Efficiencies of Generating Selectable Marker-Free Transgenic Rice with Different Transformation Methods

To study the efficiency of generating selectable marker-free （SMF） transgenic rice, two transformation methods were employed for four rice varieties （Wuxiangjing 9, Longtefu, Xieqingzao and Zhenshan 97）. One method is by using a single twin T-DNA binary vector pYH592 in one Agrobacterium strain, which is composed of two separate T-DNA regions （one carrying an antisense Wx gene and the other carrying a HPTgene）. The other one, named as two-strain/two-vector system, is by using two separate binary vectors in two separate Agrobacterium cultures. The results indicated that the average co-transformation frequencies of the antisense Wx gene and the HPT gene were 10.1% and 45.0%, respectively, for the four rice varieties. And the SMF transgenic plants selected from the offsprings of co-transformants were 55.6% and 60.0% in the two-strain/two-vector and twin T-DNA vector binary systems, respectively.