Low root-to-root transmission of a tobamovirus, yellow tailflower mild mottle virus, and resilience of its virions

Tobamoviruses are serious pathogens because they have extremely stable virions, they are transmitted by contact, and they often induce severe disease in crops. Knowledge of the routes of transmission and resilience of tobamovirus virions is essential in understanding the epidemiology of this group of viruses. Here, an isolate of the tobamovirus yellow tailflower mild mottle virus (YTMMV) was used to examine root-to-root transmission in soil and in a hydroponic growth environment. Root-to-root transmission occurred rarely, and when it occurred plants did not exhibit systemic movement of the virus from the roots to the shoots over a 30-day period. The resilience of YTMMV virions was tested in dried leaf tissue over time periods from one hour to one year under temperatures ranging from −80 to 160 °C. Infectivity was maintained for at least a year when incubated at −80 or 22 °C, or at fluctuating ambient temperatures of 0.8 to 44.4 °C, but incubation under dry conditions at 160 °C for >4 days eliminated infectivity. Exposure of virions to 0.1 m sodium hydroxide or 20% w/v skimmed milk solution for 30 min, treatments recommended for tobamovirus inactivation, did not abolish infectivity of YTMMV.