Theoretical studies on the necessary number of components in mixtures |
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Authors: | M Hühn |
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Institution: | (1) Institut für Pflanzenbau und Pflanzenzüchtung, Universität Kiel, D-2300 Olshausenstrasse 40-60, Kiel, FRG |
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Abstract: | Summary Theoretical studies on the optimal numbers of components in mixtures (for example multiclonal varieties or mixtures of lines) have been performed according to phenotypic yield stability (measured by the parameter variance). For each component i, i = 1, 2,..., n, a parameter ui with 0 ui 1 has been introduced reflecting the different survival and yielding ability of the components. For the stochastic analysis the mean of each ui is denoted by u
1 and its variance by
i
2
For the character total yield the phenotypic variance V can be explicitly expressed dependent on 1) the number n of components in the mixture, 2) the mean
of the
i
2
3) the variance of the
i
2
4) the ratio
and 5) the ratio
i
2
/2 where denotes the mean of the u
i and
u
2
is the variance of the u
j. According to the dependence of the phenotypic stability on these factors some conclusions can be easily derived from this V-formula. Furthermore, two different approaches for a calculation of necessary or optimal numbers of components using the phenotypic variance V are discussed: A. Determination of optimal numbers in the sense that a continued increase of the number of components brings about no further significant effect according to stability. B. A reduction of b % of the number of components but nevertheless an unchanged stability can be realized by an increase of the mean of the u
i by 1% (with
and
u
2
assumed to be unchanged). Numerical results on n (from A) and 1 (from B) are given. Computing the coefficient of variation v for the character total yield and solving for the number n of components one obtains an explicit expression for n dependent on v and the factors 2.-5. mentioned above. In the special case of equal variances,
i
2
=
o
2
for each i, the number n depends on v, x = (0/)2 and y = (u/)2. Detailed numerical results for n = n (v, x, y) are given. For x 1 and y 1 one obtains n = 9, 20 and 79 for v = 0.30, 0.20 and 0.10, respectively while for x 1 and arbitrary y-values the results are n = 11, 24 and 95.This publication is an extended version of a lecture given at the 1984-EUCARPIA meeting (Section Biometrics in Plant Breeding) in Stuttgart-Hohenheim (Federal Republic of Germany) |
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Keywords: | Mixtures Number of components Phenotypic yield stability Stability parameter: variance |
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