The association of Tobacco mosaic virus with green spot of cured wrapper tobacco leaves

Near-isogenic lines of cigar wrapper tobacco resistant or susceptible to Tobacco mosaic virus (TMV) were used to evaluate the association of TMV infection with green spot symptoms I'll cured leaves. TMV infection, as determined by double-antibody sandwich enzyme-linked immunosorbent assay (ELISA), was detected on susceptible but not resistant plants in field experiments. Green spot severity on cured leaves was greater for susceptible than resistant plants, even when symptoms of TMV were not evident in the field. Some green spots were present on resistant leaves despite the fact that the virus was not detected by ELISA. Resistant and susceptible plants had similar responses to virus infection and similar ELISA detection of TMV when plants were held at continuous temperatures over 28 degrees C in growth chambers. Plant resistance was not compromised in the field in cloth-covered shade tents even when 33.5 of the 96 h immediately following inoculation were above 28 degrees C. Green spot of cured leaves was strongly associated with TMV infection in susceptible plants, even when plants were infected after leaf expansion and mosaic symptoms were not present. Green spot also occurred to a lesser extent and for a limited time in inoculated resistant plants. The development of green spot symptoms on cured leaves may be the result of either systemic infection of TMV-susceptible plants or associated with the systemic resistance response to TMV inoculation of resistant plants.