Identification, Laboratory, Greenhouse, and Field Handling of Aphanomyces euteiches on Pea (Pisum sativum)

Abstract

Aphanomyces euteiches is a destructive soilborne plant pathogen, causing economic losses when adequate to excess soil moisture is available. This oomycete organism survives in the soil for decades and infects and degrades roots of plants from 11 families. Symptoms of Aphanomyces root rot are similar across the major economic hosts alfalfa (Medicago sativa subsp. sativa L.), lentil (Lens culinaris Medik.), and pea (Pisum sativum L.). Initial symptoms include the appearance of grey, water-soaked root tissue. Roots develop a golden-brown color, and lateral roots begin to disintegrate as the disease worsens. In the most severe cases, the entire root system is destroyed and aboveground chlorosis and necrosis are observed. A. euteiches isolation can be successful from both infested soil and infected plant tissue. Macroscopically, colony growth is generally nondescript and white in color. A. euteiches is self-fertile (homothallic) and produces sexual oospores in culture in addition to asexual zoosporangia and zoospores (primary and secondary) on hyphae lacking regular septa (coenocytic). Numerous molecular techniques have been developed for successful A. euteiches detection. A. euteiches can be stored in frozen soil or on agar slants, but viability should be evaluated regularly. Oospores or zoospores have been utilized for inoculation under greenhouse and field conditions; although the generation of a field site using soil infestation techniques can take several seasons of productions of a susceptible crop to be utilized to effectively screen for Aphanomyces root rot.