PHYTOPLASMA DISEASES IN ORNAMENTAL CROPS IN ISRAEL
Phytoplasma diseases have been identified in Israel in numerous species of various botanical families. The disease occurs in cultivated ornamentals, vegetables, field crops, fruit trees and in the wild crops. In cut flowers, the disease was identified in Anemone and Ranunculus, and Matthiola spp. In these cases the disease was sporadic with no serious economical losses. However, in carrots the disease is known to occur since 1995, causing losses of great economic significance. In the summer of 1998, the disease was identified in Celosia sp., causing general yellowing of leaves, stunting, witch-broom growth of axillary shoots and flower malformation (phyllody). In ultrathin sections of infected tissue, pleomorphic particles were observed in sieve elements of the diseased plants but not in healthy ones. Direct polymerase chain reaction (PCR) with universal primers resulted in amplified products of the expected size when symptomatic samples were used. No PCR products were obtained from the healthy control plants. In October 2000, the disease was identified in Limonium spp. in the Arava Valley. Symptoms included leaf yellowing, production of abundant long and narrow leaves, production of small and/or white flowers, excessive branching similar to Asparagus ferns, and occasionally production of leaf-like structures instead of flowers. Transmission electron microscopy and PCR confirmed the presence of phytoplasma in the symptomatic plants. In December 2000 work was started on monitoring potential vectors by use of yellow sticky traps and vacuum sampling. To date, four species known to vector phytoplasmas and/or spiroplasmas have been trapped: Orosius orientalis (Matsumura), Circulifer haematoceps (Mulsant et Rey), C. tenellus (Baker) and Exitanius capicola Stal. Austroagallia sinuata (Mulsant et Rey) and Psammotettix spp. have also been trapped. Field collected O. orientalis, which occurs in the largest numbers, C. haematoceps and C. tenellus have tested positive for phytoplasma by PCR analysis. Transmission studies with field-collected specimens have been initiated and initial results indicate that O. orientalis can vector phytoplasma to clean Limonium plants in the laboratory. Transmission studies are in progress with a clean colony of O. orientalis and other leafhopper species. In October 2003, phytoplasma-like symptoms were observed in Eustoma russelianum and Gypsophila.
Gera, A., Maslenin, L., Rosner, A., Zeidan, M. and Weintraub, P.G. (2006). PHYTOPLASMA DISEASES IN ORNAMENTAL CROPS IN ISRAEL. Acta Hortic. 722, 155-162
Phytoplasma, Limonium, Gypsophila, Eustoma, leafhoppers, Orosius orientalis, Circulifer tenellus