Field evaluation of imidazolinone-tolerant clearfield rice (Oryza sativa L.) at nine Louisiana locations

Clearfield rice (Oryza satva L.) developed at the Rice Research Station, Louisiana State University Agricultural Center, offers a first-ever non- genetically modified alternative to selectively eliminate notorious red rice (O. sativa L.) in a commercial rice field. The objective of this study,, was to compare Clearfield 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 Clearfield cultivars were significantly lower-than the leading conventional long-grain cultivars such as Cocodrie, Cheniere, Wells, and Francis; The average main crop grain yield of Clearfield rice was about 11.1 and 5.5% lower than that of conventional cultivars in 2003 I and 2004, respectively. However, Clearfield cultivars exhibited higher head rice yield than the leading conventional ones. No significant difference on ratoon yield was found between Clearfield rice and conventional rice. Clearfield rice also h ad similar maturity and plant height,as : conventional cultivars but better seedling vigor. Compared with conventional rice, Clearfield cultivars appeared to be more susceptible to both sheath blight and blast. The yield gap between Clearfield and conventional cultivars has been significantly reduced with the release of newer Clearfield cultivars CL161 and CL131.