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  • Electronic Resource  (4)
  • Family selection  (2)
  • inter-plot competition  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Springer
    Theoretical and applied genetics 68 (1984), S. 503-508 
    ISSN: 1432-2242
    Keywords: Kale breeding ; Population improvement ; Family selection ; Computer simulation ; Genetic drift
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three recurrent selection schemes suitable for kale (Brassica oleracea L.), involving half-sib (HS), full-sib (FS) and selfed (S) families, were compared by computer simulation. All combinations of 6, 12 and 24 families selected, out of 120 and 240 assessed, were investigated for a range of genetical models. Selection was simulated for 20 generations from an initial allele frequency of 0.05 and for 16 generations from an initial frequency of 0.20. With an initial frequency of 0.05 there was a serious loss of desired alleles ranging from 0.31 out of 20 for the HS scheme with 24 out of 240 families selected to 9.19 for the S scheme with 6 out of 120 families selected. It was concluded that if as many as 20 cultivars were included in the initial population the selection scheme should be chosen to minimise the loss. With an initial frequency of 0.20 there were no losses with 12 and 24 families selected in the HS and FS schemes respectively, and the highest loss was 2.88 for the S scheme with 6 out of 120 families selected. It was concluded that if as few as five cultivars were included in the initial population a compromise between the initial response to selection and the loss of desired alleles should be sought. Selecting 6, 12 and 24 families for the HS, FS and S schemes respectively, resulted in average relative responses per generation of 2.28, 2.74 and 2.76, respectively for the first five generations, and losses of 0.22, 0.13 and 0.35, respectively after 16 generations. Practical considerations favour the FS scheme over the S scheme.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-2242
    Keywords: Key words Potato breeding ; Family selection ; Cross prediction ; Breeders’ visual preference ; Within-family selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  In 1992, 72 seedlings from each of 198 pair crosses were grown in a glasshouse, and the tubers produced by each plant were visually assessed on a 1–9 scale of increasing preference. Three groups of four progenies with high, medium and low mean scores were chosen to progress, without selection via tuber progenies and four-plant plots at a high-grade seed site, to replicated yield trials in the third clonal generation. The three groups maintained their high, medium and low scores for visual preference over the three clonal generations and also had high, medium and low scores in the second and third clonal generations for yield, size and appearance of tubers, all of which were components of visual preference. The three groups were predicted to have 13.6%, 1.8% and 0.2% of their clones exceeding the mean of 13 control cultivars for visual preference in the replicated trials, and 12.1%, 4.9% and 1.4% for yield, and 56.8%, 37.1% and 14.8% for appearance. The experiment confirmed that selection for visual preference within crosses in the seedling and first clonal generations is very ineffective, but that worthwhile progress can be made from selection in the second clonal generation, with correlated responses for faster emergence, earlier maturity, higher yield and greater regularity of shape (appearance). Combining selection of the high group of progenies with selection in the second clonal generation of the best 34 out of the 120 clones in this group, produced a response in visual preference in the third clonal generation of 1.00 compared with a maximum possible of 1.74. Ways of achieving further improvements in early-generation selection are discussed.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 42 (1989), S. 135-140 
    ISSN: 1573-5060
    Keywords: Brassica napus ; swede breeding ; inter-plot competition ; dry-matter yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two experiments were done to evaluate the use of single-row plots for assessing dry-matter yield of swedes. In the first experiment the correlation between the dry-matter yields of 20 cultivars in unguarded single-row plots and those in guarded double-row plots was poor (r=0.39). It was improved (r=0.58) by adjusting the single-row plot fresh-weight yields for inter-plot competition, through an analysis of covariance in which the covariate was the mean of the adjacent plot yields, and then estimating the pure stand dry-matter yields. However, the correlation was still lower than that between unguarded double-row plots and the guarded double-row plots (r=0.73), and this latter correlation was also improved (r=0.82) by adjusting the fresh-weight yields of the unguarded plots for inter-plot competition. The second experiment provided an explanation for the partial success of the covariance adjustment. The individual neighbour effects of six cultivars were determined. Doon Major and Ruta Øtofte decreased the yields of adjacent cultivars whereas Dryden and Melfort increased them. Angela and Magres had little effect. The correlation between the dry-matter yield neighbour effects of cultivars and their fresh-weight yields was high (r=−0.81), but not complete. So although competitive ability was associated with root fresh-weight yield, other factors must also be involved. It was concluded that a two-replicate trial with unguarded double-row plots is preferable to a four-replicate trial with unguarded single-row plots for dry-matter yield assessment of early generation families in a pedigree swede breeding programme.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Euphytica 35 (1986), S. 433-439 
    ISSN: 1573-5060
    Keywords: Brassica oleracea ; fodder kale breeding ; inter-plot competition ; digestible organic-matter yield
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Summary Two experiments were done to evaluate the use of single-row plots for assessing digestible organic-matter (DOM) yield. In the first experiment 29 cultivars were grown in both single-row plots (unguarded) and five-row plots from which only the centre row was harvested (guarded single-row plot). The correlation between yields in the unguarded and guarded plots was very low (r=0.20). Yield was correlated (r=0.89) with cultivar height in the unguarded plots, but not in the guarded plots (r=0.19). Therefore selection for yield in unguarded single-row plots is undesirable and would favour tall kales which are prone to lodging. In the second experiment 16 cultivars were grown in single row-plots guarded by the short cultivar Maris Kestrel, the tall cultivar Vulcan and by the cultivars themselves as control. The correlations between yield in the control plots and yields in the plots guarded with Maris Kestrel and Vulcan were only moderate (r=0.56 and r=0.64 respectively). Therefore the use of a single distinct cultivar to guard single row-plots is undesirable. Selection for DOM yield should therefore be made in multiple-row plots, from which the outer rows are discarded, in order to avoid the undesirable effects of competition.
    Type of Medium: Electronic Resource
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