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  • 1
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: The wild-rice-derived dominant gene Xa21 conferring multi-race resistance to bacterial blight and a fused Bt gene cry1Ab/cry1Ac conferring resistance to lepidopteran insects were individually introduced into the same genetic background of an elite indica cytoplasm male sterile (CMS) restorer line ‘Minghui 63′. The line showed the desirable insect- and disease-resistant phenotypes. To maximize the effect, the two genes were also pyramided into the same recipient plant of ‘Minghui 63’ by marker-assisted selection. After being subjected to natural infestation of leaf-folders and yellow stem borers and inoculation of Xoo strain mixtures, the pyramiding line and its derived hybrids showed high levels of resistance against both insect damage and disease. Furthermore, data from field trials demonstrated that the hybrids made by crossing this pyramiding line with the CMS lines ‘Zhenshan 97A’ and ‘Maxie A’ retained a similar level of yield under conditions without chemical spray, indicating that the pyramiding genes have a yield-stabilizing effect on the recipient line and its hybrids.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 120 (2001), S. 0 
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Bacterial blight (BB), caused by Xanthomonas oryzae pv. oryzae (X00), is one of the most devastating diseases of rice world-wide; it is also a serious problem of hybrid rice production in China. In this study, a molecular marker-assisted introgression of Xa21, a gene highly resistant to a broad spectrum of Xoo strains, from ‘IRBB21’ was performed to improve the BB resistance of‘6078′, a new restorer line with high yielding potential. The entire process took one generation of crossing followed by three generations of backcrossing and one generation of selfing. The presence of Xa21 in each generation was determined by both polymerase chain reaction (PCR) and pathogen inoculation. Recombinations between Xa21 and flanking markers were identified by PCR analysis. Background selection was conducted in BC1F1 and BC2F1 using amplified fragment length polymorphism (AFLP) markers detecting a total of 129 polymorphic bands between‘6078’ and ‘IRBB21′. The individual selected in BC3F2, or‘6078′(Xa21), carried a fragment of less than 3.8 cM from the donor line in the Xa21 region on chromosome 11, and about 98.8% of the genetic background from the recurrent parent. The results showed that‘6078′(Xa21) had the same level and spectrum of BB resistance as the donor parent ‘IRBB21′, while maintaining the agronomic performance and combining ability of the original 6078. A significant increase in BB resistance was also achieved in the hybrid using 6078(Xa21) as the restorer line.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2242
    Keywords: Key words Oryza sativa L. ; Ratoon ; Molecular marker ; QTL
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Although F2s are the most informative populations for genetic analysis, it has been difficult to use F2 populations directly for QTL analysis because it is usually difficult to assess the reliability of the data, due to an inability to estimate the experimental errors. In this study, we performed a QTL analysis for yield and yield-component traits of an F2 population based on data from replicated field trials over 2 years using vegetative shoots of ratooned plants, making use of the ratooning habit of rice. The objective of this study was to explore the possibility of conducting QTL analyses directly based on an F2 population by means of ratooning plants. The experimental population was from a cross between ’Zhenshan 97’ and ’Minghui 63’, the parents of ’Shanyou 63’, an elite rice hybrid widely grown in China. A genetic linkage map containing 151 molecular markers was constructed for QTL mapping. A total of 20 distinct QTLs were detected; eight of these were detected in both years and remaining 12 in only 1 year. Compared with the results of our previous analysis of the F2:3 families from the same cross, it was shown that most of the QTLs detected in the ratooned F2 population were also detected in the F2:3 population. However, the estimates of both additive and dominant types of genetic effects for many of the QTLs based on F2 ratoons were substantially larger than those based on F2:3 families. The results indicate that vegetatively ratooned F2 populations may have considerable utility in the mapping of QTLs, especially if dominant types of gene actions are of concern, although there were certain technical limitations in making use of such populations in the experiments.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 101 (2000), S. 823-829 
    ISSN: 1432-2242
    Keywords: Key words Rice quality ; Grain shape ; Endosperm opacity ; Genetic analysis ; Molecular marker
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Appearance quality of the rice grain represents a major problem of rice production in many rice-producing areas of the world, especially in hybrid rice production in China. In this study, we conducted a molecular marker-based genetic analysis of the traits that are determinants of the appearance quality of rice grains, including traits specifying grain shape and endosperm opacity. The materials used in the analysis included an F2:3 population and an F10 recombinant inbred line population from a cross between the parents of Shanyou 63, the most widely grown rice hybrid in China. Molecular marker-based QTL (quantitative trait locus) analyses revealed that grain length and grain width were each controlled by a major QTL accounting for a very large proportion of the genetic variation, plus one or two minor QTLs each explaining a small proportion of the genetic variation. The major QTLs can be detected in both the F2:3 and recombinant inbred line population using both paddy rice and brown rice, whereas the minor QTLs were detected only occasionally. The QTL located in the interval of RG393-C1087 on chromosome 3 is the major locus for grain length, and the one in the interval RG360-C734a on chromosome 5 plays a major role in determining grain width. Similarly, white belly, which largely determines the opacity of the endosperm, is almost entirely controlled by a major locus on chromosome 5, located in the same genomic region as the major QTL for grain width. The implications of the results with respect to hybrid rice improvement were discussed.
    Type of Medium: Electronic Resource
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