Dissecting the Genetic Basis of Height in Sorghum Using Biparental QTL Mapping

Worldwide, sorghum is the fifth most widely grown cereal crop. As with other crops, height has a strong influence on yield in sorghum. In Africa, where it is grown for food and forage, sorghum is about 3-4 meters tall. However, in the US, sorghum grown for grain has been bred to be shorter, ~1 meter tall, to reduce lodging. More recently, sorghum has been used as a biofuel and increased height can improve stalk biomass and sugar yield. In the 1950s, Quinby and Karper identified four major genes that control height: Dw1-Dw4. One of the genes, Dw3, was map-based cloned and found to be an ABCB1 transporter of auxin. The goal of this project is to increase our knowledge of the genetics of height in sorghum through QTL mapping and map-base cloning of Dw1. QTL mapping was carried out in F2 populations of Standard Broomcorn and SC170, BTx623, or Hegari to locate Dw4. Surprisingly, no QTL were found that would fit with Quinby and Karper’s description of Dw4. Crosses with other broomcorns were made in the hopes of resolving the discrepancy. Furthermore, Hegari was found to have a novel QTL that reduced height on chromosome 7. For the map-based cloning of Dw1, a cross of Hegari and 80M was made. Two generations of HIFs were used to narrow the region to ~40kb.