Xwmc525 was the only locus displaying codominant gene
action and the stutter observed was consistent with the description of this locus in GrainGenes.
markers are also advantageous in cases of loci like Pi-[ta.sup.2], where more than one resistance gene appears to be present in this region (i.e., Pi-ta and Pi-[ta.sup.2]; Rybka et al., 1997) and one would want to sclcct for a lack of recombination in markers flanking this gene region.
These are consistent with the segregation of a single codominant gene.
This is consistent with control of the fatuoid character by a single codominant gene.
This clearly indicates the inadequacy of a model based on a single codominant gene, as reflected by significant deviations from the 1:2:1 ratio (i.e., 1 plant with naked grain only:2 mosaic plants:1 plant with hulled grain only) in all three replicate [F.sub.2] populations of both crosses (Table 1).
Given that previous studies (Huskins, 1946; Coffman, 1964) had found that variation in the fatuoid character in hulled oat germplasm could be explained by the segregation of one codominant gene, we investigated the possibility that the hulled progeny of the NO753-2/Marion and NO753-2A/Marion crosses would satisfy single-gene models better than the naked-grained progeny of the same crosses.
The observed segregation ratios of 32:72:40 and 30:75:39 for high beta-carotene homozygotes (BB): high beta-carotene heterozygotes (Bb): low beta-carotene homozygotes (bb) of [SCAR18.sub.1067] and [SCBC792.sub.779] ([chi square] = 3.29, P [is greater than] 0.10 and [chi square] = 5.00, P [is greater than] 0.05, respectively) approximated the expected 1:2:1 segregation ratio for a codominant gene
With respect to resistance to Mi the following comments can be made: (i) the major QTL on LG-O (G248A-1) explained 31% of the variation in gall number and acted additively, (ii) gall number data when classified as a single codominant gene
was 27 cM from the QTL, and (iii) the level of resistance observed in Forrest, 26 galls, (Luzzi et al., 1994b) is similar to the level of resistance observed in lines that were homozygous for the major QTL (G248A-1) derived from PI96354 and homozygous for the minor QTL (K493H-1 + 5.4 cM) derived from Bossier, 27 galls.
Inheritance and linkage of isozyme codominant genes
They may also be applied to backcross programs in which dominant or codominant genes
are to be transferred from the nonrecurrent to the recurrent parent.