Production of matroclinous maize haploids following natural and artificial pollination with a haploid inducer --Rotarenco, VA Studies carried out recently have significantly contributed to the solution of the main problem of haploidy in maize, which means the possibility for wide production of haploid plants. Mass production of haploids has become possible, mostly due to the development of efficient genetic inducers, which make it possible to obtain matroclinous haploids from practically any genotype (Tyrnov and Zavalishna, 1984; Zabirova, 1996; Chalyk, 1999).

We observed earlier that the percentage of the haploid yield varied somewhat following natural and artificial pollination with inducer pollen. Therefore we set a task for the current year (2001) of comparing the percentage of the seeds with a haploid embryo following natural and artificial pollination with an inducer of matroclinous haploids.

Two homozygous lines (092 and Rf-7) and a synthetic population (SA) were pollinated with the pollen of MHI line (Moldavian Haploid Inducer) (Chalyk, MNL 73, 1999). The material was grown also in an isolation plot, where it was pollinated with pollen of the MHI line.

The results presented in the Table show that, following artificial pollination, the percentage of the seeds possessing a haploid embryo in the inbred lines is more than twice as high in comparison with natural pollination at the isolation plot. A significant difference between the natural and artificial pollination by this criteria is also observed in the heterogeneous population.

Table. Percentage of haploids after natural and artificial pollination.
Genotypes  Number of seeds with haploid embryos, %
  Natural pollination Artificial pollination
092 3.8 8.8
Rf-7 2.3 6.0
SA (population) 2.5 4.3

The reason for the difference in the haploid yields was, most probably, a delayed pollination in this case. The delayed pollination is known to be one of the techniques of producing matroclinous haploids in various crops, including maize. Pollination with the inducer pollen was carried out when a mass appearance of stigmata occurred, as is usually done. In our opinion, this delay caused an increase in the haploid yield in comparison with the material grown in an isolation plot. It should be noted that the inducer line was planted three times with a 10 day interval in the isolation plot to increase the period of pollen availability. Thus, the ears of the material under study were able to be pollinated during the whole period of their flowering.

Accordingly it has been established that the delayed pollination might contribute to a significant growth of the matroclinous haploid yield in maize when haploid inducers are used.

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