Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 10/10/2005
Publication Date: 2/10/2005
Citation: Gealy, D.R., Estorninos, L.E., Wilson, C.E. 2005. Evidence and implications of outcrossing between red rice (Oryza sativa L.) and rice in commercial fields [abstract]. Weed Science Society of America Meeting Abstracts. 45:49. Interpretive Summary:
Technical Abstract: IMI resistant rice has generated new interest in gene flow to red rice. Of >400 red rice entries from the South, nearly all produced red, medium grain (MG) seeds, but their heights, awn lengths, and heading dates have varied greatly. Some of these (0.7%) were as short as semidwarf cultivars, suggesting that they could have originated from crosses with these cultivars. Others (<2.5%) were the height of common cultivars and produced short awns, indicating that they could be from crosses of awned red rice and rice. We used phenotypic traits and SSR markers to evaluate red rice gene flow events on three farms in Arkansas. Long grain (LG) red rice seeds found in 2001 in a Cypress seed production field at Stuttgart were suspected crosses of red rice and rice. Second generation plants grown from original seeds were slightly taller than Cypress, and produced smooth leaves, LG or MG awnless seeds that were red or white in color, and purple lower stems. These plants were likely derived from a cross of LG rice and awned red rice that had selfed for at least two generations since crossing. A short red rice type from Prairie Co., AR in 2003 had uniform erect plants with awned seeds, rough leaves, and heights similar to semidwarf rice. These plants likely were crosses of awned red rice and rice. SSR detected few heterozygous alleles, suggesting that the plants had selfed several times since crossing. A tall red rice type was segregating for leaf texture, and stem and awn color. These plants were erect, much taller than rice cultivars, and produced awned seeds. SSR detected many heterozygous alleles, suggesting that the plants had selfed few times. Awned red rice and LG rice were the likely parents. Bushy, rough leaved, IMI resistant plants with delayed heading were obtained in 2004 from a farm in Jackson Co. with high red rice populations and recent red rice control failures in IMI rice. Seeds were awnless MG. Phenotypic and SSR data indicate that these were first generation crosses of IMI rice and awnless red rice. Non bushy, rough leaved, early heading, IMI resistant plants that produced pink awned, MG seeds probably were first generation crosses of IMI rice and awned red rice. These studies show the value of using visual observation and SSR analysis to mitigate the consequences of red rice gene flow.