Systematic and Host Range Studies of Woronina Pythii (Plasmodiophoromycetes) and Host, Pythium Species, from Axenic Culture

ABSTRACT

Woronina pythii Goldie-Smith is a holocarpic, endobiotic, obligate parasite of members of the genus Pythium. The influence of various hosts on the morphology of the cystosori and the host range were studied to ascertain the validity of taxonomic criteria used to delimit W. pythii. Sesame seed cultures of test-species were grown axenically in individual Petri dishes for 24 h and inoculated with swimming secondary zoospores of the parasite at 24 h intervals for 72 h. Woronina pythii infected 15 species of Pythium, but not four species of Phytophthora, four of Saprolegnia, 26 of Achlya, one of Aplanes, Aphanomyces, Dictyuchus, and three of Brevilegnia. Cystosoral size and shape in W. pythii are influenced by the host and are of little taxonomic value in distinguishing taxa.

Key Words:

• Woronina
• host range
• systematics
• cystosorus