Comparison of symptoms induced by infection with TMV, AlMV, and Av/A4 on N. tabacum cv. Xanthi-nc at 27°C (A) and at 30°C (B). (A) TMV and Av/A4 caused necrotic local lesion formation, limiting the infection to the inoculated leaf, while AlMV moved into the upper uninoculated leaves. (B) Inoculation of N. tabacum cv. Xanthi-nc with Av/A4, AlMV, or TMV at 30°C resulted in the systemic spread of the virus. Local lesions and systemically infected leaves are indicated by circles and arrows, respectively.