Genetic engineering for resistance to bacteria in transgenic plants by introduction of foreign genes

Bacterial diseases are of high economic importance in many crop plant species including potato, different vegetable species, fruit trees, rice, cotton and grapevine. Conventional breeding efforts in potato has not resulted in the generation of varieties resistant to soft rot and black leg due to the lack of known resistance traits in lines or species which are sexually compatible with potato. Resistance traits known to be present in wild species often cannot be used for classical breeding programmes as these are genetically too distant from today's cultivars. Similarly, in other plant species susceptible to bacterial pathogens often no valuable resistance or tolerance traits are known. Furthermore, chemical plant protection is not as evolved as for other pathogens. Actually, the most prominent means of prevention of bacterial infections are phytosanitary practices and highly developed harvesting techniques minimizing wounding as well as storage conditions reducing temperature and humidity. Genetic engineering allows a new approach to an old problem. Foreign proteins or peptides can be expressed in transgenic plants and might introduce new resistance factors or complement the natural mechanisms. An excellent model host-pathogen system of high economic importance is the interaction between Solanum tuberosum and Erwinia carotovora. This bacterial species is the causative agent of soft rot and black leg in potato. Especially in tropical and subtropical climates the pathogen provokes severe damage and losses of harvest both in the field and during storage. Compared to other types of pathogens, efforts in genetic engineering allocated to the development of resistance to phytopathogenic bacteria in transgenic plants is quite small. In general, this work has focused mostly on potato or tobacco. This mini-review will summarize the different research approaches published so far.