alni (Table 2). They also survived click here at pH 7 and 9 over the 14-day period but at low rates. Like P. alni, the differences in response to different pH became less significant with increasing exposure time, and the number of colonies increased after 5 days at pH 5–9. Mycelia were observed in the treatment containers. However, they failed to form colonies at pH 11 after a 5-day exposure, indicating that they are sensitive to high pH. Colony formation by P. ramorum zoospores was relatively poor compared with P. alni and P. kernoviae. Normally, plating 1 mL 100 fresh zoospores of the suspension at pH 7 resulted

in fewer than 20 colonies. However, their relative survival rates at immediate exposure were much higher because of rapid colony formation. At pH 5–9, relative survival rates declined much slower compared with P. alni and P. kernoviae but varied significantly over time (Table 2). Like P. alni, zoospores of P. ramorum also were tolerant of basic pH, surviving at pH 9 and 11 for at least 14 days. At pH 9, the survival this website was about 4 and 6 times higher than that of P. kernoviae and P. alni, respectively (Table 2). However, the best survival was at moderately acidic conditions (pH 5), although survival was very poor, not beyond 1 day, at pH 3. Zoospore motility, encystment and

germination among P. alni, P. kernoviae, and P. ramorum responded differently to pH. Most zoospores of P. alni swam for more than 2 h at all pHs except for pH 3. Many continued swimming over 24 h, although at pH 11 there were relatively fewer. The relative count for swimming zoospores (Fig. 1) represented only those present transiently in fixed microscopic fields during the

observation, which was much lower than the actual number contained in the water column. The number of cysts was close to the actual number of zoospores present. The cyst count at pH 3 was higher than at pH 5–11, suggesting that less lysis occurred at pH 3 than at other pHs. Early cyst germination was observed for P. alni, starting as soon as 2 h after exposure at pH 5–11, while most of cysts lysed after 24 h exposure. Hypha growth and secondary sporangium production was observed after Selleck Erlotinib 5 days exposure at pH 5–11 (Fig. 2). However, the new hyphae at pH 11 appeared abnormal, forming beaded structures that were still able to grow on plates as indicated in Table 2. No germinants were observed at pH 3 (Fig. 2), consistent with their colonization on growth media (Table 2). Zoospores of P. kernoviae were less motile compared with P. alni at pH 3–11. They encysted immediately after exposure to pH 3 (Fig. 2). A few swam at pH 7–11 briefly, but did not last overnight except at pH 7 where only a very few swimmers were occasionally observed in a field. More cysts lysed compared with P. alni, which occurred in all the treatments with the most at pH 5–9. In addition, germination of the cysts was later than that of P. alni, which occurred after 24 h.