|WEERS, BROCK - Texas A&M University|
|THAKRAN, MANISH - Texas A&M University|
|EMANDACK, YVES - US Department Of Agriculture (USDA)|
|ROONEY, WILLIAM - Texas A&M University|
|MULLET, JOHN - Texas A&M University|
Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/14/2015
Publication Date: 12/30/2015
Citation: Hayes, C.M., Weers, B., Thakran, M., Burow, G.B., Burke, J.J., Xin, Z., Emandack, Y., Rooney, W., Mullet, J. 2015. Discovery of a dhurrin QTL in sorghum bicolor: colocalization of dhurrin biosynthesis and a novel stay-green QTL. Crop Science. 56:104-112.
Interpretive Summary: Post-flowering drought tolerance (stay-green) is an important trait in grain sorghum known to increase grain yields under drought conditions. Stay-green is a complex trait with multiple genes and is still not fully understood. Recently, high leaf dhurrin content has been found to associate with stay-green sorghums. This research identifies a region of the sorghum genome that associates with leaf dhurrin content. Additionally, the leaf dhurrin region is found to associate with stay-green. This research provides genetic evidence for the association between leaf dhurrin and stay-green, and also provides potential mechanisms for how dhurrin produces a stay-green response in grain sorghum.
Technical Abstract: Dhurrin [(S)-p-hydroxymandelonitrile-ß-D-glucopyranoside] is a cyanogenic glucoside produced by (Sorghum bicolor L. Moench) and is generally considered a natural defense compound capable of producing the toxin hydrogen cyanide (HCN) to deter animal herbivory. Recently, high levels of leaf dhurrin have been found in grain sorghum genotypes that also exhibit stay-green during post-anthesis water deficit. Post-flowering drought tolerance (stay-green) in sorghum is an economically important trait in sorghum production regions where drought stress post-anthesis is common. Stay-green is associated with reduced lodging, charcoal rot resistance, increased grain fill, and increased grain yield. The genetic control of stay-green is complex, with multiple QTL being identified in affecting expression of stay-grain. Here we report the discovery of a dhurrin QTL (Dhu1) on SBI01 using a RIL mapping population derived from BTx642/Tx7000. The dhurrin QTL is highly heritable and explains a large percentage of the variation in leaf dhurrin in the population. The QTL is aligned with genes involved in dhurrin biosynthesis (CYP79A1, CYP71E1, UGT85B1). Protein sequence variants found in CYP71E1 and UGT85B1 could be the cause of the observed differences in leaf dhurrin levels in BTx642, Tx7000, and other sorghum lines that vary in leaf dhurrin content. The dhurrin QTL is aligned with a previously un-identified stay-green QTL (Stg5) on SBI01, consistent with prior studies showing an association between high leaf dhurrin levels, this region of SBI01, and expression of the stay-green trait.