CHISINAU, MOLDOVA
Institute of Genetics and Physiology

Possibility to identify kernels with haploid embryo by oil content

-- Rotarenco, VA, Kirtoca, IH, Jacota, AG

To identify haploids in the dry-seed stage the R1-nj marker gene (anthocyanin coloration of the top of endosperm and embryo) is being widely used. However, there are some inhibitor genes (C1-I and others), which are able to block the expression of the marker gene and the selection of kernels with haploid embryo becomes impossible. Especially, these inhibitors are widespread in flint maize. Thus, there is a need to find an alternative way for the screening of haploid kernels.

Haploid plants significantly differ from diploids by their phenotype (Chalyk and Ostrovsky, 1993). Most likely, an embryo with the haploid number of chromosomes should differ from a diploid embryo by size, too. An embryo is known to contain up to 80% of oil of a whole kernel, and the oil content has a positive correlation with the embryo size. Therefore, it was supposed that there might be a difference in oil content in kernels with diploid and haploid embryos and it was the

The purpose of our work was to compare the oil content in kernels with diploid and haploid embryos.

Eight genotypes (4 inbred lines and 4 hybrids) have been selected for the analysis. Preliminary, they have been crossed with the MHI haploid-inducing line (Chalyk, MNL-73, 1999). The selected maternal genotypes had rather good expression of the R1-nj gene that allowed the kernels with haploid embryo to be identified easily.

Diploid, hybrids of the maternal genotypes and MHI (with colored embryos), and haploid kernels (with colorless embryos) have been used for the analysis of oil content. The sample size for each variant was 100 kernels. The analysis was carried out on the Sakslet’s device modified by Rushkovskiy (1962).

The oil percentage in the haploids was lower than in the diploids in all the genotypes. The results of the analysis are shown in the Table. The averaged excess of the diploids over the haploids is 19.4%. The coefficient of correlation is 0.76 (significant at the 0.1% level).

Oil content in kernels with haploid and diploid embryos

and difference between them

Genotype	Oil content, %		Difference, %
	n	2n (hybrids with MHI)
Inbred lines
A464	4.00	5.23	31.0
A619	4.60	5.44	18.3
MK01	4.16	4.75	14.2
Mo17	4.01	5.04	25.7
Hybrids
Modavian450	4.04	4.92	21.8
Porumbeni295	4.73	5.33	12.7
Porumbeni359	3.78	4.47	18.3
Mo17xB73	3.86	4.37	13.2
On average for all genotypes	4.14	4.94	19.4

The method of oil test used by us needed the kernels to be ground up. However, there is a way of biochemical analysis (spectral analysis) that does not destroy kernels and they can be used for further work.

Thus, an oil test can be applied as a marker to identify kernels with haploid embryo. Besides the solving the problem connected with the R1-nj-gene inhibitors, this kind of analysis might be used to mechanize the haploid-seed selection.

The first attempt to identify haploids by oil content was carried out at the Bavarian State Institute for Agronomy in 2002 (Germany), and the author of this note is very grateful to Dr. Eder for the help.