Use of Doubled Haploids in the Context of Genetic Resource Exploitation in Maize

Haploids are an effective tool to eliminate recessive genes leading to lethality or sub-vitality. The main application of (doubled) haploids (DHs) is production of completely homozygous and homogeneous lines in short time. Potentially masking genetic variation within lines or families is completely eliminated within DH lines. The usefulness of DH lines is significantly increased over F_2:3 or F_3:4 families, due to a significantly enhanced genetic variation among DH lines. Finally, substantial progress has been made in development in novel inducers and for understanding the genetics of haploid induction and response of donor plants to the induction process. The objective of this presentation is to study and discuss possibilities for using DH technology to support the germplasm enhancement in maize (GEM) allelic diversity project (http://www.public.iastate.edu/~usda-gem/). The GEM diversity project using DH lines to evaluate exotic introgressions in elite background taps into a wide diversity of maize races including Highland germplasm. No selection is made for agronomic performance in the ongoing GEM diversity project which may be an advantage to capture novel allelic diversity. Currently, 54 races (including 12 Highland races above 2,500 meters elevation) are represented in the DH materials. As a case study, the level of diversity present at the brown-midrib 3 locus, known to affect cell wall lignification, and its implications will be reported in detail.