Segregation for the marker ra1 gene in matroclinal haploids of maize --Rotarenco,VA The genetic inducers available at present allow the production of matroclinal haploids in mass quantities practically from any maize genotype (Tyrnov and Zavalishina, 1984; Zabirova, 1996; Chalyk, 1999). The absence of a directed elimination of individual genotypes and selection of ovules during the genetic induction of haploids is an important condition of their utilization in breeding and genetic programs.

P. Lashermes et al.(1988) studied the segregation of doubled haploids by isozyme markers and compared the segregation of doubled haploid lines and self-pollinated ones by phenotypical traits. The finding showed that the population of haploid plants represented a randomized set of genotypes. Lashermes showed that the directed elimination of individual genotypes was absent in the experiment. The ovule selectivity was also absent at the induction of haploids.

The goal of our work was to study the segregation for the marker ra1 gene (conical panicle and branching ear) in haploid plants in order to establish the conformity of its segregation with the theoretically expected one under our conditions and in our material.

The inbred Rf-7 line crossed with the MG line carrying a homozygote for the ra1 gene was used as initial material. The hybrid produced was crossed with the MHI line, which was an inducer of matroclinal haploids. The MHI line contains the marker A1, C1, R-nj gene, the presence of which allows the haploids to be selected reliably enough at both seed and plant level under field condition.

Segregation for the marker gene was studied on the haploid population produced. The table shows the assessment of segregation among haploid plants and the theoretically expected one.

Table. The conformity between the segregation for the marker gene in haploid plants and the theoretically expected one 1:1(cfact)
 
Haploid population Total number of haploids Normal genotype Mutant genotype c-square
Rf-7 x MG 70 38 32 0.5

The theoretical value of the c-square is 3.84 at the 5% significant level.

Since the haploids originated from the F1 hybrid, heterozygous for the gene under study, the theoretical expected segregation must be 1:1. Our experiment has confirmed that the segregation for the ra1 gene is in conformity with the theoretically expected one.

The findings of our experiment have led us to the conclusion that in this case the haploids represent a randomly segregating population. The linear elimination of individual genotypes and ovule selectivity were absent during the haploid induction. Haploid plants can be used for the genetic analysis of traits and selection of genotypes with valuable economic traits.
 
 

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