Novel approaches to improving disease resistance in plants

Abstract

Improved disease and pest resistance in plants is one of the more lucrative possibilities for utilization of recombinant DNA technology. This optimism results from recent increases in our knowledge of how naturally occurring disease resistance functions and to the fact that modulation of resistance expression is often controlled by single dominant alleles in plants. Historically these disease resistance genes could only be transferred between plants that can be intercrossed. Recently, however, technologies have been developed which permit gene transfer between taxonomically diverse plants by (i) protoplast fusion and selection of somatic recombinants or (ii) introduction of specific DNA sequence into plants via Ti plasmid vectors. Disease resistance genes have not yet been isolated to permit full utilization of these technologies, but several rationales are being pursued in attempts to molecularly clone them. These include the use of transposable elements to tag resistance gene sequences, the screening of c-DNA libraries from inoculated plants and the use of specific pathogen metabolites called elicitors as probes to detect the protein products of plant disease resistance genes.