In 1987, a new disease of citrus, citrus variegated chlorosis (CVC), was recognized in the states of Sao Paulo and Minas Gerais, Brazil. It has spread rapidly in Brazil, where it causes losses to citrus production.

Notice the yellow discolorations in the leaves of this CVC infected orange tree

Healthy orange and CVC infected orange

Symptoms. Chlorotic yellow spots appear on the leaves of affected trees. On the lower side of the leaf, lesions with extruded gum often occur opposite the chlorotic spots that are on the upper side of the leaf. Fruits are much smaller than normal and extremely firm. In comparative studies, blossom and fruit set occur at the same time on healthy and CVC affected trees, but normal fruit thinning does not occur on CVC affected trees and the fruits remain small but ripen earlier. Once a tree is affected by CVC, the growth rate of the tree slows, twigs and branches die back, and the canopy thins, but affected trees do not die. CVC affects most orange varieties, but is also seen on trees propagated on all common rootstocks in Brazil such as Rangpur lime, Cleopatra mandarin, and Volkamer lemon. See the article by R. F. Lee et al., 1991 in the references section for more details.

Xylella fastidiosa causes CVC. Electron microscopy has shown that bacteria associated with CVC have the morphological and structural characteristics of Xylella fastidiosa. Cultured isolates of Xylella fastidiosa from citrus trees with CVC disease were mechanically introduced into healthy trees and caused the CVC symptoms in the inoculated plants (see Chang et al., 1993 and Hartung et al., 1994 in references section). Several detection methods have been developed to confirm the presence of Xylella fastidiosa in diseased trees. The CVC strain of Xylella fastidiosa appears to differ genetically and biologically from other strains of the bacterium (in the references section see Barthe et al., 1993; Beretta et al., 1993; Chang et al., 1993).

Vectors. Surveys of two different citrus areas in San Paulo state has shown several species of sharpshooters occur regularly on citrus, which may explain the rapid spread of CVC within groves in Brazil (see Purcell, 1995 in references). Research on vector biology and transmission of Xylella fastidiosa is underway in Brazil (see Contacts section for persons working on vectors in Brazil).

For more information please visit:

Xylella fastidiosa Genome Project Home Page
The Fundecitrus homepage

Also visit a document on Citrus Variegated Chlorosis (CVC) and Xylella fastidiosa, by Marcos Machado

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