01781nas a2200157 4500008004100000022001400041245010300055210006900158260001600227300001600243490000700259520124500266100002401511700002301535856006501558 2015 eng d a0191-291700aBioassay Conditions for Infection of Pinus radiata Seedlings with Phytophthora pinifolia Zoospores0 aBioassay Conditions for Infection of Pinus radiata Seedlings wit cJan-09-2015 a1204 - 12090 v993 a

Phytophthora pinifolia is known to cause a devastating disease on Monterey pine in Chile. Although this pathogen is not yet present in the United States, 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. The study presented 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. Infected plants displayed necrotic crowns and stems, often resulting in wilting of the seedling. Consistent infection occurred when seedlings were wounded by trimming needles prior to inoculation and exposure of inoculated seedlings 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.

1 aWidmer, Timothy, L.1 aDodge, Stephen, C. uhttp://apsjournals.apsnet.org/doi/10.1094/PDIS-12-14-1306-RE