| dc.description.abstract | Sorghum is an important cereal crop worldwide though it is particularly important in semi-arid regions. It is grown for many uses including food, feed, forage, sugar, and bioenergy. In its native Africa, sorghum is 3-4 meters in height. However, in the U.S. shorter plants were selected for grain production to reduce lodging and to facilitate mechanical harvesting. In the 1950s, researchers determined that this variation in height was controlled by four major genes they termed the dwarfing (Dw1-Dw4) genes. In 2003, Dw3 was identified as an ABCB efflux transporter of the plant hormone auxin. The locations of Dw1 and Dw2 have also been determined though the underlying genes remain to be elucidated. Dw1 was found to be on chromosome 9 at ~57 Mbp and Dw2 is located at ~42 Mbp on chromosome 6. The location of Dw4 has not been definitively determined though locations of ~6 Mbp on chromosome 6 and ~67 Mbp on chromosome 4 have both been suggested.
In the work described in this dissertation, I determined that the gene that underlies Dw1 is Sobic.009G229800, a highly conserved gene of unknown function. Furthermore, Dw1 is found to interact with a QTL on chromosome 7. Dw2 was determined to be Sobic.006G067700 a kinase whose closest homolog in Arabidopsis is KCBP INTERACTING PROTEIN KINASE (KIPK). KIPK is a member of the AGC protein kinase family subgroup AGCVIII, which includes several kinases involved in the regulation of auxin transport. Lastly, I attempted to locate Dw4 through crosses with two different broomcorns. Surprisingly, no QTL matching the description of Dw4 was found. Overall this work increased our understanding of the genetic control of height in sorghum, as well as revealing some exciting possible new regulators of growth. | en |
