Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 1/27/2005
Publication Date: 1/27/2005
Citation: Gealy, D.R., Wilson, C.E., Estorninos, L.E., Black, H.L., Agrama, H. 2005. Identification of rice-red rice crosses in imi- and non-resistant rice fields of Arkansas [abstract]. Proceedings of Southern Weed Science Society. 58:211. Interpretive Summary:
Technical Abstract: Interest in the dynamics of outcrossing between herbicide resistant rice and red rice has increased since the introduction of IMI herbicide resistant rice cultivars because of their almost synchronous flowering. Numerous suspected red rice crosses were collected from five neighboring counties in eastern Arkansas. Allele profiles developed from 17 simple sequence repeat (SSR) markers showed that most suspected crosses share alleles that are normally specific to either rice or red rice. Ten selected SSR markers from the original group of 17 were used in all subsequent analyses. Multidimensional scaling (MDS) analysis and clustering produced similar patterns. SSR data were used to infer population structure and assign individuals to seven populations. Genetic similarity and relationships among the genotypes were examined using the Euclidean genetic distance matrix. Plants collected from Jackson County were obtained from fields that had been planted to IMI rice in the previous year or in both the current and previous years and had survived at least two applications of imidazolinone herbicide. They were bushy, rough leaved, and headed much later than the IMI resistant rice. DNA analysis showed that these plants had heterozygous alleles consistent with CL 161 (IMI rice) and a common strawhull red rice in almost all of the 10 SSR markers and grouped in between strawhull red rice and cultivated rice standards in MDS plots and dendogram plots, suggesting that the plants were F1 hybrids of IMI rice and a strawhull red rice. In Prairie County, short-statured suspected crosses had rough, green leaves, and green basal leaf sheaths (stems), and produced seeds with awns, blackhull, and red pericarp. They produced mostly homozygous alleles among red rice or cultivated rice standards. The tall-statured suspected cross from the same farm had some plants with smooth, light purple leaves and purple basal leaf sheaths, and produced awned, blackhulled or strawhulled, and red or white seeds. They produced several heterozygous alleles or had homozygous alleles consistent with red rice for some markers and CL 161 with other markers. These different phenotypic characteristics and heterozygous alleles suggest that variability was probably greater in the tall- than in the short-statured crosses. Both tall and short types appear to be crosses that have undergone multiple generations of self fertilization because they have a relatively low incidence of heterozygous alleles. Other suspected rice and red rice crosses were collected from Arkansas, Lawrence, and Woodruff Counties. They generally produced homozygous alleles of red rice or cultivated rice standards. Most of them were genetically grouped near the blackhulled and awned red rice standards although some were strawhulled and awnless. These results show the value of phenotypic characterization and SSR analysis to follow the red rice and rice gene flow.