Effect of putative mitoviruses on in vitro growth of Gremmeniella abietina isolates under different laboratory conditions

Abstract

Mitoviruses have been found in several forest pathogens (i.e. Cryphonectria parasitica, Gremmeniella abietina), and because they have been shown to reduce the virulence of host fungi there is a growing interest in studying their use as a biocontrol. This study was carried out to test the effect of temperature (5°C, 15°C, 25°C and 35°C), pH (4, 5, 7 and 9) and osmotic potential (–0.6, –1.2, –1.8 and –2.4 MPa) on the mycelial growth of seven G. abietina isolates under controlled laboratory conditions. Four of the isolates hosted mitoviruses and three of them did not. During the experiment, mycelial growth was recorded every week for a period of 8 weeks. Results showed no differences in growth behavior between mitovirus infected and non-infected isolates when placed under different pH modifications. However, the mitovirus-infected isolates presented larger mycelial growth than the mitovirus-free ones when at the fungi’s optimal growing temperature of 15°C. When growing at certain osmotic potentials (–0.6 and –1.8 MPa) a reduction in growth of the mitovirus-infected isolates was observed. The results of this experiment suggest that mycelial growth among non-infected isolates and isolates naturally infected by mitovirus vary under different culture conditions, thus providing further insight into the effects of mitovirus on Gremmeniella abietina isolates.