The influence of heterozygosis for marker loci on grain yield in maize --Mihailov, ME, Chernov, AA We studied the dependence of productivity in F2 maize plants on heterozygosis for the genome zones marked with 7 mutant and morphological loci. The hybrid combinations Ku123 x 2-9m and UIT-757 x 2-9m were used. The line 2-9m is marked with loci of chromosomes 2 (ws3, lg1, gl2), 6 (y1), 9 (sh1, wx1) and 10 (R1).

The F2 plants have been grouped in 8 classes according to number of heterozygous loci. In each class the mean grain yield has been detected. The recessive homozygotes ws3, lg1, gl2, sh1 and wx1 were excepted from analysis to avoid the pleiotropic effects.

The results are given in the table. The evident general positive trend of productivity at increase of heterozygosis is shown. The detail analysis has shown that heterozygotes are excellent for the sh1 and wx1 loci compared with analogous homozygotes. For the ws3, lg1 and gl2 loci the heterozygotes have no regular advantage. For the y1 and R1 loci the heterozygous plants are intermediate for productivity, exceeding mean value (mean a/d=0.75 for y1 and 0.92 for R1).

Further analysis is needed to test whether the positive influence of heterozygosis can be reduced to the sum of the partial effects of each locus, or if there is a non-allelic interaction between different heterozygous zones of the genome.

Table. The productivity of F2 plants (gm/plant) at different degrees of heterozygosis.
 
 
Hybrid and year
Number of heterozygous loci
Ku123 x 2-9m

1993
Ku123 x 2-9m

1995
UIT-757 x 2-9m

1993
0
 95 (1) 163 (1) 169 (1)
1
 132±32 (5) 146±15 (7) 124±20 (6)
2
 139±14 (13) 153±24 (8) 133±8 (15)
3
 147±6 (26) 164±12 (18) 148±14 (13)
4
 148±7 (31) 150±14 (16) 130±10 (31)
5
 146±7 (38) 164±16 (16) 135±7 (26)
6
 139±10 (30) 175±11 (22) 164±10 (20)
7
 155±8 (15) 181±63 (3) 167±14 (10)
Total
 145±4 (159) 162±6 (91) 142±4 (122)

Comment: in the brackets the number of plants is given.
 
 

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