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.Key words: mitoviruses; Scleroderris canker; in vitro; biological control; Gremmeniella abietina; dsRNA. Resumen Efecto de posibles mitovirus en el crecimiento in vitro de aislados de Gremmeniella abietina bajo diferentes condiciones de laboratorioLos mitovirus son virus exclusivamente fúngicos que han sido aislados de algunos patógenos forestales (i.e. Cryphonectria parasitica, Gremmeniella abietina) y ya que pueden reducir la virulencia del hongo existe un creciente interés por su posible papel como agentes de control biológico. Se ha llevado a cabo un estudio para evaluar el efecto de la temperatura (5°C, 15°C, 25°C y 35°C), el pH (4, 5, 7 y 9) y el potencial osmótico (-0.6, -1.2, -1.8, -2.4 MPa) en el crecimiento micelial de siete aislados de G. abietina bajo condiciones controladas de laboratorio. Cuatro de los aislados albergaban mitovirus y tres de ellos no. Durante el experimento, el crecimiento micelial fue registrado semanalmente hasta completar 8 mediciones. Los aislados infectados con mitovirus presentaron mayor crecimiento micelial que los no infectados a la temperatura de crecimiento óptimo del hongo de 15°C. No se observaron efectos de la presencia de mitovirus entre los aislados infectados y los no infectados en los tratamientos de modificación del pH. Cuando se modificaron los potenciales osmóticos se observó una reducción del crecimiento micelial de los aislados infectados con mitovirus en los potenciales osmóticos de -0.6 y -1.8 MPa. Los resultados de este experimento sugieren que la presencia de los mitovirus afecta al crecimiento micelial del hongo bajo distintas condiciones de laboratorio. Este estudio proporciona un conocimiento más prof...

Short communication: Effect of mycoviruses on growth, spore germination and pathogenicity of the fungus Fusarium circinatum

“…A reduction in the mycelial growth of different pathogens infested with mycoviruses has been reported to be related to hypovirulence in fungi in several studies (Bottacin et al, 1994;Ahn & Lee, 2001;Castro et al, 2003;Robin et al, 2010;Rodríguez-García et al, 2014;Zheng et al, 2014;Yu et al, 2015). Nevertheless, the effect on mycelial growth may also be determined by the species (Vainio et al, 2012;Hyder et al, 2013), isolate (Hunst et al, 1986;Rodríguez-García et al, 2014;Yu et al, 2015) temperature (Vainio et al, 2010;Bryner & Rigling, 2011;Romeralo et al, 2012;Zamora et al, 2016) or the type of mycovirus (Cryphonectria parasitica CHV1, mycovirus hypovirulences). These factors, among others, may explain the inconsistencies in the findings of different studies.…”

The European race of Gremmeniella abietina hosts a single species of Gammapartitivirus showing a global distribution and possible recombinant events in its history

“…Only biotype B appears to harbour a taxonomically unassigned species with certain endornavirus-like characteristics , and both biotypes A and B host mitoviruses (Tuomivirta & Hantula 2003b;Botella et al 2012b). Mitovirus-infected isolates appear to present greater mycelial growth than mitovirus-free isolates at the optimal growing temperature for G. abietina of 15 C (Romeralo et al 2012). The viral communities appear to be separated into biotypes A and B (Hantula & Tuomivirta 2003), except in Spain, where two species of mitoviruses occur in the genetically unique population, which was most likely derived from biotype A.…”

Interactions virus-fungus- insect in pine pitch canker disease

“…of Spanish isolates (Botella et al, 2012) and in 50% of Turkish isolates (Aday et al, 2012). In addition, three mycoviruses were found together infecting the same isolates of G. abietina var.…”

“…Three races of this fungus (European, North American and Asian) have been catalogued. The European race is subdivided into three biotypes (A, B and alpine) (Botella et al, 2010;Donaubauer, 1972;Hamelin et al, 1996;Kaitera & Jalkanen, 1992;Romeralo et al, 2012;Santamaría et al, 2005;Senn, 1999), although the taxonomy is currently under revision (Romeralo pers. com.…”

“…abietina type A (Tuomivirta & Hantula, 2005). Later, Botella et al (2012) reported the absence of mitoviruses in biotype B from Turkey, biotype A from North America and European Alpine biotype. On the contrary, biotype A from Finland and Spain hosted mycoviruses.…”