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  • 1
    ISSN: 1432-2242
    Keywords: Oryza sativa ; Hybrid vigor ; Molecular marker ; Yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Hybrid rice has contributed significantly to the dramatic increase of rice production in the world. Despite this, little attention has been given to studying the genetic basis of heterosis in rice. In this paper, we report a diallel analysis of heterosis using two classes of molecular markers: restriction fragment length polymorphisms, (RFLPs) and microsatellites. Eight lines, which represent a significant portion of hybrid rice germ plasm, were crossed in all possible pairs, and the F1s were evaluated for yield and yield component traits in a replicated field trial. The parental lines were surveyed for polymorphisms with 117 RFLP probes and ten microsatellites, resulting in a total of 76 polymorphic markers well-spaced in the rice RFLP map. The results indicated that high level heterosis is common among these crosses: more than 100% midparent and 40% better-parent heterosis were observed in many F1s, including some crosses between maintainer lines. Heterosis was found to be much higher for yield than for yield component traits, which fits a multiplicative model almost perfectly. Between 16 and 30 marker loci (positive markers) detected highly significant effects on yield or its component traits. Heterozygosity was significantly correlated with several attributes of performance and heterosis. Correlations based on positive markers (specific heterozygosity) were large for midparent heterosis of yield and seeds/panicle and also for F1 kernel weight. These large correlations may have practical utility for predicting heterosis.
    Type of Medium: Electronic Resource
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  • 2
    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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