Engineering super mycovirus donor strains of chestnut blight fungus by systematic disruption of multilocusvicgenes

Abstract

Transmission of mycoviruses that attenuate virulence (hypovirulence) of pathogenic fungi is restricted by allorecognition systems operating in their fungal hosts. We report the use of systematic molecular gene disruption and classical genetics for engineering fungal hosts with superior virus transmission capabilities. Four of five diallelic virus-restricting allorecognition [vegetative incompatibility (vic)] loci were disrupted in the chestnut blight fungusCryphonectria parasiticausing an adapted Cre-loxPrecombination system that allowed excision and recycling of selectable marker genes (SMGs). SMG-free, quadruplevicmutant strains representing both allelic backgrounds of the remainingviclocus were then produced through mating. In combination, these super donor strains were able to transmit hypoviruses to strains that were heteroallelic at one or all of the virus-restrictingvicloci. These results demonstrate the feasibility of modulating allorecognition to engineer pathogenic fungi for more efficient transmission of virulence-attenuating mycoviruses and enhanced biological control potential.