SUMMARY

The development of plant transformation and gene cloning techniques has opened new avenues for aug-menting disease and insect resistance in crops. The con-cept of ‘Genetically Acquired Resistance ’ now encom-passes a variety of strategies based on the transgenic ex-pression in plant of genes from many different origins. Some of the most potentially useful transgenes capable of enhancing resistance to attack by microbes, viruses and insects have been obtained from bacteria and fungi, which are regarded as rich sources of desirable traits for plant genetic improvement. The main research direc-tions have included: (i) the enhancement of the plant anti-microbial and insecticidal arsenal by the constitu-tive or inducible synthesis of various pathogen inhibit-ing compounds; (ii) the alteration of the plant response to pathogens by the appropriate induction of the local or systemic defence mechanisms, or by the interference with plant-pathogen signalling and (iii) the inactivation of pathogen toxins or the improvement of plant resis-tance to them. Although transgenic plants that are in-sect-resistant or bear other useful traits obtained from microbes, such as herbicide-resistance or enhanced food quality, are being commercially marketed, geneti-cally-engineered crops exhibiting resistance to fungal or bacterial diseases have yet to reach the marketplace. The main focus of this paper addresses the application of bacterial or fungal genes to improve plant resistance to insect, fungi, bacteria and viruses, and the usefulness of these microbial genomes in the development of new transgenic technologies. In addition, perspectives deal-ing with environmental concerns and important biosafety questions resulting from these technologies are briefly discussed