Advances in gene transfer technologies have enabled the production of both monocot and dicot transgenic plants. With the biolistic method, genes can be transferred in recalcitrant crop plants and forest trees, independent of their genotype. Inexpensive methods for both stable and transient gene transfers - ultrasonication, direct DNA insertion during imbibition using somatic embryos, and silicon carbide fibres - have been developed. The frequency of Agrobacterium-mediated transformation rates of cloned genes can be enhanced in plant cells. The analysis of molecular markers (RFLPs, RAPDs, DNA fingerprints) can accomplish the characterization, gene mapping and identification and certification and patent protection of cultivars. With PCR, selective amplification of a specific DNA segment from a small amount of an organism’s total DNA can be used toidentify transgenic cultivars. The expression of a target gene can be inhibited with antisense RNA. So far, a limited number of genes have been identified and cloned with genetic engineering. With specific gene transfers, many goals such as biological control of insect pests and fungi, male sterility, virus resistance, improving seed protein, and production of transgenic plants as “bioreactors” can be accomplished. T-DNA mutagenesis may lead to learning more about the genetic control of plant development and morphogenesis, and isolation of useful mutants. Before genetic engineering becomes a reliable tool of plant breeding, more attention is needed to explore: (a) new plant genetic resources in order toidentify and clone new genes, (b) fate of selective and scorable marker genes, and (c) field evaluation of transgenes in transgenic plants
