U.S. flag

An official website of the United States government

Dot gov

Official websites use .gov
A .gov website belongs to an official government organization in the United States.


Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.


Main content area

Bioassay Conditions for Infection of Pinus radiata Seedlings with Phytophthora pinifolia Zoospores

Timothy L. Widmer, Stephen C. Dodge
Plant disease 2015 v.99 no.9 pp. 1204-1209
Phytophthora, Pinus radiata, agar, bioassays, carrots, dew, disease resistance, fungal diseases of plants, host range, hosts, infection, mycelium, plant pathogenic fungi, screening, seedlings, temperature, trees, zoospores, California, Chile
Phytophthora pinifolia is known to cause a devastating disease on Monterey pines in Chile. Although this pathogen is not yet present in the U.S., there is reason for concern. The main source of Monterey pine genetic material is found in California and there is potential for other important tree species to be hosts. This study described here was conducted to develop a method to produce zoospores and determine optimal conditions for infection to be used in future host range studies. Abundant zoospores were produced when agar plugs containing P. pinifolia mycelia were ground into suspension prior to transfer in a solution of carrot broth. These zoospores then were used to inoculate Monterey pine seedlings under various conditions. Consistent infection occurred when seedlings were wounded by trimming needles prior to inoculation and exposure of inoculated seedling to constant dew for 5 days. Dew chamber temperature (15, 20, or 25°C) did not affect the infection rate. Information obtained from this study will be useful in screening other hosts for susceptibility to P. pinifolia infection.