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Comparação de alguns métodos de análise dialélica (Comparison of some methods of diallel analysis)

C.D. Cruz^I; R. Vencovsky^II

^IDepartamento de Biologia Geral, Universidade Federal de Viçosa, 36570 Viçosa, MG, Brasil. Send correspondence to C.D.C.
^IIDepartamento de Genética, ESALQ-USP, 13400 Piracicaba, SP, Brasil

ABSTRACT

Comparisons were made between Griffing's (Austr. J. Biol. Sci. 9: 463-493, 1956) models 2 and 4 and Gardner and Eberhart's (Biometrics 22:439-452, 1966) method of analysis of diallel crosses. A polygenic situation was considered, with two alleles per locus; parental populations in Hardy-Weinberg equilibrium were assumed, an arbitrary level of dominance was admitted and epistatic genetic effects were taken as negligible. Genetic parameters of the linear models, and pertinent constrasts between these parameters were expressed in terms of allelic frequencies and genetic effects.
Derivations allowed us to verify how several parameters are interrelated. Through simulation procedures, it could be verified how the parameters v_j and l j, the effects of variety j and variental heterose of parent j, respectively, contribute to the general combining ability parameter g_i. It became evident that g_i is still the best criterion for selecting among parental types, within the context of diallels. Emphasis was given to the understanding of the s_jj parameter, (the specific combining ability of parent j with itself) in genetic terms. It was shown that s_j is an important indicator of the existence of unidirectional dominance. In addition, it was demonstrated that the contrast s.- s_j,_j,, is a linear funtion of h_j - h. and and that the overal sum of s_j. , on the o_ther hand, is a linear function of h (the mean heterose effect). It was concluded that Griffing's (1956) and Gardner and Eberhart's (1966) approaches, for the analysis of diallel crosses, which include parental types, are basically equivalent, in terms of the genetic information they provide.

Keywords: comparison; methods; diallel; analysis.

REFERENCES

Falconer, D.S. (1981). Introdução à Genética Quantitativa. Imprensa Universitária da Universidade Federal de Viçosa, Viçosa, 279 p.

Gardner, C.O. (1967). Simplified methods for estimating and computing sums of square for a diallel cross analysis. Fitotecnia Latinoamericana 4: 1-12.

Gardner, C.O. and Eberhart, S.A. (1966). Analysis and interpretation of the variety cross diallel and related populations. Biometrics 22: 439-452.

Griffing, B. (1956). Concept of general and specific combining ability in relation to diallel crossing systems. Austr. J. Biol. Sci. 9:463-493.

Singh, M. and Singh, R.K. (1984). A comparison of different methods of half-diallel analysis. Theor. Appi. Genetics 67: 323-326.

Vencovsky, R. (1970). Alguns aspectos teóricos e aplicados relativos a cruzamentos dialélicos de variedades. Tese de Livre-Docência, ESALQ, Piracicaba, SP.