Mass induction of maternal haploids in corn
--O. A. Shatskaya, E. R. Zabirova, V. S. Shcherbak and M. V. Chumak

The method of genetic marking proves superior to the other methods of haploid induction in corn, including pollen culture, in number of induced haploids and in simplicity and inexpensiveness of the procedure. The markers developed at our laboratory enable us to induce rather easily a large number of haploids (from some thousands to some dozens of thousands) annually. This method does not require expensive reagents and complicated equipment. The Krasnodar markers are involved in crosses as males. They carry A C R-nj dominant genes for embryo and endosperm colour. This makes it possible to select marked stock at the stage of dry kernel. This is the merit of the method because by using other methods of selection for haploidy it is necessary to germinate all marked kernels. The other merit of it is a high frequency of haploidy due to these markers in hybrids and populations as females.

Involvement of 3MC line, one of the lines obtained from Stock 6 and selected for "haploid stimulation" (Tyrnov and Zavalisha, Dokl. Akad. Nauk SSSR 276:3, 1984) into the genotype of the advanced Chase's marker (PEM) resulted in a higher frequency of maternal haploid induction. For some years the developed markers were used in ear-to-row selection for a frequency of haploidy. The group of the markers stimulating maternal haploidy up to 6.3% and even over 10% in some ears was selected in 1992 (Table 1).

Table 1. Stimulation of maternal haploidy by various groups of markers*.
 
Frequency of haploidy
Group of markers
No. ears
No. kernels
Haploids
%
per ear
PEM 68 24,834 46 0.19 0.7
3MC 24 8,206 60 0.73 2.5
Krasnodar markers 52 10,398 655 6.30 12.6

Use of such markers at a sufficiently high frequency of diploidization (20-30%) enable us to obtain annually more than a thousand new homozygous lines. Thus, haploidization becomes a competitive method comparable to traditional inbreeding in number of developed lines, reducing the period for line development by 2-3 times.

Application of the Krasnodar markers made it possible to produce 760-1,500 new autodiploid lines in 1992 and 1993, respectively. 

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