Agrobacterium-mediated transformation of Java']Javanica rice

Difficulties frequently encountered using direct DNA transfer methods for transformation of Javanica varieties of rice (Oryza sativa L.) have limited the application of biotechnology to these varieties. We now report Agrobacterium-mediated transformation of Javanica cultivars Gulfmont and Jefferson that are, respectively, widely used or about to enter commercial cultivation in the southern USA. Vigorous, phenotypically normal, fertile plants expressing both the selectable marker and the gene of interest were obtained. Southern analysis showed that only one or two copies of the T-DNA insert were present. Sequence analysis of right border fragments of one line confirmed that insertion was into a coding region of rice nuclear DNA. This analysis also revealed the presence of relatively short regions of permuted T-DNA border sequences, similar to those found after Agrobacterium-mediated transformation of dicots. Progeny analysis of lines bearing two copies showed co-segregation, indicating that they were located relatively closely on the same chromosome. The introduced genes were transmitted to the R(1) and R(2) generations in a Mendelian fashion: confirming the suitability of this approach for biotechnological improvement of elite rice cultivars.