The Continuous Challenge of Citrus Tristeza Virus Control

Abstract

INTRODUCTIONCitrus tristeza virus (CTV) (132), an aphid-borne closterovirus (10), has ranked as one of the most important citrus diseases for the last sixty years.CTV epidemics have caused the severe decline or death of millions of trees in many areas where the sour orange (Citrus aurantium) was used as a rootstock.In other areas, the productivity of grapefruit and certain sweet orange varieties was considerably affected by CTV strains causing stem pitting decline.Unlike certain other disease agents, e.g. Spiroplasma citri (180) and Phoma tracheiphilla (93), which became associated with citrus during the acclimatization of this crop in the Near East, CTV was probably present from antiquity in citrus cultivated in China and Japan. However, CTV was not transported with its hosts, mainly because early acclimatization of citrus was from seed sources and CTV is not seed-transmitted (106). In retrospect, the tristeza disease in most citrus growing areas was a man-made problem created by the desire of horticulturists to introduce varieties from other citrus growing areas. 291 0066-4286/89/0901-0291$02.00 Annu. Rev. Phytopathol. 1989.27:291-316. Downloaded from www.annualreviews.org Access provided by Emory University on 08/06/15. For personal use only. Quick links to online content Further ANNUAL REVIEWS Annu. Rev. Phytopathol. 1989.27:291-316. Downloaded from www.annualreviews.org Access provided by Emory University on 08/06/15. For personal use only. CITRUS TRlSTEZA VIRUS CONTROL 293 quick decline obtained by grafting (61). Comparative transmission tests sug gested that the incompatibility problems in South Africa and Australia, the root problem in Brazil, and the quick decline in California were all man ifestations of the same disease (81). Other syndromes associated with CTV infection have been described, of which the most important is probably stem pitting (sp) decline (46,110,114,115,120,152,154,184) and seedling yellows (34, 63,107,141,180). Synonyms of CTV include Hassaku dwarf (164) and Natsudaidai dwarf (121). THE HOST RANGE OF CTVCTV infects most citrus species, varieties, hybrids and some citrus relatives such as Aeglopsis chevalieri Swing., Afraegle paniculata (Schum.) Engl., and Pamburus missiones (Wt.) Swing. (180). The only known hosts outside the Rutaceae are certain species of Passiflora (118, 145). Attempts to transmit CTV to non-Rutaceae species, either by aphids (145) and/or by mechanical inoculation (119), were unsuccessful. The reaction of different citrus species, hybrids, and citrus relatives to CTV infection varies considerably. Some plants, such as Poncirus trifoliata (L.) Raj., some hybrids between P. trifo tiata and sweet orange (Citrus sinensis (L.) Osb.) or grapefruits (c. paradisi), Severinia buxifolia, and Swinglea glutinosa (68), arc resistant to CTV and usually do not support detectable multiplication of the virus. Occasionally P. trifoliata or its hybrids were found to show CTV symptoms (35), although the virus was not verified as the causal agent in all trifoliate infection. In other...

Characterization of Citrus tristeza virus strains from southern China based on analysis of restriction patterns and sequences of their coat protein genes

“…Pathogenicity differentiation among CTV isolates collected from most of citrus-growing areas of the world has been reported in previous studies [2,3]. Three groups of CTV strains, namely mild strains, decline-inducing strains, and stem-pitting strains, have been characterized on the basis of their biological activities on indicator plants [4][5][6]. The virus is spread by propagation of infected buds and several aphid species [7].…”

Population structure of Citrus tristeza virus from field Argentinean isolates

“…CTV is propagated by infected buds and locally spread by several aphid species [22]. The most efficient vector is T. citricida, followed by Aphis gossypii [23][24][25][26][27].…”

Molecular characterization of a structural epitope that is largely conserved among severe isolates of a plant virus.

“…The most common, economically important symptoms include decline or death of trees grafted on sour orange rootstock, or stem pitting of the scion irrespective of the rootstock. Some isolates of CTV produce mild symptoms only in Mexican lime and do not cause decline or stem pitting (2,3).…”