Summary The influence of temperature on germination ofQuercus ilexacorns inPhytophthorainfested soils was quantified for the first time. Radicle damage and mortality ofQ. ilexseeds germinating at 17, 20, 23 and 26°C inPhytophthora cinnamomi,P. gonapodyides, P. quercinaandP. psychrophilainfested soils were assessed and related toin vitromycelium growth of the same isolates of the pathogens. The optimum growth temperatures of isolates ofP. cinnamomi,P. gonapodyides,P. quercinaandP. psychrophilawere 20–23, 23–26, 20–23 and 20°C, respectively. At 17 and 20°C, all fourPhytophthoraspecies caused 100% acorn mortality, whereas at 26°C, acorn mortality was 100, 10, 25 and 0% inP. cinnamomi,P. gonapodyides, P. quercinaandP. psychrophilainfested soils, respectively. At 23°C,P. cinnamomiandP. gonapodyidesreduced acorn radicle length more thanP. quercinaandP. psychrophila, whereas at 26°C, onlyP. cinnamomicaused further reduction in radicle length. The higher susceptibility of germinating acorns in comparison to seedlings reported in the literature indicates age‐related susceptibility ofQ. ilextoPhytophthora. The seedling/pathogen growth ratio was inversely related to the reduction in radicle length at different temperatures ( = 0.84, p < 0.0001), suggesting that rapid germination may allow seedlings to escape from infection. Increasing temperatures had different effects on damage to acorns depending on the pathogen present in the soil, indicating thatPhytophthoraspecies × temperature interactions determinedQ. ilexgermination. The effects of temperature on the impacts ofPhytophthoraspecies based on climate change predictions for Mediterranean countries are discussed.
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Martín‐García et al. (2014) studied this question.