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  • 1
    ISSN: 1432-2242
    Keywords: Cell wall ; Ideotype breeding ; Selection ; Smooth bromegrass
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A random sample of 80 families of the B8HD smooth bromegrass (Bromus inermis Leyss.) population were tested in three environments for forage yield and cell wall constituents. Expected progress from one cycle of family selection was computed for single-trait selection and multiple-trait restricted selection. Expected gains were compared to desired goals and actual results from one cycle of phenotypic selection. Desired goals were: Model I = reduced lignin and cellulose, with increased hemicellulose, resulting in no change in cell wall content; Model II = reduced lignin and cellulose with no change in hemicellulose; or Model III = reduced lignin, cellulose, and hemicellulose. Single-trait selection for high hemicellulose in first harvest or low cellulose in second harvest had the best expected responses, of any single trait, for Model I. Possible undesirable effects of selection for low cellulose would be a reduction in forage yield potential. Multiple-trait restricted selection was judged to be more effective, with responses all in the desired direction, by specifying increased hemicellulose in index development. Selection in second harvest was expected to have similar responses as first harvest, except for a greater increase in forage yield. Development of Models II or III is expected to be difficult due to a negative correlation estimate between first and second harvest cell wall concentration.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2242
    Keywords: Key words Recurrent Selection ; Fiber ; Forage yield ; Digestibility ; Inbreeding ; Forage crops ; Pollination methods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Selection for reduced fiber concentration in forage crops is considered to be an effective approach to improve the voluntary intake potential of forages. The purpose of this study was to determine the effectiveness of several modifications to phenotypic recurrent selection for reducing neutral detergent fiber (NDF) concentration and its effect on correlated variables of smooth bromegrass (Bromus inermis Leyss). The selection methods were based on differences in the growth stage sampled (vegetative vs heading), the method of determining NDF in the laboratory (wet-laboratory vs near-infrared reflectance spectroscopy), and the method of intercrossing selected individuals (in situ vs replicated polycross). Selection at the vegetative growth stage was most effective, probably, due to minimal sampling variation within plants. Polycrossing generally increased gains due to more effective interpollination, but increased cycle time by 50%, resulting in similar gains per year for in situ pollination vs polycrossing. Selection for reduced NDF did not generally affect the digestibility of the NDF fraction. Selection for reduced NDF led to reduced forage yield for all selection methods, due partly to a genetic correlation with NDF and partly to inbreeding depression. Three potential solutions were proposed to break the apparent association between reduced NDF and forage yield: increase effective population size, practice combined selection for both traits, and/or make chance hybrids between genetically divergent low-NDF strains. An empirical assessment will most likely be required to determine the best of these three potential solutions.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1432-2242
    Keywords: Germ-plasm evaluation ; Germ-plasm preservation ; Grass breeding
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Efficient utilization of divergent germ plasm sources in breeding cultivated Dactylis glomerata L. ssp. glomerata Domin depends on knowledge of quantitative variation within and among accessions. This study was undertaken to quantify variation and covariation for forage yield, maturity, disease reaction, and ground cover within a population of tetraploid Dactylis accessions. Variation was observed among families within the population for each variable. Most genetic variation (73%–93% of the family sums of squares) was within country sources or within accessions. Thus, country boundaries, which are traditionally important factors used in defining limits of plant exploration expeditions, have limited expected use in targeting future exploration for specific sources of high yield, disease resistance, or ground cover. Maturity was the exception to this; late-maturing accessions were identified as originating exclusively from the USSR. Some relationships among traits, such as that for yield and disease reaction, differed for accessions and cultivars. Several accessions and families within accessions were identified to have performance superior to most or all cultivars included in this study. Existing germ plasm from several countries was identified to have potential in breeding orchardgrass, while that from other countries appeared to have little or no potential in supplying germ plasm for hay production in humid-temperate environments.
    Type of Medium: Electronic Resource
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