ABSTRACT

Plants and pathogens interact in an endless race to evade and cause disease. This interplay dominates many important issues in plant pathology. From an evolutionary standpoint, the study of plant resistance genes involved in genefor-gene interactions illustrates the plant-pathogen survival race (Bergelson et al., 2001). Leucine-repeatencoding regions in these R-genes are fundamental to recognize pathogenicity determinants in the pathogen, the so-called avirulent (Avr) factors, and are known to evolve at unprecedented rates. These regions depict coevolutionary arm races between plants and pathogens. However, mechanisms of genetic exchange and adaptive evolution coexist with selective sweeps characteristic of the arm races, and are strongly influenced by demographic and ecological factors. This highlights the need to understand patterns of molecular diversity from perspectives centered on population and lineage. This is now possible with the ability to access genetic information at a wide scale in genomic research projects, its analysis with powerful bioinformatic tools, and the use of novel strategies capable of tracking genetic change at the molecular level. These advances involve harnessing the molecular biology of nucleic acids.