Occurrence of Lily mottle virus in Escarole

Lily mottle virus (LMoV), genus Potyvirus, an important virus of lily that also causes flower-breaking in tulip (1), is considered to have a natural host range restricted to the family Liliaceae. In 1996, escarole (Cichorium endivia L. var. latifolium LAM) plants growing in fields close to Torino, Italy, and showing mosaic and necrotic spots on outer leaves were infected by a potyvirus related to LMoV. The virus was identified by immunoelectron microscopy (IEM) done on experimentally infected Nicotiana benthamiana and Chenopodium quinoa. The virus isolated from escarole (LMoV-E) had an experimental host range similar to that of lily isolates of LMoV, although species within the Liliaceae were not tested. LMoV-E systemically infected all nine escarole cultivars and six of seven endive cultivars (C. endivia L. var. crispum LAM) but did not infect any of six lettuce and two chicory cultivars (C. intybus L. var. foliosum HEGI). Symptoms ranged from mild to severe mosaic and were generally more severe on escarole than on endive. Some of the same escarole, endive, and lettuce cultivars were inoculated with a typical LMoV isolate from lily (Le97/49, from A. F. L. M. Derks, the Netherlands), which induced mild systemic infections in only one escarole and one endive cultivar. Both cultivars were also susceptible to LMoV-E. LMoV-E was purified from N. benthamiana, and an antiserum was prepared. IEM decoration titer experiments were done with LMoV-E and four other LMoV isolates from Liliaceae and their homologous antisera. Heterologous titers ranging from identity to serological differentiation index values of 2 to 4 were obtained, confirming the identity of the escarole isolate as a LMoV strain and indicating considerable serological variability among LMoV isolates. In a field survey of endive and escarole crops in 1998, in the area where LMoV-E was first identified, the virus was again detected by enzyme-linked immunosorbent assay in 4 of 80 escarole plants tested. LMoV-E appears to be a LMoV strain particularly adapted to escarole. To our knowledge, this is the first report of LMoV identified in a naturally infected host outside monocotyledonous plants. Reference: (1) E. L. Dekker et al. J. Gen. Virol. 74:881, 1993.