Chromosome Doubling in Haploid Lines of Tropical Maize.

Doubled haploids (DHs) is an important technique in the corn breeding process responsible for accelerate the inbred development process. Better understanding the mechanisms of chromosome doubling and cell duplication could optimize the DH production system. The objectives of this study were to identify and characterize double haploid lines using flow cytometry, microsatellite markers, and pollen viability. In 2013, the inducer line KEMS was used as a pollen donor and crossed with 4 different hybrids (GNS 3225, GNS 3032, GNS 3264 and DKB 393). Seeds with white embryo and purplish pericarp were considered haploids and selected for two different chromosome doubling protocols. Flow cytometry was analyzed on the new DH lines 14 days after cell duplication. The DH lines were transplanted to the field and leaf samples were collected for DNA analysis using microsatellite markers. Different protocols for chromosome doubling had a significant effect on plant survival of the DH lines. Duplicated haploids were identified by flow cytometry and provided seven different ploidies for corn: haploid, haploid/diploid, haploid/tetraploid, haploid/octoploid, diploid, diploid/tetraploid and diploid/octoploides. Microsatellite markers were efficient in confirming the inheritance of KEMS lineage, as well as the identification of double-haploid plants. Pollen viability is a complementary technique for flow cytometry.