MOLECULAR APPROACHES TO MANIPULATION OF DISEASE RESISTANCE GENES

Various molecular approaches are greatly increasing our ability to cha racterize and manipulate disease resistance genes in plants. Molecular markers are allowing the dissection of monogenic and quantitative res istance. The utility of marker-aided selection in breeding for disease resistance is being evaluated. Markers will soon enhance the effectiv e deployment of resistance genes to provide more stable resistance. Se veral resistance genes have been characterized at the molecular level. This has led to the identification of several mechanistic classes and provides the opportunity for transgenic disease control strategies. A s the mechanisms of determining specificity and generating variation a t resistance loci are understood in greater detail, they will be manip ulated to generate new specificities, probably using microbial selecti on systems. Disease resistance strategies utilizing classical resistan ce genes will complement the use of novel transgenes.