Transgene flow to hybrid rice and its male-sterile lines.

Gene flow from genetically modified (GM) crops to the same species or wild relatives is a major concern in risk assessment. Transgenic rice with insect and/or disease resistance, herbicide, salt and/or drought tolerance and improved quality has been successfully developed. However, data on rice gene flow from environmental risk assessment studies are currently insufficient for the large-scale commercialization of GM rice. We have provided data on the gene flow frequency at 17 distances between a GM japonica line containing the bar gene as a pollen donor and two indica hybrid rice varieties and four male-sterile (ms) lines. The GM line was planted in a 640 m2 in an isolated experimental plot (2.4 ha), which simulates actual conditions of rice production with pollen competition. Results showed that: (1) under parallel plantation at the 0-m zone, the transgene flow frequency to the ms lines ranged from 3.145 to 36.116% and was significantly higher than that to hybrid rice cultivars (0.037-0.045%). (2) Gene flow frequency decreased as the distance increased, with a sharp cutoff point at about 1-2 m; (3) The maximum distance of transgene flow was 30-40 m to rice cultivars and 40-150 m to ms lines. We believe that these data will be useful for the risk assessment and management of transgenic rice lines, especially in Asia where 90% of world's rice is produced and hybrid rice varieties are extensively used.