Spiroplasma citri. [Descriptions of Fungi and Bacteria].
A description is provided for Spiroplasma citri. Information is included on the disease caused by the organism, its transmission, geographical distribution, and hosts. HOSTS: There are many natural hosts in the Rutaceae, including Citrus aurantifolia (sweet lime), C. aurantium (sour orange), C. clementina (clementine), C. jambhiri (rough lemon), C. limon (lemon), C. madurensis (syn. C. mitts, calamondin), C. maxima (syn. C. grandis, pummelo), C. paradisi (grapefruit), C. paradisi × C. reticulata (tangelo), C. sinensis (sweet orange), C. sinensis × Poncirus trifoliata (citrange), C. unshiu (satsuma) and Fortunella spp. (kumquats). Non-rutaceous natural hosts include Armoracia rusticana, Barbarea vulgaris, Brassica geniculata, B. kaber, B. nigra, B. oleracea var. botrytis, B. oleracea var. capitata, B. oleracea var. gemmifera, B. rapa, B. tournefortii, Capsella bursa-pastoris, Catharanthus roseus, Digitalis purpurea, Plantago ovata, Prunus avium, P. persica, Pyrus communis, Raphanus sativus, Sedum praealtum, Sisymbrium irio, S. orientale, Tagetes erecta, Viola cornuta, Zinnia elegans (63, 3239; 62, 2777; 59, 3154). A wide variety of plants has been infected artificially by transmission from inoculated leafhoppers. Symptoms are milder under cool conditions. Under warm conditions only Citrus spp. and hybrids survive infection more than a few months (59, 3154). DISEASE: Citrus stubborn or 'little leaf'. Affected trees are slightly to severely stunted and give low yields. Leaves are shorter, broader, upturned at the edges and may be mottled or chlorotic. Internodes of twigs are shorter and multiple axillary buds are produced. Fruits may be small, lopsided or acorn-shaped, caused by formation of very thin smooth rind at the blossom end. In horseradish, infection causes brittle root disease, in which leaves are stunted, chlorotic or necrotic and roots show a darkened ring of phloem (61, 2596). GEOGRAPHICAL DISTRIBUTION: Present in many citrus growing areas. Reports include: Algeria, Egypt, Libya, Madagascar, Morocco, Tunisia, Iran, Iraq, Israel, Lebanon, Pakistan, Saudi Arabia, Syria, Turkey, Corsica, Cyprus, Greece, Sardinia, Sicily, Mexico, United States (AR, CA), Argentina (Tucuman), Brazil (Sao Paulo), Peru, Surinam (IMl Distribution Map 375, ed. 2, 1970; 49, 1876b; 50, 1228a; 51, 1253b, 3247; 56, 5056; 63, 1797; 68, 367). TRANSMISSION: The insect vectors are leafhoppers and the following have been shown to transmit the disease: Neoaliturus tenellus[Circulifer tenellus] (sugar beet leafhopper), N. haematoceps (N. opacipennis), Scaphytopius nitridus and S. delongi. The disease is also spread in budwood, although not very consistently (68, 367).