Lisianthus Crown and Stem Rot Caused by Fusarium avenaceum in Central Italy.

Lisianthus (Eustoma russelianum, syn. E. grandiflorum), a member of the Gentian family, is grown in the greenhouse in Italy as a commercial cut-flower crop. Its cultivation is a relatively new industry with high economic potential. However, disease problems have been observed on various greenhouse-planted lisianthus in Central Italy (Tuscany): symptoms of wilting, tan leaf flecks, tan stem discoloration, crown and stem rot, and death. White mycelia and orange sporodochia were also commonly observed on diseased crowns and stems. Fusarium avenaceum isolates were recovered from diseased tissues. Four single-spore isolates were selected for artificial inoculation. Pathogenicity tests were conducted in the greenhouse on 16- to 17-week-old E. russelianum plants, cvs. Mariacki, Echo, and Heidi, by placing a colonized agar plug, or drops of a conidial suspension, at the crown previously wounded with a sterile scalpel. Moist cotton was fastened to the wound site. Control plants were inoculated with sterile agar plugs or drops of sterile, distilled water. Five plants per cultivar and per treatment were used for each isolate. All plants developed typical disease symptoms within 1 or 2 weeks when inoculated with mycelial plugs or conidial suspensions, respectively. Control plants developed no symptoms. Koch's postulates were completed by consistently reisolating the pathogen from inoculated plants. This is the first report of F. avenaceum on lisianthus in Italy and is similar to reports of the disease in California and Florida (1,2). References: (1) S. T. Koike et al. Plant Dis. 80:1429, 1996. (2) R. J. McGovern et al. Phytopathology 87:S64, 1997.