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Genetic variances of molecular markers of F₂ and related populations

Claudio Lopes de Souza Jr.

Departamento de Genética, ESALQ-USP, Caixa Postal 83, 13418-900 Piracicaba, SP, Brasil

ABSTRACT

Objective of this paper was to define the genetic variance of genetic markers as a function of additive and dominance variances. The changes of these genetic variances in several types of populations generated by self-pollinating an F₂ population were investigated. The additive and dominance variances of a marker are functions of additive and dominance variance, respectively, of the QTL linked to a marker, and of the recombination frequency (r) between the marker and the QTL. The additive and dominance variance of a marker decrease as r increases, but the decrease of the dominance variance is larger than the decrease of the additive variance. The linkage between the QTL and the marker should be less than 0.10 to ensure that the largest part of the genetic variance of a QTL can be mder the contro1 of the marker. Additive variance of a marker increased in populations generated by selfing the F₂ population for starting values of r less than 0.20, and dominance variance decreased for all situations considered. The linkage of two QTLs with one marker was also investigated. The implications of these results for marker-assisted selection are presented.

Keywords: Genetic variances; Molecular markers.

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