INVESTIGATIONS ON NATURAL SPREAD OF CHESTNUT BLIGHT HYPOVIRULENCE IN ITALY AND OTHER EUROPEAN COUNTRIES

Virulent and hypovirulent isolates of Cryphonectria parasitica are spreading in chestnut orchards, mixed forests and coppices. The impact and the effects of the disease are related to the natural balance between the different isolates of the parasite. The predominance of the hypovirulence is detectable by the presence of viable branches and trees as a consequence of a massive number of healing cankers.

Stability of hypovirulence is sustained by a high density of new infections able to produce healing cankers. Abiotic and biotic factors are involved in the establishment of the natural biological control of blight. Homogeneity of dsRNA contents was detected in the main part of the collected European hypovirulent isolates.

A decrease of hypovirulence benefits could be produced by disturbance factors such as wildfires and game or livestock grazing.

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