Chemical stimulation of sexual reproduction in Phytophthora and Pythium

The genera of Phytophthora and Pythium are two of the very destructive groups of plant pathogens in the world (Plaats-Niterink, 1981; Erwin and Ribeiro, 1996). They attack mainly mature plants and young seedlings, respectively, of forest, fruit, vegetable, flower, and ornamental species. These two groups of fungi are classified in the family Pythiaceae of the Oomycetes, which is excluded from the traditional “true fungi” of the kingdom Myceteae and included along with brown algae in the kingdom chromista according to the newer classification (Erwin and Ribeiro, 1996). One of the main reasons for such separation is that the major part of their life history is diploid whereas the other fungi are haploid.