Submitted to: Proceedings of Southern Weed Science Society
Publication Type: Abstract Only
Publication Acceptance Date: 1/30/2012
Publication Date: 1/30/2012
Citation: Singh, V., Burgos, N.R., Tseng, T.M., Black, H.L., Estorninos, L., Salas, R.A., Alcober, E.A., Botha, G.M., Batoy, M.B., Gealy, D.R. 2012. Differentiation of weedy traits in ALS-resistant red rice. Proceedings of Southern Weed Science Society. 65:233. Interpretive Summary:
Technical Abstract: Red rice is a weedy form of cultivated rice (Oryza sativa) that competes aggressively with rice in the southern U.S., reduces yields and contaminates rice grains. The introduction of ClearfieldTM rice, a nontransgenic, herbicide-resistant rice cultivar a decade ago has led to increased use of imazethapyr in rice fields to control red rice. However, prolonged use of such ALS inhibitor herbicides has led to the appearance of ALS-resistant red rice in recent years, primarily due to gene flow from ALS-resistant rice cultivars. A study was conducted to characterize the variation in weedy traits among ALS-resistant red rice accessions that had been collected from 11 counties in Arkansas and compare with 3 Clearfield rice cultivars. Thirty-nine percent of the plants were found to be resistant to imazethapyr, and 96% of them were highly resistant. Nearly 80% of the plants exhibit less than a 75 degree stem angle relative to the ground, which showed their potential for aggressive ground cover and competitive shading of other plants. Plant heights of 47% of red rice plants ranged from 130 to 160 cm, which were significantly taller than Clearfield cultivars. In more than 50% of the red rice plants, flowering dates were delayed as compared to Clearfield cultivars. The onset of flowering among all the accessions ranged from 74 to 134 days after planting, indicating that there is a significant degree of flowering synchronization between red rice populations and rice cultivars. Based upon their resistance to imazethapyr, the herbicide-resistant weedy plants observed in this study were apparently outcrosses between red rice and the Clearfield crop. The acquired herbicide resistance trait and potentially other weedy traits in these red rice populations may result in longer persistence in rice fields which will need to be investigated further.