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  • Adapted germplasm  (1)
  • Effective population size  (1)
  • 1985-1989  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Heterosis among populations of maize (Zea mays L.) with different levels of exotic germplasm (1987)
    Springer
    Theoretical and applied genetics 73 (1987), S. 445-450 
    Details
    ISSN: 1432-2242
    Keywords: Unadapted germplasm ; Adapted germplasm ; Heterotic patterns ; Gardner-Eberhart model ; Composites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Thirteen maize (Zea mays L.) populations including five adapted, five adapted x exotic, two composites of adapted and exotic, and one exotic selected for adaptability were crossed in a diallel mating system. The parents and 78 crosses and nine check hybrids were evaluated for grain yield and plant height in five environments. The Gardner-Eberhart model Analysis II indicated that additive and nonadditive gene effects accounted for 60 and 40% of the total variation among populations, respectively, for grain yield and 86% and 14% of the total variation, respectively, for plant height. Components of heterosis were significant in the combined analysis for both traits. Adapted Corn Belt populations tended to have higher performance in crosses and greater values of variety heterosis than 50% adapted populations. ‘Nebraska Elite Composite’, ‘Corn Belt’ x ‘Mexican’, and ‘Corn Belt’ x ‘Brazilian’ showed high mean yields in crosses, however, they were not among those with high estimates of variety heterosis. One exotic population (‘Tuxpeno’ x ‘Antigua Grupo 2’) and three adapted populations [‘307 Composite’, ‘NB(S1)C-3’, and ‘NK(S1)C-3’] might be combined together to form a high-yielding population. It may be possible to synthesize two useful populations for reciprocal recurrent selection by grouping ‘Tuxpeno’ x ‘Antiqua Grupo 2’, ‘NB(S1)C-3’, and ‘NS(FS)LFW-8’ into one population and ‘NK(S1)C-3’, ‘Krug’x‘Tabloncillo’, and ‘307 Composite’ in the other one.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00262514
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  • 2
    Electronic Resource
    Electronic Resource
    Methodologies for estimating the sample size required for genetic conservation of outbreeding crops (1989)
    Springer
    Theoretical and applied genetics 77 (1989), S. 153-161 
    Details
    ISSN: 1432-2242
    Keywords: Seed regeneration ; Sample size ; Random genetic drift ; Effective population size ; Allele frequency
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The main purpose of germplasm banks is to preserve the genetic variability existing in crop species. The effectiveness of the regeneration of collections stored in gene banks is affected by factors such as sample size, random genetic drift, and seed viability. The objective of this paper is to review probability models and population genetics theory to determine the choice of sample size used for seed regeneration. A number of conclusions can be drawn from the results. First, the size of the sample depends largely on the frequency of the least common allele or genotype. Genotypes or alleles occurring at frequencies of more than 10% can be preserved with a sample size of 40 individuals. A sample size of 100 individuals will preserve genotypes (alleles) that occur at frequencies of 5%. If the frequency of rare genotypes (alleles) drops below 5%, larger sample sizes are required. A second conclusion is that for two, three, and four alleles per locus the sample size required to include a copy of each allele depends more on the frequency of the rare allele or alleles than on the number. Samples of 300 to 400 are required to preserve alleles that are present at a frequency of 1%. Third, if seed is bulked, the expected number of parents involved in any sample drawn from the bulk will be less than the number of parents included in the bulk. Fourth, to maintain a rate of breeding (F) of 1 %, the effective population size (N e) should be at least 150 for three alleles, and 300 for four alleles. Fifth, equalizing the reproductive output of each family to two progeny doubles the effective size of the population. Based on the results presented here, a practical option is considered for regenerating maize seed in a program constrained by limited funds.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00266180
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    Paper (German National Licenses)
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