China, the world’s largest producer of cultivated apples (Malus × domestica), also serves as a center of apple origin with centuries of cultivation. Apple orchards face ongoing threats from latent viral infections, particularly apple stem pitting virus (ASPV), apple stem grooving virus (ASGV), and apple chlorotic leaf spot virus (ACLSV). While these viruses often remain symptomless in commercial cultivars, they can weaken root vigor, disrupt nutrient uptake, increase graft incompatibility, and reduce fruit yield and quality—especially in cases of co-infection. Because apple cultivars are propagated clonally, these viruses are commonly spread through grafting and pruning. Maintaining virus-free planting stock remains essential for global orchard health.
Although no insect vectors have been identified for these apple viruses, evidence suggests soil may act as a medium for transmission. Viruses can persist in soil for weeks or months, raising questions about their survival strategies. One hypothesis points to soil-borne microorganisms—particularly fungi—as potential carriers. This idea is supported by similar findings in crops like potato, tobacco, and cereals, where fungi are known vectors of soil-borne viruses.
Fungi naturally host their own viruses and can transmit plant viruses as well. Certain fungal pathogens, such as Olpidium and Polymyxa, are recognized vectors for multiple crop-damaging viruses. Recent research even demonstrated that Rhizoctonia solani can transfer cucumber mosaic virus to previously healthy plants.
Building on these insights, the current study screened soil fungi for apple viruses and identified Fusarium solani isolates carrying ASGV. Crucially, the infected fungi were capable of transmitting the virus to healthy plants. This discovery marks the first evidence of fungal involvement in apple virus transmission and has major implications for orchard management. Practices such as replanting in virus-contaminated soils may need to be reconsidered to prevent hidden fungal transmission pathways.
Fungi Found to Carry and Transmit Apple Viruses, Study Reveals
