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Predicting the range of inbreeding depression of inbred lines in cross-pollinated populations
C.L. Souza Jr.I; J.S.C. FernandesII
IDepartamento de Genética, ESALQ/USP, Caixa Postal 83, 13400-970 Piracicaba, SP, Brasil. Send correspondence to C.L.S.Jr.
IIDepartamento de Genética, UFPR, Caixa Postal 19071, 81531-970 Curitiba, PR, Brasil.
ABSTRACT
The objectives of this paper were to derive the genetic variance of inbreeding depression (σ2GID) and to predict the range of inbreeding depression (RID) in cross-pollinated populations. The variance of inbreeding depression is a function of the genetic variances related to dominance effects (σ2D, D2, and H ), and of the inbreeding coefficients of the two generations in which inbreeding depression is measured (Ft and Fg). The results showed that the higher the level of dominance of a trait, the higher the variance of inbreeding depression. The magnitudes of σ2GID were expected to be lower in improved (mean gene frequencies = p > 0.6) and in unimproved (p < 0.4) populations, than in composite populations (p ≈ 0.5). Data from a maize population used to illustrate the study showed that the range of inbreeding depression in the S∞ generation of selfing was from 48.7% to 85.3% for grain yield, and from 13.9% to 24.5% for plant height. A mating design minima to estimate me genetic vanance or inbreeding depression, the range or inbreeding depression, and of the range of inbred lines is presented.
Keywords: inbreeding depression; inbred lines; genetic variance.
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