Abstract

ESCALANTE-GONZALEZ, José Luis; SAHAGUN-CASTELLANOS, Jaime; RODRIGUEZ-PEREZ, Juan Enrique  and  PENA-LOMELI, Aureliano. Genetic erosion in single-cross progenitors of a synthetic variety. Rev. Chapingo Ser.Hortic [online]. 2013, vol.19, n.2, pp.151-161. ISSN 2007-4034.  https://doi.org/10.5154/r.rchsh.2012.09.047.

Randomness, finite number of individuals and genetic variability among those that represent each parent of a synthetic of crop species such as onion (Allium cepa L.) and maize (Zea mays L.) can cause genetic erosion during the development of a synthetic variety. This may happen when the parents are L/2 single crosses (SCs) derived from L lines. If the inbreeding coefficient of the lines (F_L) is less than 1, and the number (m) of plants that represent each SC is small, the number of non-identical by descent (NIBD) genes of each SC is a random variable (Xm). The objectives of this study were to determine: 1) the mean of Xm [E(Xm)], 2) the variance of Xm [Var(Xm)], and 3) the average loss of NIBD genes which are contributed by two lines to their SC. It was found that E(Xm) = 2 + [2 - (1/2)^m-2 ](1 - F_L). In addition, the average loss of NIBD genes was (1/2)^m-2(1-F_L) and Var(Xm) = [2^m+2 - 8](1-F_L)²/4^m. These two results imply that when lines are pure (F_L=1), the loss of NIBD genes and the instability of the number of these genes reach their minimum (zero), and approach to it from m = 8 on, more rapidly as F_L becomes larger.

Keywords : Allium cepa L.; Zea mays L.; synthetic variety; non-identical by descent genes; random mating.

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