Lisianthus leaf necrosis: A new disease of lisianthus caused by Iris yellow spot virus

Unusual viral symptoms were seen on lisianthus (Eustoma russellianum) grown in the Besor area in Israel. Symptoms included necrotic spots and rings on leaves and systemic necrosis. Preliminary analyses suggested that the dise ase was caused by a tospovirus. Virus particles typical of a tospovirus wer e observed with electron microscopy in samples taken only from symptomatic leaves. Double-antibody sandwich enzyme-linked immunosorbent assay tests of leaf sap, extracted from lisianthus and mechanically inoculated indicator plants, gave a strong positive reaction to Iris yellow spot virus (IYSV). P olyclonal antibodies prepared against IYSV enabled specific detection of th e virus in crude sap from infected plants. Western blot analysis showed tha t IYSV was serologically distinct from Tomato spotted wilt virus (TSWV). Pr imers specific to the nucleocapsid gene of IYSV were used in a reverse tran scription-polymerase chain reaction assay (RT-PCR) to verify the presence o f IYSV. RT-PCR gave an expected PCR product of approximately 850 bp. The se quence of the cloned nucleocapsid gene confirmed the identity of IYSV, thus confirming IYSV infection of lisianthus. This is the first report of IYSV infection in dicotyledons.