Field Evaluation of Imidazolinone-Tolerant Clearfield Rice (Oryza sativa L.) at Nine Louisiana Locations

Abstract

Clearfi eld rice (Oryza sativa L.) developed at the Rice Research Station, Louisiana State University Agricultural Center, offers a fi rst-ever non– genetically modifi ed alternative to selectively eliminate notorious red rice (O. sativa L.) in a commercial rice fi eld. The objective of this study was to compare Clearfi eld rice with the leading conventional cultivars for grain yield (main and ratoon crops), milling yield, seedling vigor, maturity, plant height, and disease reactions by analyzing the Louisiana rice commercial advanced yield test that was conducted at nine locations during 2003 to 2004. Our results indicate that the grain yields of Clearfi eld cultivars were signifi cantly lower than the leading conventional long-grain cultivars such as Cocodrie, Cheniere, Wells, and Francis. The average main crop grain yield of Clearfi eld rice was about 11.1 and 5.5% lower than that of conventional cultivars in 2003 and 2004, respectively. However, Clearfi eld cultivars exhibited higher head rice yield than the leading conventional ones. No signifi cant difference on ratoon yield was found between Clearfi eld rice and conventional rice. Clearfi eld rice also had similar maturity and plant height as conventional cultivars but better seedling vigor. Compared with conventional rice, Clearfi eld cultivars appeared to be more susceptible to both sheath blight and blast. The yield gap between Clearfi eld and conventional cultivars has been signifi cantly reduced with the release of newer Clearfi eld cultivars CL161 and CL131.