HAPLOIDY IN MAIZE (ZEA MAYS L.) BREEDING AND RESEARCH

A haploid is a plant that contains a gametic chromosome number (n). They can appear spontaneously in nature or as a result of different induction techniques. For maize (Zea mays L.), in situ induction of maternal haploids, results by using a selected inducing genotype (line). The first inducer line was Stock 6 discovered by Coe in 1959, with an induction rate of 2.3%. Over the years through hybridization and selection the induction rate improved. A homozygous line is obtained by crossing the inducer line with an initial material, selecting the resulted haploids, doubling the number of the chromosomes and performing a self-pollination. Using this technique in maize breeding allows a reduction in the time needed to obtain a homozygous line. Also, this technique can be incorporated in different breeding schemes, like recurrent selection. One of the best inducer at this moment is PHI with an induction rate of 12-15%.