RECURRENT SELECTION OF S1 MAIZE LINES AGAINST RECESIVE SIMPLE CHARACTERS

Abstract

Recurret selection is a strategy for population improvement without drastic loss of genetic variabiliity. lt is concemed mainly with quantitative traits, but, under some situations, it might be worthwhile against undesirable qualitative traits. In this study, the effect of S₁ progeny selection on the frequency of a recessive gene was analyzed from a mathematical approach. The selection was supposed to be against the recessive homozygote, with an artificial fitness of zero. lt is proved in this research, that the frequency
of the gene (q₁) after one generation of selection is a function of the initial frequency (q) and the size of the progeny per plant (n), and it can be estimated as follows: q₁ = q(3/4)ⁿ1 {q [2(3/4)ⁿ-l] +1}. After certain value of n, the efficiency of the selection does not have an appreciable growth. lt is also shown that the smaller initial frequency (q), the greater efficiency of this kind of selection compared to n as a selection. It was developed a formula to estimate n as a function of the initial gene frequency and the desired frequency to be obtained by S₁ progeny selection.