Susceptibility of some Mesophilic Hardwoods to Alder Phytophthora

Inoculation tests were carried out in the greenhouse on seedlings of five hardwoods (Alnus cordata, A. glutinosa, Castanea sativa, Juglans regia and Quercus robur) to determine their susceptibilityto an isolate of alder Phytophthora obtained in Italyfrom A. cordata. A Phytophthora cinnamomi strain was used for comparison. Host susceptibilityto infection was determined as the lesion length after stem inoculation and the percentage of necrotized rootlets after soil infestation with inoculated millet seeds. The aggressiveness of the alder Phytophthora isolate was significantlyhigher in the two Alnus species than in the other hosts. Our results were confirmed with both methods of inoculation. Alnus cordata was consistentlythe most susceptible host species when compared with the other hardwoods. Damage by P. cinnamomi was severe, particularlyafter soil infestation tests. The most susceptible species were alders, chestnut and walnut. The test also suggests that alder Phytophthora is able to spread through infected seedlings of different hardwood species