CHISINAU (KISHINEV), MOLDOVA
Institute of Genetics, Acad. Sci. Rep. Mold. Expression of plant height and cob weight in maize haploids --Mihailov, ME, Chernov, AA Haploids were obtained from 5 maize inbred lines and 7 of their hybrids by Moldavian Haploid Inducer (MHI). Two quantitative traits, plant height and weight of the top cob, were measured in these 12 diploid genotypes and their 12 haploid analogues to compare gene action in the diploid and haploid states. In 2002 the plants were grown in the field in two replications with a density of 5 plants/sq. meter. In each variant there were 17 plants on average.

The results of the measurements are presented in Table 1. Height of the haploids was highly correlated with height of analogous diploids. The coefficient of correlation within lines was 0.97, within hybrids the coefficient was 0.75. So, distinctions between diploid genotypes were reproduced at the haploid level. For weight of cob there was no correlation. For this trait, within lines the coefficient of correlation was -0.06, and within hybrids 0.30. Probably, this result was caused by low kernel set in haploid ears. Low kernel set stimulates formation of additional ears. It leads to decrease of top ear weight and to increase of its relative variation.

In Table 2, values of heterosis are presented. Heterosis was scored as (F1-P)/P, P=(P1+P2)/2. Both traits revealed obvious heterosis in the diploid state. In the haploid state only the W64 x Rf7 combination revealed significant heterosis (Table 2). Since at the haploid level allelic interaction (dominance and overdominance) cannot appear, heterosis in this case may only be due to non-allelic interaction. The results for haploids suggest, apparently, the definite role (relatively small) of positive non-allelic interactions in heterosis for some hybrids of maize.

Table 1. Plant height and ear weight in diploid and haploid maize plants
 
 
Plant height (cm)
Ear weight (g)
Genotype diploids haploids diploids haploids
Rf7 169+4 104+2 16.6+1.4 3.0+0.3
23-245/77V 128+6 72+3 18.6+1.4 1.6+0.3
MK109 178+3 110+5 12.4+1.9 3.0+0.3
W64 133+1 79+8 12.4+0.3 3.7+0.5
Ku123 154+1 101+3 17.2+2.5 6.1+0.2
Rf7 x 23-245/77V 198+5 91+3 21.4+1.6 2.7+0.4
Rf7 x MK109 224+2 115+3 29.5+2.7 3.4+0.3
MK109 x 23-245/77V 215+3 88+2 38.5+1.6 3.1+0.5
W64 x Rf7 200+2 100+4 21.7+1.4 5.0+0.4
Ku123 x Rf7 205+2 106+2 28.1+1.0 3.4+0.4
Ku123 x 23-245/77V 203+4 93+2 26.6+1.3 3.4+0.3
W64 x Ku123 193+2 88+2 21.2+1.1 4.1+0.5

 

Table 2. Relative heterosis (%) at the diploid and haploid level
 
 
Plant height (cm)
Ear weight (g)
Combination diploids haploids diploids haploids
Rf7 x 23-245/77V 33.3+1.3 2.9+3.4 21.6+10.9 19.4+33.5
Rf7 x MK109 29.3+1.6 7.3+3.8 103.5+20.4 12.3+ 8.0
MK109 x 23-245/77V 40.2+1.2 -3.1+5.8 148.6+12.8 35.5+23.5
W64 x Rf7 32.6+1.3 9.4+3.4** 50.0+11.4 50.1+12.6***
Ku123 x Rf7 26.5+2.7 2.9+2.1 66.3+10.3 -25.9+ 8.6
Ku123 x 23-245/77V 43.5+5.0 6.9+4.9 48.5+10.8 -10.2+ 8.3
W64 x Ku123 33.6+1.0 -2.8+3.9 43.2+11.4 -17.4+12.2
Total 34.1+2.2 3.4+1.9 43.3+16.3 9.1+10.7
** P<0.01, *** P<0.001
 
 
 
 

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