DETECTING GENE FLOW FROM ALS-RESISTANT HYBRID AND INBRED RICE TO WEEDY RICE USING SINGLE PLANT POLLEN DONORS

Gene flow from herbicide-resistant rice (Oryza sativa L.) cultivars can affect the biodiversity of Oryza spp. and can result in the lack of opportunity to control weedy rice through selective herbicides. The aim of the present study was to quantify the outcrossing rate from the herbicide-resistant red rice and rice cultivars carrying three different ALS (acetolactate synthase) alleles using a single plant pollen donor approach. A field experiment was performed using the encircle population combination technique. The main plots comprised the pollen-receptor IRGA 417 cultivar or a susceptible biotype of weedy rice, and the subplots comprised the pollen-donor inbred cultivars IRGA 422 CL and PUITA INTA CL, the hybrid SATOR CL or a resistant biotype of weedy rice. Among the pollen-donors, the outcrossing rate for pollen receptor susceptible weedy rice and the IRGA 417 cultivar was 0.0344% and 0.0142%, respectively. Rice cultivars carrying the ALS gene mutations Ala(122)Thr, Ser(653)Asn and Gly(654)Asn showed a similar outcrossing rate of 0.0243%. The outcrossing rate decreased over a distance of up to 3.5 m from the pollen-donor and was not affected by the wind cardinal direction. The risk of gene flow of herbicide resistance from rice to weedy rice should be reduced through the development of new strategies to contain and mitigate gene flow and of the elimination of weedy rice escapees.