Phytophthora infestans enters the genomics era

Phytophthora infestans, cause of late-blight, is the most devastating disease of potato world-wide. Recent years have seen a dramatic intensification in molecular biological studies of P. infestans, including the development of novel tools for transformation and gene silencing and the resources for genetical, transcriptional and physical mapping of the genome. This review will focus on the increasing efforts to use these resources to discover the genetic bases of pathogenicity, avirulence and host-specificity. Taxonomy: Phytophthora infestans (Mont.) de Bary-Kingdom Chromista, Phylum Oomycota, Order Peronosporales, Family Peronosporaceae, Genus Phytophthora, of which it is the type species. Host range: Infects a wide range of solanaceous species. Economically important hosts are potato, tomato, eggplant and some other South American hosts (tree tomato and pear melon) on which it causes late blight. Disease symptoms: Infected foliage is initially yellow, becomes water soaked and eventually blackens. Leaf symptoms comprise purple-black or brown-black lesions at the leaf tip, later spreading across the leaf to the stem. Whitish masses of sporangia develop on the underside of the leaf. Tubers become infected later in the season and, in the early stages, consist of slightly brown or purple blotches on the skin. In damp soils the tuber decays rapidly before harvest. Tuber infection is quickly followed by secondary fungal or bacterial infection known as 'wet rot'. Useful web sites: http://www.ncgr.org/pgc/; http://www.oardc.ohio-state.edu/phytophthora/.