Root rot disease of legumes caused by Aphanomyces euteiches.

UNLABELLED: The Oomycete genus Aphanomyces houses plant and animal pathogens found in both terrestrial and aquatic habitats. Aphanomyces euteiches Drechs. causes seedling damping off and root rot diseases on many legumes. It is the most devastating pea (Pisum sativum) disease in several countries, causing up to 80% losses each year. This strictly soil-borne pathogen may survive many years in soil and no efficient chemical control is currently available. The only way to control the disease is to avoid cultivating legumes in infested fields for up to 10 years. Although huge research effort has been devoted to the Oomycete genus Phytophthora during the last decade, A. euteiches has received little attention and mechanisms by which it infects its hosts are still unclear. A. euteiches is nevertheless an interesting parasite to study plant-oomycete interactions as it is pathogenic on the model legume Medicago truncatula. This review summarizes knowledge about the main characteristics of A. euteiches and presents research currently developed to find new strategies to control this pathogen and to gain insight into its pathogenicity. TAXONOMY: Aphanomyces euteiches Drechs belongs to a kingdom of diverse eukaryotic protists named Chromista or Straminipila. It is a member of the class Oomycetes (syn. Peronosporomycetes), which gathers organisms resembling fungi through morphological and physiological traits, but are phylogenically related to diatoms, chromophyte algae and other heterokont protists. The genus Aphanomyces is classified within the order Saprolegniales, family Saprolegniaceae s.l. or Leptolegniaceae. HOST RANGE: Several legumes were found to be hosts for A. euteiches and this pathogen was isolated from field-grown pea, alfalfa, snap bean, vetch, clover, sweet clover and several weed species. DISEASE SYMPTOMS: The disease begins with the yellowing of root tissue. At a later stage, infected roots become brown and the hypocotyl darkens at the soil line. The pathogen infects the cortex of primary and lateral roots and oospores are formed within the root tissues. USEFUL WEBSITES: http://www.indexfungorum.org/Names/Names.asp (links to taxonomy data), http://www.eugrainlegumes.org/; http://www.medicago.org/ (links to the European Union 'Grain Legume' Integrated Project).