Obligate biotroph parasitism: can we link genomes to lifestyles?

Although the oomycetes and fungi are evolutionarily very distantly related, both taxa evolved biotrophy on plant hosts several times independently, giving rise to rust- and mildew-like phenotypes. Differences in host colonization and adaptation may be reflected in genome size and by gain and loss of genes. In this opinion article we combine classical knowledge with recently sequenced pathogen genomes and present new hypotheses about the convergent evolution that led to these two distinct phenotypes in obligate biotrophs.