The influence of the marker loci of chromosomes 1 (P1), 2 (ws3, lg1, gl2), 6 (y1), 9 (c1, sh1, wx1), 10 (R1) on recombination frequency (rf) in ws3-lg1-gl2 and c1-sh1-wx1 segments was studied. The Ku123 x 2-9m hybrid heterozygous for these loci was used. On 227 F2 plants self-pollinated F3 ears were produced. F3 families were used to estimate genotype of F2 plants for marker loci, and in the suitable F3 families rf values were scored.

Only four significant effects were detected: the influence of the gl2 locus on rf(ws3-lg1), ws3 locus on rf(lg1-gl2), wx1 locus on rf(c1-sh) and c1 locus on rf(sh1-wx1) (see Table 1). The table data show that homozygosis for a marker locus leads to increasing rf value in neighbouring chromosome segments. It may be supposed that meiotic crossing over is suppressed in heterozygous chromosome areas, and the level of this suppression depends on the size of the heterozygous interval (the larger the heterozygous interval the greater the level of suppression).

Table 1. Recombination values (mean rf% ± SE) in the different genotypic classes of F2 (Ku123 x 2-9m).
 

Segment	Genotype	Number of F3 families analysed	Mean rf, %	The proportion of the factor in total dispersion
	gl2+/+	6	20.0±3.3
ws3-lg1	gl2+/-	64	12.0±0.5	36.6% ***
	gl2-/-	10	21.5±2.1
	total	80	13.8±0.7
	ws3+/+	5	25.8±1.5
lg1-gl2	ws3+/-	64	20.8±0.6	6.9% *
	ws3-/-	2	19.0±1.9
	total	71	21.1±0.6
	wx1+/+	13	7.4±0.6
c1-sh1	wx1+/-	66	5.6±0.3	33.0% ***
	wx1-/-	8	11.8±0.7
	total	87	6.4±0.3
	c1+/+	5	28.3±3.2
sh1-wx1	c1+/-	65	21.6±0.6	10.1% **
	total	87	22.2±0.6

1) * P<0.05, ** P<0.01, *** P<0.001.

2) genotype for c1 locus in some cases could not be detected because of the interaction with R1 locus.
 

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