Phytophthora cinnamomi has recently been found in highly diverse and fragile alpine and sub-alpine environments previously considered P. cinnamomi and disease free due to low temperatures. In the laboratory, we investigated the ability of P. cinnamomi isolates to adapt to cold and cause disease under conditions comparable to alpine and sub-alpine environments. Initially, the ability of P. cinnamomi isolates to produce sporangia at 10 °C (2 °C lower than previously reported in the literature) was demonstrated in vitro. The lowest temperature limit for host infection was determined (i.e., 8 °C) and the phenotypic plasticity of isolates was then explored in planta in two successive phenotypic plasticity experiments comparing cold 9, 7.5 °C, and ambient temperature 25 (±5 °C). In the phenotypic plasticity experiment-1, three of the five isolates recovered from plants grown at 9 °C produced sporangia and released zoospores (infective propagules) at 7.5 °C, even lower than determined initially, i.e., 10 °C. No changes were observed in the same set of isolates recovered from plants grown at ambient temperature in the glasshouse as a control, which shows that P. cinnamomi can exhibit phenotypic plasticity and responds rapidly to selection pressure and adapts to new environments. Although P. cinnamomi isolates could produce infective propagules at 7.5 °C in vitro, they could not be recovered from inoculated plants grown at 7.5 °C after 3 months in phenotypic plasticity experiment-2. More work is, therefore, needed to establish disease development by P. cinnamomi at 7.5 °C and below.

中文翻译：

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疫霉菌表现出表型可塑性，响应寒冷

疫霉菌最近在高度多样化和脆弱的高山和亚高山环境中被发现，以前被认为是肉桂疫菌，并且由于低温而无病。在实验室中，我们研究了P. cinnamomi菌株在与高山和亚高山环境相当的条件下适应寒冷并引起疾病的能力。最初，在体外证明了肉桂假单胞菌分离物在10°C（比以前文献报道的温度低2°C）下产生孢子囊的能力。确定宿主感染的最低温度极限（即8°C），然后在植物中探索分离株的表型可塑性在两个连续的表型可塑性实验中，比较了冷9、7.5°C和环境温度25（±5°C）。在表型可塑性实验-1中，从在9°C下生长的植物中回收的5个分离株中的3个在7.5°C下产生了孢子囊并释放了游动孢子（感染繁殖体），甚至低于最初确定的10°C。在温室中作为对照的从在室温下生长的植物中回收的同一组分离株中未观察到变化，这表明肉桂疫霉可表现出表型可塑性，并能对选择压力快速响应并适应新环境。虽然肉桂在表型可塑性实验2中，经过3个月的分离后，这些分离株可以在7.5°C的体外产生感染性繁殖体，无法从在7.5°C生长的接种植物中回收。因此，需要更多的工作来确定肉桂青枯病在7.5°C及以下温度下的疾病发展。