BIOLOGICAL CHARACTERIZATION OF CITRUS TRISTEZA VIRUS ISOLATES BY IN-VITRO TISSUE-CULTURES

Stem segments from Mexican lime, sweet orange, grapefruit, Citrus exce lsa and alemow, infected with five citrus tristeza virus (CTV) isolate s, were cultured in vitro. Regeneration of roots and shoots were modif ied as a result of infection. The effect of CTV on the morphogenesis o f stem segments cultured in vitro depended on the CTV isolate and the plant host, and showed a correlation with the in vivo effects observed in biological indexing. Evaluation of the morphogenic response of ste m segments of Mexican lime and grapefruit can be used as an additional tool for the biological characterization of CTV isolates. The symptom s on sweet orange plants obtained from regenerated shoots indicated th at CTV is unevenly distributed in the host plant cells and that the re generation process may be utilized as a tool to separate strains from complex field isolates.