Changes in the Bark Proteins of Sour Orange Rootstock Induced by Citrus Tristeza Virus

Abstract

The effect of citrus tristeza virus (CTV) infection on bark proteins of several citrus rootstocks was studied by polyacrylamide gel electrophoresis (SDSPAGE). A protein band (P6) from bark of sour orange grafted with sweet orange, grapefruit or clementine scions had lower intensity in CTV-infected than in CTV-free trees. Decrease of P6 intensity was more conspicuous in trees infected with a severe CTV isolate than in those infected with a mild isolate. No difference was observed between bark proteins of CTV infected and CTV-free sour orange sprouts. Protein profiles of healthy and tristeza-infected Troyer citrange or Cleopatra mandarin, grafted with navel orange, were also indistinguishable. Finally, protein patterns of sour orange grafted with navel orange, severely declined from Phytophthora sp. or psorosis, were similar to those of non-declined controls. Thus, decreased intensity of P6 seems to be specifically associated with tristeza in citrus trees grafted on sour orange.