Identification of Viruses Affecting Gladiolus in Kyiv Region

Introduction. The Gladiolus genus belongs to the Iridaceae Juss family. It includes more then 150 species. Most of them are native to Africa and few originated from the Mediterranean area, Asia and South Europe. Cultivars of gladiolus exhibit a great diversity of colour, size, shape, flowering time, and bulbing and dormancy behaviour [2]. Gladiolus is an important ornamental plant grown for commercial purposes, bouquets, floral baskets and cut flowers in Ukraine. Viruses represent a major problem for gladiolus and other bulb crops because the plants are propagated each year by bulbs that may harbor a virus. These viruses can cause extensive losses in the quality and quantity of flowers and corms. They cause significant economic losses to floriculture. The most widespread symptoms of virus infections in gladiolus plantings are overall stunting, colorbreaking, flower distortion, reduced flower and cormel production, severe mosaic in leaves, stunted plants, and color -breaking in flowers, notched leaf blade margin symptoms. Gladiolus plants may be infected by a number of different viruses or by strains of a particular virus [1]. The main viruses reported from gladioli in different countries are: Tomato ringspot virus (ToRSV), Tomato black ring virus (ToBRV), Tomato spotted wilt virus (TSWV), Tobacco mosaic virus (TMV), Tobacco ringspot virus (TRSV), Arabis mosaic virus (AMV), Bean yellow mosaic virus (BYMV), Cucumber mosaic virus (CMV), Tobacco rattle virus (TRV), Tobacco streak virus (TSV) [3, 4]. None of the viruses found on gladioli was specific to the crop species or to the Iridaceae family. All of these viruses have a wide host range as well as geographic distribution and some of them can be transmitted by vectors. Unfortunately the early diagnosis of virus diseases is not essential for establishing management measures. In addition to the aboveground parts of plants the corms could be a source of virus infection. To improve the quality of planting material and minimizing viral affection of gladiolus the timely diagnosis is of essential importance. Thus, identification of the source of infection, including the presence of the pathogen in planting material, is effective in controlling spread of viruses of gladioli and termination of epiphytoties. The aim of the work was to investigate and identify the viruses affecting gladiolus. Marerials and methods. For detection and identification of viruses affecting gladiolus we used 22 samples of 3 different cultivars ('Nizhnist', 'Nichnyj bluz', 'Asol') from private gardens of flower growers collected in Baryshivka town in Kyiv region. The samples were collected from gladioli expressing viral symptoms on leaves and flovers. Virus identification was carried out using standard DASELISA and indirect ELISA [9]. The samples were prepared by homogenizing plant tissue with 0.1 M phosphate buffer (pH 7.4) in the ratio 1:3 (m/v), followed by centrifugation at 5000 rpm for 20 min. For the diagnostics we used polyclonal antiserums to TMV (antiserum obtained at the virology department, the sensitivity and specificity confirmed experimentally), Turnip mosaic virus (TuMV) (antiserum kindly provided by Lesemann D.E., Julius Kühn Institute, Federal Research Center for Cultivated Plants, Institute for Epidemiology and Pathogen Diagnostics, Germany), Tomato aspermy virus (TAV), ToRSV, TRSV, CMV, Arabis mosaic virus (ArMV), Pepper mild mottle virus (PMMoV), Tomato spotted wilt virus (TSWV), Tobaco rattle virus (TRV) (Loewe, Germany). Futher, viruses were identified by bioassay and study of virus particle morphology. Biological properties of viruses were studied using the range of test plants: Nicotiana tabacum, Cucumis sativus, Lycopersicon esculentum, Phaseolus vulgaris, Capsicum annum, Tetragonia expansa, Zinnia elegans. The test plants were inoculated on early growth stages by mechanical sap transmission, applying carborundum as an abrasive. The morphology of virions was studied in leaf dip preparations negatively stained with 2% uranyl acetate. Electron microscopy (EM) was carried out using a JEOL1400 electron microscope at the magnification of 40 000 and 60 000. Results and discussion. Viral symptoms on gladiolus plants are not specific and common for wide range of viruses. Moreover, imbalance of mineral elements, their lack, high intensity lighting, damage by insects and mites, bacterial and fungal infections or genetic disorders can cause symptoms similar to those of viral infection. Although viral infection could be diagnosed in advance by specific symptoms such as ring spot, mosaic and the necrosis. The samples were collected from gladioli expressing viral symptoms on leaves and flovers. Leaves of naturally infected gladiolus plants exposed chlorotic spots and streaks of irregular shape. Some samples demonstrated coarse breaking patterns, expressed as disappearance of pigment in flowers (Fig.1). Severe color breaking and deformation of flowers are the most common symptoms associated with CMV infection in gladiolus [9].