1), not only seed sprouting was inhibited, but also the seed energy was affected (Fig.2). The retardation of germination and lowing of germination rate were resulted from ABA treatment and MH treatment respectively (Fig.3). When the seeds were treated with ABA, GA(1) level was decreased (Fig.4). The expression of amylase was delayed and their levels become lowed by ABA treatment (Fig.5). However, those seeds maintained a certain level of GA(1) and amylase and still have germination ability. During germination, the GA(1) content and amylase activity did not decrease significantly by MH treatment, but the GA(1) content and amylase activity were significantly decreased in non-germination MH treated seeds (Fig.4, 5). Therefore, the sprouting retarding effects of ABA was considered as "post-harvest effects" and sprouting inhibiting effect of MH was considered as "inhibition effects" by the authors.

Abscisic Acid↗
PubMed2006

[Cd uptake and accumulation in grains by hybrid rice in two paddy soils: interactive effect of soil type and cultivars].

Cd translocation through soil-food crop-diet is considered as one of most important pathway for human Cd exposure. Rice is considered as a particular crop with high Cd uptake and accumulation in grains among the main food crops. In this study, a pot experiment was conducted to elucidate mutual interaction of soil and cultivars on uptake and grain accumulation of Cd by hybrid rice with or without Cd spiking at 2.5 mg x kg(-1) under continuous submerging condition. Two hybrid rice cultivars (Shanyou 63, a common hybrid rice and II Youming 86, a super-rice) and two paddy soils (a Wushantu, Gleyic Stagnic Anthrosols and a Hongshanitian, Ultic Stagnic Anthrosols) were used. The results show significant differences in Cd uptake and grain partitioning between soils, cultivars and the soil-cultivar interactions. The cultivars effect on uptake of indigenous soil Cd seems stronger than the soil effect while soil effect turns significant over that of cultivars on spiked Cd. However, intense Cd accumulation in grains is found under the positive interaction of soil with high Cd availability and cultivar with high Cd affinity (super rice on acidic paddy soil). This study demonstrates a phenomenon of intense Cd uptake and grain accumulation by super rice and, thus, imposing a very high Cd exposure risk (as several times as the acceptable daily intake, ADI) to subsistence-diet farmers. The low Cd cultivar Shanyou 63 tends to hamper the up-taken Cd in root while the super rice II Youming 86 promotes higher partitioning to grain. Furthermore, the difference in total biomass between the two cultivars is small compared to that in total Cd uptake under Cd spiking. It is suggested that the Cd uptake behavior should be taken into account in super rice breeding and practical measures should be taken while spread of super rice cultivars in rice areas with acidic soils and under Cd pollution in order to control the human Cd exposure by diet.

Cadmium↗
PubMed2002

A bentazon and sulfonylurea sensitive mutant: breeding, genetics and potential application in seed production of hybrid rice.

The use of a thermosensitive genic male sterility (TGMS) system in two-line hybrid rice breeding is affected greatly by the sterility instability of TGMS lines caused by temperature fluctuation beyond their critical temperatures for fertility reversion. To prevent seed production from self contamination, we have developed a system to secure seed purity using a herbicide-sensitive TGMS mutant, M8077S, obtained by radiation. Genetic analysis, using the F(1), F(2) and F(3) populations derived from this mutant and other normal varieties, revealed that bentazon lethality/sensitivity was controlled by a single recessive gene, which was named bel. The mutant can be killed at the seedling stage by bentazon at 300 mg/l or higher, a dosage that is safe for its F(1) hybrids and all other normal varieties. This mutant is also sensitive to all the tested sulfonylurea herbicides. Response of segregating plants to these two types of herbicide indicated that sulfonylurea sensitivity was also controlled by bel. By crossing this mutant with Pei-Ai 64S, an F(2) population was developed for genetic mapping. Surveying the two DNA pools from sensitive and non-sensitive F(2) plants identified four markers that were polymorphic between the pools. The putative linked markers were then confirmed with the F(2) population. The bel locus was located on chromosome 3, 7.1 cM from the closest microsatellite marker RM168. Phenotypic analysis indicated that the bel gene had no negative effect on agronomic traits in either a homozygous or heterozygous status. The mutant M8077S is valuable in the development of a TGMS breeding system for preventing impurity resulting from temperature fluctuation of the TGMS. Several two-line hybrid rice crosses using this system are under development.

Journal Article↗
PubMed2001

Development of a STS marker assay for detecting loss of heterozygosity in rice hybrids.

The RAPD (random amplified polymorphic DNA) markers OPE15750 and OPE15300 were affected by loss of heterozygosity (LOH) in rice hybrids AMR x 'M202' and AMR x 'L202'. The markers were mapped to the same locus at or near the centromere of rice chromosome 2. The two RAPD products were cloned, sequenced, and found to have lengths of 734 bp and 297 bp, respectively. The 297-bp sequence shares a 98% homology with one end of the 734-bp sequence, accounting for the cross-hybridization previously observed between the two clones. Based on the DNA sequence of the 734-bp fragment, a pair of STS (sequence-tagged site) primers was designed and tested. Rice plants homozygous for either OPE15734 or OPE15297 all produced PCR fragments of the same length, 482 bp. However, the two PCR products were discernible by digestion with the restriction enzyme XbaI prior to gel electrophoresis. The STS product from plants homozygous for OPE15734 was cut into two fragments of 239 and 240 bp, which appeared as one single band in an agarose gel; whereas the STS product from plants homozygous for OPE15297 was not cut by XbaI and was characterized by a 482-bp band in the agarose gel. These STS primers were tested in rice hybrids and F2 progenies derived from the hybrids of AMR x 'M202' and AMR x 'L202'. Homozygosity for OPE15297 was confirmed for all F2 panicle rows derived from AMR x 'M202'. In contrast, F2 panicle rows of AMR x 'L202' exhibited two different segregation patterns (genotypes), i.e., either uniformly homozygous for the 240-bp marker (OPE15734/OPE15734) or segregating for the 482- and 240-bp markers (OPE15734/OPE15297). This STS-marker system provides a robust assay for detecting the occurrence of LOH in rice hybrid progenies.

Base Sequence↗
PubMed2026

Haplotype-resolved 3D genome maps reveal RNAPII-mediated allelic regulation in hybrid rice.

To understand how the two parental genomes coordinate transcription in hybrids, chromatin architecture must be resolved at the haplotype level. Here, using phased Bridge-Linker Hi-C, we reconstructed a haplotype-resolved three-dimensional (3D) genome of the elite hybrid rice (Oryza sativa) line Shanyou 63 (SY63). We identified extensive allele-specific chromatin conformations. Furthermore, we generated allele-resolved RNAPII ChIA-PET maps and phased transcriptomes to explore how chromatin interactions contribute to allelic regulation. Although maternal and paternal homologs share broadly similar chromatin features, we detected widespread haplotype-biased RNAPII binding and chromatin looping at high resolution. These allele-specific RNAPII-mediated contacts were significantly associated with biased expression. Stronger RNAPII binding on one haplotype promoted the formation of long-range regulatory loops with distal genes, thereby contributing to allele-biased transcription at a subset of loci, even when promoter-proximal RNAPII occupancy was comparable between alleles. These results demonstrate that subtle differences in RNAPII engagement and 3D regulatory wiring between parental haplotypes can reshape transcriptional output in hybrids, providing new insights into the mechanisms underlying the allelic regulation of gene expression.

Allele-specific chromatin interactions↗
PubMed2002

[Genetic analysis and identification of three groups three-line hybrid rice and their parents by RAPD markers].

A total of 248 arbitrary 10-mer oligonucleotide primers were screened using RAPD (random amplified polymorphic DNA) techniques with the genome DNA of three groups of three-line hybrid rice and their parents. Thirteen primers produced 43 polymorphism fragments. Six primers of them produced 20 obviously repeatable polymorphic markers among rice lines tested. Using this RAPD markers,the hybrid rice combinations (sterile-line, maintainer-line, restorer-line and F1) can be effectively identified, and the genetic relationship among them can be shown.

English Abstract↗
PubMed2005

[Correlation of intersubspecific hybrid rice spikelet fertilization rate with temperature and related statistic model].

Using four types of rice, i. e., indica-japonica hybrid, intermediate hybrid, indica and japonica cultivars as test materials, this paper studied the sensitivity of intersubspecific hybrid rice to climatic factors, and the correlations between spikelet fertilization rate (SFR) and daily meteorological factors during 2000 and 2001. The results showed that the SFR of intersubspecific hybrids was lower than that of indica and japonica cultivars. Among eleven meteorological factors, temperature was the key factor, and the mean temperature within five or seven days around panicle flower blooming affected the SFR significantly. A comprehensive model of SFR-temperature was established, with which, the fittest temperature and safe temperature for fertilization of intersubspecific hybrids was estimated to be 28.2 - 29.3 degrees C and 23.4 - 24.3 degrees C, 2.2 degrees C and 1.5 degrees C higher than those of indica and japonica cultivars, respectively. It was suggested that the safe heading date for planting intersubspecific hybrid should be moved up to the last ten-day of September to the first ten-day of October in southern China, the first ten-day of September in middle and lower reaches of Yangtze River Valley, and the last ten-day of August to the first ten-day of September in rice planting area between Yangtze and Huai River.

Chromosomes, Plant↗
PubMed2005

[Dynamics of water retaining capacity and chlorophyll content of two-line hybrid rice during heading-grain filling stage and their relations with grain yield].

The study with 25 two-line hybrid rice strains showed that their water retaining capacity was different with their combinations. On the whole, the water content in leaf and stem-sheath decreased during heading-grain filling stage, while that in panicle increased first and then decreased, with a peak at 7th day after heading. Stem-sheath was the main organ for water retaining. The correlation of panicle yield with both leaf and stem-sheath water content was positive at the 1st day after heading but became negative later, and that with whole stem-plant water content was positive after heading. The chlorophyll content of the two-line hybrids increased first and then decreased, with a peak at the 7th day after heading. Comparing with normal rice (male parent), the chlorophyll content of most two-line hybrids was lower, and the decreasing rate was faster than that of normal rice after heading. For two-line hybrid rice breeding, it should preferentially consider to select those hybrids which have a clearer dominance of plant water retaining capacity and a higher chlorophyll content at earlier and middle heading-grain filling stage, and an obvious dry matter transportation from leaf and stem-sheath at later heading-grain filling stage. For two-line hybrid rice planting, it should not only pay attention to the supply of water and nutrients, especially nitrogen at earlier and middle heading-grain filling stage, but also control nitrogen and water in time to prevent leaf green clinging and to promote dry matter transportation from leaf and stem-sheath to grain at later heading-grain filling stage.

Biomass↗