Abstract
The detection of CTV decline strains is at this time done by serological and biological methods. One of the drawbacks of the current system is that no one serological test can detect all strains of decline. The current method depends on the specificity of the antibody to determine the presence of the virus. Tests of this kind do not, however, determine the decline potential of an isolate. The presence of the virus can cause a devastating affect on the overall tree growth and production. It is especially important to determine if new root stock/scion combinations are compatible and that when infected with CTV they do not decline in vigor. This work describes a method using small buds from ELISA-tested sources, infected with CTV onto immature rootstock material, which can then detect CTV decline strains. Two CTV isolates were tested, which were classified as decline strains on sour orange (Citrus aurantium L.) or large flower trifoliate orange (Citrus trifoliata) as a rootstock and sweet orange ( Citrus sinensis L. Osbeck) as the scion. The CTV strains used for this work were T68, an Australian strain found in Florida, T67, a Florida decline strain, and a noninfected control. A new technique was developed and tested for rapidly evaluating CTV isolates based on symptoms by grafting small buds from source trees on immature rootstock. Large differences in growth occurred between bud sources from decline strains and those of healthy or decline strain sources and the rootstocks. Differences in growth reduction also occurred between the two decline strains. The method reliably determines the loss of growth potential due to the presence of CTV viral strains.
