Tooley Paul W, Browning Marsha, Berner Dana
United States Department of Agriculture-Agricultural Research Service, Foreign Disease-Weed Science Research Unit, Ft. Detrick, MD 21702.
Plant Dis. 2008 Mar;92(3):431-437. doi: 10.1094/PDIS-92-3-0431.
We examined the impact of exposure to high and low temperature extremes on recovery of Phytophthora ramorum both as free chlamydospores and within infected rhododendron tissue over a 7-day period. Chlamydospores held in moistened sand were incubated at 30, 35, 40, 0, -10, and -20°C for up to 7 days. Infected Rhododendron 'Cunningham's White' leaf disks held in sandy loam, loam, or sand at two different soil moisture levels also were subjected to these temperatures for up to 7 days, and to a variable temperature regimen for 12 weeks. Recovery was characterized by growth of P. ramorum on selective agar medium following exposures to temperature treatments. Chlamydospores held in moistened sand showed a high rate of recovery at 30°C, steadily declining recovery at 35°C, and no recovery at 40°C over the 7-day period. Chlamydospores were recovered from 0°C after 7 days, with little or no recovery observed at -10 or -20°C. In infected rhododendron tissue, P. ramorum was recovered at 20 and 30°C after 7 days but, at 35°C, the pathogen showed a decline within 2 days and no recovery by 4 days. A 40°C treatment allowed no recovery of P. ramorum from infected tissue after 2 days. For cold treatments, P. ramorum was recovered from infected leaf disks at 0 and -10°C after 7 days. At -20°C, recovery declined rapidly after 1 to 3 days and no recovery was obtained after 4 days. P. ramorum showed nearly 100% recovery from leaf disks subjected to a 12-week variable temperature treatment based on ambient summer temperatures in Lewisburg, TN. The results suggest that P. ramorum is capable of surviving some highly adverse temperature conditions for at least 7 days both as free chlamydospores in sand and within infected host tissue. Thus, P. ramorum present as free chlamydospores or within tissue of infected plants shipped to the eastern United States has the potential to survive some of the adverse conditions encountered in summer and winter in many eastern states.
我们研究了在7天时间内，暴露于高温和低温极端条件下，樟疫霉作为游离厚垣孢子以及在感染的杜鹃花组织内恢复生长的情况。将保存在湿润沙子中的厚垣孢子分别在30、35、40、0、-10和-20°C下培养长达7天。保存在砂壤土、壤土或沙子中、处于两种不同土壤湿度水平的感染了‘坎宁安白’杜鹃花的叶盘，也在这些温度下处理长达7天，并在12周内接受变温处理。恢复情况通过在温度处理后，樟疫霉在选择性琼脂培养基上的生长来表征。保存在湿润沙子中的厚垣孢子在30°C时恢复率很高，在35°C时恢复率稳步下降，在40°C时7天内没有恢复。7天后，在0°C下可回收厚垣孢子，在-10或-20°C下几乎没有或没有回收。在感染的杜鹃花组织中，7天后在20和30°C下可回收樟疫霉，但在35°C下，病原菌在2天内数量下降，4天后没有恢复。40°C处理2天后，感染组织中未回收樟疫霉。对于冷处理，7天后在0和-10°C下从感染的叶盘中回收了樟疫霉。在-20°C下，1至3天后恢复率迅速下降，4天后未回收。基于田纳西州刘易斯堡夏季环境温度，樟疫霉在接受12周变温处理的叶盘中恢复率接近100%。结果表明，樟疫霉作为沙子中的游离厚垣孢子以及在感染的宿主组织内，能够在一些极端不利的温度条件下存活至少7天。因此，作为游离厚垣孢子或存在于运往美国东部的感染植物组织中的樟疫霉，有可能在许多东部州的夏季和冬季遇到的一些不利条件下存活下来。
