During a survey of Lisianthus (Eustoma grandiflorum) plots in the Northern Negev in Israel, plants infected with Iris yellow spot virus (IYSV) (Genus Tospovirus; 1) were identified. In addition, during electron microscope observations of ultrathin sections through parenchyma phloem cells from some of the IYSV-infected plants, vesicles and virus particles typical of closteroviruses (850 × 12 nm) were observed. As sweet potatoes grown in this area often are infected with Sweet potato sunken vein virus (SPSVV), it was of interest to see if SPSVV also had naturally infected Lisianthus. Using immunosorbent electron microscopy (ISEM) with an antiserum developed against SPSVV (2), trapping and decoration of the suspected chlostero-like particles were observed in some of the field-collected Lisianthus plants. This antiserum did not react with two other closteroviruses, Citrus tristeza virus and Lettuce infectious yellow virus. Inoculation of non-infected Lisianthus plants with SPSVV acquired from sweet potato by whitefly (Bemisia argentifolii), resulted in the presence of vesicles and clostero-like particles in ultrathin sections of parenchyma phloem cells 1 month after inoculation. ISEM tests with SPSVV antiserum were positive. Inoculations of sweet potato from SPSVV-infected Lisianthus plants by whiteflies were not successful. No leaf symptoms of SPSVV were observed in Lisianthus plants, but flower stems were shorter by about one third. These data indicate that Lisianthus is a host for SPSVV. To our knowledge, this is the first report of SPSVV infecting Lisianthus and any species of the Genetianaceae.
References: (1) A. Kritzman, H. Beckelman, S. Alexandrov, J. Cohen, J. Lampel, M. Zeidan, B. Raccah and A. Gera. Plant. Dis. 84:1185, 2000. (2) J. Cohen, A. Franck, H. J. Vetten, D. E. Lesemann and G. Loebenstein. Ann. Appl. Biol. 121:257, 1992.