Mycoviruses at the Crossroads: Molecular Mechanisms, Cross‐Kingdom Interactions, and Abiotic Stress in the Phytobiome

Abstract

Mycoviruses, viruses that infect fungi, have emerged as pivotal modulators of fungal biology with far‐reaching consequences for plant health. Once regarded as mere curiosities of mycology, mycoviruses are now recognized as key players in tripartite mycovirus–fungus–plant interactions that reshape disease outcomes, endophytic lifestyles, and ecosystem resilience. Recent discoveries of cross‐kingdom infection, core virome‐mediated thermal tolerance, and reactive oxygen species (ROS) signaling hubs have substantially expanded our understanding of mycovirus biology. In parallel, mounting evidence implicates abiotic stressors—temperature fluctuations, drought, and elevated CO2—as critical yet underappreciated modulators of these tripartite interactions. This minireview synthesizes advances from 2018 to 2026, with emphasis on: (i) the expanding diversity and cross‐kingdom capacity of mycoviruses, (ii) molecular mechanisms underlying hypovirulence, hypervirulence, and endophyte conversion, (iii) the emerging ROS–autophagy–RNA silencing signaling nexus, and (iv) how abiotic stress reshapes mycovirus–fungus–plant dynamics. We propose an integrative framework positioning mycoviruses as environmental sensors and ecological switches within the phytobiome, and identify critical knowledge gaps that must be addressed to harness mycoviruses for sustainable crop protection under climate change.