Anatomy of stem lesions caused by Citrus leprosis

Abstract

The citrus leprosis is responsible for causing major damage in fruit production. The disease, in the stems, is characterized by caused “scaly bark” lesions of reddish tone, depending on the stage they can be called blisters and make ruptures in the longitudinal direction. The aim of this study was to analyze the evolution of leprosis lesions of type CiLV-C and the anatomical alterations in the twigs of field-collected plants in order to compare to the evolution of the foliar and twigs lesions of inoculated plants already described in literature. For anatomical analysis, the samples were fixed in Karnovsky solution, dehydrated in a graded ethylic series, embedded in hidroxy-ethyl methacrylate resin (Leica Historesin), sectioned (5-7 μm thick), and stained with Toluidine blue for usual histological analysis. Histochemical tests were also carried out. The digital images were capture in a microscope with video camera. The analyzed lesion followed the same pattern as described to foliar lesions, i.e., there was a necrotic center surrounded by a halo also necrotic. In the necrotic region there was the accumulation of lipid compounds. The cortical and, or phloematic parenchyma exhibited hyperplasia. In both lesions it was verified the decrease of starch amount and the increase of quantity of prismatic calcium oxalate crystals, and the presence of gummosis traumatic ducts.

Key words:
Citrus sinensis; crystals; gummosis ducts; starch