Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract only
Publication Acceptance Date: 2/4/2013
Publication Date: 2/4/2013
Citation: Gealy, D.R., Liu, Y., Vigueira, C., Jia, Y., Caicedo, A., Burgos, N.R., Olsen, K. 2013. Evolutionary insights into the origins of weediness in U.S. red rice. Weed Science Society of America Meeting Abstracts. 53:96. Interpretive Summary:
Technical Abstract: Weedy red rice is a widespread, economically challenging problem in Southern U.S. rice fields. The two major U.S. red rice types, strawhull and blackhull, are thought to have arisen independently from Asian rice populations in the distant past. Red rice is a weedy relative of rice, a genomic model species, and thus can be exploited to better understand the genetic and evolutionary mechanisms by which weediness has evolved in this species. Increased knowledge of the contemporary and longer-term evolution of this weed and its important weedy traits may help us improve its management. In 2011, red rice populations were obtained from farm surveys of Arkansas rice fields with a history of imidazolinone-resistant (IR) rice production systems (Clearfield®). Numerous instances of IR weedy rice populations were detected by sequential spraying of the imidazolinone herbicide, imazethapyr, suggesting recent gene flow between IR cultivated rice and red rice. Almost all sampled fields with a history of Clearfield® rice produced some IR weedy rice. These populations also ranged greatly in their plant size and shape, leaf dimensions, flowering date, color of plants, seeds, and awns, and seed shattering and germination. Many of the populations appeared to be segregating for one or more of the above traits, further suggesting that gene flow had occurred recently. In a different study, we used Asian strawhull indica rice, which is a putative cultivated progenitor of U.S. red rice, and made a cross (using cv Dee Geo Woo Gen) with two different red rice lines that had been obtained from southern U.S. rice farms. These were a late-flowering blackhull line from Mississippi (PI 653419; MS-1996-9), and an early flowering strawhull line from Arkansas (PI 653435; AR-2001-1135). Recombinant inbred mapping populations up to F6 were generated from these crosses in a greenhouse, and evaluated in the field in 2012. Phenotypic measurements of weedy traits and other important productivity traits from these populations were recorded. These included plant height, flowering date, seed shattering, and resistance to blast disease. QTL mapping using genotyping by sequencing, whole genome sequencing, and other analyses of key genomic regions will allow us to distinguish the DNA sequence variation in U.S. red rice from indica rice and how this is associated with weedy traits. Ultimately, these findings may provide insights into management strategies for red rice.