Risk assessment of the transfer of imazethapyr herbicide tolerance from Clearfield rice to red rice (Oryza sativa)
Hybridization between Clearfield rice and weedy red rice would have a direct impact on management and long-term strategies of imazethapyr technology for rice weed control. The objective of this research was to determine rates and agronomic consequences for outcrossing between Clearfield rice and red rice. Red rice populations showed extensive variation for plant height, panicle length, tillers/plant, seeds/plant, seed set and grain weight. Outcrossing was detected from all Clearfield rice cultivars (‘CL121’, ‘CL141’, ‘CL161’, and ‘CLXL8’) to red rice and was confirmed by phenotypic and DNA marker analyses. An overall outcrossing frequency of 0.17% was observed in 2002 red rice samples with a range from 0% to 0.46%. Tolerance of 2002 red rice samples to imazethapyr corresponded to levels of acetohydroxyacid synthase (AHAS) activity. A majority (94%) of the progeny from the 2002 samples segregated 3 resistant:1 susceptible for tolerance to imazethapyr, indicating that a single dominant gene from Clearfield rice was associated with tolerance in the hybrid material. The remaining samples did not segregate for tolerance, suggesting that spontaneous mutations for tolerance were present in this material before or after crossing with Clearfield rice. A four-fold increase in outcrossing frequency of 0.68% was observed in 2003 red rice samples with the highest outcrossing frequency for a single location at 3.2%. Results from this study indicate that outcrossing between Clearfield and red rice will occur rapidly at rates that warrant early-season field scouting and a crop rotation scheme to prolong usefulness of the Clearfield technology.
KeywordsClearfield rice Imazethapyr Outcrossing Risk assessment Red rice
Unable to display preview. Download preview PDF.
- Anonymous (2005) Clearfield hybrids (http://www.ricetec.com/hybridProducts.asp?hybrid=CLEARFIELD%20XL8)
- Constantin MJ (1960) Characteristics of red rice in Louisiana. Ph.D. dissertation. Louisiana State Univ., Baton Rouge, LA, p. 94Google Scholar
- Croughan TP (1994) Application of tissue culture techniques to the development of herbicide-resistant rice. Louis Agric 37:25–26Google Scholar
- Dilday RH, Nastasi P, Smith RJ, Khodayari K (1990) Herbicide-tolerant germplasm in rice. In: Janick J, Simon JE (ital: eds.), Advances in new crops. Timber Press, Portland, pp. 146–150Google Scholar
- Gianessi LP, Silvers CS, Sankula S, Carpenter JE (2002) An analysis of 40 case studies in US agriculture. National Center for Food and Agricultural Policy (http://www.icsu.org/1icsuinscience/GMO/PDF/NCFAP2002%20Main.pdf)
- Lago AA (1982) Characterization of red rice (Oryza sativa L.) phenotypes in Mississippi. Ph.D. dissertation. Mississippi State, MS: Mississippi State Univeristy, p. 143Google Scholar
- Noldin JA, Chandler JM, McCauley GN (1999) Red rice (Oryza sativa) Biology. I. Characterization of red rice ecotypes. Weed Technol 13:12–18Google Scholar
- Oard JH, Dronavall S (1992) Rapid isolation of rice and maize DNA for analysis by random-primer PCR. Plant Mol Biology Rep10:236–241Google Scholar
- Wenefrida I, Croughan TP, Utomo HS, Meche MM, Wang XH, Herrington JA (2004) Herbicide resistance profiles in Clearfield rice. Proceedings, 30 Rice Technical Working Group, New Orleans, pp. 178–179Google Scholar