Improvement and expansion of doubled haploid technology

Vanous, Kimberly
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Doubled haploid (DH) technology offers a shortcut for one of the most time-consuming processes in plant breeding: arriving at homozygous inbred lines which are in turn used for hybrid production. Therefore, DH systems have been widely adopted, highly utilized in commercial production, and viewed as an invaluable tool for those crops that have it available. Spontaneous production of haploids is a rare phenomenon and is not efficient enough to rely on for commercial production. Therefore, discovering a reliable method of haploid production, which is not something many crops have, is essential to utilize DH systems. Maize breeding programs have a reliable method of producing haploids, making this system possible in commercial production. Past studies have recognized several QTL regions that are involved in haploid induction, which may be utilized in efforts to discover underlying genes and create transgenic inducers in other crops. Although DH systems have shaped the image of a modern maize breeding program, there is always an interest in research to further improve upon this tool. The incorporation of embryo culture, for instance, offers several benefits such as a shorted generation time as well as increased genome doubling rates. This thesis contains four chapters that (1) outline the protocol of standard DH systems in maize, (2) explore distinguishing root morphological features that allow for selection of maize haploid embryos via embryo culture, (3) observe doubling rates when colchicine is added to the growth media during embryo culture, and (4) discover the gene responsible for a QTL (qhir8) of haploid induction in maize. Through these studies, it was found that maize haploids can be selected by primary root length within the first three days of growth within DH program utilizing embryo culture. This selection method is efficient and allows for the addition of embryo culture to a non-transgenic DH program. The addition of embryo culture is beneficial because it not only decreases generation time, but also significantly increases doubling rates. Finally, these studies have identified a gene responsible for qhir8 involved with haploid induction in maize. Finding this gene may allow for the creation of transgenic inducers in orphan crops, allowing for the expansion of DH technology to other crops.

Doubled Haploid, Embryo Culture, Embryo Rescue, Haploid induction, Maize, Root