Three versions of estimates of the effective number of loci are given without their standard errors. nE1, nE2, and nE3 for the silking date are similar for F2 and more different for F2 Syn. 10. While nE1 and nE2, for plant height are similar for F2 and F2 Syn. 10, nE3 (33.97 and 35.45) almost reached a recombination index of about 36 (Darlington, 1937 in Lande, 1981).
According to Zeng (1992) only at ear
height were all three favorable conditions met: 1) the two parental populations
are "many" (approx. 10) phenotypic standard deviations apart. In this experiment
three deviations for silk date, plant height and ear height are 5.66, 4.91,
and 17.21, respectively; 2) no linkage; and 3) large sample size (>200).
Estimates of the number of genes for ear height, however, seem underestimated.
Linkage did not affect the estimates because the number of estimated genes
are similar for F2 and F2 Syn. 10 populations. Consequently, unequal effects
of alleles seem to be important. There is no reliable procedure for correcting
the bias from unequal effects of alleles. Zeng (1992) suggests use of parameter
composite measure of variability of allelic effects and frequencies among
loci. There are difficulties, though, in estimating the parameter
Linkage effects, however, summarized by the mean recombination frequency
is estimable, and can be corrected (Zeng, 1992). Hence, efforts of intermating
are not necessary. Additionally, random intermating plants within F2 populations
did not increase the genetic variability. Similar results were reported
by Covarrubias-Prieto, Hallauer and Lamkey (1889) and Han and Hallauer
(1989). Linkage was, probably, primarily in repulsion phase (Cavalli, 1952).
On the basis of the estimates obtained for the F2 and F2 Syn. 5 populations,
however, it does not seem that repulsion phase linkages had a large affect
on the estimates of s2A
(Han and Hallauer, 1989). We could not obtain estimates of the dominance
parameter in our experiment because no backcross data were available.
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