A Missense Mutation in Tomato mosaic virus L11A-Fukushima Genome Determines Its Symptomless Systemic Infection of Tomato

The genome of an attenuated isolate L11A-Fukushima (L11A-F) of Tomato mosaic virus was cloned, its complete nucleotide sequence was determined, and full-length clone of L11A-F was then assembled. Its transcripts systemically infected tomato without causing any symptom development. When a missense back mutation at the nucleotide correspondent to nucleotide 2350 of the genome was introduced into the clone, its transcripts produced distinct mosaic on the upper leaves of the inoculated tomato, and virus accumulation in the upper leaves increased about five times. The missense mutation in the L11A-F genome was thus confirmed to be sufficient to attenuate its virulence on tomato.