engleski

Recovery of chestnut from chestnut blight depends on combination of virus strains used for biocontrol

Chestnut blight is a disease caused by the fungus Cryphonectria parasitica which infects chestnut trees through wounds, and induces bark cankers. This severe disease can be controlled by naturally-occurring hypovirus Cryphonectria hypovirus 1 (CHV1) which significantly reduces fungal virulence, sexual reproduction, pigmentation and sporulation. Hypovirulent (CHV1- infected) C. parasitica isolates cause healing of cankers which were previously induced by virulent fungal isolates. The hypovirus can be transmitted horizontally via hyphal anastomosis and vertically with asexual conidia. In Europe CHV1 occurs as several subtypes that differ in their virulence towards C. parasitica. French CHV1 subtypes F1 and F2 were believed to be more virulent towards C. parasitica and inhibit its growth and sporulation more than Italian subtype I, which is the only subtype widespread in Croatia. Our recent results reveal that three lateral interaction of chestnut, pathogen C. parasitica and biocontrol agent – CHV1 is crucial for successful biocontrol. Both, susceptibility and recovery of chestnut from chestnut blight are influenced by genotypes of chestnut, fungus and virus: certain hypovirulent fungal isolates harboring specific virus strains are more or less efficient against chestnut blight, depending on chestnut genotype. Therefore, generally efficient hypovirulent C. parasitica isolate does not exist, only isolates which are efficient on majority of chestnut genotypes. Furthermore, as opposed to previously published results that imply higher virulence of French than Italian CHV1 subtype towards chestnut blight fungus, our results reveal that some virus strains that belong to subtype I are more efficient or equally efficient biocontrol agents as the strong strain CHV1/EP713 that belongs to the subtype F.

biological control ; CHV1 subtypes ; CHV1 virulence

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