Oomycetes have many fungus-like characteristics, but lack taxonomic affinity with true fungi. Instead oomycetes are phylogenetically relatives of diatoms and brown algae within the Kingdom Straminipila. Members of the genera Phytophthora and Pythium cause destructive diseases of thousands of plant species including commercially important hosts. Identification to species levels in both genera is important due to their importance as plant pathogens and the acquisition of resistance to fungicides observed in certain species.

PHYTOPHTHORA
- The importance of the genus Phytophthora both to human history and to the origin of the science of plant pathology has been recognized since the 1840's at the time when the unexpected "potato disease" affected crops in Europe and the USA culminating in the famous "Irish Potato Famine."
- Eighty-one species have been described to the present since De Bary in 1876 coined the name Phytophthora ("plant destroyer") and described P. infestans as the type species for the genus. Over the years, Phytophthora has turned out to be the most studied genus of plant pathogens.

PYTHIUM
- The genus Pythium is ecologically and physiologically an exceptional group of straminipiles with world-wide distribution and occupying a high level of niche diversity that cannot be surpassed by any other straminopile or fungi.
- Since the description of P. monospermum by Pringsheim in 1858, more than 150 species have been reported. A wide range of variation in pathogenicity is observed in plant-associated species (High, moderate, low aggressive). Yet, some of the plant pathogenic species are among the most destructive, causing serious economic losses of crops by destroying seed, storage organs, roots, and other plant tissues.

For more information contact:
Dr. Gloria Abad
<gloria_abad@ncsu.edu>