A New Phytophthora sp. Causing a Basal Canker on Beech in Italy

Area of Science:

• Plant Pathology
• Mycology
• Forest Pathology

Background:

• Bleeding cankers were observed on European beech (Fagus sylvatica L.) in Italy in 2001.
• A Phytophthora species was consistently isolated from infected trunk bark.

Purpose of the Study:

• To identify the Phytophthora species causing bleeding cankers on European beech.
• To characterize the isolated Phytophthora species morphologically, culturally, and genetically.
• To assess the pathogenicity of the isolate on beech seedlings.

Main Methods:

• Isolation of Phytophthora from infected bark using whole apples.
• Morphological and cultural characterization on various agar media (V8A, cornmeal agar, PDA).
• Determination of growth rates at different temperatures.
• Microscopic examination of sporangia, oogonia, and oospores.
• Electrophoretic analysis of mycelial proteins and isozymes.
• Internal transcribed spacer (ITS)-restriction fragment length polymorphism (RFLP) analysis.
• Pathogenicity tests on beech seedlings.

Main Results:

• The isolated Phytophthora exhibited distinct morphological and cultural characteristics.
• Electrophoretic banding patterns and ITS-RFLP analysis differentiated the beech isolate from other semipapillate Phytophthora species.
• The isolate's genetic profile matched a reference isolate (Ph24) previously suggested to be a new species, Phytophthora pseudosyringae.
• Pathogenicity tests confirmed the isolate's ability to cause lesions on beech seedlings, though less severe than Phytophthora cambivora.

Conclusions:

• The study reports the first occurrence of this new Phytophthora species, likely Phytophthora pseudosyringae, on European beech in Italy.
• The findings contribute to understanding the diversity of Phytophthora pathogens affecting forest trees.
• This research highlights the importance of accurate pathogen identification for forest health management.