Systemic necrosis in tomato induced by a Japanese isolate of rehmannia mosaic virus in a temperature‐sensitive manner

The Japanese isolate of rehmannia mosaic virus (ReMV‐J) was initially isolated from chilli pepper in Japan. The leaves of diseased chilli pepper plants, which hold no tobamovirus‐resistance genes, have mosaic symptoms. As the symptoms progress, the infected plants develop prominent leaf necrosis and severe leaf fall, followed by stem necrosis and fruit distortion. Additionally, ReMV‐J systematically infects tomato and this reportedly leads to mottle in tomato when incubated at 20 °C. This study found that ReMV‐J induces systemic necrosis of tomato – except for cultivar Micro‐Tom – when incubated at 25 °C. To determine the virus factor involved in the induction of temperature‐sensitive systemic necrosis on tomato, intergenic recombinants between ReMV‐J and tomato mosaic virus were constructed. All recombinant viruses systemically infected tomato similar to ReMV‐J. Recombinant viruses with the movement protein (MP) gene of ReMV‐J induced systemic necrosis on tomato. Incubation at 20 °C significantly reduced the ability of recombinant viruses with the MP gene of ReMV‐J to induce systemic necrosis. Thus, the ReMV‐J MP gene is involved in the temperature‐sensitive induction of systemic necrosis on most tomato cultivars tested. This study is the first to report the involvement of the MP gene in temperature‐sensitive induction of systemic necrosis by tobamovirus on tobamovirus‐susceptible tomato.