Viroids in Tahiti Lime Scions Showing Bark Cracking Symptoms

Abstract

The so-called quebra-galho clone of Tahiti lime is very popular in Brazil, because the small size of the trees is suitable for high-density plantings. These Tahiti lime trees are easily recognized because they show bark-cracking symptoms, that have been claimed to be associated with infection. Viroid infection of three quebra-galho Tahiti lime trees from a farm near Araraquara in the state of Sao Paulo, Brazil, was assessed by Northern-blot hybridization using viroid-specific probes. Similarly, eight clones of Tahiti lime from different origins and available at Topara Nursery, near Chincha, Peru, were also tested for viroids. The four clones that displayed characteristic bark-cracking symptoms were found to be infected with Citrus exocortis viroid (CEVd), Hop stunt viroid (HSVd) and Citrus viroid III (CVd-III), whereas the clones that did not show bark-cracking symptoms were either viroid-free or infected only with CVd-III. A study is being conducted to establish if viroids, and in particular CEVd, are indeed the cause of quebra-galho bark cracking symptoms. Preliminary observations indicated that 2-yr old CEVd-infected lime trees at Moncada, Spain showed cracks.