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1.
Origin, dispersal, cultivation and variation of rice   总被引:49,自引:0,他引:49  
There are two cultivated and twenty-one wild species of genus Oryza. O. sativa, the Asian cultivated rice is grown all over the world. The African cultivated rice, O. glaberrima is grown on a small scale in West Africa. The genus Oryza probably originated about 130 million years ago in Gondwanaland and different species got distributed into different continents with the breakup of Gondwanaland. The cultivated species originated from a common ancestor with AA genome. Perennial and annual ancestors of O. sativa are O. rufipogon and O. nivara and those of O. glaberrima are O. longistaminata/, O. breviligulata and O. glaberrima probably domesticated in Niger river delta. Varieties of O. sativa are classified into six groups on the basis of genetic affinity. Widely known indica rices correspond to group I and japonicas to group VI. The so called javanica rices also belong to group VI and are designated as tropical japonicas in contrast to temperate japonicas grown in temperate climate. Indica and japonica rices had a polyphyletic origin. Indicas were probably domesticated in the foothills of Himalayas in Eastern India and japonicas somewhere in South China. The indica rices dispersed throughout the tropics and subtropics from India. The japonica rices moved northward from South China and became the temperate ecotype. They also moved southward to Southeast Asia and from there to West Africa and Brazil and became tropical ecotype. Rice is now grown between 55°N and 36°S latitudes. It is grown under diverse growing conditions such as irrigated, rainfed lowland, rainfed upland and floodprone ecosystems. Human selection and adaptation to diverse environments has resulted in numerous cultivars. It is estimated that about 120000 varieties of rice exist in the world. After the establishment of International Rice Research Institute in 1960, rice varietal improvement was intensified and high yielding varieties were developed. These varieties are now planted to 70% of world's riceland. Rice production doubled between 1966 and 1990 due to large scale adoption of these improved varieties. Rice production must increase by 60% by 2025 to feed the additional rice consumers. New tools of molecular and cellular biology such as anther culture, molecular marker aided selection and genetic engineering will play increasing role in rice improvement.  相似文献
2.
IR64, the most widely grown indicarice in South and Southeast Asia, possesses many positive agronomic characteristics (e.g., wide adaptability, high yield potential, tolerance to multiple diseases and pests, and good eating quality,) that make it an ideal genotype for identifying mutational changes in traits of agronomic importance. We have produced a large collection of chemical and irradiation-induced IR64 mutants with different genetic lesions that are amenable to both forward and reverse genetics. About 60,000 IR64 mutants have been generated by mutagenesis using chemicals (diepoxybutane and ethylmethanesulfonate) and irradiation (fast neutron and gamma ray). More than 38,000 independent lines have been advanced to M4 generation enabling evaluation of quantitative traits by replicated trials. Morphological variations at vegetative and reproductive stages, including plant architecture, growth habit, pigmentation and various physiological characters, are commonly observed in the four mutagenized populations. Conditional mutants such as gain or loss of resistance to blast, bacterial blight, and tungro disease have been identified at frequencies ranging from 0.01% to 0.1%. Results from pilot experiments indicate that the mutant collections are suitable for reverse genetics through PCR-detection of deletions and TILLING. Furthermore, deletions can be detected using oligomer chips suggesting a general technique to pinpoint deletions when genome-wide oligomer chips are broadly available. M4 mutant seeds are available for users for screening of altered response to multiple stresses. So far, more than 15,000 mutant lines have been distributed. To facilitate broad usage of the mutants, a mutant database has been constructed in the International Rice Information System (IRIS; http: //www.iris.irri.org) to document the phenotypes and gene function discovered by users.  相似文献
3.
We have developed an RFLP framework map with 146 RFLP markers based on a doubled haploid population derived from a cross between an indica variety IR64 and a japonica variety Azucena. The population carries 50.2% of IR64 loci and 49.8% of Azucena loci, indicating an equal amount of genetic materials from each parent has been transmitted to the progenies through anther culture. However, some markers show segregation distortion. These distorted marker loci are located on 10 chromosomal segments. Using this map we were able to place 8 isozymes, 14 RAPDs, 12 cloned genes, 1 gene for brown planthopper (BPH) resistance, and 12 QTLs for grain length, grain width and length/width ratio onto rice chromosomes. The major gene for BPH resistance was mapped on chromosome 12 near RG463 and isozyme Sdh-1. Most of the QTLs identified for the three grain characters were closely linked on chromosomes 1, 2, 3 and 10. We concluded that the RFLP framework map presented here will be useful for mapping other genes segregating in this doubled haploid population. Thus rapid generation of doubled haploid lines and their unbiased segregation make it very attractive for gene mapping.  相似文献
4.
Rice cultivars of isozyme group V include high-quality, aromatic rices that are difficult to improve by traditional methods because of the loss of quality characters upon sexual hybridization. Their low-tillering plant type predisposes them to economic loss from attack by stem borers, a group of insects to which they are susceptible. We report here the enhancement of stem borer resistance in cv. Tarom Molaii through transformation by microprojectile bombardment. Embryogenic calli derived from mature seeds were bombarded with gold particles coated with plasmid pCIB4421, carrying a synthetic truncated toxin gene based on the cryIA(b) gene from Bacillus thuringiensis, and plasmid pHygII, carrying the hygromycin phosphotransferase (hpt) selectable marker gene. Inclusion of 50 mg/l hygromycin B in culture media from bombardment through to rooting of plantlets eliminated escapes. The procedure generated three independent hpt transformants of which two also contained the cryIA(b) gene. One such line (No. 827) produced truncated (67 kDa) CryIA(b) protein equivalent to about 0.1% of total soluble protein. The cryIA(b) gene was controlled by the promoter of the maize C4 PEP carboxylase gene and was expressed in leaf blades but was not expressed to a detectable level in dehulled mature grain. Line 827 contained about 3 copies of the cryIA(b) gene which segregated as a single dominant Mendelian locus in the second (T1) and third (T2) generations and co-segregated with enhanced resistance to first-instar larvae of striped stem borer (Chilo suppressalis) and yellow stem borer (Scirpophaga incertulas). T2 line 827-6 homozygous for the cryIA(b) gene showed no dead hearts or whiteheads after infestation with stem borers, whereas T2 line 827-25 lacking the gene averaged 7 dead hearts per plant and 2.25 whiteheads per plant. These results establish that transformation of high-quality rices of group V is a feasible alternative to sexual hybridization.  相似文献
5.
Identification and characterization of bacterial endophytes of rice   总被引:6,自引:0,他引:6  
We isolated seven different bacteria from rice seedlings grown from surface sterilized seeds. Three were associated with the rice seed husk and the other four were growing endophytically within the seed. Microscopic studies revealed that the endophytes were concentrated in the root stele region. Some of the bacteria exhibited strong anti-fungal activity against Rhizoctonia solani, Pythium myriotylum, Guamannomyces graminis and Heterobasidium annosum.  相似文献
6.
Meiotic chromosome cytology was compared betweenSolanum pennellii, Lycopersicon esculentum, and the F1 hybrid. Pachytene chromosomes are very similar in gross morphology, but several of theS. pennellii chromosomes were found to have somewhat longer chromatic regions with discrete chromomeres, and darkly staining chromomeres in the achromatic regions.Little evidence could be found for the existence of rearrangements between chromosomes of the two species. With respect to chromomere pattern, on the other hand, a number of differences were seen. Meiosis in the hybrid is strictly regular. Only size inequalities occur in certain bivalents.Considering the evidence from chromosome pairing, hybridization compatibility, hybrid fertility, and plant morphology, it is concluded that the phylogenetic relationship is much closer betweenS. pennellii andL. esculentum than it is between either one andS. lycopersicoides. Attention is called to the present unsatisfactory placement ofS. pennellii and to the need for revising the taxonomy to place it andL. esculentum in the same genus, possibly in the same subgeneric category.This research was supported in part by grant G-10704 of the National Science Foundation.  相似文献
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We have cloned two rice homologues of yeast DMC1, a meiosis-specific gene required for recombination between homologous chromosomes. We show that rice DMC1A and DMC1B were produced by a gene duplication event that occurred after rice separated from the common ancestor of the cereals. The predicted proteins contain 344 amino acids, of which all but 7 are conserved between the two homologues. Between bases -1 and -245, the two promoters share six invariant blocks of sequence of 10-28 bp, interspersed in variable sequences. Both DMC1A and DMC1B are expressed in pollen mother cells coincident with meiosis, and in diploid non-meiotic tissues such as calli and root tips. DMC1B is also expressed in haploid male gametophytes during pollen maturation and in diploid zygotic embryos and endosperm after pollination. These data suggest that DMC1B, either alone or in combination with DMC1A, contributes to recombination during meiosis and during haploid and diploid mitosis.  相似文献
10.
Chromosomal locations of 10 isozyme loci in rice (Oryza sativa L.) were determined through trisomic analysis. All 10 genes produced altered allozyme banding patterns in specific F1 trisomics. This served as the primary source of evidence for chromosome locations ofEst-5, Icd-1, Acp-1, andPgd-1. The locations ofAmp-1, Amp-2, Amp-4, Pox-5, Got-1, andCat-1 were further confirmed from segregation data in BC1 generations, as the ratios deviated significantly from 1:1 in the critical trisomics but agreed with the expected trisomic ratios. Triallelic heterozygotes were recovered forAmp-1 andAmp-2. On the basis of these dataGot-1, Est-5, andIcd-1 were located to chromosome 1,Amp-1 to chromosome 2,Cat-1 andPox-5 to chromosome 3,Acp-1 to chromosome 6,Amp-2 andAmp-4 to chromosome 8, andPgd-1 to chromosome 11. BecauseAcp-2 andPox-2 are known to be linked withAcp-1, they must also be on chromosome 6. The gene order and recombination values between isozyme loci on chromosomes 3, 6, 8, and 11 are presented.The senior author wishes to acknowledge the financial support from the Chinese government.  相似文献
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