Influence of a selectable marker gene hpt on agronomic performance in transgenic rice

This study was performed to determine whether agronomic traits in transgenic rice (Oryza sativa L.) plants are affected by the expression of a selectable marker gene, hpt. The hpt gene was transferred to embryogenic calli derived from mature rice embryos by Agrobacterium-mediated transformation. These transgenic lines represented a range of copy number and their gene expression at mRNA level was approximately proportional to the transgene copy number up to three copies. The genetic analysis showed that the transgenes generally segregated in a Mendelian inheritance pattern assuming co-integration (3:1; 15:1) in the T₁ generation. In transgenic rice plants, most of agronomic traits were similar to those of nontransgenic plants, except that fertility was different from that of nontransgenic plants. We conclude that differences of agronomic traits of transgenic lines between their parents could be overcome by shortening in vitro culture duration or by backcrossing transgenic lines with their parents and selecting for the desirable genotype.