CITRUS WILSONII: BIOLOGICAL RESPONSE TO INFECTION WITH DIFFERENT CITRUS TRISTEZA VIRUS GENOTYPES

Citrus wilsonii Tanaka is cold-resistant, rarely grown chance hybrid between Citrus ichangensis and Citrus grandis with a potential to be used as a rootstock in colder climates. In order to evaluate its reaction to Citrus tristeza virus (CTV), C. wilsonii seedlings were graft-inoculated with previously characterized CTV isolates monophyletic with respect to the p25 gene and clustering to phylogenetic groups Gp 1, Gp 2, Gp 3a, Gp 4, Gp 5 and Gp M. The evaluation of C. wilsonii symptoms and comparison with the reaction of standard citrus indicators infected with the same CTV isolates revealed that C. wilsonii infected with isolates Gp 2 and Gp 4 developed stem pitting (SP). This is in accordance with the SP-inducing potential of these CTV isolates in the standard sweet orange SP indicator. The obvious and numerous pits shown by C. wilsonii stems suggests that it reacts strongly to severe SP CTV isolates.