How is lettuce mosaic potyvirus primarily transmitted?

Lettuce mosaic potyvirus is primarily transmitted through seed transmission, which means that the virus can be passed from infected parent plants to their seeds. When these seeds germinate, they can produce new plants that are already infected with the virus. This method of transmission can lead to widespread infection in lettuce crops since once the seeds are sown, the new plants carry the virus right from the start, facilitating the rapid spread of the infection among cropping systems.

In contrast, airborne transmission, soil contamination, and water splashing are methods associated with the spread of other pathogens but are not the primary transmission pathways for lettuce mosaic potyvirus. Airborne transmission typically involves vectors like aphids carrying the virus; however, this is secondary compared to seed transmission. Soil contamination and water splashing do not play significant roles in the lifecycle or spread of this particular virus, making seed transmission the most critical pathway to understand for effective pest and disease management in lettuce cultivation.