Mycoviruses as biocontrol of plant pathogens

Publikation: Bog/antologi/afhandling/rapportPh.d.-afhandling

Abstract

Viruses are increasingly recognized as essential contributors to ecosystem diversity, playing vital roles in many processes such as nutrient cycling and the regulation of microbial populations. Mycovirology, the study of fungal viruses, has also gained increasing attention in recent years, with many new strains being identified across a wide range of fungal species. However, significant gaps remain in our understanding of their diversity, distribution, and effects on their hosts.
A critical global challenge is ensuring sufficient food production to meet the needs of a growing population. Fungal diseases, particularly those affecting
crops, pose a serious threat to food security. While various strategies have
been developed to mitigate these diseases, ongoing innovation is necessary.
Biological control methods, which offer environmentally friendly alternatives,
are particularly promising. Among these, mycoviruses have been suggested as
potential biocontrol agents (BCAs) against fungal pathogens. In this context, our
research focuses on exploring the potential of mycoviruses to combat Fusarium
species responsible for Fusarium head blight (FHB), with particular focus on
F. culmorum. Our goal is to contribute to the expanding knowledge base on
mycoviruses and evaluate their potential for managing FHB, with implications
for global food security.
In this thesis, we isolated and sequenced 54 Fusarium isolates associated with
FHB and identified 16 mycoviruses, with F. culmorum showing greater mycovirus
diversity than F. graminearum. We then focused on two key mycoviruses:
Fusarium culmorum phenuivirus 1 (FcPV1), a newly identified virus, and
Cryphonectria hypovirus 1 (CHV1), a mycovirus that is known for inducing
hypovirulence in several other fungi. Since F. culmorum is not a native host
for CHV1, we successfully introduced it through transfection and confirmed its
replication. We tested their effects on the growth and sporulation of F. culmorum. Furthermore, we also assessed their impact on the pathogenicity of F. culmorum in spring wheat. We tested this in two environments with increasing complexity (greenhouse and semifield), as well as two plant cultivars (a FHB-susceptible and a moderately resistant one).
The findings showed that while FcPV1 did not affect F. culmorum growth in laboratory settings, it exhibited contrasting effects in more complex environments, showing hypervirulence in the greenhouse and hypovirulence in semifield conditions, particularly in the susceptible cultivar. However, mycotoxin production remained unaffected. On the other hand, CHV1-infected F. culmorum
had a reduced growth rate, showed no significant effect in the greenhouse, and
displayed mild reductions in disease severity and mycotoxin production under
semifield conditions.
Although we did not identify a mycovirus capable of effectively controlling FHB, our results demonstrate the intricate nature of mycovirus-host interactions
and the critical role of environmental factors in determining the efficacy of
mycoviruses as BCAs. Increasing the complexity of environmental conditions,
such as moving from controlled greenhouse settings to semifield trials, was crucial in revealing these effects. Furthermore, the choice of plant cultivar also influenced the outcomes. These findings challenge the perception that mycoviruses are typically cryptic and highlight the importance of considering environmental context and host specificity in future biocontrol research.
OriginalsprogEngelsk
Antal sider163
StatusAfsendt - 2024

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