Morphology and Phenology of Putative Outcrosses Between Imazethapyr-Resistant Rice and Red Rice (Oryza sativa L.)

Red rice and rice belong to the same genus and species. Both are selfpollinated plants, but some outcrossing has been documented. Due to outcrossing, there are chances of resistant gene transfer from herbicide-resistant rice to red rice, which may increase the weediness of red rice. In 2000 simultaneous flowering was observed between Clearfield® CL2551 and red rice at the Rice Research and Extension Center, Stuttgart, AR. In 2001 the natural population of red rice in the field was sprayed three times with imazethapyr at 0.07 kg/ha. Seven-hundred twenty plants (F1) survived these applications, and 283 plants (39%) were presumed crosses. These plants had either vegetative or seed characteristics somewhere between red rice and resistant rice. A field experiment was conducted in 2002 to compare the morphological and phenological characteristics of selected presumed crosses from the 283 putative crosses mentioned above at RREC, Stuttgart, AR. Stuttgart strawhull red rice and Clearfield® rice were used as standards. Imazethapyr at 0.07 kg/ha was sprayed at 3, 4, and 5 weeks after planting (WAP). Segregation of morphological and phenological characteristics in F2 plants were observed. Seeds were also classified for the segregation of characteristics, such as presence or absence of hairs, color, and size. A majority of herbicideresistant F2 plants and their seed maintained weedy characteristics from red rice. There was also synchronization in flowering between Clearfield rice, red rice, and the crosses. BREEDING, GENETICS, AND PHYSIOLOGY AAES Research Series ###